Paleobotany Blog

Cretaceous pollen cone sheds light on the evolution of cycads

2023-05-02T17:37:00.000-04:00

Cycads were long thought to be “living fossils,” a group that had evolved minimally since the time of the dinosaurs. Now, a well-preserved 80-million-year-old pollen cone discovered in California has provided a new scientific understanding of the plants.

The findings are detailed in a paper by paleobotanists, Andres Elgorriaga and Brian Atkins, published in New Phytologist.

A lack of fossil cycad evidence and confusion over the years about how to classify some fossil specimens has led to a murky scientific grasp of the plants’ evolutionary history. One prominent idea was that cycads today are nearly identical to their prehistoric ancestors.

In this study, researchers describe a fossil cone from the Campanian Holz Shale formation located in Silverado Canyon, California, which is preserved as a permineralization. The researchers indicate that is clearly assignable to cycads because it has internal anatomy and pollen grains typical of this group. However, the external morphology of this pollen cone is different from living cycads today. This finding suggests cycads probably have a more dynamic evolutionary history than previously thought.

To perform their analysis, Elgorriaga and Atkinson studied the specimen’s cone’s architecture, anatomical details and vasculature organization using serial sectioning, scanning electron microscopy and 3D reconstruction. They also performed a series of evolutionary analyses to place the fossil within the cycad family tree.

Relying partly on the shapes of the cone’s scales, pollen, and pollen sacs, they assigned the ancient plant to Skyttegaardia, a recently described genus based on isolated cone scales found in Denmark. Further, they erase some initial doubt about the new genus’ placement in the cycad group.

The 3D reconstruction shows that this plant only had two pollen sacs per cone scale, and the form of this cone scale was reminiscent of a fossil from Scandinavia called Skyttegaardia. There were many similarities, but the original material from Scandinavia was described based on isolated cone scales (Friis et al. 2021). They cautiously explored the idea that the fossil belonged to cycads, but were uncomfortable with firmly concluding this primarily because it only had two pollen sacs per cone scale, while cycads today have 20 to 700. Most cycad pollen cones are quite large, while this fossil was only half a centimeter in length.

With the additional information from the new fossil plant, the researchers were “quite confident” in their phylogenetic analysis showing the close relationship of Skyttegaardia with cycads.

Entombed together: Rare fossil flower and parasitic wasp make for amber artwork

2022-10-12T10:00:00.031-04:00

Research from a scientist at Oregon State University has found a long-stemmed fossil flower together with a parasitic wasp encased in 30-million-year-old amber.

The study, published in Historical Biology, reports the first description of a fossil flower of the spurge family (Euphorbiaceae) encased in Dominican amber, home to some of the world’s clearest fossilized tree resin.

The flower, named Plukenetia minima, is the first record of this genus, and the mature female flower is noteworthy for its small size but lengthy stalk, which at the tip has four distinct capsules.

The wasp, Hambletonia dominicana, was described as a new species in a separate paper published in Biosis: Biological Systems. It’s an encyrtid, a group of wasps known for attacking a wide range of insects.

The flower has already bloomed and contains four maturing seed pods or capsules. One of the pods contains a developing fly larva. Unrelated organisms frequently become entombed together in amber just by chance, but it is possible that the wasp was attracted to the flower, either for obtaining nectar or in an attempt to deposit an egg on the capsule that contains the fly larva.

The wasp egg would then hatch, enter the pod and devour the fly larva enabling the wasp to survive in the ecological niche created by the vegetation and flower heads of Plukenetia.

Green algae, from 541 million years ago, offers insights into the plant origins

2022-10-12T09:58:00.000-04:00

Above: Reconstruction of the fossil Protocodium

Paleontologists have identified a new fossil algae from China, dating back to 541 million years ago (Late Ediacaran Period). The fossil called Protocodium sinense is the oldest green alga to be preserved in three dimensions, enabling the researchers to investigate its internal structure. The whole fossils and their fine cellular details were preserved in three dimensions due to the replacement of the original organic material with phosphate. This mode of preservation allowed the researchers to use various electron and X-ray microscopy techniques to virtually slice the fossil, unveil its internal structure with precision and ultimately identify it as a close relative of the modern Codium alga, a type of seaweed.

Protocodium fossils are small spheres, half a millimeter wide, about the size of large grains of pollen, covered by a multitude of smaller domes. Thanks to the 3D examination, the researchers determined the domed surface to be part of a complex, single cell that contains thin strands called siphons. This “siphonous” morphology is typical of some modern seaweeds that contain cells with many nuclei.

Above: Living Codium

Protocodium belongs to the ulvophyte green alga and has a surprisingly modern architecture. Like living ulvophytes, Protocodium was similar in structure to living Codium, showing that these algae were already well diversified by the end of the Proterozoic.

The study was published this week in BMC Biology.

From Extinction to Ginkgo...

2021-06-25T14:52:00.001-04:00

Check out installment #3 of the Great Moments in Plant Evolution on the Brooklyn Botanic Garden's website... this time we are talking about the origin of seeds, gymnosperms, and the Permian extinction.

Eukaryotic algae present 1,400 million years ago

2021-04-21T16:19:00.002-04:00

The first photosynthetic oxygen-producing organisms on Earth were cyanobacteria. Their evolution dramatically changed the Earth allowing oxygen to accumulate into the atmosphere for the first time and further allowing the evolution of oxygen-utilizing organisms including eukaryotes. When, however, did algae begin to occupy marine ecosystems and compete with cyanobacteria as important phototrophic organisms?

In a study by Zhang et al. (2021), the molecular remains of ancient algae (so-called biomarkers) are used to show that algae occupied an important role in marine ecosystems in the Mesoproterozoic Era (1,400 million years ago). This may be 200 million years earlier than previously recognized.

The specific biomarkers explored by the researchers are a group of sterane molecules derived from sterols that are prominent components of cell membranes in eukaryotic organisms. The steranes indicated the presence of both red algae and green algae.

This work shows that the red and green algal lineages had certainly evolved by 1,400 million years ago, and this should be a useful constraint in timing the overall history of eukaryote evolution. This work also shows that at least some ancient marine ecosystems functioned more similarly to modern ecosystems than previously thought, at least with respect to the types of photosynthetic organisms producing organic matter. This also means that there was sufficient nutrients and oxygen available to drive the presence of algae-containing ecosystems.

Fossil reveals last meal of Cretaceous pollinator

2021-04-21T16:01:00.001-04:00

Fossil of a Cretaceous beetle has shed some light on the diet of one of the earliest pollinators of flowering plants. The animal’s remains were unearthed by researchers at the University of Bristol and the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) who were able to study its fossil fecal matter, which was composed solely of pollen.

Besides being a visitor of flowering plants, researchers now have conclusive evidence that the new fossil named Pelretes vivificus also fed on their pollen. The beetle is associated with clusters of pollen grains, suggesting that short-winged flower beetles visited angiosperms in the Cretaceous. Some aspects of the beetle’s anatomy, such as its hairy abdomen, are also adaptations associated with pollination.

The fossil is associated with beetle coprolites, which provide a very unusual but important insight into the diet of short-winged flower beetles in the Cretaceous. The coprolites are completely composed of pollen, the same type that is found in clusters surrounding the beetle and attached to its body. Therefore, researchers know that Pelretes visited angiosperms to feed on their pollen. This finding provides a direct link between early flowering plants in the Cretaceous and their insect visitors; it shows that these insect fossils were not just incidentally co-preserved with pollen, but that there was a genuine biological association between the two.

Little is known about the origin of the intimate association between flowering plants and insects. Cretaceous amber fossils provide an important source of evidence for understanding the biology of early angiosperms before they became the dominant group of plants on Earth.

Two hundred million years ago the world was as green as today, overgrown with dense vegetation. But it was not as colourful – there were no flowers. Flowering plants that make up over 80% of all plant species today, only begun to diversify in the Cretaceous, about 125 million years ago.

The flower beetle Pelretes vivificus lived in the Burmese amber rainforest some 98 million years ago. Its closest relatives are short-winged flower beetles (Kateretidae) that today occur in Australia, visiting a diverse range of flowers and feeding on their pollen. The pollen associated with the beetle can be assigned to the fossil genus Tricolpopollenites, a eudicot.

The Origin of Trees and Forest

2020-12-14T12:23:00.000-05:00

Installment 2 of the Great Moments in Plant Evolution on the BBG website... this time we are talking about the origin of trees and forests.

Plants Invade the Land

2020-11-21T15:45:00.000-05:00

Check out my new blog post on the BBG website! It is part 1 of 4 series on the Great Moments in Plant Evolution

Oldest Known Fossil Forest

2019-12-20T10:29:00.000-05:00

A research team led by faculty at Binghamton University, State University of New York has uncovered evidence that the transition toward forests as we know them today began earlier than typically believed.

While sifting through fossil soils in the Catskill region near Cairo, N.Y., researchers uncovered the extensive root system of 385-million-year old trees that existed during the Middle Devonian Period (Givetian).

While seed plants didn’t appear until some 10 million years later, in the Late Devonian, these preserved root systems show evidence of the presence of trees with leaves and wood—both of which are common in modern seed plants.

The finding, published December 19, 2019 in Current Biology, is the first piece of evidence that the transition toward modern forests began earlier than previously believed.

The Cairo fossil forest covered an area of at least 3,000 square meters, and is one or two million years older than the Devonian fossil forest at Gilboa, also in New York and around 40 km away from the Cairo site.

The Cairo site presents three unique root systems, leading Stein and his team to hypothesize that much like today, the forests of the Devonian Period were heterogeneous with different trees occupying different places depending on local conditions.

First, Stein and his team identified a rooting system that they believe belonged to a palm tree-like tree called Eospermatopteris. This plant, first identified at the Gilboa site, had relatively rudimentary roots. Like a weed, Eospermatopteris likely occupied many environments, explaining its presence at both sites. But its roots had relatively limited range and probably lived only a year or two before dying and being replaced by other roots that would occupy the same space.

The researchers also found evidence of a progymnosperm tree called Archaeopteris, which possesses wood like a conifer, but was spore-bearing (not seed-bearing) like a fern. At Cairo, this tree was now found to also have a strikingly modern underground system allowing for continuous expansion of roots accommodating continuous growth of a long-lived larger type of tree, and potentially dominating the local forest ecosystem.

Stein and his team were also surprised to find a third root system in the fossilized soil at Cairo belonging to a tree thought to only exist during the Carboniferous Period and beyond: “scale trees” belonging to the class Lycopsida.

Earliest evidence of flower pollination

2019-11-12T09:41:00.002-05:00

A new study co-led by researchers in China and the United States has pushed back the first-known physical evidence of insect flower pollination to 99 million years ago, during the mid-Cretaceous period (Cenomanian).

The revelation is based upon a tumbling flower beetle with pollen on its legs discovered preserved in amber deep inside a mine in northern Myanmar. The fossil is described Nov. 11 in the journal of the Proceedings of the National Academy of Sciences. The fossil, which contains both the beetle and pollen grains, pushes back the earliest documented instance of insect pollination to about 50 million years earlier than previously thought.

The 99-million-year-old fossil, recovered from a mine in northern Myanmar, also contains 62 pollen grains from a eudicot flower. It is the earliest known physical evidence of insect pollination.

The pollen was revealed hidden in the insect's body hairs under a confocal laser microscopy. The analysis took advantage of the fact that pollen grains glow under fluorescent light, contrasting strongly with the darkness of the insect's shell.

The insect in the amber is a newly discovered species of beetle, which was named Angimordella burmitina. Its role as a pollinator was determined based upon several specialized physical structures, including body shape and pollen-feeding mouth parts. These structures were revealed through an imaging method called X-ray micro-computed tomography, or micro-CT.

Prior to this study, the earliest physical evidence of insect pollination of flowering plants came from the Eocene. The age of the new fossil was determined based upon the age of other known fossils in the same location as the fossilized beetle's discovery.

Mutated spores elucidate Triassic extinction

2019-10-29T15:41:00.002-04:00

Most researchers believe that the mass extinction 201 million years ago was caused by release of CO2 by volcanism with global warming as a consequence. Now, new data from fern spores suggest there might have been more to it than that.

At the end of the Triassic around 201 million years ago, three out of four species on Earth disappeared. Up until now, scientists believed the cause of the catastrophe to be the onset of large-scale volcanism resulting in abrupt climate change. Now, new research suggest there might be several factors in play.

An international research team led by the Geological Survey of Denmark and Greenland (GEUS) show that increased concentrations of the toxic element mercury in the environment contributed to the mass extinction. They recently published their finds in Science Advances.

Through observations of fern spores in sediments from the mass extinction, it was evident that these ferns were negatively affected by the mercury levels. Since mercury is accumulated in the food chain, it seems likely that other species would have have suffered as well.

The results suggest that the end-Triassic mass extinction was not just caused by greenhouse gases from volcanoes causing global climate change, but also from the emitted toxins such as mercury.

One of the co-authors of the study, Professor Hamed Sanei from Aarhus University, has previously demonstrated increased mercury levels from volcanism in a Large Igneous Province (LIP) during the most severe mass extinction known, the end-Permian crisis, where perhaps as much as 95% of life on Earth disappeared. Volcanic activity in LIPs is thought to be responsible for four of the five largest mass extinctions during the last 500 million years.

Other previous studies have shown elevated mercury concentrations in Triassic-Jurassic boundary sediments over a very large area stretching from Argentina to Greenland and from Nevada to Austria and that made the team curious about the impact on the end-Triassic event.

When looking at fern spores from core samples dating from 201 million years ago at the end of the Triassic the team indeed saw a link between increased mercury levels and mutations in the spores. During the mass extinction mutated spores become increasingly common in cores.

This rise in mutations happened during a period of increased volcanic activity in a LIP called the Central Atlantic Magmatic Province (CAMP) leading to rising mercury levels. Since mercury is a mutagenic toxin, its' increased distribution from the volcanic activity could help to explain the sudden deterioration of the ecosystem. Therefore, the fern spores could serve as indicators of increased mercury poisoning.

Previous studies have found increased amounts of malformed pollen during the end-Permian mass extinction 252 million years ago, which like the end-Triassic crisis is blamed on volcanism. These studies have suggested that the mutations during the end-Permian crisis were caused by increased UVB radiation, due to thinning of the ozone layer from the volcanism.

It is important to realize that such a global crisis may not be caused by one factor. This study suggests there could very well be a cocktail effect of CO2 and global warming, toxins like mercury, and other factors as well

Most of the prehistoric mass extinctions have indeed come in the wake of LIP volcanism, causing climate change and emitting toxic substances.

Single-celled algae evolve multicellularity

2019-02-24T18:25:00.003-05:00

Chlamydomonas green alga

Some point in evolutionary history, around 1.2 billion years ago, single-celled organisms evolved into more complex multicellular life, but now researchers have been able to recreate this event through experiments with green algae.

Researchers from the George Institute of Technology and University of Montana have produced evidence of single-celled algae evolving multicellularity in 50 weeks, triggered by the introduction of an alga predator.

In this experiment, the team was trying to figure out exactly what drove single-celled organisms to become multicellular all those years ago. One hypothesis proposes that predation was the selective pressure on single-celled organisms, creating complex forms to avoid being eaten.

To test the validity of this idea, the team grew populations of single-celled green alga Chlamydomonas reinhardtii, and then put a filter-feeding predator in the mix, Paramecium tetraurelia to observe the effects. In just 50 weeks, two out of five experimental populations of the single-celled creatures evolved into multicellular life.

Fifty weeks is an incredibly short period of time on an evolutionary scale, but during this time, the algae produced 750 generations.

Their result suggests that predation could have played some kind of role in at least part of the evolution of multicellularity back in the Proterozoic. These multicellular traits provided effective protection against predation, and the resulting forms were all incredibly varied, just like you'd expect in natural evolution.

The ancient symbiosis of plants and fungi

2019-02-07T12:46:00.004-05:00

It is assumed that neither plants nor fungi existed on land before the Cryogenian Period (~720 million years ago), due to several factors with the environment. Research in Nature Communications indicates that the successful plant and fungi invasion of land was an outcome of co-evolutionary interactions between these two groups.

In order to examine this idea, researchers methodologically explored the evolution of plants and fungi using molecular and bioinformatic techniques. They first established phylogenetic trees for plants and fungi, independently, using gene sequence data. They estimated evolutionary divergence dates of plant and fungal lineages using both gene mutations and the fossil record.

Then they computed major shifts in diversification rates of major lineages in the two kingdoms independently. Once these studies were accomplished, the resulting phylogenetic relationships for plants and fungi were aligned on the same geological time scale, which allowed the researchers to pinpoint the origins of various key plant-fungal co-evolutionary events, particularly symbiotic relationships and the decomposition of plants by fungi. They noticed drastic shifts in diversification rates in the two kingdoms that they attribute to the plant-fungal co-evolution and interdependence across their long history.

Fungal colonization of land was associated with and aided by at least two origin events of terrestrial green algae, which preceded the origin of land plants. This coincided with the loss of fungal flagellum in derived groups, around 720 million years ago. Ancestral fungi, known as the chytrids, still possess flagella. Nearly 250 million years later, during the Ordovician Period, land plants successfully colonized the land, which was likely facilitated by a mutualism with arbuscular fungi. This was followed by the origin of extant lichens.

One of the significant biological, ecological, and environmental events on Earth is the origin and initial diversification of a lineage containing all plants that bear seeds (Spermatophytes). Significantly, one of the distinguishing traits of this plant lineage was the origin of the cambium and the production of wood. This led to the evolution of large woody trees, known as Archaeopteris, which in turn, resulted in the establishment of the first inland forests based on lignin-rich wood as their backbone.

Researchers propose that such forests could not have been successful without the linked evolution with fungi and their capacity to digest the structural polymer lignin and cellulose of plant cell walls. This evolutionary novelty was instrumental in organic matter recycling, which led to the forest system being sustained. The origin and early diversification of the seed plant lineage was in turn followed by the evolution of the largest classes of fungi, the Agaricomycetes.

The origin of ectomycorrhizal fungi (fungi associated externally with plant roots) seems to have resulted from a series of evolutionary innovations in plants including the origins of wood, seeds, and roots. These consequential evolutionary events were crucial in promoting the diversification leading to existing seed plants, and their expansion to drier environments.

The macroevolution of plants and fungi has been studied mostly separately; however, this study clearly demonstrates that their respective evolutionary histories are deeply interconnected and can be understood only through a simultaneous study of their phylogenies within a robust timeframe.

It is expected that the same will hold true for the evolution of the animal kingdom, a group highly dependent on photoautotrophic plants, as well as microorganisms in general.

Lutzoni, F., M.D. Nowak, M.E. Alfaro, V. Reeb, J. Miadlikowska, M. Krug, A.E. Arnold, L.A. Lewis, D.L. Swofford, D. Hibbett, K. Hilu, T.Y. James, D. Quandt, and S. Magallón. 2018. Contemporaneous radiations of fungi and plants linked to symbiosis. Nature Communications 9: 5451.

Jurassic flowers?

2019-01-18T15:15:00.002-05:00

In December 2018, researchers published a paper that describes fossils that they are suggesting are flowers from the Early Jurassic, more than 174 million years ago. Currently, flowering plants have a good fossil history starting in the Early Cretaceous, around 130 million years.

The origin of angiosperms is a hotly debated topic in paleobotany, and if this new discovery (Nanjinganthus dendrostyla) is verified, the origin of angiosperms would be reset by 50 million years.

The research team studied 264 specimens of 198 individual flowers preserved on 34 rock slabs from the South Xiangshan Formation -- an outcrop of rocks in the Nanjing region of China renowned for bearing fossils from the Early Jurassic epoch. The abundance of fossil samples used in the study allowed the researchers to dissect some of them and study them with high-resolution microscopes.

The defining feature of an angiosperm, when compared to their sister seed plants (=the gymnosperms), is that flowering plants have seeds / ovules that are completely encased inside a fruit / ovary. The pollen from the male never comes in contact with these ovules. Pollination in the gymnosperms, on the other hand, occurs directly on the ovule. This is why they are "naked seeded" plants.

Ascertaining where and how pollination occurs on Nanjinganthus will be crucial for determining whether this plant is truly an early angiosperm, or whether it is another strange gymnosperm from the Jurassic. Over the years, there have many early Mesozoic gymnosperms that have been attributed to the flowering plants, to only be reinterpreted with better evidence later on (e.g. Caytoniales, Benettitales, Petriellales, etc.)

In the current study, researchers claim that the fossil exhibits a cup-form receptacle and an ovarian roof that together encloses the ovules / seeds, thus making it an angiosperm. As these fossils are examined by others, and new fossils are found, it is will be interesting to see if this extraordinary claim is verified as true. Until that time, many paleobotanists will remain skeptical about this Early Jurassic fossil's taxonomic placement.

Fu, Q., J. Bienvenido Diez, M. Pole, M. Garcıa Avila, Z.-J. Liu, H. Chu, Y. Hou, P. Yin, G.-Q. Zhang, K. Du, and X. Wang. 2018. An unexpected noncarpellate epigynous flower from the Jurassic of China. eLife

Large angiosperm forests during Late Cretaceous

2018-10-03T11:54:00.000-04:00

Flowering plants appear in the fossil record around 130 million years ago, during the Early Cretaceous. There is debate as to the size and form of these earliest plants, but there is evidence that they may have been herbaceous and aquatic during these early years. From these humble beginnings, angiosperms diversified in form and niche during the Cretaceous.

A newly discovered fossil shows the result of the next 40 million years over evolution: angiosperms had already become towering giants on the landscape. New evidence from researchers at Adelphi University and the Burpee Museum of Natural History shows that large, flowering trees grew in North America during the Late Cretaceous, over 90 million years ago. They found a large fossilized log from an extinct species named Paraphyllanthoxylon; an angiosperm possibly in the Lauraceae family. Using calculations to estimate the length/ height of the tree, researcher estimate that the tree was at least 50m (165 ft).

These large trees were part of the forest canopies there nearly 15 million years earlier than previously thought. Researchers found the fossil in the Mancos Shale Formation in Utah, in ancient delta deposits formed during a poorly understood interval in the North American fossil record.

Aside from the large petrified log, the team reports preserved foliage of ferns, conifers and angiosperms, which confirm that there was forest or woodland vegetation in the area during the Late Cretaceous, covering a large delta extending into the sea. The team also reports the first turtle and crocodile remains from this geologic layer, as well as part of the pelvis of a duck-billed dinosaur; previously, the only known vertebrate remains found were shark teeth, two short dinosaur trackways, and a fragmentary pterosaur.

How plants became three-dimensional

2018-07-28T11:50:00.000-04:00

The Earth is filled with diverse and remarkable plant forms from the tallest redwoods that pierce forest canopies, to the smallest mosses that blanket the ground underfoot.

However, these striking forms came from much simpler origins. The ancestors of land plants were string-like, similar to Spirogyra in the image to the left. These aquatic green algae looked very different from the three-dimensional (3D), upright stems and leaves of plants we are familiar with today.

Now, researchers at the University of Bristol have revealed exciting insights into how land plants evolved these 3D forms that were crucial for their advancement onto land.

The research, published today in the journal Current Biology, led by Dr Jill Harrison from the University’s School of Biological Sciences, and collaborators, found that small proteins known as CLAVATA peptides, control the growth and division of cells at the very tips of plants, which generate organs such as the shoots and leaves.

CLAVATA is a peptide and receptor based signalling system. The peptide moves to the receptor to set the cell division planes.However, when the researchers looked for CLAVATA molecules in the aquatic algae ancestors, they could not find them.This showed that CLAVATA proteins evolved just as the first plants moved onto land.

Using mosses to exemplify the 2D to 3D growth transition, the researchers showed that CLAVATA protein rotate cell divisions at the tips of plant stems enabling growth in multiple directions.

Dr Harrison, a Royal Society University Research Fellow, said: “The CLAVATA genes were found to be specific to land plants to regulate their unique 3D growth patterns and so it looks like these genes were instrumental in enabling plants to get going on land.

“After this fundamental change in cell division patterns, plants could now develop many different forms, enabling them to dominate almost every environment on Earth, and so this work reveals a key role for these small proteins in plants’ conquest of land.”

Whitewoods et al. 2018. CLAVATA Was a Genetic Novelty for the Morphological Innovation of 3D Growth in Land Plants. Current Biology.

Dino Paleo Diet

2018-07-23T11:31:00.000-04:00

Scientists have measured the nutritional value of herbivore dinosaurs' diet by growing their food in atmospheric conditions similar to those found roughly 150 million years ago.

Previously, it was believed that plants grown in an atmosphere with high carbon dioxide levels had low nutritional value. To test this idea, a research team grew living representatives of plant groups that dinosaurs might have eaten, such as horsetails (Equisetum) and Ginkgo, under high levels of carbon dioxide mimicking atmospheric conditions similar to when sauropod dinosaurs would have been widespread.

An artificial fermentation system was used to simulate digestion of the plant leaves in the sauropods' stomachs, allowing the researchers to determine the leaves' nutritional value. The findings, published in Palaeontology, showed many of the plants had significantly higher energy and nutrient levels than previously believed.

This suggests that the megaherbivores would have needed to eat much less per day and the ecosystem could potentially have supported a significantly higher dinosaur population density, possibly as much as 20% greater than previously estimated.

The climate was very different in the Mesozoic era -- when the huge Brachiosaurus and Diplodocus lived -- with possibly much higher carbon dioxide levels. There has been the assumption that as plants grow faster and/or bigger under higher CO2 levels, their nutritional value decreases. The results show this isn't the case for all plant species.

The large body size of sauropods at that time would suggest they needed huge quantities of energy to sustain them. When the available food source has higher nutrient and energy levels it means less food needs to be consumed to provide sufficient energy, which in turn can affect population size and density.

This research doesn't give the whole picture of dinosaur diet or cover the breadth of the plants that existed at this time, but a clearer understanding of how the dinosaurs ate can help scientists understand how they lived.

Plants play greater role than megaherbivore extinctions in changes to ecosystem structure

2018-04-30T14:25:00.002-04:00

Plants may have exerted greater influence on our terrestrial ecosystems than the megaherbivores that used to roam our landscapes, according to new research.

Previously, scientists believed that the Late Quaternary extinction event, which took place between ~11,000 and 15,000 years ago across much of northern Europe, played a significant role in the subsequent expansion of woody plants and declining nitrogen availability over the last 10,000 years.

But in a new study, published in Ecology Letters, researchers suggest the changes had already started to occur in Britain and Ireland at the same time these mammals -- such as the woolly mammoth, Giant Irish Deer, reindeer and wild horse -- began to die out.

They also believe that natural fires had a greater role to play in these processes than previously thought, and that the natural burning of land should be taken into account when considering rewilding projects in the UK in order to ensure the sustainability of open, fertile habitats for grazing animals.

The research was conducted by academics at the University of Oxford, University of Plymouth, Queen's University Belfast, Swansea University and the Natural History Museum, London.

Dr Elizabeth Jeffers, from Oxford's Department of Zoology, led the study. She said: "Our results challenge the ecological argument underpinning trophic rewilding by showing that the fauna living in these regions at the end of the last glacial period were unable to stem the expansion of woody plants across the northern hemisphere."

For the study, scientists produced an unprecedented amount of ecological and climatic information (spanning the transition from the Late Pleistocene to the middle Holocene period, 16,000 to 4,800 years ago) for five study sites in England, Scotland and Ireland. Their dataset included: proxy measurements of plant and large herbivore biomass; nitrogen availability; growing season temperatures; and fire activity.

Two-thirds of the region's megaherbivore species became extinct during this time; using previously available fossil bone data of these species, the authors applied statistical modelling to their dataset in order to investigate the relative impacts of plants, herbivores, fire, and summer temperatures on ecosystem structure and function.

They found that shrubs were consistently one of the strongest predictors of ecosystem change, with increasing shrub biomass reducing ecosystem-scale nitrogen availability and promoting the growth and expansion of trees. Natural fires, not herbivory, were the most significant factor in reversing these effects, however, declining fire activity in the early Holocene enabled shrubs (and ultimately trees) to dominate terrestrial ecosystems.

The findings provide new empirical evidence for the long-term ecosystem engineering effects of woody plants and demonstrate the importance of burning for maintaining the structure and function of open ecosystems in northern biomes.

Dr Nicki Whitehouse, Associate Professor (Reader) in Physical Geography at the University of Plymouth and one of the senior authors of the study, added: "This research started when we became interested in the ecological consequences of the megaherbivore extinctions. It led us to look at a range of ecological processes that may have been affected by the loss of these species, including decreasing levels of nitrogen as a nutrient. "What we have found could have significant conservation management consequences; people talk about using large grazing animals to maintain open, fertile habitats, but in fact you need a range of different processes including burning. In the past, fire played an important role in maintaining some of our open ecosystems and grasslands and it should be considered again as an important management tool particularly as part of any rewilding programmes planned across the UK and beyond."

Jeffers, E.S., N.J. Whitehouse, A. Lister, G. Plunkett, P. Barratt, E. Smyth, P. Lamb, M.W. Dee, S.J. Brooks, K.J. Willis, C.A. Froyd, J.E. Watson, M.B. Bonsall. 2018. Plant controls on Late Quaternary whole ecosystem structure and function. Ecology Letters.

Warming planet led to bogs

2018-04-29T11:26:00.002-04:00

Rising temperatures were a key driver of peatland formation after the last glacial maximum, according to new research.

Researchers from the University of Leeds, the University of Bristol and Memorial University in Canada, have simulated the local changes in climate that took place across the world during the last 26,000 years, when the glaciers of the last ice age began to retreat.

Combining the simulations with radiocarbon dates of peatland initiation they discovered that higher local summer temperatures, rather than increased rainfall, led to the formation of peatlands in formerly glaciated regions such as North America, northern Europe, and Patagonia.

Lead researcher Dr Paul Morris, from the University of Leeds' School of Geography, said: "This work helps explain the genesis of one of the world's most important ecosystem types and its potentially fragile carbon store.

"It is important that we strengthen our knowledge about the causes of peat initiation, particularly given the concern about future climates, and the important role that peatlands play in combatting climate change."

Peatlands are important ecosystems because they are one of the largest biological carbon stores on the planet, and have captured vast quantities of carbon into the soil. They are formed entirely of organic matter but are thought to be sensitive to climate change. Peat forms over thousands of years when plants and organic matter are unable to fully decompose in waterlogged, acidic conditions, keeping their carbon from being released into the atmosphere.

The new research helps build an understanding of the role of climate in peat formation, which is particularly relevant when considering how the distribution and abundance of peatlands might change under future climates.

The research also shows the climatic changes that the world's peatlands have endured since they first developed, providing context for future warming. The authors warn that the likely rates and severity of future climate change far exceed what the world's peatlands have previously experienced, leaving their huge carbon stores potentially vulnerable to degradation.

Morris, P.J., G.T. Swindles, P.J. Valdes, R.F. Ivanovic, L J. Gregoire, M.W. Smith, L. Tarasov, A.M. Haywood, and K.L. Bacon. 2018. Global peatland initiation driven by regionally asynchronous warming. Proceedings of the National Academy of Sciences.

How Earth's earliest trees grew

2017-11-02T10:31:00.000-04:00

Fossils of early trees from the Late Devonian (Frasnian) found in the northwest of China have revealed a plant with a unique vascular pattern. These trees were amazingly complex, research has revealed from partnership between Chinese Academy of Sciences, Cardiff University, the State University of New York - Binghamton.

The fossils revealed an interconnected web of woody strands within the trunk of the tree that is much more intricate than that of the trees we see around us today.

The strands, known as wood or secondary xylem, are responsible for both strengthening the trunk and conducting water from a tree's roots to its branches and leaves for photosynthesis. In modern woody trees the secondary xylem forms a single cylinder (trunk) to which new growth is added in annual growth rings. In other tree-like plants, notably palms or bamboo, wood is absent. These plant only make pockets of primary xylem for moving water, which are embedded in softer tissues throughout the trunk. Modern palms add strengthening rods or fibers to the trunk to prevent the plant from buckling.

Rather than possessing one large column of wood, these fossil trees possessed hundreds of individual woody strands which were each creating their own growth rings. These xylem strands were arranged in an interconnected pattern to allow water movement throughout the plant. These woody strands were dispersed in the outer 5 cm of the tree trunk only, while the center of the trunk was hollow.

As the woody strands grew in girth, the soft tissues between the strands also increased, and the girth of the trunk expanded. During growth, the connections between the strands would split apart and resultant damage would be repaired by the plant.

As the girth of the tree expanded, the woody strands rolled out from the side of the trunk at the base of the tree, forming a characteristic flat base and bulbous shape. This bulbous pattern is found in other trees during this time from a fern-like group of plants known as the Cladoxylopsids. In the Catskill Mountains of New York State, well-known cladoxylopsids called the Gilboa trees, also display this pattern. The preservation in these Chinese fossils is remarkable, and has greatly increased our understanding of the growth and development of this group.

Chris Berry, from Cardiff University's School of Earth and Ocean Sciences, said: "There is no other tree that I know of in the history of the Earth that has ever done anything as complicated as this. The tree simultaneously ripped its skeleton apart and collapsed under its own weight while staying alive and growing upwards and outwards to become the dominant plant of its day."

"By studying these extremely rare fossils, we've gained an unprecedented insight into the anatomy of our earliest trees and the complex growth mechanisms that they employed."

"This raises a provoking question: why are the very oldest trees the most complicated?"

Xu, H.-H., Berry, C.M., Stein, W.E., Wang, Y., Tang, P., and Fu, Q. 2017. Unique growth strategy in the Earth’s first trees revealed in silicified fossil trunks from China. Proceedings of the National Academy of Sciences

Red algae strengthen coral reefs throughout geologic history

2017-09-05T15:45:00.003-04:00

The Great Barrier Reef, and most other large reefs around the world, owe their bulk in large part to crustose coralline red algae that grows on corals and strengthens them. New research from the University of Texas at Austin Jackson School of Geosciences, has found that ancient coral reefs were also bolstered by their bond with red algae, a finding that could help scientists better understand how reefs will respond to climate change.

Coral reefs are a product of a long term coral-coralline algae relationship, and preservation of coral reefs requires attention to the health of these red algae.

Coralline red algae help build coral reef ecosystems in a variety of ways. They encourage reef growth by attracting coral larvae; they serve as a food source for reef animals; and help patch up broken coral skeletons by growing over breaks. The most important role of the algae when it comes to reef long term growth is directly reinforcing the limestone skeletons of corals with calcite, the hard mineral that forms the algae’s skeleton. This allows coral reefs to maintain long-term structures that serve as the foundation of reef ecosystems.

Paleontologists think that the algae found in fossilized reefs plays a similar role in reef ecosystems as it does today. This study is the first to test that assumption by quantifying and statistically measuring that the algae has a significant, long term effect on reef diversity and structure.

This research involved analyzing data from 128 fossilized coral reefs with coralline algae present cited in the research literature. She zeroed in specifically on reefs that were fossilized in the late Cretaceous and Cenozoic, a period that spans from 100 million years ago to the present.

Reefs with significant algae fortification were strongly associated with having higher structural integrity and more active ecosystems than those with little or no signs of algae—a correlation that is also found in modern day coral reefs.

Today, climate change is warming ocean water and making it more acidic, putting stress on coral reefs around the world. Other research indicates that the algae may be more vulnerable to the effects of climate change than coral, a finding that she said exemplifies the importance of learning more about algae’s relationship with corals now and in the past.

Weiss A, and Martindale RC. 2017. Crustose coralline algae increased framework and diversity on ancient coral reefs. PLoS ONE 12(8)

Evolution of Leaves in Ferns

2017-08-16T14:54:00.000-04:00

In the modern sense, ferns are plants with frond-like leaves, and underground creeping stems. The earliest ferns to appear on Earth evolved during the Early Devonian (419–393 million years ago) and did not possess these familiar features. Instead, most of these "ferns" were leafless with a wide range of branching patterns and stems that were photosynthetic. Fortunately, they exhibit internal anatomy that allows researchers to connect these fossil plants to the ferns.

So when do ferns evolve leaves?

By the Late Devonian (383–359 million years ago), most land plant lineages had evolved leaves, but the evolution of leaves in ferns remains unclear.

In 2015, Wang et al. identified a fern-like plant, Shougangia bella, from the Late Devonian that has very small leaves on the upper-most portions of its branches. The plant probably grew similarly to modern ferns, creeping along the ground, but this ancient plant also had upright stems. The lower portions of these stems lacked leaves, but the upper-most portions exhibit tiny, flattened leaves. With leaves about 4mm long, this plant would not have appeared very leafy from a distance, but evolutionarily, this plant marks the origins of leaves in ferns on Earth.

This fossil plant suggests that fern-like plants, along with other plant lineages, had independently evolved leaves by the Late Devonian, possibly coinciding with rapidly declining levels of CO2 in the atmosphere.

New Cretaceous Fossil Flowers

2017-08-16T09:23:00.003-04:00

Seven intact fossil flower specimens, dating to around 100 million years ago (Cenomanian epoch), have been identified as a new species of Cretaceous tree.

George Poinar Jr., professor emeritus in Oregon State University’s College of Science, said it’s the first time seven flowers of this age have been reported in a single study. The flowers range from 3.4 to 5 millimeters in diameter, requiring a microscope for examination.

Poinar and collaborator Kenton Chambers, professor emeritus in OSU’s College of Agricultural Sciences, named the discovery Tropidogyne pentaptera based on the flowers’ five firm, spreading sepals (“penta” = five; “pteron” = wing).

“The amber preserved the floral parts so well that they look like they were just picked from the garden,” Poinar said. The flowers landed in resin deposits on the bark of an Araucaria conifer tree, which is presumed to be the source of resin that turned to amber during fossilization.

This study builds on earlier research also involving Burmese amber in which Poinar and Chambers described another species in the same angiosperm genus, Tropidogyne pikei; that species was named for its flower’s discoverer, Ted Pike. Findings were recently published in Paleodiversity.

“The new species has spreading, veiny sepals, a nectar disc, and a ribbed inferior ovary like T. pikei,” Poinar said. “But it’s different in that it’s bicarpellate, with two elongated and slender styles, and the ribs of its inferior ovary don’t have darkly pigmented terminal glands like T. pikei.”

Both species have been placed in the extant family Cunoniaceae, a widespread Southern Hemisphere family of 27 genera.

Poinar said T. pentaptera was probably a rainforest tree.

“In their general shape and venation pattern, the fossil flowers closely resemble those of the genus Ceratopetalum that occur in Australia and Papua-New Guinea,” he said. “One extant species is C. gummiferum, which is known as the New South Wales Christmas bush because its five sepals turn bright reddish pink close to Christmas.”

Another extant species in Australia is the coach wood tree, C. apetalum, which like the new species has no petals, only sepals. The towering coach wood tree grows to heights of greater than 120 feet, can live for centuries and produces lumber for flooring, furniture and cabinetwork.

So what explains the relationship between a mid-Cretaceous Tropidogyne from Myanmar, formerly known as Burma, and an extant Ceratopetalum from Australia, more than 4,000 miles and an ocean away to the southeast?

That’s easy, Poinar said, if you consider the geological history of the regions.

“Probably the amber site in Myanmar was part of Greater India that separated from the southern hemisphere, the supercontinent Gondwanaland, and drifted to southern Asia,” he said. “Malaysia, including Burma, was formed during the Paleozoic and Mesozoic eras by subduction of terrains that successfully separated, and then moved northward by continental drift.”

Poinar, G.O. and K.L. Chambers. 2017. Tropidogyne pentaptera, sp. nov., a new mid-Cretaceous fossil angiosperm flower in Burmese amber. Palaeodiversity 10: 135-140. http://www.bioone.org/doi/10.18476/pale.v10.a10

Earliest evidence of orchids

2017-07-27T14:41:00.002-04:00

The orchid family has some 28,000 species – more than double the number of bird species and quadruple the mammal species. As it turns out, they've also been around for a while.

A newly published study documents evidence of an orchid fossil trapped in Baltic amber that dates back to the Early Eocene (45-55 million years ago), shattering the previous record for an orchid fossil found in Dominican amber some 20-30 million years old.

Results of the discovery have just been published in the Botanical Journal of the Linnean Society.

"It wasn't until a few years ago that we even had evidence of ancient orchids because there wasn't anything preserved in the fossil record," said George Poinar, Jr., a professor emeritus of entomology in the College of Science at Oregon State University and lead author on the study. "But now we're beginning to locate pollen evidence associated with insects trapped in amber, opening the door to some new discoveries."

Orchids have their pollen in small sac-like structures called pollinia, which are attached by supports to viscidia, or adhesive pads, that can stick to the various body parts of pollinating insects, including bees, beetles, flies and gnats. The entire pollination unit is known as a pollinarium.

In this study, a small female fungus gnat was carrying the pollinaria of an extinct species of orchid when it became trapped in amber more than 45 million years ago. The pollinaria was attached to the base of the gnat's hind leg. Amber preserves fossils so well that the researchers could identify a droplet of congealed blood at the tip of the gnat's leg, which had been broken off shortly before it was entombed in amber.

At the time, all of the continents hadn't even yet drifted apart.

The fossil shows that orchids were well-established in the Eocene and it is likely that lineages extended back into the Cretaceous period. Until such forms are discovered, the present specimen provides a minimum date that can be used in future studies determining the evolutionary history and phylogeny of the orchids.

How the orchid pollen in this study ended up attached to the fungus gnat and eventually entombed in amber from near the Baltic Sea in northern Europe is a matter of speculation. But, Poinar says, orchids have evolved a surprisingly sophisticated system to draw in pollinating insects, which may have led to the gnat's demise.

"We probably shouldn't say this about a plant," Poinar said with a laugh, "but orchids are very smart. They've developed ways to attract little flies and most of the rewards they offer are based on deception."

Orchids use color, odor and the allure of nectar to draw in potential pollinating insects. Orchids will emit a scent that suggests to hungry insects the promise of food, but after entering the flower they will learn that the promise of nourishment was false.

Likewise, female gnats may pick up a mushroom-like odor from many orchids, which attracts them as a place to lay their eggs because the decaying fungal tissue is a source of future nutrition. Alas, again it is a ruse. In frustration, they may go ahead and lay their eggs, dooming their offspring to a likely death from a lack of food.

Finally, male insects are attracted by the ersatz scent of female flies and they actually will attempt to copulate with a part of the orchid they think is a potential mate.

All three of these processes are based on deception, Poinar said, and they all have the same end result.

"Though the deception works in different ways, the bottom line is that the orchid is able to draw in pollinating insects, which unwittingly gather pollen that becomes attached to their legs and other body parts, and then pass it on to the next orchid flowers that lure them in," he said.

"Orchids are, indeed, pretty smart."

Using infrared spectroscopy to decipher fossil leaves

2017-07-24T11:32:00.001-04:00

For the first time, researchers have succeeded in establishing the relationships between 200-million-year-old plants based on chemical fingerprints. Using infrared spectroscopy and statistical analysis of organic molecules in fossil leaves, they are opening up new perspectives on the dinosaur era.

The unique results stem from a collaboration between researchers at Lund University, the Swedish Museum of Natural History in Stockholm, and Vilnius University.

“We have solved many questions regarding these extinct plants’ relationships. These are questions that science has long been seeking answers to”, says Vivi Vajda, a professor at the Department of Geology at Lund University and active at the Swedish Museum of Natural History.

The researchers have collected fossil leaves from rocks in Sweden, Australia, New Zealand and Greenland. Using molecular spectroscopy and chemical analysis, the fossil leaves were then compared with the chemical signatures from molecules in plant leaves picked at the Botanical Garden in Lund.

The use of genetic DNA analysis in modern research to determine relationships is not possible on fossil plants. The oldest DNA fragments ever found are scarcely one million-years-old. Therefore, the scientists searched for organic molecules to see what these could reveal about the plants’ evolution and relationships.

The molecules were found in the waxy membrane, which covers the leaves and these showed to differ between various species. The membrane has been preserved in the fossil leaves, some of which are 200 million-years-old.

Using infrared spectroscopy, the researchers carried out analyses in several stages. Firstly, they examined leaves from living plants that have relatives preserved in the fossil archive. The analysis showed that the biomolecular signatures were similar among plant groups, much in the same way as shown by modern genetic DNA analysis.

When the method was shown to work on modern plants, the researchers went on to analyse their extinct fossil relatives. Among others, they examined fossil leaves from conifers and several species of Ginkgo. The only living species of Ginkgo alive today is Ginkgo biloba, but this genus was far more diverse during the Jurassic.

“The results from the fossil leaves far exceeded our expectations, not only were they full of organic molecules, they also grouped according to well-established botanical relationships, based on DNA analysis of living plants i.e. Ginkgoes in one group, conifers in another,” says Vivi Vajda.

Finally, when the researchers had shown that the method gave consistent results, they analysed fossils of enigmatic extinct plants that have no living relatives to compare them with Among others, they examined Bennettites and Nilssonia, plants that were common in the area that is now Sweden during the Triassic and Jurassic around 250–150 million years ago. The analysis showed that Bennettites and Nilssonia are closely related. On the other hand, they are not closely related to cycads, which many researchers had thought until now.

Per Uvdal, Professor of Chemical Physics at Lund University and one of the researchers who conducted the study, considers that the overall results are astounding.

“The great thing about the biomolecules in the leaves’ waxy membranes is that they are so much more stable than DNA. As they reflect, in an indirect way, a plants DNA they can preserve information about the DNA. Therefore, the biomolecules can tell us how one plant is related in evolutionary terms to other plants”, he says.

The researchers are now going to extend their studies to more plant groups.