Diet and locomotion, but not body size, differentiate mammal communities in worldwide tropical ecosystems

Diet and locomotion, but not body size, differentiate mammal communities in worldwide tropical ecosystems

Authors:

Lintulaakso et al

Abstract:

Aim

To test whether tropical habitat groups across the world can be differentiated by using taxon-free mammalian community structures and to discuss the implications of this analysis for palaeoecological community studies.

Materials and methods

We used mammalian community data for 169 localities, which were assigned a priori to hierarchical Olson (1983) vegetation categories. Species over 500 g were classified into dietary, locomotion, and body mass groups and the resulting group structures were analysed using community structure analyses (NPMANOVA, CAP, SIMPER).

Results

The test results show that the mammalian community structures are significantly different between all of Olson's categories. These differences are highest at Olson's major and minor ecosystem levels, and require the least number of variable categories. At the vegetation level, the number of variable categories required to distinguish between them becomes higher. Of the dietary groups, the number of frugivore–granivores, frugivore–omnivores, grazers and mixed feeders contribute most to these differences, while the number of arboreal, arboreal–terrestrial and subterranean–terrestrial species are the key locomotor groups. Body mass was not a good discriminator.

Main conclusions

As general ecosystem categories are broken down into more precisely defined habitats, it requires more detailed knowledge of the species adaptations to distinguish between them. Many of Olson's vegetation groups represent a continuum of cover that are, at least at the worldwide comparison, too detailed to differentiate when broad generalities are sought. We suggest using three worldwide tropical major ecosystems in mammalian community structure analyses: “Humid, closed forests”, “Seasonal or interrupted forests and grasslands”, and “Seasonal, open drylands”. Our results also demonstrate that community structures defined by both dietary and locomotor adaptations are powerful discriminators of tropical ecosystems and habitats across the continents we examined, but body mass should be interpreted with caution when the research question pertains to multiple continents.

The Loss of Megafauna From Tropical Forests Will Worsen Climate Change

The extinction of large animals from tropical forests could make climate change worse -- according to researchers at the University of East Anglia.

New research published today in Science Advances reveals that a decline in fruit-eating animals such as large primates, tapirs and toucans could have a knock-on effect for tree species.

This is because large animals disperse large seeded plant species often associated with large trees and high wood density -- which are more effective at capturing and storing carbon dioxide from the atmosphere than smaller trees.

Seed dispersal by large-bodied vertebrates is via the ingestion of viable seeds that pass through the digestive tract intact.

Removing large animals from the ecosystem upsets the natural balance and leads to a loss of heavy-wooded large trees, which means that less CO2 can be locked away.

link.

Coniacian Cretaceous Antarctic Flora Suggest a Warm Temperate to Tropical PaleoClimate

Late Cretaceous flora of the Hidden Lake Formation, James Ross Island (Antarctica), its biostratigraphy and palaeoecological implications

Authors:

Kvaček et al

Abstract:

Plant fossils from the volcano-clastic marine deposits of the Coniacian Hidden Lake Formation of James Ross Island in Antarctica are described based on their macromorphology. Stratigraphic positions of fossiliferous horizons and details of the lithostratigraphic situation of the middle part of the Hidden Lake Formation are published for the first time. The flora consists primarily of leaf impressions and petrified wood. There are also small amounts of mesofossils, dispersed cuticles and charcoalified wood. The megafossils typically occur fragmented, underpinning their allochtonous origin. The plants are described in systematical order. This contribution in contrast to earlier observations reports a high diversity of pteridophytes (11 taxa) and conifers (6 taxa). Angiosperms representing families Nothofagaceae, Atherospermataceae, probably Lauraceae and Sterculiaceae are the most abundant and common plant groups of the flora (12 taxa). The presence of the tropical fern family Marattiaceae and rarity of the genus Nothofagus are of interest, arguing for the prevalence of a warm temperate to tropical humid climate during the Coniacian in this part of Antarctica.

A New Cisuralian Permian Fauna From Tropical Gondwana

New Permian fauna from tropical Gondwana

Authors:

Cisneros et al

Abstract:

Terrestrial vertebrates are first known to colonize high-latitude regions during the middle Permian (Guadalupian) about 270 million years ago, following the Pennsylvanian Gondwanan continental glaciation. However, despite over 150 years of study in these areas, the biogeographic origins of these rich communities of land-dwelling vertebrates remain obscure. Here we report on a new early Permian continental tetrapod fauna from South America in tropical Western Gondwana that sheds new light on patterns of tetrapod distribution. Northeastern Brazil hosted an extensive lacustrine system inhabited by a unique community of temnospondyl amphibians and reptiles that considerably expand the known temporal and geographic ranges of key subgroups. Our findings demonstrate that tetrapod groups common in later Permian and Triassic temperate communities were already present in tropical Gondwana by the early Permian (Cisuralian). This new fauna constitutes a new biogeographic province with North American affinities and clearly demonstrates that tetrapod dispersal into Gondwana was already underway at the beginning of the Permian.

pop sci write up.

Decreased Tropical Ciruclation Under Global Warming?

Direct weakening of tropical circulations from masked CO2 radiative forcing

Author:

Merlis

Abstract:

Climate models robustly simulate weakened mean circulations of the tropical atmosphere in direct response to increased carbon dioxide (CO2). The direct response to CO2, defined by the response to radiative forcing in the absence of changes in sea surface temperature, affects tropical precipitation and tropical cyclone genesis, and these changes have been tied to the weakening of the mean tropical circulation. The mechanism underlying this direct CO2-forced circulation change has not been elucidated. Here, I demonstrate that this circulation weakening results from spatial structure in CO2’s radiative forcing. In regions of ascending circulation, such as the intertropical convergence zone, the CO2 radiative forcing is reduced, or “masked,” by deep-convective clouds and high humidity; in subsiding regions, such as the subtropics, the CO2 radiative forcing is larger because the atmosphere is drier and deep-convective clouds are infrequent. The spatial structure of the radiative forcing reduces the need for the atmosphere to transport energy. This, in turn, weakens the mass overturning of the tropical circulation. The previously unidentified mechanism is demonstrated in a hierarchy of atmospheric general circulation model simulations with altered radiative transfer to suppress the cloud masking of the radiative forcing. The mechanism depends on the climatological distribution of clouds and humidity, rather than uncertain changes in these quantities. Masked radiative forcing thereby offers an explanation for the robustness of the direct circulation weakening under increased CO2.

Tropical Deforestation has Global Impacts

A new study released today presents powerful evidence that clearing trees not only spews carbon into the atmosphere, but also triggers major shifts in rainfall and increased temperatures worldwide that are just as potent as those caused by current carbon pollution. Further, the study finds that future agricultural productivity across the globe is at risk from deforestation-induced warming and altered rainfall patterns.

The report, "Effects of Tropical Deforestation on Climate Change and Agriculture," published today in Nature Climate Change and released in collaboration with Climate Focus provides the most comprehensive analysis to date of the climate impacts of tropical forest destruction on agriculture in the tropics and thousands of miles away. Specifically, the study finds that deforestation in South America, Southeast Asia and Africa may alter growing conditions in agricultural areas in the tropics and as far away as the US Midwest, Europe and China.

The study is also the only global synthesis of research based on cutting-edge climate models and empirical data on the direct local, regional and global impacts of cutting down tropical forests, which regulate interactions between the earth and the atmosphere. It predicts that atmospheric impacts resulting from complete tropical deforestation could lead to a rise in global temperature of 0.7 degrees Celsius (on top of the impact from greenhouse gases), which would double the observed global warming since 1850. Currently, climate change negotiators are shaping policies that focus on greenhouse gases, in particular carbon. To date, they have overlooked policy responses that address other ways that forests affect climate.

"Tropical deforestation delivers a double whammy to the climate--and to farmers," said Deborah Lawrence, Professor of Environmental Sciences at the University of Virginia, the study's lead author. "Most people know that climate change is a dangerous global problem, and that it's caused by pumping carbon into the atmosphere. But it turns out that removing forests alters moisture and air flow, leading to changes--from fluctuating rainfall patterns to rises in temperatures--that are just as hazardous, and happen right away. The impacts go beyond the tropics--the United Kingdom and Hawaii could see an increase in rainfall while the US Midwest and Southern France could see a decline."

link.

Tropical Waters may Become More Oxygenated From Global warming

As the complex story of climate change unfolds, many of the endings are grim. But there are exceptions. Predictions that the lowest-oxygen environments in the ocean would get worse may not come to pass. Instead, University of Washington research shows climate change, as it weakens the trade winds, could shrink the size of these extreme low-oxygen waters.

"The tropics should actually get better oxygenated as the climate warms up," said Curtis Deutsch, a UW associate professor of oceanography. He is lead author of the study published Aug. 8 in Science.

Warmer water contains less gas, so climate change is expected to reduce oxygen levels worldwide. Observations show this is already taking place in many places. Declines during the past 20 years in the tropical low-oxygen zones, the lowest-oxygen waters on the planet, had led to a 2008 study proposing that these zones would also get worse over time.

Tropical regions are usually associated with an abundance of life, but they have some of the most inhospitable places for ocean dwellers. The oxygen minimum zones off Mexico and Peru have oxygen levels already too low to support most animals (so, unlike in other low-oxygen zones, here there's no risk of killing fish).

But when those levels drop even further, a particular group of bacteria, which can use nitrogen instead of oxygen as a source of energy, thrive. Nitrogen is an essential and very scarce nutrient for marine plants. When oxygen levels get low enough for that particular group of bacteria to take over, significant amounts of the ocean's fertilizer get deep-sixed to the bottom of the tropical ocean.

The new paper shows that water flowing into the tropics is indeed likely to get lower in oxygen, decreasing the initial oxygen supply. But demand will also shift under climate change. Specifically, as the trade winds weaken, the whole sequence of events that feeds this bacterial food chain will slow down, and the low-oxygen zone will shrink.

link.

Is the Amazon Rain Forest Only 2,000 Years Old?

Swathes of the Amazon may have been grassland until a natural shift to a wetter climate about 2,000 years ago let the rainforests form, according to a study that challenges common belief that the world’s biggest tropical forest is far older.

The arrival of European diseases after Columbus crossed the Atlantic in 1492 may also have hastened the growth of forests by killing indigenous people farming the region, the scientists wrote in the U.S. journal Proceedings of the National Academy of Sciences (PNAS).

"The dominant ecosystem was more like a savannah than the rainforest we see today," John Carson, lead author at the University of Reading in England, said of the findings about the southern Amazon.

The scientists said that a shift toward wetter conditions, perhaps caused by natural shifts in the Earth’s orbit around the sun, led to growth of more trees starting about 2,000 years ago.

The scientists studied man-made earthworks, uncovered by recent logging in Bolivia, that included ditches up to about a kilometer (1,100 yards) long and up to 3 meters deep and 4 meters wide.

They found large amounts of grass pollen in ancient sediments of nearby lakes, suggesting the region had been covered by savannah. They also found evidence of plantings of maize, pointing to farming.

link.

paper link.

Powerful, Destructive Tropical Cyclones Moving North and South,

Powerful, destructive tropical cyclones are now reaching their peak intensity farther from the equator and closer to the poles, according to a new study co-authored by an MIT scientist.

The results of the study, published today in the journal Nature, show that over the last 30 years, tropical cyclones — also known as hurricanes or typhoons — are moving poleward at a rate of about 33 miles per decade in the Northern Hemisphere and 38 miles per decade in the Southern Hemisphere.

"The absolute value of the latitudes at which these storms reach their maximum intensity seems to be increasing over time, in most places," says Kerry Emanuel, an MIT professor and co-author of the new paper. "The trend is statistically significant at a pretty high level."

And while the scientists who conducted the study are still investigating the atmospheric mechanisms behind this change, the trend seems consistent with a warming climate.

"It may mean the thermodynamically favorable conditions for these storms are migrating poleward," adds Emanuel, the Cecil and Ida Green Professor of Earth and Planetary Sciences at MIT.

The implications are serious, since the movement of peak intensity means regions further north and south of the equator, which have not previously had to face many landfalls by violent cyclones, may now have greater exposure to these extreme weather events. That, in turn, could lead to "potentially profound consequences to life and property," the paper states. "Any related changes to positions where storms make landfall will have obvious effects on coastal residents and infrastructure."

link.

Tropical Belt Widening is Being Driven by Natural and Anthrogenic Reasons

Recent studies have shown that the Earth's tropical belt — demarcated, roughly, by the Tropics of Cancer and Capricorn — has progressively expanded since at least the late 1970s. Several explanations for this widening have been proposed, such as radiative forcing due to greenhouse gas increase and stratospheric ozone depletion.

Now, a team of climatologists, led by researchers at the University of California, Riverside, posits that the recent widening of the tropical belt is primarily caused by multi-decadal sea surface temperature variability in the Pacific Ocean. This variability includes the Pacific Decadal Oscillation (PDO), a long-lived El Niño-like pattern of Pacific climate variability that works like a switch every 30 years or so between two different circulation patterns in the North Pacific Ocean. It also includes, the researchers say, anthropogenic pollutants, which act to modify the PDO.

Study results appear March 16 in Nature Geoscience.

"Prior analyses have found that climate models underestimate the observed rate of tropical widening, leading to questions on possible model deficiencies, possible errors in the observations, and lack of confidence in future projections," said Robert J. Allen, an assistant professor of climatology in UC Riverside's Department of Earth Sciences, who led the study. "Furthermore, there has been no clear explanation for what is driving the widening."

Now Allen's team has found that the recent tropical widening is largely driven by the PDO.

"Although this widening is considered a 'natural' mode of climate variability, implying tropical widening is primarily driven by internal dynamics of the climate system, we also show that anthropogenic pollutants have driven trends in the PDO," Allen said. "Thus, tropical widening is related to both the PDO and anthropogenic pollutants."

link.

Tropical Cyclones Warm Ocean, May Cause Positive Feedback Cycle

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean

Authors:

1. Wei Mei (a)
2. François Primeau (a)
3. James C. McWilliams (b)
4. Claudia Pasquero (c)

Affiliations:

a. Department of Earth System Science, University of California, Irvine, CA 92697;

b. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095; and

c. Department of Earth and Environmental Sciences, University of Milan-Bicocca, I-20126 Milan, Italy

Abstract:

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean–atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback.

Out of Tropics: Species Originate in Tropics and Spread

Although scientists have known since the middle of the 19th century that the tropics are teeming with species while the poles harbor relatively few, the origin of the most dramatic and pervasive biodiversity on Earth has never been clear.

New research sheds light on how that pattern came about. Furthermore, it confirms that the tropics have been and continue to be the Earth's engine of biodiversity.

By examining marine bivalves (two-shelled mollusks including scallops, cockles and oysters), a model system for large-scale ecological and evolutionary analysis, the study shows that most evolutionary lineages started in the tropics and expanded outward.

"This 'out of the tropics' dynamic is the major process that shapes the latitudinal pattern of biodiversity that we see today on land and sea," said lead author David Jablonski, the William R. Kenan Jr. Professor in Geophysical Sciences at the University of Chicago. His team focuses on marine bivalves because they combine a wealth of important biological patterns with a large but manageable number of living species (about 8,000) and a rich fossil record.

The new research will be published this week in the online Early Edition of the Proceedings of the National Academy of Sciences presents evidence that the "out of the tropics" process is driven mainly by bridge species, a new term referring to evolutionary lineages that straddle the boundary between the tropics and cooler neighboring regions.

"We thought the 'out of the tropics' process would be driven by the formation of new species at the edge of the tropics, but that doesn't seem to be true," Jablonski said. "Whether bridge species really are the conduit, 'out of the tropics' for all those lineages still needs to be confirmed. We'll tackle that next, by examining molecular data on species within these lineages, inside and outside the tropics, to see how they're related."

As with the PNAS study, this follow-up research would require examining data on both fossils and living organisms. "Alas, it's still rare for paleontologists to integrate the fossil record with data on present-day organisms, but for large-scale biodiversity studies like this, it's a very powerful approach, often an essential one," Jablonski said. "Biodiversity is a product of origination, extinction and immigration, and when the fossil record is adequate, as it is with bivalves, it provides the most robust window into the dynamics that produced present-day patterns."

Neo-Oligocene or Neo-Eocene? Hints of Precipitiation Change Under Climate Change in the Tropics

Projections of rainfall changes from global warming have been very uncertain because scientists could not determine how two different mechanisms will impact rainfall. The two mechanisms turn out to complement each other and together shape the spatial distribution of seasonal rainfall in the tropics, according to the study of a group of Chinese and Hawaii scientists that is published in the April 14, 2013, online issue of Nature Geoscience.

The one mechanism, called "wet-gets-wetter," predicts that rainfall should increase in regions that already have much rain, with a tendency for dry regions to get dryer. The second mechanism, called the "warmer-gets-wetter," predicts rainfall should increase in regions where sea surface temperature rises above the tropical average warming.

The team of scientists compared current rainfall in the tropics with future rainfall projections from simulations of 18 cutting-edge climate models forced with a likely scenario of atmospheric greenhouse gas concentrations. They found that rainfall in the models increases more in regions that currently are already wet and decreases slightly in currently dry regions, supporting the wet-gets-wetter mechanism. But they also found evidence for the warmer-gets-wetter mechanism in that the higher the surface temperature in a region, the more the rainfall. By merging the impact from the two mechanisms, they noted that they could account for nearly 80 percent of the variations in the models' projected rainfall changes from global warming.

The complementary action of the two mechanisms is because the pattern of ocean warming induces more convection and rainfall near the Equator, where the temperature warming peaks, and subsidence and drying further away from the Equator, reflecting the warmer-gets-wetter view. But as this band of increased rain marches back and forth across the Equator with the Sun, it causes seasonal rainfall anomalies that follow the wet-gets-wetter pattern.

The wet-gets-wetter mechanism contributes more to the projected seasonal rainfall changes, whereas the warmer-gets-warmer mechanism more to the mean annual rainfall changes.

"Because our present observations of seasonal rainfall are much more reliable than the future sea surface temperatures, we can trust the models' projections of seasonal mean rainfall for regional patterns more than their annual mean projections," says co-author Shang-Ping Xie, meteorology professor at the International Pacific Research Center, University of Hawaii at Manoa and Roger Revelle Professor at Scripps Institution of Oceanography, University of California at San Diego. "This is good news for monsoon regions where rainfall by definition is seasonal and limited to a short rainy season. Many highly populated countries under monsoon influences already face water shortages."

Canadian Eocene Mountain Insect Biodiversity Parallels Modern Tropics

Simon Fraser University evolutionary biologists Bruce Archibald and Rolf Mathewes, and Brandon University biologist David Greenwood, have discovered that modern tropical mountains' diversity patterns extended up into Canada about 50 million years ago.

Their findings confirm an influential theory about change in modern species diversity across mountains, and provide evidence that global biodiversity was greater in ancient times than now.

The scientific journal Palaeogeography, Palaeoclimatology, Palaeoecology has published their research.

About 45 years ago, an evolutionary biologist at the University of Pennsylvania theorized that change in species from site to site across mountain ranges in the tropics should be greater than in temperate latitudes.

Daniel Janzen reasoned that the great difference between summer and winter in temperate latitudes (high seasonality) offers a wide window to migrate across mountainous regions. The small difference in the tropics (low seasonality) allows a very narrow opportunity, annually. Consequently, communities across tropical mountains should have fewer of the same species. Many studies examining modern communities support this theory.

Archibald, Mathewes and Greenwood realized that fossil beds across a thousand kilometres of the ancient mountains of British Columbia and Washington provided a unique lens through which to deepen evaluation of this theory. Fifty million years ago, when these fossil beds were laid down, the world had low seasonality outside of the tropics, right to the poles. Because of this, if Janzen's theory is right, the pattern of biodiversity that he described in modern tropical mountains should have extended well into higher latitudes.

"We found that insect species changed greatly across British Columbia's and Washington State's ancient mountain ranges, like in the modern tropics," Archibald says, "exactly as Janzen's seasonality hypothesis predicted.

This implies that it's the particular seasonality now found in the modern tropics, not where that climate is situated globally, that affects this biodiversity pattern." He adds: "Sometimes it helps to look to the ancient past to better understand how things work today." The findings also bolster the idea that ancient Earth was a much more diverse world than now with many more species.

Climate Change Could Devastate Tropical Frogs

Most of the more than 6,000 species of frogs in the world lay their eggs in water. But many tropical frogs lay their eggs out of water. This behavior protects the eggs from aquatic predators, such as fish and tadpoles, but also increases their risk of drying out. Justin Touchon, post-doctoral fellow at the Smithsonian Tropical Research Institute, discovered that climate change in Panama may be altering frogs' course of evolution.

By analyzing long-term rainfall data collected by the Panama Canal Authority, Touchon discovered that rainfall patterns are changing just as climate-change models predict.

"Over the past four decades, rainfall has become more sporadic during the wet season," said Touchon. "The number of rainy days decreased, and the number of gaps between storms increased."

The eggs of the pantless treefrog, Dendropsophus ebraccatus, are extremely susceptible to drying. The embryos die within a day when there is no rain. Heavy rains trigger breeding, so as storms become sporadic, the chance of rain within a day of being laid decrease and so does egg survival.

As weather patterns have changed, the advantage of laying eggs out of water has decreased, not only for pantless treefrogs but potentially for many species. "Pantless treefrogs can switch between laying eggs in water or on leaves, so they may weather the changes we are seeing in rainfall better than other species that have lost the ability to lay eggs in water," said Touchon. "Being flexible in where they put their eggs gives them more options and allows them to make decisions in a given habitat that will increase the survival of their offspring."

More Biotic Influence on Climate: Deforestation Has Impact on Tropical Rainfall

Deforestation can have a significant effect on tropical rainfall, new research confirms. The findings have potentially devastating impacts for people living in and near the Amazon and Congo forests.

A team from the University of Leeds and the NERC Centre for Ecology & Hydrology found that for the majority of the Earth's tropical land surface, air passing over extensive forests produces at least twice as much rain as air passing over little vegetation. In some cases these forests increased rainfall thousands of kilometres away.

By combining observational data with predictions of future deforestation, the researchers estimate that destruction of tropical forests would reduce rain across the Amazon basin by up to a fifth (21 per cent) in the dry season by 2050. The study is published today in Nature.

Lead author Dr Dominick Spracklen from the School of Earth and Environment at the University of Leeds said: "We were surprised to find that this effect occurs strongly across more than half of the tropics. We found that the Amazon and Congo forests maintain rainfall over the periphery of the forest basins - regions where large numbers of people live and rely on rainfall for their livelihoods.

"Our study implies that deforestation of the Amazon and Congo forests could have catastrophic consequences for the people living thousands of kilometres away in surrounding countries."

Scientists have debated whether vegetation increases rainfall for hundreds of years. It is well established that plants put moisture back in the air through their leaves by a process known as evapotranspiration, but the quantity and geographical reach of rainfall generated by large forests has – until now – been unclear. While there is plenty of anecdotal evidence that forests significantly increase rainfall, until now there has been a lack of observational evidence.

The team used newly available NASA satellite observations of rainfall and vegetation, along with a model which predicts atmospheric wind flow patterns, to explore the impact of the Earth's tropical forests.

"We looked at what had been happening to the air over previous days – where it came from and how much forest it had travelled over," Dr Spracklen said.

To understand the relationship in detail, they investigated the journey of air masses arriving over different parts of the forest, to see the cumulative amount of leaf cover the air had moved over during the previous ten days, not just the amount of vegetation it was over when it rained. This showed that the more vegetation the air had travelled over, the more moisture it carried and more rain was produced.

Dr Stephen Arnold from the University of Leeds, a co-author on the paper, said: "The observations show that to understand how forests impact rainfall, we need to account for how air has interacted with vegetation during its journey through the atmosphere often over thousands of kilometres. This has significant implications for how policy makers should consider the environmental impacts of deforestation, since its effects on rainfall patterns may be felt not only locally, but on a continental scale.

"

link.

This nicely dovetails with the recent findings about the Maya.

Carbon Biomass Maps of Tropical Forests

Rain Forest Correlated Characteristic IDed in Flowering Plants

A team of scientists, including several from the Smithsonian Institution, discovered that leaves of flowering plants in the world's first rainforests had more veins per unit area than leaves ever had before. They suggest that this increased the amount of water available to the leaves, making it possible for plants to capture more carbon and grow larger. A better plumbing system may also have radically altered water and carbon movement through forests, driving environmental change.

"It's fascinating that a simple leaf feature such as vein density allows one to study plant performance in the past," said Klaus Winter, staff scientist at the Smithsonian Tropical Research Institute in Panama, who was not an author, "Of course, you can't directly measure water flow through fossil leaves. When plants fix carbon, they lose water to the atmosphere. So to become highly productive, as many modern flowering plants are, requires that plants have a highly elaborate plumbing system."

A walk through a tropical forest more than 100 million years ago would have been different than a walk through a modern rainforest. Dinosaurs were shaded by flowerless plants like cycads and ferns. Fast-forward 40 million years. The dinosaurs have disappeared and the first modern rainforests have appeared: a realm of giant trees—with flowers. By examining images of more than 300 hundred kinds of fossil leaves, the team, led by Taylor Feild from the University of Tennessee, Knoxville, counted how many veins there were in a given area of leaf. Flowerless plants then and now have relatively few veins. But their work shows that even after flowering plants evolved, it took some time before they developed the efficient plumbing systems that would allow them to develop into giant life-forms like tropical trees. The density of veins in the leaves of flowering plants increased at least two different times as the transition from ancient to modern rainforests took place, according to this research reported in the journal, Proceedings of the National Academy of Sciences.

The first jump—when the vein density in fossil leaves of flowering plants first exceeded vein density in the leaves of flowerless plants—took place approximately one hundred million years ago. The second and more significant increase in vein density took place 35 million years later. Petrified tree trunks more than a meter in diameter were first found from this period, indicating another landmark—the evolution of flowering trees. Soon the leaves of flowering plants had twice more veins per unit leaf area than the non-flowering plants. By the end of the Cretaceous period about 65 million years ago, the number of leaf veins per unit area was very similar to that of modern rainforest leaves.

PreColumbian Agricultural Impacts in the Amazon

Pre-Columbian agricultural landscapes, ecosystem engineers, and self-organized patchiness in Amazonia

1. Doyle McKey (a,1)
2. Stéphen Rostain (b)
3. José Iriarte (c)
4. Bruno Glaser (d,2)
5. Jago Jonathan Birk (d)
6. Irene Holst (e)
7. Delphine Renard (a)


a. Université Montpellier II and Centre d'Ecologie Fonctionnelle et Evolutive, Unité Mixte de Recherche (UMR) 5175 Centre National de la Recherche Scientifique (CNRS), F-34293 Montpellier Cedex 5, France;

b. Archéologie des Amériques, UMR 8096 CNRS, F-92323 Nanterre, France;

c. Department of Archaeology, School of Geography, Archaeology, and Earth Resources, University of Exeter, Exeter EX4 4QE, United Kingdom;

d. Department of Soil Physics, University of Bayreuth, Bayreuth D-95447 Germany; and

e. Smithsonian Tropical Research Institute, Apartado Postal 0843 -03092, Balboa, Republic of Panama

1. To whom correspondence should be addressed. E-mail: doyle.mckey@cefe.cnrs.fr.

2. Present address: Terrestrial Biogeochemistry, Martin-Luther-University Halle-Wittenberg, 06108 Halle, Germany.

Abstract:

The scale and nature of pre-Columbian human impacts in Amazonia are currently hotly debated. Whereas pre-Columbian people dramatically changed the distribution and abundance of species and habitats in some parts of Amazonia, their impact in other parts is less clear. Pioneer research asked whether their effects reached even further, changing how ecosystems function, but few in-depth studies have examined mechanisms underpinning the resilience of these modifications. Combining archeology, archeobotany, paleoecology, soil science, ecology, and aerial imagery, we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of well-drained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity. Like anthropogenic dark earths in forested Amazonia, these self-organizing ecosystems illustrate the ecological complexity of the legacy of pre-Columbian land use.

no time.

Cerrejón Formation, Colombia: Earliest Record of Neotropical Forest

Late Paleocene fossils from the Cerrejón Formation, Colombia, are the earliest record of Neotropical rainforest



1. Scott L. Wing (a,1)
2. Fabiany Herrera (b,c)
3. Carlos A. Jaramillo (b)
4. Carolina Gómez-Navarro (b,d)
5. Peter Wilf (e)
6. Conrad C. Labandeira (a)



a. Department of Paleobiology, P.O. Box 37012, Smithsonian Institution, National Museum of Natural History, Washington, DC 20013;

b. Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Balboa, Ancon, Panamá, República de Panamá;

c. Florida Museum of Natural History and Department of Biology, University of Florida, P.O. Box 117800, Gainesville, FL 32611-7800;

d. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and

e. Department of Geosciences, Pennsylvania State University, University Park, PA 16802

1. To whom correspondence should be addressed. E-mail: wings@si.edu

Abstract:

Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Nevertheless, some of their most important characteristics can be preserved in the fossil record: high plant diversity, dominance by a distinctive combination of angiosperm families, a preponderance of plant species with large, smooth-margined leaves, and evidence for a high diversity of herbivorous insects. Here, we report on an ≈58-my-old flora from the Cerrejón Formation of Colombia (paleolatitude ≈5 °N) that is the earliest megafossil record of Neotropical rainforest. The flora has abundant, diverse palms and legumes and similar family composition to extant Neotropical rainforest. Three-quarters of the leaf types are large and entire-margined, indicating rainfall >2,500 mm/year and mean annual temperature >25 °C. Despite modern family composition and tropical paleoclimate, the diversity of fossil pollen and leaf samples is 60–80% that of comparable samples from extant and Quaternary Neotropical rainforest from similar climates. Insect feeding damage on Cerrejón fossil leaves, representing primary consumers, is abundant, but also of low diversity, and overwhelmingly made by generalist feeders rather than specialized herbivores. Cerrejón megafossils provide strong evidence that the same Neotropical rainforest families have characterized the biome since the Paleocene, maintaining their importance through climatic phases warmer and cooler than present. The low diversity of both plants and herbivorous insects in this Paleocene Neotropical rainforest may reflect an early stage in the diversification of the lineages that inhabit this biome, and/or a long recovery period from the terminal Cretaceous extinction.

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