New Year, New Species

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Rock lizards, pigment producing fungus, eagle rays, ant garden parasites, and Antarctic sea anemones: new species are discovered all the time and there are likely still millions that we simply haven’t yet discovered or assessed. Species are identified by researchers using a range of criteria including DNA, appearance, and habitat. PLOS ONE typically publishes several new species articles every month, and below we are pleased to help introduce five that were discovered in 2013.

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Iranian Rock Lizards

Thought previously to consist of only three species, this group of lizards are now seven distinct species. They appear very similar to one another, making it difficult to tell which characteristics define different species, and which are just variations present in the same species. They also have a variety of habitats, from trees to rocky outcrops, and the genus is widespread. Iranian, German, and Portuguese scientists used genetic variation and habitat to help describe four new species of Iranian rock lizards, Darevskia caspica, D. Kamii, D. kopetdaghica, and D. schaekeli. These techniques, in addition to analysis of the the lizards’ physical features, as in the photo of the four new species’ heads at the top of this page, helped to identify them definitively.

 

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Pigment producing fungus

Found in soil, indoor environments, and fruit, Talaromyces atroroseus produces a red pigment that might be good for manufacturing purposes, especially in food. Some other species of this type of fungus produce red pigments, but they are not always as useful because they can also produce toxins. T. atroroseus produces a stable red pigment with no known toxins, making it safer for human use, according to the Dutch and Danish researchers who identified it.

 

 

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Naru eagle ray

Fish, like rays and sharks, are at high risk for extinction as a group, but as rare as they are, they can be plentiful enough in some locations to make them undesirable to locals. The discovery of the Naru eagle ray, Aetobatus narutobiei, splits a previously defined species, A. flagellum, that, due to its shellfish-eating habits, is considered a pest and culled in southern Japan. The discovery by Australian and Japanese scientists that this species is actually two species prompted the authors to encourage a reassessment of the conservation status of the rays.

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Fungal parasites in ant gardens

In the Brazilian rainforest of Minas Gerais, leafcutter ants cultivate fungus, their primary source of food, on harvested leaf clippings. But scientists from Brazil, United Kingdom, and The Netherlands have discovered that their food source is threatened by four newly identified mycoparasites, Escovopsis lentecrescens, E. microspora, E. moellieri, and Escovopsioides nivea. The parasites grow like weeds in the ants’ gardens, crowding out more desirable fungus used for food. Unfortunately for the ants, researchers expect there are many similar unidentified species yet to be discovered.

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Antarctic sea anemone

Living on the previously undocumented ecosystem of the underside of the Ross Ice Shelf in Antarctica, American researchers discovered the first species of sea anemone known to live in ice, Edwardsiella andrillae. Fields of anemone were discovered using a scientist-driven remote-controlled submersible. The anemone burrows and lives within the ice and dangles a tentacle into the water beneath, almost as if it is dipping a toe in the water to test the chilly temperature.

 

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Look here to read more about new species.

 

Citations

Ahmadzadeh F, Flecks M, Carretero MA, Mozaffari O, Böhme W, et al. (2013) Cryptic Speciation Patterns in Iranian Rock Lizards Uncovered by Integrative Taxonomy. PLoS ONE 8(12): e80563. doi:10.1371/journal.pone.0080563

Frisvad JC, Yilmaz N, Thrane U, Rasmussen KB, Houbraken J, et al. (2013)Talaromyces atroroseus, a New Species Efficiently Producing Industrially Relevant Red Pigments. PLoS ONE 8(12): e84102. doi:10.1371/journal.pone.0084102

White WT, Furumitsu K, Yamaguchi A (2013) A New Species of Eagle RayAetobatus narutobiei from the Northwest Pacific: An Example of the Critical Role Taxonomy Plays in Fisheries and Ecological Sciences. PLoS ONE 8(12): e83785. doi:10.1371/journal.pone.0083785

Augustin JO, Groenewald JZ, Nascimento RJ, Mizubuti ESG, Barreto RW, et al. (2013) Yet More “Weeds” in the Garden: Fungal Novelties from Nests of Leaf-Cutting Ants. PLoS ONE 8(12): e82265. doi:10.1371/journal.pone.0082265

Daly M, Rack F, Zook R (2013) Edwardsiella andrillae, a New Species of Sea Anemone from Antarctic Ice. PLoS ONE 8(12): e83476. doi:10.1371/journal.pone.0083476

Figures are all from their respective articles.

 

 

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The Balancing Act in Borneo: Managing Deforestation, Sustainability, Biodiversity, Health, and the Value of Rainforests

Borneo

Borneo: the third largest island in the world, one-third of which is home to 220,000 km2 of diverse and beautiful rainforest. Borneo is divided among three countries—Brunei, Indonesia, and Malaysia—and at approximately 130 million years old, the Borneo rainforests are some of the oldest in the world.

The landscape of Borneo, however, is rapidly changing. Natural forest resources provide significant income for both Malaysia and Indonesia, and oil palm plantations, which require the clearing of natural land cover, produced an annual revenue of US $40 billion for Indonesia and Malaysia in 2012. In contrast, Borneo rainforests present the only opportunity for large-scale conservation in Southeast Asia and are one of the few places still called home by large, endangered animals like orang-utans, elephants, bears and rhinos.

This summer, three different PLOS ONE studies addressed the complex issues surrounding deforestation. Separate groups of researchers mapped forest cover and logging roads, conducted statistical analyses on different uses of land, and investigated how Indonesian and Malaysian villagers of Borneo value and use these forests.

To better understand the troubling state of forests in Malaysian Borneo, researchers in one PLOS ONE study mapped forest coverage and conditions. Tracking the condition of big areas of land is no easy task. To accomplish the feat, scientists imaged forests areas using high-definition satellite imagery, charted logging roads, and did some serious number crunching.

Key to this assessment was the actual condition of the rainforests.  Are they intact, or have they been degraded—maybe severely so—by the effects of repeated logging? Critical damage is done to soil, waterways, and forest structure when forests are repeatedly logged without enough time to regenerate properly. To assess the condition of the residual forest, researchers distinguished between different types of coverage—bare, mangrove, plantation, and various levels of degradation, for example—and charted the number of logging roads created between 1990 and 2009. The image below depicts the forest cover and condition of Malaysian Borneo and Brunei in 2009.

Oct blog Type of Coverage

If one road was built in an area since 1990, the area was classified as degraded. If more than one road had been built in an area since 1990, that area was classified as severely degraded. Researchers charted enough roads built between 1990 and 2009 to circle Earth nine times if placed end-to-end. The image below depicts the new roads constructed in a forested region known as the ‘Heart of Borneo’ in purple.

Oct Blog Roads

Needless to say, a great deal of the forests in Malaysian Borneo was classified as severely degraded. Researchers found that rainforests covered only 22% of land area in Malaysian Borneo in 2009, and of that 22%, only 38% remained intact. What then is the future for these degraded rainforests?

The researchers of a second PLOS ONE study evaluated the role logged forests play in maintaining natural rainforests in Kalimantan, Indonesian Borneo, by conducting statistical analyses on areas designated as protected areas, areas designated for logging, and industrial plantations. Researchers concluded that, when logged responsibly, areas designated for logging, called timber concessions, maintained forest cover just as well as protected areas during 2000-2010. Protecting timber concessions would increase the amount of land dedicated to sustaining larger forest landscapes.

Oct blog 2 Transition

The alternative to returning these logged areas, often considered beyond the point of regeneration, to a state of natural regrowth is reclassification as industrial plantation. Palm oil plantations are economically viable options for Indonesia. However, to make the land viable for industrial planation use, workers must first strip larger trees, burn smaller trees and shrubs, and finally clear the remaining land. These researchers view responsible logging as a compromise in which forests continue to provide economic output to communities, but also are allowed to maintain the veracity of their biodiversity. Rather than being seen as wastelands and turned into industrial plantations, researchers consider timber concessions as valuable areas of tree coverage and biodiversity, which merit classification as IUCN Protected Areas.

However, as researchers from a third PLOS ONE paper state, “Striking a balance between economic development and maintenance of biodiversity is increasingly challenging in the face of climate change, rapid human production growth, and concomitant demand for natural resources.” To address the range of ways the forest is valuable, researchers assessed Indonesian and Malaysian Borneo’s peoples’ perceptions of the values and uses of forests, as well as the factors influencing these perceptions.

Of 1,837 people surveyed from 185 villages in Indonesian and Malaysian Borneo, 67% considered the forest to be important for maintaining their good health. The authors state that the forest was generally perceived as a provider of good health. Moreover, natural forest resources, even in those forests degraded by repeated logging, are important for local people. In their responses, participants frequently mentioned using forests for timber, rattan, fire wood, bushmeat and fish, traditional medicine, and forest gardens. Most people reported using forest resources even in areas severely degraded by logging, or where no canopy cover exists. Researchers therefore concluded that considering these areas “wastelands” or degraded beyond the point of use, with the result that these areas are converted into industrial plantations, is not warranted due to the value placed on resources obtained from forests, regardless of level of degradation.

Researchers also found that many believed small-scale deforestation benefitted welfare. 48% of respondents reported small scale clearing for purposes of farming as positive. Respondents were much less supportive of large-scale deforestation.

Initiatives to strike a balance between economic need and maintenance of these diverse rainforests in Borneo are ongoing. Researchers are divided about the most effective ways to conserve Borneo’s important natural forests; whereas the construction of palm oil plantations in place of forests is unquestionably destructive to conservation efforts, the place of logging in Borneo remains less defined. Conserving biodiversity, responsibly maintaining the economy, and valuing the input of local people must all be taken into account when devising compromises for the difficult issue of deforestation. In the meantime, research in Borneo continues to enable a better understanding of Borneo’s complex balancing act.

Citations:

Bryan JE, Shearman PL, Asner GP, Knapp DE, Aoro G, et al. (2013) Extreme Differences in Forest Degradation in Borneo: Comparing Practices in Sarawak, Sabah, and Brunei. PLoS ONE 8(7): e69679. doi:10.1371/journal.pone.0069679

Gaveau DLA, Kshatriya M, Sheil D, Sloan S, Molidena E, et al. (2013) Reconciling Forest Conservation and Logging in Indonesian Borneo. PLoS ONE 8(8): e69887. doi:10.1371/journal.pone.0069887

Meijaard E, Abram NK, Wells JA, Pellier A-S, Ancrenaz M, et al. (2013) People’s Perceptions about the Importance of Forests on Borneo. PLoS ONE 8(9): e73008. doi:10.1371/journal.pone.0073008

Image 1: Flora and Fauna of the Borneo Rainforest by Rainforest Action Network

Image 2: Figure 2 journal.pone.0069679

Image 3: Figure 1 journal.pone.0069679

Image 4: Figure 2 journal.pone.0069887

Announcing the Ecological Impacts of Climate Change Collection

Ecoclimate change collection

Post authored by Collection Curator Ben Bond-Lamberty 

The ecological impacts of climate change are broad and diverse, and include alterations to species’ range limits, plant phenology and growth, carbon and nutrient cycling, as well as biodiversity and extinction risk. Recent PLOS articles have used a variety of experimental and observational approaches to examine these subjects.

Identifying at-risk regions, taxa, and species is a critical first step in adaptation and conservation efforts. A study by Mouillot et al. suggested that rare species are particularly important in conservation efforts, as rare species in diverse ecosystems are not replaceable by other species that fulfill the same ecological functions. At the same time, both rare and more common species experience the ecological impacts of climate change. Foden et al. combined biology and ecology to assess, on a global scale, the climate change vulnerability of birds, amphibians, and corals based on expert assessment and literature surveys. In a more regionally focused study, Gardali et al. assessed climate-change risk for California’s vulnerable bird species.

Birds were also the focus of two studies documenting how particular species can be ‘winners’ or ‘losers’ in a changing climate. Receding glaciers and thus increased breeding habitat have led to population increases for Adélie penguins in the southern Ross Sea. The outlook was more mixed for Pacific western grebes , which have shifted south, perhaps in response to changes in their forage fish prey. Further down the food chain, Suikkanen et al.  used thirty years of marine data to infer that climate change and eutrophication drove a trophic shift in Baltic Sea food webs.

Long-term data were also used to study how flowering dates have changed since the mid-19th century. In a study that received extensive media coverage, Ellwood et al. used flowering records initiated as early as 1852 to show that high spring temperatures in 2010 and 2012 resulted in the earliest flowering in recorded history in the eastern United States. The biological pathways through which temperature affects seasonal timing in endotherms were discussed by Caro et al. Two other widely-covered studies focused on coffee: predicting future trends and identifying priorities, and climate change impacts on this plant and one of its important pests. Both examine adaptation possibilities for managing coffee crops over the coming century.

Adaptation and vulnerability were central themes for Guest et al., who reported that corals under thermal stress showed lower bleaching susceptibility at locations that bleached a decade earlier, implying an adaptive or acclimatization response. The molecular mechanisms behind such thermal tolerance were explored by Bellantuono et al.

Finally, the ecological impacts of climate change affect our health, the urban environment, and the agricultural economy. Airborne pollen counts have been increasing across Europe, and Ziello et al. suggest that rising CO2 levels may be influencing this increase. In another study, Meineke et al. used an elegant combination of observation and manipulative experiments to show that urban warming was a key driver of insect pest outbreaks in the southeastern U.S. Rising temperatures are a significant driver for the expanding range of Asian tiger mosquitoes, known vectors for West Nile and other viral infections. Warming was also found to contribute to the decreasing quality of grassland for grazers such as bison and cattle, although the effects are often exerted via complex interactions with other factors.

The broad range of these papers emphasize not only the multi-faceted impacts of climate change on ecological and human systems, but also the breadth and depth of research on these subject being reported in the PLOS journals. These journals seem a particularly appropriate venue for the ‘citizen science’ and other long-term data used by many of these studies.

Collection Citation: Ecological Impacts of Climate Change Collection (2013) http://www.ploscollections.org/ecoclimatechange

Image Credit: (Clockwise from top) William Warby. Flickr.com. Thomas Vignaud. PLOS Biology. 2011. 9(4). Colombi et al. PLOS ONE. 2013. Soto-Azat et al. PLOS ONE. 2013.

This Collection is also available on Flipboard, please search “PLOS Collections” to subscribe.

 

The Poop Will Tell Us: Do Elephants and Rhinos Compete for Food?

Africa

A recent study of the two animals in Addo Elephant National Park, called “Shift in Black Rhinoceros Diet in the Presence of Elephant: Evidence for Competition?” suggests the answer is yes.

Scientists interested in helping endangered species like the African elephant and the black rhinoceros would like to know whether these animals compete for resources in the wild, as such food contests could impact the population and health of both species. Unfortunately, our favorite rough-skinned big guys have IUCN statuses of vulnerable and critically endangered, respectively, so competition for food between them may present a bit of an ecological puzzle.

To gain evidence of food competition, researchers from Australia and the Centre for African Conservation Ecology took a close look at elephant and rhino poop (no, seriously) across different seasons to identify the types of plants each herbivore  was eating. Poop collecting was performed at times of the year when rhinos and elephants ate in the same region, and then again when only rhinos grazed in the area (in the absence of elephants). Variations in the plant types found in the feces were counted as indicators of dietary differences.

While it’s been shown that the presence of elephants can help some herbivores with habitat and food access, limited studies have been conducted on how the elephants’ foraging behavior may affect that of specifically megaherbivores. The authors state that there is clear evidence that elephants hog and monopolize food, a behavior that they suspected would affect the diets of other large herbivores. Indeed, the results of this study revealed that resource use was clearly separated by season, and rhinos munched on different grasses depending on whether or not the elephants were present. Without elephants around, rhinos ate more diverse plants, like woody shrubs and succulents, but in their presence, rhinos restrained themselves and consumed more grasses. This may not seem like a big deal, but rhinos are known to be strict browsers (read: picky about their food choices), so this dietary difference discovery was surprising to researchers.

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The authors go on to suggest that elephants living at high population densities in certain regions may significantly affect the foraging opportunities of other grazers, and these close living quarters may have long-term effects on the overall fitness of the other animals. These behaviors may have particularly important consequences in smaller or fenced-in wildlife parks, where populations tend to grow at the same time that food availability goes down.

Citation: Landman M, Schoeman DS, Kerley GIH (2013) Shift in Black Rhinoceros Diet in the Presence of Elephant: Evidence for Competition? PLoS ONE 8(7): e69771. doi:10.1371/journal.pone.0069771

Image Credits: African wildlife photo by Chris Eason (Mister E); plot from article

Balancing nutrient diets determines how ecosystems age

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From rainforests to rocky glaciers, the life of an ecosystem is rooted in the balance of nutrients in its soil. Shifting levels of soil nitrogen (N) and phosphorus (P) define how ecosystems evolve, and understanding the dynamics of these key nutrients can help ecologists identify crucial factors to help mitigate climate change.

A new model to understand N and P dynamics over different time scales was described in the PLOS ONE paper, “Nitrogen and Phosphorus Limitation over Long-term Ecosystem Development in Terrestrial Ecosystems”. Recently awarded the Ecological Society of America’s prize for an outstanding theoretical ecology paper, the study determines whether N or P are more likely to limit the productivity of ecosystems over short, intermediate and long timescales. Author Duncan Menge explains the background and results of their study:

How do N and P levels change with the age of an ecosystem like a rainforest?

A good question. Levels of both N and P are very low in very young ecosystems (which typically have rocky soils; see picture above), higher in intermediate-aged ecosystems (see picture), and often lower in old ecosystems.  How N levels change relative to P, though, is a trickier subject.  The best-studied sites show relatively low N in younger ecosystems and relatively high N in older ecosystems, but there are some places that show opposing trends.

Prior to your research, how did theoretical models assess the impact of these two nutrients on ecosystem dynamics?

Prior to our work there were a series of conceptual developments, which I will call “the classic model,” but there was no previous mathematical model of N and P dynamics during long-term ecosystem development.  The classic model states that ecosystems should progress from N deficiency in younger ecosystems to P deficiency in older ecosystems, as is seen on the best-studied sites.  According to the classic model, this happens because of the differences in where N and P come from.  P is present in most rocks, whereas N is not, so P inputs are largely controlled by the weathering of rocks.  Consequently, very young ecosystems have large P inputs, whereas very old ecosystems have small P inputs.  On the other hand, N comes primarily from rain, so N inputs don’t necessarily depend on ecosystem age.

Franz500yearsite_groundYour paper mentions that these models don’t account for several possible trajectories of ecosystem evolution. What was missing? 

There are a number of missing elements that jumped out as potentially important.  First, the input side of the story isn’t as simple as “P comes from rocks, N comes from rain.”  P also comes from dust that is blown in from upwind, whereas N can also come from organisms like soybean or alder that “fix” N from the air.  Second, N and P losses from ecosystems should be as important as inputs in determining N and P levels, but these weren’t the focus of the classic model.  These facts have been known for a long time in the scientific community, but no one had looked at what their implications might be for ecosystem development.

What was your new model and how did it cover these aspects?

Our model is novel for a couple of reasons.  First, we considered a broader set of N and P input and loss dynamics than the classic model, which made for a richer set of possible ecosystem trajectories.  Second, the type of mathematical analysis we did was unlike anything previous researchers had done in this particular field, and made it possible to pin down the types of conditions that might lead to different soil conditions.

What were some of the key data accounted for in your model that were overlooked in previous analyses?

Aside from the input and loss dynamics mentioned above, one piece of data we keyed in on was that microbes in the soil have an easier time accessing P than N in dead plant material.  Again, this “preferential P mineralization” is something that has been known for a long time, but we thought that the effects of this quirk might not be fully appreciated.

What were the main findings of your analyses?

In addition to the classic “N limitation to P limitation” path, our model shows that many other trajectories are feasible.  For example, if dust deposition is high and N-fixing organisms are abundant in young ecosystems (as they often are), an ecosystem might start out P limited and end N limited.  One of the more surprising findings was that the levels of N and P in soil organic matter (mostly dead plant material) don’t necessarily correspond to N versus P limitation in an intuitive way.

What are some of the practical applications of this model- for example, for developmental activities in rainforests, or human activities planned in other ecosystems?

Whether N or P has a greater effect in an ecosystem has important implications for many environmental issues. The most important application is enhancing our climate models.  Excess N can be transformed into a greenhouse gas, whereas P cannot.  So, a better understanding of nutrient levels will improve predictions about the extent of climate change.

Congratulations to the authors on receiving an ESA award for this outstanding research paper!

Citation: Menge DNL, Hedin LO, Pacala SW (2012) Nitrogen and Phosphorus Limitation over Long-Term Ecosystem Development in Terrestrial Ecosystems. PLoS ONE 7(8): e42045. doi:10.1371/journal.pone.0042045

Photos by Duncan Menge:

top: the rocky soil of a very young ecosystem, Franz Josef glacier in New Zealand.  The rainforests in the valley formed by the Franz Josef glacier are some of the best studied ecosystem development sites in the world.

below: a rainforest on 500 year old soil near the Franz Josef glacier.

The Rhinoceros: Saving an Icon

8526743557_5c3a36734eThe rhino is an iconic animal. With their tough demeanor and unforgettable horn, what’s not to love?

This majestic creature has been on earth more than 9.2 million years, according to a recent PLOS ONE article, where researchers describe a fossil belonging to a large two-horned rhinocerotine species in central Turkey.  This rhino was preserved in volcanic rock, a process which accounts for less than two percent of the earth’s fossils. The scientists believe an eruption similar to that of Mt. Vesuvius must be responsible for the impeccable preservation. This study gave us a sense of just how long these brilliant beasts have been among us; however their existence is in grave danger today.

Yesterday May 1st, was Save the Rhino day. The purpose of this day is to bring awareness to rhino conservation and the threats this animal faces in the wild. The rhinoceros does not have any known predators, except for us! Humans have been poaching the rhino at astounding rates for their distinctive horn. The horn is made of keratin, the same protein in our finger nails and hair, and is thought to offer health benefits in traditional medicine. The horn has also been poached for luxury items in other parts of the world.

Today, there are fewer than 29 thousand rhinos on earth, with the white rhino on the brink of extinction. In a recent PLOS ONE article, authors have investigated how potential losses in conservation efforts would affect the white rhino population in South Africa. The authors specifically looked into Kruger National Park where the rhino population increased from 1998 to 2008. Despite this increase, researchers have predicted that by 2015 more white rhinos will be poached than bred, bringing the species into a negative growth phase. Due to the high demand for rhino horns, the authors urge conservationists to find innovative approaches to curb the financial incentive driving the poaching.

Global awareness and conservation is desperately needed to ensure the rhinoceros continues to graze the earth for millions of years to come. For more research on conservation and the glorious rhinoceros, visit our site here.

 

Citations:

Citation: Antoine P-O, Orliac MJ, Atici G, Ulusoy I, Sen E, et al. (2012) A Rhinocerotid Skull Cooked-to-Death in a 9.2 Ma-Old Ignimbrite Flow of Turkey. PLoS ONE 7(11): e49997. doi:10.1371/journal.pone.0049997

Citation: Ferreira SM, Botha JM, Emmett MC (2012) Anthropogenic Influences on Conservation Values of White Rhinoceros. PLoS ONE 7(9): e45989. doi:10.1371/journal.pone.0045989

Image on Flickr by wwarby

Spreading seeds: Animals assist forest fruits

Dwindling numbers of a single mammal species involved in seed dispersal could change the nature of Brazilian Atlantic forests in far-reaching ways. A recent study in PLOS ONE examined the role of two fruit-eating species, tapirs and woolly spider monkeys, in dispersing seeds across tropical forests in southeastern Brazil. Together, the two species are responsible for spreading the seeds of over 300 plant species, and are thus important contributors to plant biodiversity.

The study found significant differences in the frequency and patterns with which the two species dispersed seeds. Woolly spider monkeys, or muriquis, dispersed 5 times more plant species and 13 times more seeds than tapirs living in the same area did. Tapirs dispersed fewer seeds and spread fewer numbers of plant species across the forest than the muriquis did. However, they also dispersed larger seeds than muriquis and moved the plants into sites not reached by the monkeys, such as large gaps in the forest and fragmented open areas nearby.

Tapirs and woolly spider monkeys are extensively hunted in tropical forests, including in the Brazilian Atlantic forests where only 12% of the original forest cover remains. Though both species share the ecological task of dispersing fruit seeds in the forests they live in, this study reveals how the two species contribute to maintaining plant diversity in unique ways.

Though previous research has suggested that species with similar diets may be able to compensate for each other’s roles in maintaining plant diversity, this new research demonstrates that these two large fruit-eaters play complementary rather than redundant roles as seed dispersers. A change in the population of either of these two species will change the way plants are distributed through the forest. Such a change is likely to have the greatest impact on plants with large seeds, for which muriquis and tapirs may be the last living seed dispersers.

Citation: Bueno RS, Guevara R, Ribeiro MC, Culot L, Bufalo FS, et al. (2013) Functional Redundancy and Complementarities of Seed Dispersal by the Last Neotropical Megafrugivores. PLoS ONE 8(2): e56252. doi:10.1371/journal.pone.0056252

Images: muriqui (top) and tapir (below) from the PLOS ONE paper 

For animals, ‘Value meals’ are not just about quantity

Animals that hunt or forage for prey can be just as picky as humans about their food, and recent studies show that their choices are based on the quality of food they consume rather than its quantity.

For example, some bugs and spiders have a Spidey sense for regulating their diet to get the nutrients they need without gorging on less nutritious prey. In a recent paper published in PLOS ONE, scientists fed wolf spiders with flies that had been raised on either nutrient-rich or nutrient-poor diets. They found that the spiders hunted both kinds of flies, but chose which ones to eat based on the nutritional quality of the flies, and the spiders’ own dietary history.

Though such carefully controlled experimental diets aren’t always possible in the wild, two other recent studies rely on observations of how changes in food availability affect mammals in oceans and tropical forests.

Unlike wolf spiders, marine mammals are frequently believed to thrive eating any kind of fish, as long as there is enough of it. However, another study published this month in PLOS ONE questions this idea by analyzing the food habits of 11 species of dolphins, whales and porpoises.

These researchers discovered that although some marine mammals ate most kinds of prey, others were more finicky, and only ate certain fast-moving varieties of fish.  Fast-moving fish are more energy-rich as food than slower moving species, but it also takes more effort to catch them. This energy expenditure is, quite literally, the price that marine animals pay for their dinner. According to this study, these preferences appear linked to the muscle performance of the predators- faster moving predators require high-energy prey, while others can afford to be more liberal in their food choices.

Marine life is widely affected by climatic shifts, global warming and fishing, which are causing the populations of high-energy fish to drop and increasing the numbers of low-energy species, a phenomenon the authors describe as “the emergence of junk-food in the ecosystem.” This ‘junk-food’ is likely to have a greater impact on more selective eaters, and the authors suggest that understanding the dietary preferences of these marine mammals could help manage and prioritize conservation efforts.

Changing weather also causes land animals to adopt different diets. Several monkey species switch to fallback foods when the foods they prefer are out of season, and a study published today found that these behavioral changes can have effects beyond just simple changes in nutritional value. Scientists studying blue monkeys in tropical forests found that levels of a stress marker increased in female monkeys when they had to eat lower-quality fallback foods like leaves instead of their first preference of insects or fresh fruit. The dietary change also affected the female monkeys’ reproductive health, although that of the males remained unchanged.

These and other studies reveal how animals’ dinner decisions aren’t just about quantity but quality, and how changes in their food habits impact their health. Read other PLOS ONE papers to learn about salt-loving flies, how brightly colored birds choose foods with more pigments, why pandas eat bamboo, and more.

Photo credits:

Burger by Ewan-M on flickr, wolf spider by jack_246, dolphin by Brian Branstetter, Cercopithecus by Steffen Foerster 

Citations:

Schmidt JM, Sebastian P, Wilder SM, Rypstra AL (2012) The Nutritional Content of Prey Affects the Foraging of a Generalist Arthropod Predator. PLoS ONE 7(11): e49223. doi:10.1371/journal.pone.0049223

Spitz J, Trites AW, Becquet V, Brind’Amour A, Cherel Y, et al. (2012) Cost of Living Dictates what Whales, Dolphins and Porpoises Eat: The Importance of Prey Quality on Predator Foraging Strategies. PLoS ONE 7(11): e50096. doi:10.1371/journal.pone.0050096

Foerster S, Cords M, Monfort SL (2012) Seasonal Energetic Stress in a Tropical Forest Primate: Proximate Causes and Evolutionary Implications. PLoS ONE 7(11): e50108. doi:10.1371/journal.pone.0050108

Manta ray preferences revealed

Image credit: Fabrice Jaine, PLOS ONE (2012)

If the thought of a calm moonlit night out on a tropical island makes you want to be at the beach, you may have something in common with the reef manta ray. Researchers studying the habits of manta rays in the waters off an island in the Great Barrier Reef have found that the rays aggregate in larger numbers when wind speeds are low and tides are particularly high or low (because of a new or full moon). Published today in PLOS ONE, their findings may help understand how manta ray populations are affected by climate and ocean conditions, they say.

This type of insight is particularly important because reef manta rays are classified a ‘vulnerable’ species by the International Union for Conservation of Nature (IUCN), just one step away from being endangered. Though they have few natural predators, they are hunted for their supposed efficacy in traditional Chinese medicine and are frequently trapped accidentally in fisheries. In several regions around the world, their populations are thought to have declined by about 80%, and globally, the IUCN estimates a drop of approximately 30% in the last 75 years. Little is known, however, about what factors predict their behavior or abundance in a particular geographical area; such knowledge is critical to conservation efforts, particularly in the context of a changing climate.

To begin addressing this question, the authors of today’s paper recorded weather and water conditions around the island and correlated these to the population of rays around the island and the kinds of behaviors they displayed. To study the animals themselves, the researchers enlisted volunteer SCUBA divers and tour operators on the island to watch for rays and their behavior. Another paper recently published in PLOS ONE uses a similar approach to track the decline of baiji, a freshwater dolphin in the Yangtse River. The authors of this paper surveyed local fishing communities along the river to estimate the abundance and decline of large species in the ecosystem, tracking the river dolphin, finless porpoise and two large fish now considered critically endangered or possibly extinct. They found that plotting the decline in frequency of sightings reported by the locals could help establish the dynamics of species decline and extinction.

Protecting larger animals like dolphins and manta rays can help more than just a single species.  In addition to acting as attractive poster children for conservation efforts, these animals frequently act as indicator or umbrella species. As indicators, their presence (or absence) can be a marker to monitor environmental conditions known to impact other species in the area, and targeting conservation efforts towards these animals can help conserve the habitat of several other species. Information on whether manta rays can serve as indicator or umbrella species is sparse, but research such as this study should help to answer this question.

Citations:

Jaine FRA, Couturier LIE, Weeks SJ, Townsend KA, Bennett MB, et al. (2012) When Giants Turn Up: Sighting Trends, Environmental Influences and Habitat Use of the Manta Ray Manta alfredi at a Coral Reef. PLoS ONE 7(10): e46170. doi:10.1371/journal.pone.0046170

Turvey ST, Risley CL, Barrett LA, Yujiang H, Ding W (2012) River Dolphins Can Act as Population Trend Indicators in Degraded Freshwater Systems. PLoS ONE 7(5): e37902. doi:10.1371/journal.pone.0037902