Showing posts with label biodiversity. Show all posts
Showing posts with label biodiversity. Show all posts

Saturday, January 28, 2012

Endemic Species, Biodiversity Hot Spots & Overlooked and Underestimated Species Diversity

Three undescribed species 
of Plica, with locations and
number of scale rows at 
midbody. Many undescribed
species of reptiles and amphibians
remain to be discovered
Conservation International reports that biodiversity hotspots hold high numbers of endemic species, but their combined area of remaining habitat cover only 2.3% of the Earth's land surface. Each hotspot is considered threatened and has lost at least 70 percent of its original natural vegetation. Over 50 percent of the world’s plant species and 42 percent of all terrestrial vertebrate species are endemic to the 34 biodiversity hotspots.

In a forthcoming paper, Swenson et al. (2012) report the Andes-Amazon basin of Peru and Bolivia as one of the most data-poor, and biologically rich areas of the world. While conservationists and scientists agree the region has extremely high endemism, perhaps the highest in the world, little was known about the geographic distributions of these species and ecosystems within country boundaries. Swenson et al. developed conservation data on endemic biodiversity (~800 species of birds, mammals, amphibians, and plants) and terrestrial ecological systems (~90; groups of vegetation communities resulting from the action of ecological processes, substrates, and/or environmental gradients) to conduct a fine scale conservation prioritization across the Amazon watershed of Peru and Bolivia. The authors modeled the geographic distributions of 435 endemic plants and all 347 endemic vertebrate species, from existing museum and herbaria specimens at a regional conservation practitioner’s scale (1:250,000- 1:1,000,000), based on the best available tools and geographic data. They mapped ecological systems, endemic species concentrations, and irreplaceable areas with respect to national level protected areas.  They found that sizes of endemic species distributions ranged widely, from a minimum of about 20  km2 to more than 200,000  km2 across the study area. Endemic bird and mammal species richness was greatest within a narrow 2500-3000 m elevation band along the length of the Andes Mountains. Endemic amphibian richness was highest at 1000-1500 m elevation and concentrated in the southern half of the study area. Of interest, amphibians displayed peaks of endemism (21-29 species per 1-km2 cell) on lower slopes, between 1000 and 1500 m elevation. These areas were concentrated in southern Peru, northern Bolivia, and in an isolated endemic area in the northern Peruvian department of San Martin. In the study region they found 177 endemic species of amphibians in 30 genera. Given that the region is poorly known many species undoubtedly remain to be found and the challenges involved in conserving the biodiversity of this region are considerable.

Thee more undescribed
species of Plica. The
top photo, may be the real, 
Plica plica
While the authors looked at most of the major groups of terrestrial vertebrates, for some unknown and unstated reason they left out reptiles. For the past few months I have been looking at some widespread neotropical reptiles and am finding a considerable amount of cryptic diversity that has been overlooked and ignored. An excellent example is the widespread lizard, Plica plica. Some times called the tree runner, these arboreal lizards sit on tree trunks and lap up ants as they march passed. While there are currently three recognized species in the genus (P. umbra, P. plica, and P. luminaria), Plica plica appears to be a superspecies. The most recent discussion of this species is probably Avila-Pires' (1997) account where she reports  Plica plica has 121-162 scales around the middle of the body and 74-95 ventrals. The list of specimens she examined included material from Guyana, Peru, Suriname, as well as Brazil.

To date I have looked at more than 60 specimens from about 25 localities ranging from Trinidad and Venezuela to Ecuador and southern Peru. My range for scales around midbody is 97 to 202, with a ventral range of 48 to 96. Conservatively, these specimens represent at least 12 species, but probably 14 or 15 species. This is of concern because species like Plica plica are often considered species of least concern,due to their perceived widespread distribution. So, yes biodiversity hot spots are of interest but it appears that much of the rest of the world is also harboring undetected, cryptic biodiversity also.

Avila-Pires, TCS, 1997. Lizards of Brazilian Amazonia (Reptilia: Squamata). Zoologische Verhandelingen 299:1-706.

Swenson JJ, Young BE, Beck S, Comer P, Cordova JH, Dyson J, Embert D, Encarnacion F, Ferreira W, Franke I, Grossman D, Hernandez P, Herzog SK, Josse C, Navarro G, Pacheco V, Stein BA, Timana M, Tovar A, Tovar C, Vargas J, Zambrana-Torrelio CM 2012. Plant and animal endemism in the eastern Andean slope: Challenges to conservation. BMC Ecology 2012, 12:1 (27 January 2012).

Sunday, December 18, 2011

Old & New Species

Two new dwarf homalopsid snakes of the genus Myron described in 2011. A. Myron karnsi from the Aru Islands in eastern Indonesia. B. Myron resetari from Western Australia. Both species have been long confused with Myron richardsonii, a species from northern Australia.These are small (less than 400 mm), coastal species that probably hunt fish in marine environments. They are two of a small number of snakes, other than true sea snakes and file snakes, that have been able to adapt to saltwater. M. karnsi is known from a single specimen, M. resetari was known from two specimens when described, but other specimens have been found in the last few months. JCM
This is the time of year for retrospection and it is everywhere. One of the re-occurring stories is the number of new species described during the year. One press release from the California Academy of Sciences reports CAS researchers discovered 140 new species in 2011, including 72 arthropods, 31 sea slugs, 13 fishes, 11 plants, nine sponges, three corals, and one reptile (a tortoise).

A press release from 27 June of 2011 reports scientists discovered 1,060 previously unknown species during a decade of research in New Guinea, the world's second largest island; the majority of new species listed are plants and insects, but the inventory includes 134 amphibians, 71 fish, 43 reptiles, 12 mammals, and 2 birds. A similar, more recent, press release pertaining to the greater Mekong region of Southeast Asia from World Wildlife Fund (WWF) reports 1068 species were discovered or newly identified by science between 1997 and 2007 – which averages two new species a week and includes 519 plants, 279 fish, 88 frogs, 88 spiders, 46 lizards, 22 snakes, 15 mammals, 4 birds, 4 turtles, 2 salamanders and a toad.

Using AmphibiaWeb and the Reptile Database it is possible to tract the number of species of amphibians and reptiles described during a given year. Despite the week or so left in 2011 it is of interest to note that as of now (December 17) 84 new species of reptiles were described during 2011 (one turtle, 21 snakes, and 62 lizards) and 134 species of amphibians (one caecilian, five salamanders, and 128 frogs). Combined that works out to 218 species, or about 0.59 new species per day. So, we can expect another five or six new species of amphibians and reptiles to be described this year.

What is more difficult to track is the number of species rescued from synonymy. During the late 19th century, and well into the mid to late 20th century it was popular to lump species, thus many species described during the 200 years after Linnaeus were considered mistakes and their names were placed in the synonymy of other names. Reviewers of species and genera often find old names placed in the synonymy of even older names are in fact valid species. Thus, 20th century zoologists were led to believe that the diversity of life on earth, in this case, the diversity of amphibians and reptiles was much less than what we know it to be today. So, while new names are easy to count, old names become more of a challenge - but they still count because they represent real species that have been misplaced and overlooked for decades, or in some cases centuries. 

Murphy, J. C. 2011. The Nomenclature and Systematics of Some Australasian Homalopsid Snakes (Squamata: Serpentes: Homalopsidae). Raffles Bulletin of Zoology 59(2):229-236.

Thursday, September 22, 2011

Diverse Ecosystems May Reduce Threat From Bd

The Western Toad, Anaxyrus boreas.

Photo Credit: Ivan Phillipsen, OSU

The following is a press release from Oregon State University.

CORVALLIS, Ore. – Researchers at Oregon State University have shown for the first time that loss of biodiversity may be contributing to a fungal infection that is killing amphibians around the world – a finding that provides more evidence for why biodiversity is important to many ecosystems.

The research, being published this week in Proceedings of the National Academy of Sciences, used laboratory studies of amphibians to show that increased species richness decreased both the prevalence and severity of infection caused by the deadly chytrid fungus, Batrachochytrium dendrobatidis.

“With greater diversity of species, you get a dilution effect that can reduce the severity of disease,” said Catherine Searle, an OSU zoologist and lead author on the study. “Some species are poor hosts, some may not get infected at all, and this tends to slow disease transmission.

“This has been shown in other systems like Lyme disease which infects humans, mice and deer,” she said. “No one has really considered the dilution effect much in amphibians, which are experiencing population declines throughout the world. It’s an underappreciated value of biodiversity.”

It’s generally accepted, the researchers said, that a high diversity of species can protect ecosystem function, help to recycle nutrients, filter air and water, and also protect the storehouse of plant or animal species that may form the basis of medicines, compounds or natural products of value to humans.

Protection against the spread of disease should more often be added to that list, they said.

“Emerging infectious diseases are on the rise in many ecosystems,” said Andrew Blaustein, a co-author on this study, professor of zoology at OSU and leading researcher on the causes of amphibian declines.

“Protection of biodiversity may help reduce diseases,” he said. “It’s another strong argument for why diverse ecosystems are so important in general. And it’s very clear that biodiversity is much easier to protect than it is to restore, once it’s lost.”

The fungus, B. dendrobatidis, can lead to death from cardiac arrest when it reaches high levels in its amphibian hosts. It is not always fatal at lower levels of infection, but is now causing problems around the world. One research team has called the impact of the chytrid fungus on amphibians “the most spectacular loss of vertebrate biodiversity due to disease in recorded history.”

Amphibians face threats from multiple causes, including habitat destruction, pollution, increases in ultraviolet light due to ozone depletion, invasive species, and infectious disease.

The dilution effect can occur in plants and animals, but also in human diseases. In a different report published last year in Nature, researchers noted an increased risk of West Nile encephalitis in the U.S. in areas with low bird diversity. And in more diverse communities, the infection of humans by schistosomiasis – which infects 200 million people worldwide – can be reduced by 25-99 percent.

Catherine L. Searle, Lindsay M. Biga, Joseph W. Spatafora, Andrew R. Blaustein. A dilution effect in the emerging amphibian pathogen Batrachochytrium dendrobatidis. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1108490108

Wednesday, August 17, 2011

Species Believed Extinct Rediscovered, Hope for Biodiversity

Extinction is a focal issue among scientists, policy makers and the general public. Each year, numerous species which are thought to have disappeared are rediscovered. Yet, these rediscoveries remain on the brink of extinction.

A first-ever study conducted by researchers from the National University of Singapore (NUS), University of Adelaide and Princeton University on the full extent of amphibian, bird and mammal species rediscoveries globally has found that over the past 122 years, at least 351 species which are thought to have disappeared have been rediscovered. The rediscovery of these once-missing amphibians, birds, and mammals occur mostly in the tropics.

However, despite many rediscoveries, 92% of amphibians, 86% of birds and 86% of mammals are highly threatened, independent of how long they were missing or when they were rediscovered.

Under the current trends of widespread habitat loss, particularly in the tropics, most rediscovered species remain on the brink of extinction.

According to the lead researcher, Brett R. Scheffers, who is from the Department of Biological Sciences at NUS, most rediscovered species have small range size, which is the main driver in species extinction globally. "Rediscoveries, without aggressive conservation, likely represent the delayed extinction of doomed species and not the return of viable populations. In short, there is hope but we must step up rapid conservation efforts," he said.
“Endangered” and “Vulnerable” species; Non-threatened (blue line) includes “Near Threatened” and “Least Concern” species; Data Deficient (black dotted line) includes “Data Deficient” species, and Total (black solid line) includes Threatened, Non-threatened, and Data Deficient species. Additionally, 3 “Extinct” and 1 “Extinct in the Wild” amphibian species are included in threatened accumulation curves as individuals of each species were recently rediscovered in the wild. Top photograph: the Critically Endangered, Atelopus seminiferus, rediscovered in Peru in 2001; middle photograph: the Endangered, Gallicolumba hoedtii, rediscovered in Indonesia in 2008; and bottom photograph: the Critically Endangered, Prolemur simus, rediscovered in Madagascar in 1986. Photo credits: A. seminiferus courtesy of Jan Post, G. hoedtii courtesy of Philippe Verbelen. and P. simus courtesy of N. Rowe/

To make matters worse, the average number of years a species went missing is 61 years. This long duration makes conservation planning for missing species very difficult, particularly in areas that are of high value to humans. For instance, the protected areas that have been put aside for a particular species that has not been seen for numerous years could have be converted for agricultural use.

Findings from the study, which was published in PLoS One in July, are indicative of the limited knowledge of biological diversity in the poorly known tropics. Scheffers elaborated, "We still have much to discover and these results indicate that it may not be too late for many species that have gone unseen for many years."

"We support and encourage more biodiversity surveys in the poorly known tropics. This is particularly important as many museums are experiencing shortened budgets or event budget cuts," Scheffers added

Friday, August 5, 2011

Protected Geography Fails to Slow Decline in Biodiversity

Protected habitat has increased dramatically over the past 40 years yet the rapid decline in biodiversity continues. Seven million square miles of terrestrial habitat and one million square miles of ocean have been protected since 1960. Camilo Mora and Peter F. Sale have documented the problem in Marine Ecology Progress Series. Despite the number and size of protected areas the diversirty of terrestrial and marine species continues to decline during this 40 year period. Protecting land and water is a common conservation strategy worldwide, but it has failed to prevent the steady disappearance of the planets creatures. The following is an edited version of a Huffington Post article by Tom Zeller. The full article can be found here.
"The problem is bigger than one we can realistically solve with protected areas -- even if they work under the best conditions," said Camilo Mora, an assistant professor in the Department of Geography at the University of Hawaii at Manoa and lead author of the study. "The protected area approach is expensive and requires a lot of political and human capital," Dr. Mora continued in an email message to The Huffington Post. "Our suggestion is that we should redirect some of those resources to deal with ultimate solutions."
The steady loss of biodiversity -- defined roughly as the rich variety of living things -- can, in turn, have profound implications for human civilization, which relies on healthy, variegated ecosystems to provide a host of ecological services from water filtration and oxygen generation to food, medicine, clothing and fuel.

The precise value of such services is difficult to quantify, but one economic analysis estimated they were worth as much as $33 trillion globally.

While the study concedes that individual protected areas that are well-designed and well-managed can be successful in preventing the imminent extinction of species and ecosystems, a variety of other forces conspire to further reduce biodiversity overall.
"Protected areas, as usually implemented, can only protect from over-exploitation, and from habitat destruction due to exploitation and other direct human actions within their borders. They are a tool for regulating human access and extraction," said Peter F. Sale, assistant director of the United Nations University Institute for Water, Environment and Health, and the study's co-author. "Biodiversity loss is also caused by pollution, by arrival of invasive species, by decisions to convert habitat to other uses -- farms, villages, cities -- and by various components of climate change," he told HuffPost. "None of these are mitigated by the creation of protected areas except, possibly, the removal of habitat to other uses."
In other words, the researchers, who based their analysis on a broad range of global data and a review of existing literature, suggest that the implementation of habitat protection is unable to keep pace with other stressors contributing to species loss overall.
This is partly due to lack of enforcement. Only about 5.8 percent of terrestrial protected areas and 0.08 percent of marine sanctuaries see reliable and consistent enforcement.
Further, the authors note most research suggests that between 10 percent and 30 percent of the world's ecosystems need to be protected to preserve optimal biodiversity. But despite what appears to be a rapid increase in protected lands, the pace is too slow to achieve those targets anytime soon. On land, the 10 percent target, under the best of circumstances, would not be reached until 2043, the study estimated. The 30 percent target would not be achieved until 2197. The same target percentages for marine sanctuaries would be reached by 2067 and 2092, respectively.
And these projections are almost certainly too optimistic, the authors note, because the rate of establishment of new protected areas would be expected to slow considerably as conservation efforts runs up against the needs of a rapidly expanding human population.
Global population is expected to pass 7 billion in Octoberaccording to new estimates from the population division of the Department of Economic and Social Affairs at the United Nations. That's an increase of 1 billion people in about a dozen years.

Other challenges include the size of protected areas -- which are often too small for larger species to survive -- and the lack of connectivity between protected areas, which is needed for healthy genetic dispersal.
The authors of Thursday's analysis suggest that reversing biodiversity losses will require a vast rethinking of conservation strategy -- one that redirects limited resources toward more holistic solutions. 

Monday, May 23, 2011

Oil Palms & Species Diversity

Oil palm plantations are having a 
devastating effect on biodiversity. 
Photo Credit:Matthew Struebig.
The following press release discusses the impact of bat diversity in oil palm plantations, while some forest frogs can survive in these human made ecosystems, they too suffer a loss of species.

Forest fragmentation driven by demand for palm oil is having a catastrophic effect on multiple levels of biodiversity, scientists from Queen Mary, University of London have discovered.

The researchers are worried that unless steps are taken to safeguard and manage the remaining forest, then certain species will struggle to survive.

The study, which focused on bats as an indicator of environmental change, was published in one of the leading scientific journals, Ecology Letters.
The team conducted bat surveys in pristine forest and also in forest patches of varying size in central Peninsular Malaysia. They recorded the numbers of different species present and also assessed the level of genetic diversity within populations of some species.

Lead author Matthew Struebig, jointly based at Queen Mary University of London and the University of Kent, said: “We found that smaller forest areas support fewer species, and that those species that remain face an eventual decline, potentially leading to local extinction in the long-term.”

When the team compared the number of species present to genetic diversity within populations they found that fragmentation appeared to have an even greater impact on genetic loss, which might also be important for long-term population viability.

“We found that in order to retain the numbers of bat species seen in pristine forest, forest patches had to be larger than 650 hectares, however to retain comparable levels of genetic diversity, areas needed to be greater than 10,000 hectares,” he said.

Co-author Stephen Rossiter, also at Queen Mary, emphasised that the findings could have important implications for forest management in the face of the ever-growing demand for oil palm plantations.

He said: “We found that while more species existed in larger forest patches, even small fragments contributed to overall diversity. Therefore, conservation managers should aim to protect existing small fragments, while seeking to join up small forest areas to maximise diversity.”

Friday, May 6, 2011

Species Accumulate Over Time - Amazonian Treefrog Assemblages

For more than two hundred years, the question of why there are more species in the tropics has been a biological enigma. A particularly perplexing aspect is why so many species live together in a small area in the tropics, especially at some sites in the rainforests of the Amazon Basin in South America.

New research on the evolution and ecology of treefrogs, published online in the journal Ecology Letters, sheds new light on the puzzle. The patterns found in treefrogs may also help to explain the high species richness of other groups of organisms -- such as trees, birds and insects -- in the Amazon rainforests.

"Treefrogs are a particularly important group to study for understanding amphibian diversity, because they can make up nearly half of all amphibian species in some rainforest sites," says lead author John J. Wiens, an Associate Professor in the Department of Ecology and Evolution at Stony Brook University. "Treefrogs also offer a striking example of the high local-scale biodiversity in the Amazon. At some sites in the Amazon rainforest, there are more treefrog species in a small area than there are across all of North America or Europe."

The researchers compiled data on the number of treefrog species at 123 sites around the world and analyzed the data with a new evolutionary tree (based on DNA sequence data) for 360 treefrog species. They discovered that the richness of treefrog species in the Amazon rainforest sites is not explained by wet, tropical climatic conditions alone.

"In fact, we found that many tropical rainforest sites that are outside the Amazon Basin have no more species than do some sites in temperate North America," explains Dr. Wiens.

Instead, the researchers discovered that the high biodiversity of Amazonian sites is related to different groups of treefrogs occurring together in the Amazon Basin for more than 60 million years -- since before most dinosaurs became extinct. In contrast, those sites in tropical rainforests that have relatively few treefrog species are in areas that were colonized by treefrogs much more recently.

These results also have important implications for humans. "The results suggest that the incredible biodiversity of amphibians in some sites in the Amazon Basin took more than 50 million years to develop," says Dr. Wiens. "If the Amazon rainforests are destroyed and the amphibian species are driven to extinction by human activities in the next few decades, it may take tens of millions of years for this incredible level of biodiversity to ever return.

John J. Wiens, R. Alexander Pyron, Daniel S. Moen. Phylogenetic origins of local-scale diversity patterns and the causes of Amazonian megadiversity. Ecology Letters, 2011; DOI: 10.1111/j.1461-0248.2011.01625.x

Saturday, March 5, 2011

Are We In The 6th Mass Extinction?

The following is a University of California press release.While the following study looks at mammals, it seems likely that similar situations exist with amphibians and reptiles.

Tigers are one of Earth's most critically endangered species. Extinction of the majority of such species would indicate that the sixth mass extinction is in our near future. With the steep decline in populations of many animal species, from frogs and fish to tigers, some scientists have warned that Earth is on the brink of a mass extinction like those that occurred only five times before during the past 540 million years.

Each of these ‘Big Five’ saw three-quarters or more of all animal species go extinct.

In a study published in the March 3 issue of the journal Nature, University of California, Berkeley, paleobiologists assess where mammals and other species stand today in terms of possible extinction, compared with the past 540 million years, and they find cause for hope as well as alarm.

“If you look only at the critically endangered mammals – those where the risk of extinction is at least 50 percent within three of their generations – and assume that their time will run out, and they will be extinct in 1,000 years, that puts us clearly outside any range of normal, and tells us that we are moving into the mass extinction realm,” said principal author Anthony D. Barnosky, UC Berkeley professor of integrative biology, a curator in the Museum of Paleontology and a research paleontologist in the Museum of Vertebrate Zoology.

“If currently threatened species – those officially classed as critically endangered, endangered and vulnerable – actually went extinct, and that rate of extinction continued, the sixth mass extinction could arrive within as little as 3 to 22 centuries,” he said.

Nevertheless, Barnosky added, it’s not too late to save these critically endangered mammals and other such species and stop short of the tipping point. That would require dealing with a perfect storm of threats, including habitat fragmentation, invasive species, disease and global warming,

“So far, only 1 to 2 percent of all species have gone extinct in the groups we can look at clearly, so by those numbers, it looks like we are not far down the road to extinction. We still have a lot of Earth’s biota to save,” Barnosky said. “It’s very important to devote resources and legislation toward species conservation if we don’t want to be the species whose activity caused a mass extinction.”

Coauthor Charles Marshall, UC Berkeley professor of integrative biology and director of the campus’s Museum of Paleontology, emphasized that the small number of recorded extinctions to date does not mean we are not in a crisis.

“Just because the magnitude is low compared to the biggest mass extinctions we’ve seen in a half a billion years doesn’t mean to say that they aren’t significant,” he said. “Even though the magnitude is fairly low, present rates are higher than during most past mass extinctions.”

“The modern global mass extinction is a largely unaddressed hazard of climate change and human activities,” said H. Richard Lane, program director in the National Science Foundation’s Division of Earth Sciences, which funded the research. “Its continued progression, as this paper shows, could result in unforeseen – and irreversible – negative consequences to the environment and to humanity.”

The study originated in a graduate seminar Barnosky organized in 2009 to bring biologists and paleontologists together in an attempt to compare the extinction rate seen in the fossil record with today’s extinction record. These are “like comparing apples and oranges,” Barnosky said. For one thing, the fossil record goes back 3.5 billion years, while the historical record goes back only a few thousand years. In addition, the fossil record has many holes, making it is impossible to count every species that evolved and subsequently disappeared, which probably amounts to 99 percent of all species that have ever existed. A different set of data problems complicates counting modern extinctions.

Dating of the fossil record also is not very precise, Marshall said.

“If we find a mass extinction, we have great difficulty determining whether it was a bad weekend or it occurred over a decade or 10,000 years,” he said. “But without the fossil record, we really have no scale to measure the significance of the impact we are having.”

To get around this limitation, Marshall said, “This paper, instead of calculating a single death rate, estimates the range of plausible rates for the mass extinctions from the fossil record and then compares these rates to where we are now.”

Barnosky’s team chose mammals as a starting point because they are well studied today and are well represented in the fossil record going back some 65 million years. Biologists estimate that within the past 500 years, at least 80 mammal species have gone extinct out of a starting total of 5,570 species.

The team’s estimate for the average extinction rate for mammals is less than two extinctions every million years, far lower than the current extinction rate for mammals.

“It looks like modern extinction rates resemble mass extinction rates, even after setting a high bar for defining ‘mass extinction,’” Barnosky said.

After looking at the list of threatened species maintained by the International Union for Conservation of Nature (IUCN), the team concluded that if all mammals now listed as “critically endangered,” “endangered” and “threatened” go extinct, whether that takes several hundred years or 1,000 years, Earth will be in a true mass extinction.

“Obviously there are caveats,” Barnosky said. “What we know is based on observations from just a very few twigs plucked from the enormous number of branches that make up the tree of life.”

He urges similar studies of groups other than mammals in order to confirm the findings, as well as action to combat the loss of animal and plant species.

“Our findings highlight how essential it is to save critically endangered, endangered and vulnerable species,” Barnosky added. “With them, Earth’s biodiversity remains in pretty good shape compared to the long-term biodiversity baseline. If most of them die, even if their disappearance is stretched out over the next 1,000 years, the sixth mass extinction will have arrived.”

Barnosky, A. D., N. Matzke, S. Tomiya, G. O. U. Wogan, B. Swartz, T. B. Quental, C. Marshall, J. L. McGuire, E. L. Lindsey, K. C. Maguire, et al. Has the Earth’s sixth mass extinction already arrived? Nature, 471, 51-57. DOI: 10.1038/nature09678

Monday, November 29, 2010

Keeping Some of the Pieces, The Importance of Shade in Cacao Plantations

Cacao and coffee are shade crops that provide habitat for plants and animals dependent upon tropical forest. Unlike corn, they enhance biodiversity in agricultural landscapes locally but they may also have a more global role when they are cultivated in regions of high endemism suffering heavy deforestation. Sulawesi is one of those places that still conceals many undescribed species, but like many other places the forests are being logged and converted into human landscapes. Deforestation and subsequent land-use changes are rampant in the tropics and will eventually force the species that survive the upheaval to use altered habitats such as agro-ecosystems and urban areas that tend to be warmer, drier, brighter and less structurally complex than natural forests.
Southeast Asian amphibians and reptiles are among the most poorly studied and the most threatened vertebrates  (estimated at 30% and 31%, respectively based on IUCN 2008 data). Tropical amphibians and reptiles are highly sensitive to habitat modifications and climate change, making mitigating the effects of land-use change on herpetological diversity in Southeast Asia a conservation priority. Wanger et al. (2010) studied a land-use modification gradient ranging from primary forest, secondary forest, natural-shade cacao agro-forest, planted-shade cacao agro-forest, to open areas in central Sulawesi, Indonesia. They determined species richness, abundance, turnover, and community composition in all habitat types and related these to environmental correlates, including canopy cover and thickness of leaf litter. Human disturbances create environments that favor some species over others. Lizards and snakes for example, thermoregulate by basking in open patches of sun and it may be better to have several (or many) small openings in the canopy than just one large open patch. Therefore, many small openings in the canopy may be a better predictor for species richness and abundance of lizards. Frogs, on the other hand avoid direct exposure to the sun and a closed canopy may be a predictor of their diversity and abundance. Wanger and colleagues used Bayesian model selection to identify the best environmental predictors for amphibian and reptile species richness and abundance, including the lacunarity index (a measure of the degree of gaps) to measure canopy heterogeneity. Their results show that amphibians in Sulawesi were more negatively impacted by land-use changes than reptiles. Amphibian species richness and abundance declined as disturbance increased from pristine forest to open areas, while reptile species richness peaked in natural-shade cacao agro-forest between mildly (secondary forest) and strongly (planted-shade cacao agro-forest) disturbed habitats. Studies done in the Neotropics produced similar responses of amphibians and reptiles to disturbance in humid forests.  Thus conserving species of amphibians and reptiles in tropical environments may be best done long-term by allowing shade trees to rejuvenation on cacao plantations and allowing leaf litter to accumulate.

Wanger, T. C.,  D. T. Iskandar, I. Motzke, B. W. Brook, N. S. Sodhi, Y. Clough and T. Tscharntke. 2010. Effects of Land-Use Change on Community Composition of Tropical Amphibians and Reptiles in Sulawesi, Indonesia. Conservation Biology 24: 795–802.

Changing Vegetation & the Herpetofauna

Sceloporus undulatus
Managing forests (logging, reforestation, clearing brush, using herbicides, etc) can have unforeseen consequences for wildlife. As vegetation goes through succession it creates a variety of changing micro-environments that favor some species over others, so as the stages of succession change the animal populations change with them. This concept has been long known and its application to rattlesnakes was noted in Philip Tome’s 1845 book, Thirty Years a Hunter. Tome lived in northeastern Pennsylvania and described frequent encounters with Timber Rattlesnakes (Crotalus horridus).  Tome described the early setters burning forests to control rattlesnakes. Of course, in the long term this opened up the canopy and provided more basking sites. Jäggi and Baur (1999) linked the decline of Viper aspis populations to changes in vegetations, and other authors have made similar reports of changes in snake populations to changes in vegetation.

Kevin Shoemaker and James Gibbs of the State University of New York now report that the Eastern Massasauga (Sistrurus c. catenatus) persists as two isolated populations at the eastern edge of the species’ geographic range, and those two populations are threatened by the increasing density of woody plants. They found microhabitat temperatures were substantially lower at the closed-canopy site, where catenatus selected the warmest available basking sites.
At an open-canopy catenatus selected basking sites that afforded greater cryptic cover. And, they recommend the experimental reduction of shrub cover to improve basking habitat at the closed-canopy site. But they caution that management efforts to reduce shrub cover for basking should maintain adequate cryptic cover, (that is the grasses, leaf litter, rocks, and other cover) used by the snakes to conceal themselves.

In another paper, Charlotte Matthews and colleagues (2010) report that the recent use of prescribed fire and fire surrogates to reduce fuel hazards has spurred interest in their effects on wildlife. They conducted studies to determine the impact of “reducing fuel” in forests on amphibian and reptile populations in areas that were twice burned, had the understory cut mechanically, and in an area that had the understory cut mechanically followed by two burns. They trapped the herpetofauna using pitfall and funnel traps. The study was done at the Green River Game Land, Polk County, North Carolina. The results revealed that salamanders were reduced in number in the twice burned, mechanically opened habitats – possibly because this site had reduced leaf litter.  While these same habitats supported larger numbers of lizards and snakes, undoubtedly due to the increased number of basking sites and the newly created thermal gradients.

Jaggi, C., and B. Baur. 1999. Overgrowing forest as a possible cause for the local extinction of Vipera aspis in the northern Swiss Jura mountains. Amphibia-Reptilia 20:25–34.

Matthews, C. E., C. E. Moorman, C. H. Greenberg, and T. A. Waldrop. 2010. Response of Reptiles and Amphibians to Repeated Fuel Reduction Treatments. Journal of Wildlife Management 74(6):1301-1310.

Shoemaker, K. T. and J. P. Gibbs. 2010. Evaluating basking-habitat deficiency in the threatened Eastern Massasauga Rattlesnake. Journal of Wildlife Management 74(3):504-513.

Tome, P. 1854. (1989 reprint) Pioneer Life; or, Thirty Years a Hunter. Baltimore: Gateway Press.