Very excited to be going back to the beautiful Archbold Biological Station for a seminar on March 1st at 3:30 pm. I'll be talking about our lab research on fungal disease and amphibian biodiversity. I spent a year at Archbold in 2007, as a postdoc with Henry Mushinsky and Earl McCoy in a project studying the effects of prescribed fire on Florida sand skinks. Archbold protects a large tract of undisturbed Florida scrub, and is restoring adjacent land to help with the recovery of threatened scrub species. This unique ecosystems hosts several endemic species, many of which are adapted to a regime of frequent natural fires. Because of human development and agriculture modification and encroachment into scrub habitats, fire is generally suppressed. But Archbold operates a very active fire management plan that contributes to maintaining the landscape as a mosaic of frequently burned to long unburned patches, benefiting a variety of native organisms.
Our lab contributed to a publication by collaborator Justin Nowakowski published this week (early view) in Ecology Letters. The study explored the hypothesis that ecophysiological traits of amphibians and reptiles, specifically tolerance to heat (i.e., Critical Thermal Maximum of righting reflex), variation in body temperatures experienced by animals in their habitats, and evaporative water loss were associated with sensitivity to habitat modification. Field data from focal studies in Costa Rica and Colombia were supplemented by a meta-analysis drawing from multiple studies and continents. The results of the analyses were generally consistent across locations and communities, and showed that tolerance to heat can explain roughly 40% and up to 2/3 of variation in sensitivity to habitat modification. For example when tropical forests are logged, the loss of canopy cover dramatically increases maximum daily temperatures. Species of amphibians and reptiles that are unable to tolerate the new high temperatures are thus locally extirpated. Because several ecophysiological traits are conserved within families, an association between these traits and sensitivity to habitat modification can help predict impacts of human disturbance on herpetological biodiversity, and develop mitigation strategies to reduce such impacts.
Bryophryne mancoinca is the newest addition to the genus Bryophryne, a genus of 14 species, 13 of which have been described in the past 10 years. And this year has seen the largest number of new Bryophryne species : in addition to B. mancoinca and B. phuyuhampatu, De la Riva and collaborators have described B. quellokunka, B. tocra and B. wilakunka, extending the known geographic range from Department Cusco to Puno. The description of the new B. mancoinca (photo by Alex Ttito) was led by our collaborator Luis Mamani and has been published in the journal Phyllomedusa.
Research by former lab member David Burkart is featured on the cover of the December issue of Animal Conservation, which also publishes an article from David's M.S. thesis. The photograph illustrates a brooding female of Gastrotheca excubitor and her recently hatched newborn froglet from the highlands of Manu National Park in Peru. Embryos undergo direct development within the eggs, which are carried by the female inside a specialized, sealed dorsal pouch. We previously published a blog post regarding David's research on the role of skin peptides and symbiotic bacteria as defenses against fungal disease in these frogs. This research is also in the SIU News this week. Congratulations David!
Another lab contribution was published this week in the journal Zootaxa, describing a new arboreal species of gymnophthalmid lizard (spectacled lizards). This is a fairly large group of lizards distributed in Central and South America, most species are ground-dwelling and inhabit the forest leaf litter, rocky areas or mosses and grasslands at high elevations, but several species are semi-aquatic and can dive, such as species of Potamites. The new species, named Euspondylus excelsum, however is arboreal and was discovered when the lizard's habitat was flooded by a hydroelectric project in the Amazonian slopes of the Andes in Central Peru. Additional surveys in the area surrounding the flooded area failed to find lizards on the ground; instead all captured lizards were found on leaves and other arboreal microhabitats. Photograph by Lesly Luján.
Doctoral candidate Alex Shepack and collaborators have published a review paper on the salamander-killing fungus, Batrachochytrium salamandrivorans (Bsal) in the journal EcoHealth (available here). The study reviews current research on Bsal, which is currently threatening native salamanders in Europe. This virulent fungus has yet to be detected in the Americas, and multiple efforts are under way to prevent its introduction in North America, which supports one of the most diverse salamander fauna. The article also explains the role of the Bsal Task Force, risks associated with the spread of Bsal, and policy measures proposed or enacted to date.
We are excited to announce that our lab is going tropical! We will be moving next January to Florida International University in Miami. The lab will join the Department of Biological Sciences at the main university campus in Miami (Modesto A. Maidique campus). More updates will be posted soon.
A lab contribution published today explores fungal disease-frog host dynamics in the species-rich frog communities of the eastern slopes of the tropical Andes, near Manu National Park in Peru. We have been studying these communities since 1996, when chytrid disease had not yet caused sharp declines in frog species richness and abundance. Following the epizootic of chytridiomycosis that swept southern Peru in the early 2000s, 19 out of 55 species vanished from the cloud forest (1200-3600 m), as reported previously. Unfortunately most of these species have not been seen since then. But how are the surviving species faring in this environment where chytrid is now established?
Our general approach was to compare species vulnerability to infection by chytrid with observed changes in population abundances for eight common species of frogs. We selected these species to maximize sample size, to provide opportunities for within genus comparisons, and to cover the elevational range where we recorded declines. Our infection experiments were difficult to conduct at the remote Wayqecha Biological Station, but dedication and creativity go a long way towards making things possible. In addition to Vance Vredenburg and Andrea Swei from SFSU, our team was composed by then undergraduate students Emily Foreyt (Gonzaga) and Lauren Wyman (Princeton; shown above), and Jacob Finkle (UC Berkeley), who all co-author our publication.
As shown in the survival curve above and the video below, some "survivors" continue to be susceptible to infection by chytrid. In the example here, Pristimantis toftae quickly succumbs to chytridiomycosis following experimental infection; the videos shows tetanic spasms in a highly infected individual. As pane C shows, most individuals in our "control" group (which was supposed to be negative for disease) were infected at low levels, because our itraconazole baths failed to completely clear infection. Although this limits interpretation of our results, it also suggests that the immunoprotective effect of previous Bd exposure might not be a common response across all amphibian species - in fact we saw little evidence for such effect in our species.
Overall, three out of eight tested species are susceptible to chytridiomycosis. Populations of these three species, and of all other species but one, have somewhat to sharply declined during the decade from 1999 to 2009. Phylogenetic relatedness did not appear to be a good predictor of susceptibility: while two Pristimantis species were susceptible, two other species were not. Among Gastrotheca, one was highly susceptible while the second was not; our previous work suggests that anti-fungal skin bacteria might protect the non-susceptible Gastrotheca excubitor.
Does this mean that more species will vanish? While the results of our experiments suggest trouble for several species, other factors such as transmission risks and environmental exposure to fungal propagules play important roles in driving disease-host dynamics. For example terrestrial-breeding frogs such as Pristimantis are less exposed to infection by the aquatic zoospores of the chytrid fungus, because they generally avoid water bodies. On a positive note, populations of some "surviving" species have recently recovered - hopefully a trend that will continue in the future.
Our lab expeditions over the last few weeks led to the rediscovery of a long-forgotten and rarely seen species, Atractus vertebralis. This species was described by Boulenger in 1904, but as far as we know it has not been collected ever since. Boulenger used material collected by Keays around the "Inca mine" of Santo Domingo, near Bahuaja-Sonene National Park. The discovery will allow a better characterization of the species, as well as molecular analyses to reveal the phylogenetic relationships of these poorly known, fossorial snakes.
We found these snakes under a thick layer of wet mosses, along with Proctoporus lizards, terrestrial-breeding frogs of the genus Noblella and the Pristimantis platydactylus group, and Pristimantis danae. In the picture, Isabel Diaz and Alex Ttito are searching for herps along the trail -- despite this being our third day of all-day hiking! There is always some energy left for a nice discovery.
News from the lab