During the month of March we resurveyed amphibian communities along the elevational gradient in the Kosñipata Valley of southern Peru, near Manu National Park. These amphibian communities collapsed during the early 2000s during epizootics of chytridiomycosis, as we have previously documented. Our previous surveys compared anuran communities observed in 2008 and 2009, after chytridiomycosis invaded the valley, with those observed from 1996 to 1999, when we started working in this region. Furthermore, there are rich specimen collections made by teams of the Smithsonian in the early 90s, and Kansas University in the early 70s, which further document the diversity of anuran communities prior to epizootics of chytridiomycosis. Nine years after our last comprehensive survey (2009), we decided to return to the valley and re-sample the same localities from 1200 to 3700 m.
Our previous comprehensive surveys in the wet seasons of 1999, 2008 and 2009 consisted of two approaches: surveys of leaf-litter frogs using 10x10m quadrats, with four quadrats within each 100-m elevational band; and nocturnal surveys along the road that connects the mountain pass of Acjanaco at 3400 m to the town of Chontachaca at 900 m. We returned to the same sites along the road, and repeated the same sampling design during this last wet season. Our field crew included students and recent graduates from the University in Cusco, along with field assistants from the nearby town of Pilcopata, including two people who had already participated in previous surveys. We were able to sample all 100 leaf-litter quadrats (each takes about 2 hours to complete by three people), and to survey at night at elevations up to 3100 m (above 3100 m, nocturnal surveys are not effective because few frogs are active at night).
We captured over 600 frogs over the course of three weeks. Ccommunities of arboreal and stream-breeding frogs observed during nocturnal surveys continue to show a substantial deficit in species richness (see graph). Our data are preliminary because we still need to compute sampling effort, but the snapshot shows a slight recovery in species richness. This pattern is corroborated by "rediscoveries" of a few species that were abundant in 1999, but absent in 2008 and 2009. However, our preliminary data also suggest a decrease in frog density, and confirm that most species that disappeared from 2000 to 2008 continue to be absent from the valley.
We will next process swab samples to examine how infection dynamics have changed over the years. In the years following the epizootics of the early 2000s, prevalence varied widely along the elevational gradient, with populations at mid elevation (1500-2000 m) most infected by the chytrid fungus. We are especially interested in studying current infection patterns in species that have persisted despite being susceptible to chytridiomycosis. Understanding how susceptible species are able to persist and even recover despite the continuous presence of the pathogen may help develop strategies to mitigate the negative effects of the fungal disease on amphibians.
The work of our collaborator Vanessa Uscapi is featured in this beautiful video made by Katie Garrett. Vanessa, seen below weighing a frog with the help of a field assistant, has been working with the frogs of the Madre Selva montane forest near Quincemil, in the Peruvian Andes, for several years. As part of her field work, she discovered a new, minute terrestrial-breeding frog, Noblella madreselva, which we described in 2015. Her studies contribute to the protection of this fragile ecosystem. Many montane forests in the Andes are threatened by logging and the expansion of agriculture. Yet they often contain highly endemic species such as Noblella madreselva and other small frogs that inhabit the humid leaf litter at high elevations.
After our contributions on tadpole thermal performance, we continued investigating the effects of dam-altered thermal regimes on river-breeding amphibians by looking at the consequences of hypolimnetic releases (cold water being released from the bottom of artificial reservoirs) for digestion, assimilation and vulnerability to predators of tadpoles. Our study Consequences of dam‐altered thermal regimes for a riverine herbivore's digestive efficiency, growth and vulnerability to predation, was a collaboration with Dr. Sarah Kupferberger and was published this week in Freshwater Biology.
We again worked on the foothill yellow-legged frog, Rana boylii in California. At present, R. boylii occupies less than half its historic range, due to the existence of large dams in many river systems. During the springs and summers of 2008, 2009 and 2010 we monitored temperature conditions at many breeding sites of R. boylii in regulated (i.e., downstream of dams) and unregulated rivers in northern California (see sensor placed by a rock that was subsequently used as egg attachment site in the image above) to understand changes in thermal regime caused by hypolimnetic releases. We then mimicked the colder conditions existing downstream of dams in experimental settings and investigated how tadpole's digestive efficiency responded to lower temperatures. Finally, we exposed tadpoles of different sizes and developmental stages to natural odonate and hemipteran predators (see a Ranatra eating a tadpole in one of our experimental enclosures in the image below).
Tadpoles reared in cold water had the lowest digestive efficiency of epilithic periphyton, albeit efficiency was ameliorated when tadpoles had access to highly nutritious dinitrogen‐fixing diatoms. However, these nutritious diatoms, which can be common in natural, unregulated rivers are often replaced by unpalatable, poorly nutritious periphyton downstream of rivers. In our experiments, growth rate of tadpoles correlated with assimilation efficiency, which is crucial for R. boylii because tadpoles need to metamorphose and get out of the water by the end of summer and before the fall rains cause deadly river floods. Low growth rate also affected tadpole survival, with small tadpoles much more likely to succumb to predation. Non‐lethal effects of predators on tadpole growth and tail injury, however, depended on both rearing temperature and exposure temperature. Contrary to the expectation that the cost of predator avoidance behaviours may be greater at warmer exposure temperatures because basal metabolic rates are higher, our results indicated that the energetic cost of foraging less was amplified at cool temperatures. Therefore, tadpoles growing in cold water face multiple, synergistic hurdles from lower assimilation efficiency and growth to increased predation by invertebrates, thus contributing to population recruitment bottlenecks.
The lab photo below won first place of the FIU Tropics Photo Contest! Young vicuña (Vicugna vicugna) taking a bath in a high-Andean creek at 13,000 feet. Vicuñas are the smallest of the four species of South American camelids, but they are highly prized because of the very fine fiber that can be produced with their wool. As a consequence of the high economic value of this fiber, vicuñas were driven to near extinction in the 1960s, until biologists promoted the sustainable management of wild populations in the high-Andes of southern Peru. One of the first and most successful project was conducted at Pampas Galeras in Ayacucho (shown in the photograph), today a national reserve honoring the memory of environmental journalist Barbara D'Achille.
Our lab contributed a publication naming two new species of frogs from Manu National Park, further increasing the number of amphibian species of the park. Manu NP already boasts the highest number of amphibian species living inside a natural protected area. The two new species, Pristimantis antisuyu (in the image below) and Pristimantis erythroinguinis (in the image on the left), are closely related but their elevational distributions do not overlap.
Pristimantis antisuyu lives in the cloud forest (image on right with good old Shigella), while P. erythroinguinis is found the Andean foothills and adjacent Amazon lowlands. Both species share with P. cruciocularis the unique pattern of having an iris with a cruciform pattern. Our molecular analyses suggest that P. cruciocularis and the two new species are part of the P. platydactylus-P. llojsintuta species complex, which is likely to contain more cryptic species.
Our paper on frog skin bacteria along the Amazon-Andes elevational transect (500 - 3800 m a.s.l.) was published today in Frontiers in Microbiology. We found lower numbers of anti-Bd isolates at elevations where amphibian declines had been greatest, and high proportion of anti-Bd isolates of high inhibitory strength in Bd-resistant frogs, supporting the idea that symbiotic bacteria play a functional role in amphibian skin defense. Yet this association does not consistently explain the fate of amphibian hosts along the elevational gradient, suggesting complex interactions among bacterial symbionts, hosts, and environmental factors in determining frog persistence in a region of high disease prevalence.
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.
The lab will co-organize a field course on high-elevation amphibians in the spectacular Pampas Galeras Barbara D'Achille National Reserve (see our previous blog here) on 1-6 August 2018. Please contact us for more information, number of participants will be limited. Click here to apply.
See attached document with additional information.
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.
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