Ganci, C. C. | bioRxiv Science

bioRxiv2020

High species turnover shapes anuran community composition in ponds along an urban-rural gradient

The rapid expansion of urban areas in which natural and semi-natural areas are replaced by human infrastructure, such as buildings and streets, is a major threat to biodiversity worldwide. However, little is known about how the structure of biotic communities is affected by urbanization in the tropics. Here, we tested the effect of land use types in urban and peri-urban areas on frog species richness and community composition in central Brazil. We selected 20 ponds differing in size and surrounding levels of urbanization as well as natural forest cover. We then used a Poisson GLM and a distance-based Redundancy Analysis (db-RDA) to relate species richness and community composition, respectively, to environmental variables. Variation in species richness was best explained by pond size (positive effect) and amount of urbanization (negative effect) in the surrounding 500 m. Community composition was mainly driven by species turnover than by nestedness, with db-RDA showing that turnover was explained primarily by urban infrastructure and forest cover. Our results indicate that urbanization negatively influences species richness. Moreover, as the amount of urbanization increased, several species were replaced by others taxa that appear better adapted to urban environments. Our results indicate that maintaining large ponds with surrounding native vegetation in urban environments might be an effective strategy for conserving frog communities.

ecology↗

bioRxiv2020

Harlequin Frogs (Lysapsus) prefer mild places to park

Temperature affects most aspects of ectotherms life history, including physiology and behavior. Studying thermal sensitivity of jumping performance in frogs can help understanding the influence of temperature on different aspects of frog life. Still, studies on the effects of temperature on amphibians are commonly carried out on terrestrial and tree species, creating a gap for aquatic species. We experimentally tested the thermal sensitivity of jumping performance of the Uruguay Harlequin Frog, Lysapsus limellum, assessing three measures: response time, distance of first jump, and total distance travelled. We hypothesized that individuals submitted to extreme temperatures would increase response time, decrease first jump distance, and increase total jump distance. We used an arena with a gradient of air temperature (Ta) ranging from 20 to 40 {degrees}C. We placed frogs at different Ta and stimulated them to jump. Then, we analysed the influence of Ta on the three estimates of jumping performance, using generalized additive models. We found that temperature affected all three measurements of jumping performance, but some relationships were stronger than others. Extreme temperatures increased response time, reduced first jump distance, and increased total distance. The effect was weaker for response time and first jump distance, but substantially stronger for total distance jumped. Although individuals under extreme temperatures experience a reduced jumping performance, they travelled longer distances to find areas with milder temperatures. Thus, we showed that L. limellum thermoregulates by means of behavior, moving through places at different thermal conditions. Additionally, benefits of displacing to thermally suitable places -in terms of enhanced jumping performance-are bigger than the costs of jumping at reduced locomotor performance, at least under experimental conditions. Our results can help understand how climate change affects the locomotor performance of Neotropical amphibians.

ecology↗