Modeling the potential impact of climate change on range expansion in Eleutherodactylus cystignathoides (Anura)

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Rebecca T. Chastain, Biology, UT Rio Grande Valley, Edinburg, TX and Teresa Patricia Feria Arroyo, Biology, The University of Texas Rio Grande Valley, Edinburg, TX

Background/Question/Methods
Climate change has already begun to induce changes in the distributions of many species, causing declines, range shifts, and habitat loss, as well as facilitating invasions. Climate change has been a broad contributor to the global amphibian decline currently underway, leading to mass extinctions and extirpations of amphibian populations over the last and coming decades. The critically understudied direct-developing Eleutherodactylus cystignathoides, or Rio Grande chirping frog (Anura: Eleutherodactylidae), is a notable outlier, having rapidly expanded its known distribution in recent years. Originally found in the lower Rio Grande Valley and a narrow strip of northern Mexico, E. cystignathoides has now established populations far into north and east Texas, as well as in southern Louisiana and Alabama. This expansion has largely been dismissed as ecologically neutral due to lack of evidence of negative impact; however, no investigation has occurred into the potential impacts of this species in its non-native range whatsoever, meaning its impact is essentially unknown. The dearth of information about this species’ dispersal and ecology, coupled with the documented negative impacts of other successful Eleutherodactylid invaders such as E. coqui or E. planirostris, warrants investigation that preempts waiting for any potential consequences of this invasion to make themselves known. To conduct such an investigation into the potential range limits of this species as they are defined by climatic variables, both now and in the future, we used spatially rarefied presence data and selected future climate models to develop Maxent projections of the potentially suitable habitat of E. cystignathoides in the southern and eastern United States.
Results/Conclusions
Our preliminary models suggest the existence of currently non-invaded potentially suitable habitat under both current and future models. Particularly, the future projection models predict significant expansion of suitable habitat along the Gulf and Atlantic coasts, as well as in the lowlands around the Appalachian and Ozark-Ouachita formations. In addition, we present projections which suggest that this species may experience climate-induced habitat loss in its native range in south Texas and northern Mexico. These results are cause for concern, especially because the impact of E. cystignathoides on other amphibian populations is uncharacterized in terms of its capacity to compete, displace, hybridize, or spread disease; it is also unknown if this frog will have additional negative impacts on the trophic interactions of the habitats it is introduced to. We encourage caution in managing the spread of E. cystignathoides and other direct-developing frogs.