Temporal and spatial diversification along the Amazonia-Cerrado transition in Neotropical treefrogs of the Boana albopunctata species group.

Despite extensive research on biodiversity in Neotropical forests, biodiversity in seasonally dry, open biomes in South America has been underestimated until recently. We leverage a widespread group, Boana albopunctata, to uncover cryptic lineages and investigate the timing of diversification in Neotropical anurans with a focus on dry diagonal biomes (Cerrado, Caatinga and Chaco) and the ecotone between Amazonia and the Cerrado. We inferred a multilocus phylogeny of the B. albopunctata species group that includes 15 of 18 described species, recovered two cryptic species, and reconstructed the timing of diversification among species distributed across multiple South American biomes. One new potential species (B. aff. steinbachi), sampled in the Amazonian state of Acre, clustered within the B. calcara-fasciata species complex and is close to B. steinbachi. A second putative new species (B. aff. multifasciata), sampled in the Amazonia-Cerrado ecotone, is closely related to B. multifasciata. Lastly, we place a recently identified Cerrado lineage (B. aff. albopuncata) into the B. albopunctata species group phylogeny for the first time. Our ancestral range reconstruction showed that species in the B. albopuctata group likely dispersed from Amazonia-Cerrado into the dry-diagonal and Atlantic Forest. Intraspecies demography showed, for both B. raniceps and B. albopunctata, signs of rapid expansion across the dry diagonal. Similarly, for one clade of B. multifasciata, our analyses support an invasion of the Cerrado from Amazonia, followed by a rapid expansion across the open diagonal biomes. Thus, our study recovers several recent divergences along the Amazonia-Cerrado ecotone in northern Brazil. Tectonic uplift and erosion in the late Miocene and climate oscillations in the Pleistocene corresponded with estimated divergence times in the dry diagonal and Amazonia-Cerrado ecotone. Our study highlights the importance of these threatened open formations in the generation of biodiversity in the Neotropics.

Rapid adaptation to cold in the invasive cane toad Rhinella marina.

Understanding rapid adaptation to novel environments is essential as we face increasing climatic change. Invasive species are an ideal system for studying adaptation as they are typically introduced to novel environments where they must adapt if they are to persist. We used the invasive cane toad, Rhinella marina, to investigate the contribution of plasticity and evolution to rapid adaptation in a novel environment. Rhinella marina is a neotropical toad that has invaded areas with climates outside of its native environmental niche. The goal of this research was to understand how cane toads persist in northern Florida, the coldest region of their combined natural and invasive range, and originally thought to be beyond their thermal breadth. We measured Critical thermal minima in cane toads from the original, warm introduction location (Miami), and their northern range edge (Tampa) to determine whether northern toads were more cold-tolerant, and to examine the contribution of adaptive plasticity and evolution to any changes in tolerance. Our results show that following acclimation to cold temperatures, southern toads are less tolerant of cold than northern toads. This persistent population difference implies selection for cold-tolerance in northern populations. Differences in individual responses indicate that plasticity is also involved in this response. Our findings have implications for conservation because predatory cane toad invasions threaten local faunas, especially native amphibians. Characterizing specific adaptive mechanisms that allow R. marina to expand its range will identify evolutionary processes that shape a highly successful invasive species.