Effects of Fragmentation and Sea-Level Changes upon Frog Communities of Land-Bridge Islands off the Southeastern Coast of Brazil

Abstract

We investigate the composition of anuran communities of land-bridge islands off the southeastern coast of Brazil. These islands provide natural long-term experiments on the effects of fragmentation in the Brazilian Atlantic Forest (BAF). We hypothesize that Pleistocene sea-level changes, in combination with other abiotic variables such as area and habitat diversity, has affected anuran species richness and community composition on these islands. Data from the literature and collections databases were used to produce species lists for eight land-bridge islands and for the mainland adjacent to the islands. We assess the effects of area, number of breeding habitats and distance to the mainland upon anuran species richness on land-bridge islands. Additionally we use nestedness analysis to quantify the extent to which the species on smaller and less habitat-diverse islands correspond to subsets of those on larger and more diverse ones. We found that area has both direct and indirect effects on anuran species richness on land-bridge islands, irrespective of distance to the mainland. However, on islands with comparable sizes, differences in species richness can be attributed to the number and quality of breeding habitats. Anuran communities on these islands display a nested pattern, possibly caused by selective extinction related to habitat loss. Common lowland pond-breeders were conspicuous by their absence. In the BAF, the conservation of fragments with a high diversity of breeding habitats could compensate for the generally negative effect of small area upon species richness. We suggest that sea-level changes have an important role in shaping composition of anuran species on coastal communities.

Local and Landscape Factors Driving the Structure of Tropical Anuran Communities: Do Ephemeral Ponds have a Nested Pattern?

“…NESTEDNESS AND COMMUNITY STRUCTURE.-We did not detect a nested pattern in the anuran communities studied, which contrasts with the nested structure found in other frog communities in islands (Yiming et al 1998, Hecnar et al 2002, Bittencourt-Silva & Silva 2014, ponds (Hecnar & M'Closkey 1997, Werner et al 2007, or forest fragments (Vallan 2000, Watling et al 2009). For example, in a study evaluating the tadpole communities in 37 ponds, those that were found in ponds with high canopy cover, small area, and short hydroperiod were nested subsets of those with contrasting characteristics (Werner et al 2007).…”

“…, Hecnar et al . , Bittencourt‐Silva & Silva ), ponds (Hecnar & M'Closkey , Werner et al . ), or forest fragments (Vallan , Watling et al .…”

“…). In frog communities of land‐bridge islands also in the Rio de Janeiro state most lowland ephemeral‐pond breeding frogs were absent, but were abundant in the adjacent mainland (Bittencourt‐Silva & Silva ). A process of selective extinction was suggested as the main driver of nested pattern in these insular frog communities, possibly because of the rise of sea level (Bittencourt‐Silva & Silva ).…”

“…Nestedness commonly occurs in animal and plant communities when the sets of species in species-poor sites are subsets of the species present in the species-rich areas (Almeida-Neto et al 2008, Frick et al 2009, Ulrich et al 2009, Wang et al 2010. Selective extinction and colonization may produce nested distribution patterns in patchy environments (Hecnar & M'Closkey 1997, Werner et al 2007, Watling et al 2009, Bittencourt-Silva & Silva 2014, based on the assumptions of island biogeography theory that extinction rates are inversely related to patch area, and that colonization rates are inversely related to patch isolation (MacArthur & Wilson 1967). A nested structure can result from constraints of natural or human origin, such as elevation and habitat heterogeneity, landscape changes, and resource specialization (Ulrich et al 2009, Tinker et al 2012, Torn es & Ruh ı 2013, Dauby et al 2014.…”

Phylogeography of West Indies Coral snakes (Micrurus): Island colonisation and banding patterns

“…In the western Caribbean, two species inhabit islands, Micrurus nigrocintus in the Greater Corn Islands and Corn Islands, east of Nicaragua and M. ruatans is the islands of Roatán, off the coast of Honduras (Crother, ), both these islands were connected to the mainland during the Pleistocene (Petuch, ; Woodburne, ). In South America, M. corallinus inhabits several coastal Brazilian islets (Cicchi, Sena, Peccinini‐Seale, & Duarte, ), which were connected to the mainland when sea level fell between 10–20 Kya (Bittencourt‐Silva & Silva, ; Bueno, Schmidt Dias, & Stelle, ; Violante & Parker, ). Hence, New World coral snakes seem to lack the long‐distance dispersal capabilities of other snakes (e.g.…”