Dendropsophus gaucheri

Fouquet, Antoine, Noonan, Brice P., Blanc, Michel & Orrico, Victor Goyannes Dill, 2011, Phylogenetic position of Dendropsophus gaucheri (Lescure and Marty 2000) highlights the need for an in-depth investigation of the phylogenetic relationships of Dendropsophus (Anura: Hylidae), Zootaxa 3035, pp. 59-67 : 65

Dendropsophus gaucheri : Distribution and Evolutionary History

All specimens of D. gaucheri analyzed herein are not only recovered as a monophyletic group but also display strikingly little genetic distance among them (Mean K2P distance = 0.009). Even if not included in the molecular analyses the conspecificity of the populations in isolated savannas in Pará ( Brazil) is unambiguous. This confirms the occurrence of D. gaucheri populations over the eastern part of the Guiana shield. This species is co-occurring in this region with at least four other member of the D. microcephalus group ( D. leali , D. minusculus , D. sp. & D. nanus ).

The type locality (Sinnamary, French Guiana) is situated on the oriental limit of a formation of coastal savannas occurring almost continuously through Suriname to the eastern coast of Guyana. According to Ávila-Pires et al. (2010) D. gaucheri also occurs in coastal savannas of Suriname. Therefore the species probably occurs throughout this area, possibly as far as Guyana and even Venezuela. On the east however, one hilly forested area on the French Guiana coast apparently constitutes a barrier that limits the connection with coastal savannas in Amapá ( Brasil). This region represents a distributional edge for many open habitat species ( Lescure & Marty 2000). However, as the species is known to also occur in isolated savannas in the interior of the Guiana shield close to the Amazon River, it seems likely that D. gaucheri also occurs in the coastal savannas in Amapá.

Interestingly, the genetic distance between the sample from French Guiana and samples from interior savannas is low. Given the fragmented distribution of the habitat of this species, this isolation is probably recent. Since the data are very limited, any further interpretation is subject to caution. Nevertheless, we argue that these data provide interesting support for hypothesized forest openings during Quaternary, a highly controversial subject ( Haffer 2008; Colinvaux et al. 2000; Bush 1994). A similar pattern of isolated populations with low genetic divergence has been observed in Crotalus durissus by Wüster et al. (2005). They interpreted such pattern in an open habitat species as the testimony of dispersal during periods of forest opening in Amazonia. Initially, the observed biogeographic patterns in Amazonia led Haffer (1969) to suggest isolation of moist forest refugia during periods of increased aridity coincident with temperate glacial maxima. However, palynology, geomorphology ( Colinvaux et al. 2000) and climate modeling ( Mayle et al. 2004) suggests that Quaternary climatic changes were not strong enough to produce broad fragmentation of Amazonian forest. Though there is little empirical data supporting broad scale turnover of biomes (forest vs. savannas) within Amazonia, there is evidence that peripheral and ecotonal areas, like in the GS, have suffered reduced precipitation and forest fragmentation ( Mayle et al. 2004). In French Guiana, palynological evidence suggests two phases of forest retreat at least during the Holocene ( Ledru et al. 2000) and charcoal deposits indicate widespread burning during this time ( Charles-Dominique et al. 1998). Moreover, patches of savanna and different types of forests peppered through the eastern GS are the testimony of these recent changes in vegetation distribution ( Servant 2000). Further investigation focusing on comparing phylogeographic patterns across open habitat adapted species vs. forest adapted species should provide important insights into how these changes have impacted biodiversity in Amazonia.