Drivers of geographical patterns of North American language diversity.

Although many hypotheses have been proposed to explain why humans speak so many languages and why languages are unevenly distributed across the globe, the factors that shape geographical patterns of cultural and linguistic diversity remain poorly understood. Prior research has tended to focus on identifying universal predictors of language diversity, without accounting for how local factors and multiple predictors interact. Here, we use a unique combination of path analysis, mechanistic simulation modelling, and geographically weighted regression to investigate the broadly described, but poorly understood, spatial pattern of language diversity in North America. We show that the ecological drivers of language diversity are not universal or entirely direct. The strongest associations imply a role for previously developed hypothesized drivers such as population density, resource diversity, and carrying capacity with group size limits. The predictive power of this web of factors varies over space from regions where our model predicts approximately 86% of the variation in diversity, to areas where less than 40% is explained.

Ancestral reconstruction of reproductive traits shows no tendency toward terrestriality in leptodactyline frogs.

BACKGROUND: Traditionally, the evolution of terrestrial reproduction in anurans from ancestors that bred in water has been accepted in the literature. Still, the existence of intermediate stages of water dependency, such as species that lay eggs close to water (e.g., in burrows) instead of in bodies of water, supports the hypothesis of an ordered and gradual evolution in the direction of a more terrestrial form of reproduction. However, this conventional view has recently been challenged for some anurans groups. Leptodactylinae frogs are a remarkable example of anurans with an outstanding diversity in terms of reproductive features, with distinct water dependency among lineages. Here, we tested the hypothesis of a gradual and ordered tendency towards terrestriality in Leptodactylinae, including the existence of obligatory intermediate stages, such as semi-terrestrial reproductive strategies. We also addressed the association between reproductive modes and the morphological and ecological features. RESULTS: An ancestral reconstruction analysis indicated that even though shifts from aquatic to terrestrial breeding occurred throughout the history of Leptodactylus and Adenomera, shifts from terrestrial to aquatic reproduction happened at almost the same frequency. Our results also demonstrated that reproductive modes for semi-terrestrial tadpoles were not necessarily an intermediate form between aquatic and terrestrial breeds. Correlations among reproductive modes and other life-history traits suggested that tadpole environment, clutch size, nuptial spines, and egg pigmentation were co-evolving and driven by water dependency. CONCLUSIONS: Our results found no evidence of evolutionary tendencies toward terrestriality in Leptodactylinae. We found reversals from terrestrial to aquatic tadpole development and no evidence of obligatory intermediate stages, such as semi-terrestrial reproductive strategies. We also found correlations between reproductive modes and other life-history traits driven by water dependence. Aquatic reproductive modes are associated with higher clutch sizes, lentic waters, and the presence of nuptial spines and egg pigmentation.

Diversidade de anuros (Amphibia) em áreas recuperada de atividade mineradora no cerrado e de plantio de Eucalyptus urophyla no Brasil Central / Anura diversity (Amphibia) in recovered areas of mining activity in cerrado and Eucalyptus urophyla planting in Central Brazil

A diversidade de anfíbios no Cerrado é ameaçada principalmente pelo aumento das atividades antrópicas. A legislação vigente exige de empreendimentos potencialmente impactantes a implantação de programas ambientais que incluem a recuperação de áreas degradadas e o estudo dos mecanismos ecológicos associados à recolonização de áreas alteradas. Os objetivos deste estudo foram: avaliar possíveis diferenças na composição de espécies em assembléias de anuros entre áreas de topografia modificada (ATM) e áreas de topografia não modificada (ATNM); e comparar a riqueza de anuros entre ATM e ATNM. Apesar do maior número de espécies registradas na ATM (28 espécies) em relação à ATNM (22 espécies), não houve diferença na riqueza quando comparamos as curvas de rarefação ou a riqueza estimada (jackknife1). Entretanto, as duas assembléias diferiram quanto às curvas de abundância relativa, especialmente quanto ao padrão das espécies mais abundantes. Localmente, a análise de co-ocorrência demonstrou que as espécies na ATM co-ocorrem menos do que o esperado ao acaso, o que indica a partilha dos ambientes para reprodução mediada por interações competitivas. A presença de corpos d'água artificiais com alta heterogeneidade estrutural, associados a fragmentos florestais em bom estado de conservação são fatores que contribuem para a manutenção de uma alta diversidade de anfíbios na área.