Into and out of the tropics: the generation of the latitudinal gradient among New World passerine birds

摘要: Aim One prominent explanation for the latitudinal gradient in biodiversity proposes that its prime cause is greater age and/or higher origination rates of tropical clades, and infrequent or delayed dispersal their component species into temperate regions. An alternative species’ carrying capacities vary regionally, which influences time-averaged diversification via ecological opportunity. We contrast these hypotheses, order to assess potential historical upon New World passerine birds (order Passeriformes), comparing patterns among two suborders present (oscines suboscines), are known have had different routes across region. Location New World. Methods We examine diversity patterns, abiotic biotic correlates, distributions phylogenetically old young species. Results Strong gradients within both oscine suboscine birds, with maximum towards equator, but overall shapes differ. Among oscines, older lineages found north, progressively younger further south. Regional variation richness statistically well explained by a combination productivity elevation (R2 = 0.76). In contrast, few groups colonized so current correlated temperature seasonality (R2 = 0.74). Main conclusions Because oscines Americas from must reflect regional differences rates, not time region. The derived phylogenetic data strong predictive power normalized difference vegetation index (NDVI) suggest radiation consistent idea entry new region stimulates burst diversification, continues longer areas capacity. Conversely, potentially large barrier niche conservatism climatic tolerances, possibly coupled competition oscines. Although contemporary conditions can explain much history has an important influence on taxonomic composition this gradient.