The drivers of tropical speciation

Abstract

Since the recognition that allopatric speciation can be induced by large-scale reconfigurations of the landscape that isolate formerly continuous populations, such as the separation of continents by plate tectonics, the uplift of mountains or the formation of large rivers, landscape change has been viewed as a primary driver of biological diversification. This process is referred to in biogeography as vicariance. In the most species-rich region of the world, the Neotropics, the sundering of populations associated with the Andean uplift is ascribed this principal role in speciation. An alternative model posits that rather than being directly linked to landscape change, allopatric speciation is initiated to a greater extent by dispersal events, with the principal drivers of speciation being organism-specific abilities to persist and disperse in the landscape. Landscape change is not a necessity for speciation in this model. Here we show that spatial and temporal patterns of genetic differentiation in Neotropical birds are highly discordant across lineages and are not reconcilable with a model linking speciation solely to landscape change. Instead, the strongest predictors of speciation are the amount of time a lineage has persisted in the landscape and the ability of birds to move through the landscape matrix. These results, augmented by the observation that most species-level diversity originated after episodes of major Andean uplift in the Neogene period, suggest that dispersal and differentiation on a matrix previously shaped by large-scale landscape events was a major driver of avian speciation in lowland Neotropical rainforests.

Rates of ecological divergence and body size evolution are correlated with species diversification in scaly tree ferns

“…evolution as primary drivers of diversification in tropical ferns [21,54]. Several studies, especially in animals, have analysed the correlation between ecological or morphological variation and species diversification, but with inconsistent results [10,17,19,20,26,52]. This inconsistency suggests a varying role of ecologically mediated phenotypic evolution in the diversification of different animal lineages [26].…”

“…Variation in species richness, ecology and morphology among lineages is a major feature of evolution [1,10,17,25,26,52]. While there are several reasons to expect a positive correlation between these three aspects of biodiversity, we initially expected species richness in scaly tree ferns to be a function of the age of clades due to their long evolutionary history [4,10,17].…”

“…Many studies have suggested that several groups of plants and animals have accelerated speciation rates in tropical mountains [4,6,8,10,23,25,30]. Ecological and geographical factors have led to the invasion of 'new' ecological space that, facilitated by morphological innovations, has been followed by a dramatic burst in species diversification [5,9,[13][14][15]18].…”

“…In general, differences in species richness can be associated with heterogeneity in the rates of species diversification, but the drivers of such rate heterogeneity remain poorly explored for many groups of species. As exemplified by well-known radiations [7][8][9][10][11], high species diversity is often mirrored by high levels of eco-morphological variation, suggesting that species diversification is linked to evolutionary change [12 -14]. However, little is known about the ubiquity of the coupling between ecological divergence, phenotypic evolution and species diversification.…”

Mitonuclear coevolution as the genesis of speciation and the mitochondrial DNA barcode gap

“…For instance, in a study of radiations of South American birds, it was estimated that 75% of species diverged ≤2.6 million years ago (Smith et al. 2014). Avian speciation is even more rapid at higher latitudes where all sister taxa were estimated to have diverged <1 million years ago (Weir and Schluter 2007).…”