Global patterns of speciation and diversity

Abstract

In recent years, strikingly consistent patterns of biodiversity have been identified over space, time, organism type and geographical region. A neutral theory (assuming no environmental selection or organismal interactions) has been shown to predict many patterns of ecological biodiversity. This theory is based on a mechanism by which new species arise similarly to point mutations in a population without sexual reproduction. Here we report the simulation of populations with sexual reproduction, mutation and dispersal. We found simulated time dependence of speciation rates, species-area relationships and species abundance distributions consistent with the behaviours found in nature. From our results, we predict steady speciation rates, more species in one-dimensional environments than two-dimensional environments, three scaling regimes of species-area relationships and lognormal distributions of species abundance with an excess of rare species and a tail that may be approximated by Fisher's logarithmic series. These are consistent with dependences reported for, among others, global birds and flowering plants, marine invertebrate fossils, ray-finned fishes, British birds and moths, North American songbirds, mammal fossils from Kansas and Panamanian shrubs. Quantitative comparisons of specific cases are remarkably successful. Our biodiversity results provide additional evidence that species diversity arises without specific physical barriers. This is similar to heavy traffic flows, where traffic jams can form even without accidents or barriers.

Espaço e diversificação: uma perspectiva teórica

“…In accordance to earlier work (de Aguiar et al 2009), an initial period of diversification rapidly ceased as raising extinction rates counteracted speciation. After this initial diversification phase, two distinct behaviors were observed in the simulations.…”

“…This indicates that this effect is probably not an artifact of a particular implementation of the model. Accordingly to ecological data and previous theoretical investigations, simulations set in one-dimensional environments reached a more biodiverse steady state than those set in two-dimensional environments (de Aguiar et al 2009;Moyle and Cech 2004), as long as the mutation rates were below the critical value. However, for mutation rates above the critical values, the species richness steady states for simulations ran in both one and two-dimensional environments were equivalent regardless of the mechanism behind the spatial patterning (figure 3) as well as the species distributions (figure 4).…”

“…Simulações espaciais adotando modos de especiação realistas baseados em paisagens adaptativas esburacadas geraram distribuições de diversidade compatíveis com as previsões originais da teoria neutra e também com padrões observados (de Aguiar et al 2009). Posteriormente foi mostrado que esse tipo de mecanismo de especiação é contingente às propriedades geográficas das simulações (Martins, de Aguiar, and BarYam 2013).…”

“…Following (de Aguiar et al 2009) each prey was endowed with a haploid binary genome of 100 loci, initially all set to zero. In order to reproduce, a prey would select a potential mate within a geographic and genetic distance.…”

“…The migration distance of the prey is also expected to affect the rate of speciation, as it promotes the spread of emerging genetic diversity, and consequently decelerates regional differentiation (de Aguiar et al 2009). Because of this, comparisons where only drawn between simulations where prey migrated taking the same step sizes (one lattice unit).…”