A coalescent framework for comparing alternative models of population structure with genetic data: evolution of Celebes toads

Abstract

Isolation of populations eventually leads to divergence by genetic drift, but if connectivity varies over time, its impact on diversification may be difficult to discern. Even when the habitat patches of multiple species overlap, differences in their demographic parameters, molecular evolution and stochastic events contribute to differences in the magnitude and distribution of their genetic variation. The Indonesian island of Sulawesi, for example, harbours a suite of endemic species whose intraspecific differentiation or interspecific divergence may have been catalysed by habitat fragmentation. To further test this hypothesis, we have performed phylogenetic and coalescent-based analyses on molecular variation in mitochondrial and nuclear DNA of the Celebes toad ( Bufo celebensis ). Results support a role for habitat fragmentation that led to a population structure in these toads that closely matches distributions of Sulawesi macaque monkeys. Habitat fragmentation, therefore, may also have affected other groups on this island.

Synchronous diversification of Sulawesi’s iconic artiodactyls driven by recent geological events

“…Populations of Babirusa and SWP in these zones of endemism were also strongly morphologically differentiated ( Figure 2). Altogether, these data and analyses indicate that, despite some differences, the zones of endemism identified in tarsiers, macaques, toads and lizards [18,[40][41][42][43][44][45]47] are largely consistent with the population structure and morphological differentiation in the three species studied here. This is particularly striking for the north arm of Sulawesi (NW, NC, and NE in Figure 4), where we identify two highly differentiated populations (reflected in both mtDNA and nuclear data sets) in all three taxa.…”

Sex-Linked Inheritance in Macaque Monkeys: Implications for Effective Population Size and Dispersal to Sulawesi

“…All of these assumptions are undoubtedly violated to some degree, and in particular, none of the models we tested accommodate macaque population structure on Sulawesi (Evans et al 2001(Evans et al , 2003, as in, for example, Evans et al (2008). Although violation of some model assumptions can lead to biased parameter estimates (Becquet and Przeworski 2009), the estimated divergence time from Borneo M. nemestrina recovered from the analysis using all Sulawesi macaques is similar to that recovered using only the western population of M. tonkeana.…”

The Biogeography of Sulawesi Revisited: Is There Evidence for a Vicariant Origin of Taxa on Wallace's “Anomalous Island”?

“…However, subsequent to colonization of the island, geology, or climate-related changes in paleogeography seem to have played an important role in driving diversification processes on Sulawesi. A pronounced and at least partly congruent geographic structure of Sulawesi populations or species has been found in all taxa that have been sufficiently extensively sampled on the island (see, e.g., Bridle et al 2001;Evans et al 2003cEvans et al , 2008Larson et al 2005;Brown et al 2010;T. von Rintelen et al unpubl.…”