Observed niche disparity markedly exceeds levels expected from a Brownian model of ecological diversification, thus providing no evidence for past phylogenetic niche conservatism in these multivariate niches.
Evidence suggests that niche conservatism, i.e., the stability of ecological niches over time, is a common pattern in closely related species and that it is a major force driving allopatric speciation [32] [37].
Generally, these models are based on an understanding of the modern ecological parameters of species, and often incorporate an assumption of niche conservatism, i.e. the idea that ecological niches are maintained over long time scales [4] [6].
The 88 % overlap indicates strong niche conservatism.
Under niche conservatism, species maintain the parameters of their original ecological niche through time.
Among other reasons for the observed patterns, the tropical niche conservatism is invoked as an explanation.
However, the degree of niche conservatism declined significantly during the invasion interval (Dudei and Stigall 2010; Malizia and Stigall 2011).
During the gradual abiotic changes of the pre-invasion interval, species exhibited high levels of niche conservatism.
The fact that they are allopatric suggests they are too similar ecologically to coexist (termed niche conservatism; see McCormick et al. 2010), and hence, they remain allopatrically distributed.
Species that persisted through the invasion interval may have exhibited one of two end-member responses to invasion pressure: niche conservatism or niche evolution (Stigall 2012b).
For example, closely related species might have a similar pattern of interaction, simply because of niche conservatism (Rezende et al. 2007).
