IMPACTS OF PHYLOGENETIC DILUTION AND CONCENTRATION EFFECTS ON SPECIES DIVERSITY AND DISTRIBUTION PATTERNS

In theoretical ecology and community ecology, it is still unclear how phylogenetic community structure and species distributions are linked together. In this paper, a neutral model for evaluating phylogenetic constraints on species diversity and distribution patterns is developed to address these issues. To accomplish this, temporal species distribution and diversity patterns are evaluated and simulated by considering the impact of phylogenetic relatedness of species in a lattice landscape with square grids. A continuous patch for the resultant distributional range map of a species is defined as a group of grids in which the interior grids are adjacent to each other while the edge grids of the patch are isolated from other remaining grids in the range map. The adjacency or isolation of a grid with respect to another grid follows the von Neumann neighborhood criterion. The hypothesis tested is: phylogenetically closely related species tend to avoid each other (phylogenetic dilution), which produces a phylogenetic overdispersion pattern. In this case, all species have similar species abundances and distribution-patch size patterns. In contrast, if closely related species tend to associate together (phylogenetic concentration), a phylogenetic clustering pattern emerges: phylogenetically distinct species tend to have higher abundances and more large distribution patches. Using simulations, this paper presents results which demonstrate the reverse phenomenon: if it is assumed that phylogenetic relatedness of species is modeled as a dilution effect, the resultant distributional maps for evolutionarily distinct species present significantly increased numbers of continuous large patches. An evolutionarily distinct clade tends to have significantly higher relative abundance than other clades in all simulations. It was also found that if phylogenetic relatedness of species is modeled as a concentration effect, the simulated distributional map of each species would present a similar percentage of large patches for both evolutionarily unique and common clades for many cases when the community size is large enough. However, being similar to dilution effect, the resultant species relative abundance for evolutionarily unique clade is significantly higher than that for evolutionarily common clade. In conclusion, evolutionary distinct species will have more chances to survive with high populations and less fragmented distributional range in environments where the phylogenetic dilution effect is functioning. It is hoped that these results contributed to clarifying the complex associations generated by phylogenetic community structure in future ecological and evolutionary studies.