Evolutionary Substitution and Replacement in N-Species Lotka-Volterra Systems

The successful invasion of a multi-species resident system by mutants has received a great deal of attention in theoretical ecology but less is known about what happens after the successful invasion. Here, in the framework of Lotka-Volterra (LV) systems, we consider the general question where there is one resident phenotype in each species and the evolutionary outcome after invasion remains one phenotype in each species but these include all the mutant phenotypes. In the first case, called evolutionary substitution, a mutant appears in only one species, the resident phenotype in this species dies out and the mutant coexists with the original phenotypes of the other species. In the second case, called evolutionary replacement, a mutant appears in each species, all resident phenotypes die out and the evolutionary outcome is coexistence among all the mutant phenotypes. For general LV systems, we show that dominance of the resident phenotype by the mutant (i.e. the mutant is always more fit) in each species where the mutant appears leads to evolutionary substitution/replacement. However, it is shown by example that, when dominance is weakened to only assuming the average fitness of the mutants is greater than the average for the resident phenotype, the residents may not die out. We also show evolutionary substitution occurs in two-species competitive LV systems when the initial invasion of the resident system (respectively, of the new coexistence system) is successful (respectively, unsuccessful). Moreover, if sequential evolutionary substitution occurs for either order that the two mutant phenotypes appear (called historically independent replacement), then it is shown evolutionar

Broad scale variation in seagrass benthic macrofaunal assemblages along the coast of Japan

Broad scale studies in seagrass benthic macrofauna are important for future regional marine conservation. We examined spatial variation in the community structure of seagrass-associated benthic macroinvertebrates collected by sediment coring in 2010 at six seagrass sites of Japan covering the latitudinal range of 24A degrees-43A degrees N. Total species richness and ES(50) at site level did not show clear site variations and relationship with latitude. At core level, site variations of mean species richness, ES(50), Simpson diversity and abundance showed inconsistent pattern, but with more cases of statistically significant association with latitude. Variations were generally influenced by the seagrass species, often among subtropical species, among temperate Zostera species, and between Zostera and subtropical species. Finally, the community composition differed significantly across all sites and community similarity decreased rapidly with geographic distance, with only 5% similarity retained at the distance of 400 km. The dissimilarity among sites was higher with the similar distance compared to other types of coastal communities such as rocky intertidal assemblages, which is associated with minor occurrence of species with broad distributional range