Some Differences between Invasion-Structured and Coevolution-Structured Competitive Communities: A Preliminary Theoretical Analysis

Abstract

Two algorithms are proposed which stimulate the buildup of island faunas. The 1st assembles communities using Lotka-Volterra population dynamics to determine the outcome of the invasions and the 2nd alternates population dynamic events with the coevolution of the competitors in this community. The communities formed in the 1st algorithm are called invasion-structured communities and those from the 2nd algorithm coevolutionary communities. Invasion-structured communities have more species and are more vulnerable to disturbance than are coevolutionary communities. The faunal-buildup paths leading to these communities show complex branching, but do not show community cycling (the path of faunal buildup does not repeat itself). When asymmetry is present in interspecific competition, invasion-structured communities have species distributions skewed towards the niche positions that have a competitive advantage. Coevolutionary communities show less diversity than comparable invasion-structured communities. With asymmetric competition the faunal buildup process always involves community cycling and coevolution-mediated species turnover. With coevolution, asymmetric competitioin causes the distribution of niche positions occupied by community members to be skewed towards the niche position with a competitive disadvantage. The coevolutionary faunal buildup algorithm can explain the patterns of distribution noted in the Anolis lizards of the Lesser Antilles, as well as several aspects of Wilson''s taxon cycle.