Are metapopulation species drivers of metacommunity structure in sandstone outcrop communities?

Abstract

Questions The extent to which metacommunities contain species exhibiting metapopulation dynamics is poorly understood. We investigate this issue within sandstone outcrop plant communities scattered across an upland hardwood forest. We investigate the life forms of metapopulation species and relationships between taxonomic, phylogenetic, and functional diversity, composition, and environmental factors. Location Twenty‐three sandstone outcrop communities in southern Illinois, USA. Methods Following vegetation surveys, species exhibiting metapopulation dynamics were identified and compared to all species based on origin, growth form, and lifecycle. Cohesion, turnover, and boundary clumping were utilized to determine metacommunity structure. Correlations evaluated associations between site‐based variables, and regressions evaluated associations between diversity indices. Multivariate analyses compared sites to determine which variables contributed to compositional differences. Results Twenty of 130 species exhibited metapopulation dynamics and were usually annual or biennial exotics. Metacommunity elements indicated a metacommunity structure where groups of species tended to replace one another across sites, in which species exhibiting metapopulation dynamics were subordinate as opposed to dominant or transient. The largest sites were the most regularly shaped, but not the most diverse. Species richness and species exhibiting metapopulation dynamics determined phylogenetic and functional diversity, but largely non‐standardized measures of diversity, indicating independence between types of diversity. Multivariate analyses showed that diversity metrics explained community composition differences, where more species‐rich sites with more metapopulation species were also more phylogenetically and functionally diverse. Conclusions Sandstone outcrop communities exhibited diverse plant communities, where phylogenetic and functional diversity were driven by both the number of all species and the subset of metapopulation species independently. SM dynamics were usually short‐lived and exotic species with their low number likely constrained via dispersal limitations. The communities exhibited a metacommunity structure indicating predictable community assemblages which tend to be replaced with others as opposed to just individual species being replaced individually, consistent with the concept of an integrated community. Functional traits indicated that these communities include species adapted to xeric, substrate‐poor conditions.