Understanding local diversity, turnover and community structure are key goals in community ecology. Increasingly, trait based approaches are used to identify generalities across communities- however this is generally constrained to specific fields and taxa (ie studies of tropical trees). I compare phytophagous insect (Hemiptera) functional and taxonomic diversity across community succession using a space for time chronosequence, and the role of environmental and spatial variables associated with this succession in explaining turnover in species composition.
I sampled arboreal arthropod communities on the Hawaiian Islands, where geological ages of the substrate range from historic to Pleistocene. Native Hawaiian mesic forests are dominated by the polymorphic tree species Metrosideros polymorpha, allowing comparison of arboreal phytophagous insect communities on the same host across age and community development. I use novel model-based methods for multivariate abundance data as well as constrained ordination to analyze community composition. I compiled traits based on literature and morphological measurements related to mobility and resource use as well as body size.
Results/Conclusions
Results indicate that Hemiptera species richness and abundance peaks at intermediate age high productivity plots. Similarly, turnover in taxonomic species composition is driven primarily by foliar nitrogen availability. In contrast, functional richness increases across geological age. Communities on younger substrates are functionally similar with the largest dissimilarities in functional composition being with the community on the oldest substrate. This response is driven primarily by differences in traits related to mobility; species on the oldest site have longer metatibia proportionate to their protibia indicating higher speed of movement and better jumping ability, larger wing areas and large body sizes. This fits with the hypothesis that young substrates are dominated by small organisms that arrive mostly by wind dispersal, where the increased structural complexity of the habitat on older substrates gives rise to communities with traits that facilitate navigation of complex forest. These results shed light on the structure of phytophagous insect communities across forest succession and the importance of considering community assembly from a functional perspective.