Past studies of phylogentic beta-diversity have examined how it relates to trait-based hypotheses of community assembly across habitat gradients. Again using the chronosequence of the Hawaiian Islands I seek to evaluate how the evolutionary process itself shapes beta-diversity. I am collecting field data on and sequencing five spider lineages distributed on a gradient of adaptive to neutral diversification histories:
- Spiny-leg Tetragnatha, an adaptive radiation
- Ariamnes, a possible, though less diverse, adaptive radiation
- Mecaphesa, a group dominated by dispersal but with some color variation
- Philodomidae, a group with high dispersal and large body size variation
- Orsonwlles, a group with very limited morphological variability and slow allopatric speciation.
I will quantify beta-diversity as the distance decay of phylogenetic similarity and document how it differs between the five different lineages and across the islands. Each lineage represents a different diversification scenario and each island corresponds to a different duration of evolutionary assembly according to its age. Pairwise comparisons of phylogenetic similarity will only be made within the same group and on the same island.
I will use evolutionary rates (speciation, extinction and immigration) reconstructed from each lineages’ phylogeny as covariates in a hierarchical model of distance decay. I will also measure traits directly, instead of assuming correspondence with phylogenetic distance, and include the morphological diversity of each lineage as another covariate in the model.