Hawaiian endemic Nesosydne planthoppers are a species-rich group of monophagous sap-feeders notable for the breadth of their host-plant use. Isolation within and among islands is likely an important factor in this group for promoting species diversity (82 described species; 80% endemic to single-islands), host-use diversity (27 plant families used) and host-specificity (ca. 80% known from only one host-plant). We collected field data on relative abundance and host-use for a subset of Nesosydne from the largest and youngest Hawaiian Island, Hawaii. We compared these factors and constructed a planthopper phylogeny using samples from an isolated habitat patch and nearby continuous habitats. Plant apparency was positively correlated with prevalence of use as a host-plant within and across field sites. The relative abundance of planthoppers on the primary regional host-plant was lower for the isolated habitat than the comparison sites, yet molecular diversity was comparable. These findings show that although habitat isolation may reduce planthopper abundance, genetic diversity can be maintained provided there are nearby areas suitable for immigration. Combined with other data, these results have implications for the evolution of novel host-plant associations under the study conditions. Within islands (or local regions of large islands), new host associations must arise as successful host-shifts at localities between bouts of emigration, or they must arise relatively early in the island's colonization history. The latter seems more the case for the taxa sampled. Most host associations are of roughly the same age in the planthopper phylogeny, and planthopper sister clades share the same host-plants.
Species 1: Homoptera Delphacidae Nesosydne
Keywords: host plants, evolution
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