Biodiversity in montane grasshoppers: From population genetics to community parameters

Relatively little is known about the ecology and population dynamics of the alpine and montane grasshoppers that currently inhabit “sky islands” in the Rocky Mountains of western North America. This study looks at biodiversity at several organismal and spatial scales. A total of 215 individuals of Melanplus alpinus was collected from 43 meadows in 10 drainages of 4 mountain ranges in Wyoming and Montana, allowing for genetic analysis at four spatial scales. Genetic differentiation was greatest among drainages and meadows within mountain ranges, and least among ranges. This fact, along with the paraphyletic distribution of rare haplotypes from three mtDNA lineages and near-ubiquitous distribution of one haplotype (H), indicates that M. alpinus was a widely distributed, panmictic species during periods of the Pleistocene. Drift appears to be the major evolutionary force currently affecting the population dynamics of this species. Whether M. alpinus' phylogenetic structuring represents three distinct species or three highly divergent lineages of a single species, these taxonomic units appear to predominate in select soil textures. Genotype-habitat associations did not extend beyond soil. Spatial analyses were also conducted for grasshopper communities in relation to ecological variables. Grasshopper population density, species richness, species diversity, species evenness, and percent-of- Melanoplus individuals were assessed among mountain ranges for relationships with elevation, elevation-latitude index, percent of bare ground, and slope aspect. The ecological patterns of this regional spatial scale were compared to those of single montane ecosystems to assess scale dependence/invariance in grasshopper density, species richness, and species diversity. Scale invariance existed for species richness in relation to elevation and percent of bare ground. Scale dependence existed for grasshopper density and species diversity in relation to elevation and aspect. Extrapolating ecological patterns of a localized scale to a regional one can be misleading if regional spatial analyses have not been conducted.