We examined the response of montane butterflies to a 1300‐m elevational gradient in the Toiyabe Range, a mountain range in the central Great Basin. We tested whether elevational ranges of montane butterflies conform to Rapoport’s elevational rule (species at higher elevations have greater elevational ranges). We also tested whether the Rapoport‐rescue hypothesis (emigrants from higher elevation populations inflate the species richness of lower‐elevation sites) could explain the species richness patterns we observed. In addition, we predicted whether global climate change is likely to perturb current elevational gradients in butterfly species richness. Species presence data were collected from 105 100‐m vertical elevational bands in 17 canyons. Elevation and species richness were significantly negatively correlated, although species richness peaked at intermediate elevations, and butterflies in species‐rich areas had significantly narrower elevational ranges than species in more depauperate areas. Toiyabe Range butterflies conformed to Rapoport’s elevational rule. The Rapoport effect we documented did not result from sampling bias. However, the Rapoport‐rescue hypothesis cannot fully explain the elevational gradient in species richness. Environmental severity at either end and favorable conditions near the middle of the elevational gradient likely contributed to high species richness at intermediate elevations. Our models indicated that few butterfly taxa will be lost from the Toiyabe Range in the face of climate change. To maintain present species richness and maximize the potential of Great Basin butterflies to adapt to rapid climate change, we recommend that habitat protection and restoration efforts target not only high elevation Wilderness Areas but also intermediate elevations.

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Butterfly species lists were assembled for 18 Great Basin mountain ranges for which distributional data on mammals and birds have been analysed previously by other workers. The ranges represent remnant islands of the boreal habitat that once was continuous across the Great Basin but is now restricted to higher elevations as a result of climatic change at the close of the Pleistocene. The effects of biogeographic factors (area, distance, elevation) and habitat diversity on butterfly species number were examined. The Great Basin boreal butterfly faunas were found to be depauperate overall relative that of the principal mainland source, the Rocky Mountains, and were found to have fewer species than predicted by the mainland species-area data. However, only a weak area effect, and no distance effect, was detected by bivariate and multivariate analysis. Furthermore, the habitat diversity score found to explain virtually all the variation in bird species number in the same ranges in previous studies is only marginally significantly correlated with butterflies. When the butterflies are subdivided according to their vagility, the relative differences in the species-area correlation and slope (z-value) between the vagility categories were consistent with those found previously for mammals and birds, and, as predicted by theory, less vagile taxa exhibit higher species-area correlations and z-values. Overall, differences in the insular biogeography of buttterflies and vertebrates seem to reflect fundamental ecological differences between the taxa.

A sample of over 400 co-occurring species of Neotropical Hesperiidae attracted to artificial lures was used to test for temporal structure among species and explore potential consequences of temporal partitioning within assemblages. Five years of intermittent transect samples at the same site revealed that diel activity was significantly partitioned among subfamilies, genera and species within this species assemblage. Calculations of reproductive isolation indicate that partitions in activity times are sufficient to provide significant prezygotic reproductive isolation among some congeneric species pairs. Temporal patterns in this assemblage are considered in light of field observations and temporal partitions are examined as a potential isolating barrier among insects.