Abstract
Mountainous areas contain a substantial part of the world species richness,but the evolutionary origins and diversification of this biodiversity remainelusive. Diversification may result from differences in clade age (longer timeto diversify), net diversification rates (faster speciation rate) or carryingcapacities (number of niches). The likelihood of these macroevolutionary scenarioswas assessed for six clades of Apollo swallowtails (Parnassius) thatdiversified mainly in the Himalayan–Tibetan region. The analyses suggestthat neither the clade age nor the speciation rate could explain the mountainbutterfly diversification. Instead diversity-dependence models were stronglysupported for each group. Models further estimated clades’ carryingcapacities, which approximate to the current number of species, indicatingthat diversity equilibrium has been reached (or close to being reached).The results suggest that diversification of mountain butterflies was controlledby ecological limits, which governed the number of niches, and providemacroevolutionary justification for regarding mountains as islands.