Résumé
Mountainous areas comprise a substantial part of the world species
richness, but the evolutionary origins and diversification of this
biodiversity remain elusive. Diversification may result from differences
in clade age (longer time to diversify), net diversification rates (faster
speciation rate), or carrying capacities (number of niches). The
likelihood of these macroevolutionary scenarios was assessed for six
clades of Apollo swallowtails (Parnassius) that diversified mainly in the
Himalayan-Tibetan region. The analyses suggest that neither the clade age,
nor the speciation rate could explain the mountain butterfly
diversification. Instead diversity-dependence models were strongly
supported for each group. Models further estimated clades’ carrying
capacities that approximate the current number of species, indicating that
diversity equilibrium is reached (or close to be). The results suggest
that diversification of mountain butterflies was controlled by ecological
limits, which governed the number of niches, and provide macroevolutionary
justification for regarding mountains as islands.