Tracing the origin of disjunct distributions: a case of biogeographical convergence in Pyrgus butterflies

Aim To study the biogeographical factors responsible for the current disjunct
distributions of two closely related species of butterflies (Pyrgus cinarae and
Pyrgus sidae, Lepidoptera: Hesperioidea). Both species have small populations in
the Iberian Peninsula that are isolated by more than 1000 km from their nearest
conspecifics. Because these species possess similar ecological preferences and
geographical distributions, they are excellent candidates for congruent
biogeographical histories.
Location The Palaearctic region, with a special focus on the Mediterranean
peninsulas as glacial refugia.
Methods We integrated phylogeography and population genetic analyses with
ecological niche modelling. The mitochondrial gene cytochrome c oxidase
subunit 1 (COI) and the non-coding nuclear marker internal transcribed spacer 2
(ITS2) were analysed for 62 specimens of P. cinarae and for 80 of P. sidae to infer
phylogeography and to date the origin of disjunct distributions. Current and
ancestral [Last Glacial Maximum using MIROC (Model for Interdisciplinary
Research on Climate) and CCSM (Community Climate System Model)
circulation models] distribution models were calculated with Maxent. Using
present climatic conditions, we delimited the ecological space for each species.
Results The genetic structure and potential ancestral distribution of the two
species were markedly different. While the Iberian population of P. cinarae had an
old origin (c. 1 Ma), that of P. sidae was closely related to French and Italian
lineages (which jointly diverged from eastern populations c. 0.27 Ma). Ecological
niche modelling showed that minor differences in the ecological preferences of
the two species seem to account for their drastically different distributional
response to the last glacial to post-glacial environmental conditions. Although the
potential distribution of P. cinarae was largely unaffected by climate change,
suitable habitat for P. sidae strongly shifted in both elevation and latitude. This
result might explain the early origin of the disjunct distribution of P. cinarae, in
contrast to the more recent disjunction of P. sidae.
Main conclusions We show that convergent biogeographical patterns can be
analysed with a combination of genetic and ecological niche modelling data. The
results demonstrate that species with similar distributional patterns and ecology
may still have different biogeographical histories, highlighting the importance of
including the temporal dimension when studying biogeographical patterns.