Two ways to be endemic. Alps and Apennines are different functional
refugia during climatic cycles
Abstract
Endemics co-occur because they evolved in situ and persist regionally or
because they evolved ex situ and later dispersed to shared habitats,
generating evolutionary or ecological endemicity centres, respectively.
We investigate whether different endemicity centres can intertwine in
the region ranging from Alps to Sicily, by studying their butterfly
fauna. We gathered an extensive occurrence dataset for butterflies of
the study area (27,123 records, 269 species, in cells of 0.5x0.5 degrees
of latitude-longitude). We applied molecular-based delimitation methods
(GMYC model) to 26,557 COI sequences of Western Palearctic butterflies.
We identified entities based on molecular delimitations and the most
recent checklist of European butterflies and objectively attributed
occurrences to their most probable entity. We obtained a zoogeographic
regionalisation based on the 69 endemics of the area. Using phylogenetic
ANOVA we tested if endemics from different centres differ from each
other and from non-endemics for key ecological traits and divergence
time. Endemicity showed high incidence in the Alps and Southern Italy.
The regionalisation separated the Alps from the Italian Peninsula and
Sicily. The endemics of different centres showed a high turnover and
differed in phenology and distribution traits. Endemics are on average
younger than non-endemics and the Peninsula-Sicily endemics also have
lower variance in divergence than those from the Alps. The observed
variation identifies Alpine endemics as paleoendemics, now occupying an
ecological centre, and the Peninsula-Sicily ones as neoendemics, that
diverged in the region since the Pleistocene. The results challenge the
common view of the Alpine-Apennine area as a single “Italian
refugium”.