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Figure 5. Correlations between species occurrences (x-axis) and population genetic differentiation, Dst
(y-axis) for the species occurring on the studied islands. The colours indicate if a certain square is significantly
filled (blue), significantly empty (orange) or shows no significant difference compared to values obtained by
chance (white). All islands are significantly enriched in widespread species with low genetic variation, and most
are impoverished in rare ones.

a key biogeographic region. Similar comprehensive assessments of island communities are scarce, especially due to
the difficulty of acquiring high quality data at both faunistic and genetic levels for large groups of organisms 8,22,26,27 .
The evaluation of the contribution of singular factors in characterizing island diversity facilitated the identification
of species that deserve conservation consideration on individual islands. The composition of butterfly communities
and their genetic structure were shaped by neutral (frequency at source) and non-neutral (differences in dispersal
tendency among species, interactions generating chequered patterns) determinants. In particular, frequency at source
had a strong contribution in determining the occurrence of species on islands, as expected according to a neutral
hypothesis, but species dispersal tendency also played an important role and many sedentary species were rare on
islands despite their ubiquitous presence on mainland and Sicily (M. jurtina, C. pamphilus, P. aegeria, P. cecilia and
Aricia spp.
One of the main findings of this study, stemming from the community and genetic data, is that even in a rela-
tively restricted area, island populations have very different histories and are subjected to different re-colonization

Scientific RepoRts | 6:28828 | DOI: 10.1038/srep28828 6