Evolutionary
history of the Maltese wall lizard Podarcis
filfolensis: insights on the ‘Expansion–Contraction’ model
of
Pleistocene biogeography
DANIELE
SALVI,* PATRICK J . SCHEMBRI ,† ARNOLD SCIBERRAS‡ and D. JAMES HARRIS*
*CIBIO, Centro de Investigac_~ao em Biodiversidade e Recursos Gen_eticos, Campus Agr_ario
de Vair~ao, 4485-661 Vair~ao, Portugal,
†Department of Biology, University of Malta, Msida MSD2080 Malta, ‡133, Arnest, Arcade Str., Paola, Malta
Abstract
The
expansion–contraction
(EC) model predicts demographic and range contraction of
temperate
species during Pleistocene glaciations as a consequence of climate-related
habitat
changes, and provides a paradigm for explaining the high intraspecific
diversity
found
in refugia in terms of long-term demographic stability. However, recent
evidence
has
revealed a weak predictive power of this model for terrestrial species in
insular
and coastal settings. We investigated the Pleistocene EC dynamics and their
evolutionary
consequences on temperate species using the Maltese archipelago and its
endemic
lizard Podarcis filfolensis as a model system. The evolutionary and demographic
history
of P. filfolensis as
inferred from mitochondrial and nuclear sequences
data
does not conform to the EC model predictions, supporting (i) demographic and
spatial
stability or expansion, rather than contraction, of the northern and southern
lineages
during
the last glacial period; and (ii) a major role for allopatric differentiation
primed
by sea-level dynamics, rather than prolonged demographic stability, in the
formation
of the
observed genetic diversity. When combined with evidence from other
Mediterranean
refugia, this study shows how the incorporation of Pleistocene sea-level
variations
in the EC model accounts for a reverse demographic and range response of
insular
and coastal temperate biotas relative to continental ones. Furthermore, this
cross-archipelago
pattern in which allopatric diversity is formed and shaped by EC
cycles
resembles that seen between isolated populations within mainland refugia and
suggests
that the EC model, originally developed to explain population fluctuations
into
and out-of refugia, may be appropriate for describing the demographic and
evolutionary
dynamics
driving the high genetic diversity observed in these areas.
Keywords: Allopatric divergence, genetic diversity, glacial expansion,
historical demography,
Mediterranean
islands, phylogeography
Received 31 August
2012; revision received 30 December 2013; accepted 9 January 2014
Because of copyright
issues the whole work could not be uploaded in this blog. For further info
contact me on bioislets@gmail.com
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