Abstract
AimThe study of the factors that influence population connectivity and spatial distribution of genetic variation is crucial for understanding speciation and for predicting the effects of landscape modification and habitat fragmentation, which are considered severe threats to global biodiversity. This dual perspective is obtained from analyses of subalpine mountain species, whose present distribution may have been shaped both by cyclical climate changes over ice ages and anthropogenic perturbations of their habitats. Here, we examine the phylogeography, population structure and genetic diversity of the lacertid lizard Iberolacerta monticola, an endemism considered to be facing a high risk of extinction in several populations.LocationNorthwestern quadrant of the Iberian Peninsula.MethodsWe analyzed the mtDNA variation at the control region (454 bp) and the cytochrome b (598 bp) loci, as well as at 10 nuclear microsatellite loci from 17 populations throughout the distribution range of the species.ResultsAccording to nuclear markers, most sampling sites are defined as distinct, genetically differentiated populations, and many of them show traces of recent bottlenecks. Mitochondrial data identify a relatively old, geographically restricted lineage, and four to six younger geographically vicariant sister clades, whose origin may be traced back to the mid-Pleistocene revolution, with several subclades possibly associated to the mid-Bruhnes transition. Geographic range fragmentation of one of these clades, which includes lowland sites, is very recent, and most likely due to the accelerated loss of Atlantic forests by human intervention.Main ConclusionsAltogether, the data fit a “refugia within refugia” model, some lack of pattern uniformity notwithstanding, and suggest that these mountains might be the cradles of new species of Iberolacerta. However, the changes operated during the Holocene severely compromise the long-term survival of those genetic lineages more exposed to the anthropogenic perturbations of their habitats.
Highlights
The Quaternary period is punctuated by a series of cyclic large glacial-interglacial climate changes, intense in the northern hemisphere, primarily determined by parameters of the Earth’s orbit [1]
The changes operated during the Holocene severely compromise the long-term survival of those genetic lineages more exposed to the anthropogenic perturbations of their habitats
Glacial dynamics in the NW of the Iberian Peninsula [20,21] indicate that large parts of the current range of I. monticola at middle high altitude must have been unsuitable for the species during the last ice age, a situation that most likely took place repeatedly during the cyclical climate changes of the Pleistocene [22]
Summary
The Quaternary period is punctuated by a series of cyclic large glacial-interglacial climate changes, intense in the northern hemisphere, primarily determined by parameters of the Earth’s orbit [1]. Iberolacerta monticola (Boulenger 1905) is one of the species included in the Iberian rock-lizard group, whose phylogenetic relationships and evolutionary histories are relatively well known [9,10,11,12,13,14]. It is defined as ‘‘vulnerable’’ [B1ab(iii)] in the IUCN Red List of Threatened Species, according to its extent of occurrence (less than 20,000 km2), its distribution (severely fragmented), and the quality and extent of its habitat (in continuing decline) [15]. Glacial dynamics in the NW of the Iberian Peninsula [20,21] indicate that large parts of the current range of I. monticola at middle high altitude (in principle, most sites .700– 1,000 m asl, meters above sea level) must have been unsuitable for the species during the last ice age, a situation that most likely took place repeatedly during the cyclical climate changes of the Pleistocene [22]
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