Causes and Evolutionary Consequences of Population Subdivision of an Iberian Mountain Lizard, Iberolacerta monticola

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.

Thermoregulation in a cold-adapted species (Cyren’s Rock Lizard, Iberolacerta cyreni): influence of thermal environment and associated costs

“…Also, mean field T b of I. cyreni (30.8°C) were comparatively low, being situated at the coldest end of the field T b reported for 53 species of lacertid lizards (range from 27 to 40°C, T mean = 33.8°C, with 50% of values between 31.9 and 35.5°C; Castilla et al 1999), and close to the other species of Iberolacerta, all inhabiting mountain environments (Arribas 2013). The strong similarities between the species of the genus Iberolacerta in presenting low field T b together with the low T pref exhibited by the few species in which this feature is known (Bauwens et al 1996; I. cyreni: this paper; Iberian Mountain Lizard (Iberolacerta monticola (Boulenger, 1905)): S. Aguado and F. Braña, unpublished data) suggest that the thermal preferen-dum is a conserved trait in the Iberolacerta clade and is related to the adaptation of this species group to mountain environments and their isolation in fragmented habitats during cold periods of the Pleistocene (Carranza et al 2004;Crochet et al 2004;Remón et al 2013).…”

Environmental temperatures shape thermal physiology as well as diversification and genome-wide substitution rates in lizards

“…This suggests a need for conservation assessment and thermophysiological work especially on the largely understudied lacertid taxa occurring in aseasonal tropical environments. Yet, current declines among lacertids seem to especially affect specialists inhabiting montane, and/or cool and moist environments 10,57 such as Z. vivipara (Supplementary Fig. 17b), whereas species with very high T pref such as Pedioplanis husabensis so far appear to remain unaffected by contemporary climate change 25 .…”

Karyological Characterization of the Endemic Iberian Rock Lizard, <b><i>Iberolacerta monticola</i></b> (Squamata, Lacertidae): Insights into Sex Chromosome Evolution

“…However, the karyological affinities unveiled between I. monticola and I. galani are not consistent with molecular data [Arribas et al, 2006;Remón et al, 2013], which indicate that I. monticola is the sister taxon to the clade formed by I. galani and I. martinezricai (online suppl. fig.…”

“…All 4 studied populations are currently isolated, and according to recent molecular analysis [Remón et al, 2013], their independent evolution began roughly between 1.5 and 0.9 mya, possibly as a consequence of climatic fluctuations during the Pleistocene. Even so, the sex chromosome pairs of any of these populations are highly similar in terms of relative size and in the amount and distribution of heterochromatin, albeit they could exhibit some differentiation at finer scales hardly evidenced by Cbanding and fluorochrome staining.…”