BackgroundStudies of the phylogeography of Mexican species are steadily revealing genetic patterns shared by different species, which will help to unravel the complex biogeographic history of the region. Campostoma ornatum is a freshwater fish endemic to montane and semiarid regions in northwest Mexico and southern Arizona. Its wide range of distribution and the previously observed morphological differentiation between populations in different watersheds make this species a useful model to investigate the biogeographic role of the Sierra Madre Occidental and to disentangle the actions of Pliocene tecto-volcanic processes vs Quaternary climatic change. Our phylogeographic study was based on DNA sequences from one mitochondrial gene (cytb, 1110 bp, n = 285) and two nuclear gene regions (S7 and RAG1, 1822 bp in total, n = 56 and 43, respectively) obtained from 18 to 29 localities, in addition to a morphological survey covering the entire distribution area. Such a dataset allowed us to assess whether any of the populations/lineages sampled deserve to be categorised as an evolutionarily significant unit.ResultsWe found two morphologically and genetically well-differentiated groups within C. ornatum. One is located in the northern river drainages (Yaqui, Mayo, Fuerte, Sonora, Casas Grandes, Santa Clara and Conchos) and another one is found in the southern drainages (Nazas, Aguanaval and Piaxtla). The split between these two lineages took place about 3.9 Mya (CI = 2.1-5.9). Within the northern lineage, there was strong and significant inter-basin genetic differentiation and also several secondary dispersal episodes whit gene homogenization between drainages. Interestingly, three divergent mitochondrial lineages were found in sympatry in two northern localities from the Yaqui river basin.ConclusionsOur results indicate that there was isolation between the northern and southern phylogroups since the Pliocene, which was related to the formation of the ancient Nazas River paleosystem, where the southern group originated. Within groups, a complex reticulate biogeographic history for C. ornatum populations emerges, following the taxon pulse theory and mainly related with Pliocene tecto-volcanic processes. In the northern group, several events of vicariance promoted by river or drainage isolation episodes were found, but within both groups, the phylogeographic patterns suggest the occurrence of several events of river capture and fauna interchange. The Yaqui River supports the most diverse populations of C. ornatum, with several events of dispersal and isolation within the basin. Based on our genetic results, we defined three ESUs within C. ornatum as a first attempt to promote the conservation of the evolutionary processes determining the genetic diversity of this species. They will likely be revealed as a valuable tool for freshwater conservation policies in northwest Mexico, where many environmental problems concerning the use of water have rapidly arisen in recent decades.

Fourteen polymorphic microsatellite loci are described for the Iberian rock lizard, Iberolacerta monticola. Genetic variation in a sample of 20 individuals from Piornedo (northwestern Spain) was quantified both by the number of alleles per locus, which ranged from six to 13, and by the expected frequency of heterozygotes under random mating (heterozygosity), which ranged from 0.761 to 0.902. Single locus and global exclusion probabilities were also computed, and indicate a high power of these markers for paternity assignments and mating system studies of I. monticola. All the analysed loci were also polymorphic in Iberolacerta galani, but only seven in Zootoca vivipara.

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.

The fragmentation and destruction of natural habitats by human intervention is producing a continuous and inexorable reduction of the size of populations in multitude of species all over the world. Small and isolated populations face higher extinction risks, due to demographic and environmental stochasticity, and also because of several genetic threats, among which inbreeding is considered the most important one. For many of these species, the extinction of a population is an irreversible event, so that determining the immediate importance of these risk factors and understanding their interactions is crucial for conservation plans. Iberolacerta monticola is a small lacertid endemic to the northwestern Iberian Peninsula, distributed mainly across moderate/high altitude mountainous regions. Some populations are found nearly at sea-level, though, in fluvial valleys with relict Atlantic forests, in the severely fragmented western part of its range. One of them has been dramatically reduced over the last 30 years, and presently is on the brink of extinction. Using microsatellite nuclear markers, we obtained different measures of genetic variation at this site, together with demographic and breeding data. Both the level of heterozygosity and the number of alleles per locus indicate that the level of variation in this population is comparatively high, and the average inbreeding coefficient is very low. Individuals appear healthy and long-lived, and are related by a few different lines of descent. These findings are discussed in the context of current theories and experimental evidence of associative overdominance and purging of the genetic load of populations, with special emphasis on the evolutionary potential of recovery of small evolutionary units.

Iberolacerta populations from the Northern Montes de Leon (NML) were studied by means of external morphology (scalation and biometry), osteology and genetics (mtDNA and microsatellites), searching for their homogeneity ("intrazonalanalysis") and, once verified, comparing them with Iberolacerta monticola s. str. (from Central Cantabrian Mountains)and/. gal ani (from Southern Montes de Leon) ("extrazonal analysis") from neighboring areas.Our "intrazonal analysis" revealed discordances between the different approaches, especially the patterns of variation of nuclear microsatellites (congruent with external morphology) and mtDNA, namely a very low nuclear differentiation between relatively highly differentiated mtDNA lineages. The morphological approach was unable to discriminate any of the populations as significantly different from the others in the NML. Mitochondrial DNA revealed a haplotype lineage closely related to I. galani (MNL-II in our text) in some specimens of Sierra de Villabandfn and Suspiron, but these populations are morphologically indistinguishable from the main part of the other populations that belong to lineage NML-1,phylogenetically closer to/. monticola. After a separation from I. manti cola ca. 1.8 Mya, the populations in this geographic region must have suffered at least two different waves of gene flow from I. gal ani, the second one not much later than 0.5 Mya. Microsatellite results indicate that all the NML populations are genetically similar in terms of their nuclear genomes,independently of their mitochondrial differentiation (NML-I vs. NML-II haplotype groups). Since all the morphological and microsatellite evidences point towards the fact that, independently of the mitochondrial haplotypes that they bear (NML-1 or NML-II), there is only one taxon in the area, we describe it as: Iberolacerta monticola astur ssp. nov.Concerning the relationships of I. m. astur ssp. nov. with I. monticola s. str. and I. gal ani ("extra zonal analysis"), in the female analyses the new taxon centroid is closer to I. monticola s. str. than to I. gal ani (more similarity with I manticolas.str.), whereas in the male analyses the relationship is just the contrary (closer to I. gal ani, paralleling the direction of the hypothesized past hybridization). Moreover, in both sexes' ANOVA, I. m. astur ssp. nov. results more similar (lessP<0.05 differences) to I. galani than to I. monticola s. str. Osteologically, I. m. astur ssp. nov. is slightly more similar toI. monticola s. str. than to I. galani, especially in the squamosal bone, which is regularly arched (primitive shape). Genetically,as indicated above, the NML populations can be subdivided in two groups according to their mitochondrial DNA,namely NML-I (bearing clearly differentiated haplotypes, phylogenetically closer to I. monticola) and NML-II (whose haplotypes could have been mistaken for those of an I. gal ani population). This mitochondrial subdivision has at most a subtle nuclear correlate, however. According to the nuclear microsatellite markers, all t...