Galemys Research Articles

Need for speed: Preference for fast‐flowing water by the endangered semi‐aquatic Pyrenean desman (Galemys pyrenaicus) in two contrasting streams

Abstract The Pyrenean desman (Galemys pyrenaicus) is an endangered, semi‐aquatic, insectivore mammal, endemic to the northern Iberian Peninsula and the Pyrenees. Owing to its small populations, evasive behaviour, and nocturnal activity, knowledge of its ecological requirements is still limited. Continuing population decline over most of its distribution range – even in regions where water quality has clearly improved – points to other factors as the main conservation threat. Nevertheless, at present there is a lack of information on its habitat preferences within its area of occupancy (e.g. stream microhabitat characteristics), a key point for assessing or improving its habitat. This study used radio‐telemetry data to determine the use of space at microhabitat level by the desman, and how this changed depending upon environmental conditions. Desmans were studied in two contrasting rivers in the Basque Country (northern Iberian Peninsula): Elama, a nearly pristine stream, and the Leitzaran, a clean‐water stream affected by hydropower diversions. Fifteen desmans were captured and radio‐tracked in Elama and 16 were captured and radio‐tracked in the Leitzaran, and nocturnal activity points were assigned to one of three habitat types: riffles, runs, or pools. Habitat use was compared against availability to measure habitat selection in each stream and between streams. Desmans selected riffles positively and pools negatively, with this selection being stronger in the Leitzaran. The results highlight the ecological relevance of riffles as foraging habitats of desmans, and therefore as key features for their conservation. It suggests that channel modifications that reduce the areal cover of riffles impair habitat quality for this species. In addition, water diversion for hydropower is likely to be detrimental for desmans, as it reduces discharge and flow velocity in the bypassed river sections.

Los micromamíferos (Eulipotyphla, Chiroptera, Rodentia y Lagomorpha) del yacimiento del Pleistoceno Superior de la cueva de El Castillo (Cantabria, España)

El material de micromamíferos del yacimiento del Pleistoceno Superior de la cueva de El Castillo, objeto de estudio detallado en este trabajo, proviene de los niveles auriñacienses 18b y 18c (datados en 40.000-45.000 BP), nivel 19, y niveles musterienses 20b, 20c, 20d, 20e (datados en 41.000-49.000 BP), 21a y 21b. La asociación de micromamíferos es la siguiente: Erinaceus europaeus, Crocidura russula, Sorex coronatus, Sorex minutus, Neomys fodiens, Talpa europaea, Galemys pyrenaicus, cf. Miniopterus schreibersii, Chiroptera indet., Pliomys lenki, Microtus arvalis – Microtus agrestis, Microtus lusitanicus, Microtus oeconomus, Chionomys nivalis, Arvicola terrestris, Apodemus sylvaticus – Apodemus flavicollis y Lepus sp. La mayoría de estas especies están presentes en la fauna actual de Cantabria, excepto Pliomys lenki que se extinguió en el último tercio del Pleistoceno Superior, y Microtus oeconomus, que persistió en la península ibérica durante el Holoceno bien avanzado hasta su desaparición en tiempos históricos, y que actualmente está en regiones euroasiáticas más septentrionales. Hay una gran continuidad de la gran mayoría de los taxones en todos los niveles. La fauna en su conjunto parece indicar un medio predominantemente abierto, por lo general de praderas húmedas (y en mucha menor medida praderas secas) con una buena cobertura vegetal a nivel del suelo, en el que habría también algunas zonas arboladas o boscosas, y algún curso de agua. Los indicadores termófilos son escasos y poco abundantes, lo que podría indicar que el clima podría ser algo menos templado que en otros periodos del Pleistoceno Superior y quizás también que actualmente en la zona.

Altered hemoglobin co-factor sensitivity does not underlie the evolution of derived fossorial specializations in the family Talpidae.

The high O2 affinity of European mole (Talpa europaea) blood is postulated to largely arise from the presence of two β-globin chain residues (β4 Ser and β5 Gly) that weaken the interaction of its hemoglobin (Hb) with the red cell organophosphate 2,3-diphosphoglycerate (DPG). This latter trait is generally accepted to be an 'adaptation to subterranean life', despite the fact that no data are available for more basal mole lineages that have no evolutionary history of fossoriality (i.e. the ambulatory, high-elevation shrew-like moles and the semi-aquatic desmans), and which may similarly benefit from an elevated blood O2 affinity. To test whether evolution of a low DPG sensitivity phenotype is linked to derived fossorial lifestyles or represents an ancestral trait for the family, we determined the globin gene sequences and measured the intrinsic O2 affinity and co-factor sensitivity of the major Hb component of the gracile shrew-like mole (Uropsilus gracilis) and the Pyrenean desman (Galemys pyrenaicus). Our results unequivocally demonstrate that the presence of β4 Ser and β5 Gly, together with a low DPG sensitivity Hb phenotype, predates the radiation of the family Talpidae, and hence did not evolve as a specific adaptation to fossorial life. By contrast, our comparative analyses suggest that variations in whole blood O2 affinity among members of this family predominantly arose from amino acid substitutions that increase or decrease the intrinsic O2 affinity of the protein.

Comparison of diet and prey selectivity of the Pyrenean desman and the Eurasian water shrew using next-generation sequencing methods

In this study, the interactions between two semi-aquatic mammals, the endangered Pyrenean desman Galemys pyrenaicus and the Eurasian water shrew Neomys fodiens, were investigated through the analysis of their summer diet using next-generation sequencing methods, combined with analyses of prey selectivity and trophic overlap. The diet of these predators was highly diverse including 194 and 205 genera for G. pyrenaicus and N. fodiens respectively. Overall, both species exhibited rather non-selective foraging strategies as the most frequently consumed invertebrates were also the most frequent and abundant in the streams. This supported a generalist foraging behaviour for G. pyrenaicus and N. fodiens in the study area. The Pianka index (0.4) indicated a significant but moderate dietary overlap as G. pyrenaicus mostly relied on prey with aquatic stages whereas prey of N. fodiens were mainly terrestrial. Moreover, no difference in G. pyrenaicus prey consumption was found in presence or absence of N. fodiens. A differential use of trophic resources through mechanisms such as plastic feeding behaviour or differences in foraging micro-habitat are likely to facilitate the coexistence between these two mammal species.

Faecal DNA template as non-invasive tools in order to distinguish the endangered Pyrenean desman (Galemys pyrenaicus, Eulipotyphla, Talpidae) from Mediterranean water shrews (Neomys anomalus, Soricomorpha, Soricidae)

The molecular genetic tools using non-invasive samples such as faeces have an important role for the monitoring of wildlife and identification of elusive and rare species of semi-aquatic vertebrates. However, under aquatic environmental conditions the faeces undergo physical changes that harm the direct identification by visual inspection and leads to the confusion of the deposits from different cohabitating species. Consequently, the need of a refinement of molecular procedures is suggested. In this study this task was focused on the study of the reliability of the PCR-RFLP method to easily distinguish the faeces of the desman ( Galemys pyrenaicus ) from ecologically related species, including N. a. anomalus , but using an in silico-RFLP strategy. In this work, the faecal samples were collected from 2013 to 2014 from the LIC “Sierra de Gredos y Valle del Jerte” in the Mountain Central System of Spain, where the southernmost European population of the Pyrenean desman still survives. One primer pair was designed to amplify a very short portion of the mitochondrial cytochrome b gene containing targets for the restriction enzymes Hinf I, Mbo I and Hpy CH4 V, because the combination provides species-specific identifications. Pyrenean desman or Mediterranean water shrews were undoubtedly identified in the collected faeces. Moreover, the degree of homoplasy was studied under different scenarios of the three enzymes combination. Finally, the in silico-RFLP profiles given by the three enzymes combination have contributed with valuable information for a successful discrimination of faeces of the Pyrenean desman from those derived of Neomys fodiens , Neomys anomalus , Nectogale elegans and Cinclus cinclus . Click here to access supplementary files .

Novel insights into the diet of the Pyrenean desman (Galemys pyrenaicus) using next-generation sequencing molecular analyses

Novel insights into the diet of the Pyrenean desman (Galemys pyrenaicus) using next-generation sequencing molecular analyses

Postglacial dispersal patterns and mitochondrial genetic structure of the Pyrenean desman (Galemys pyrenaicus) in the northwestern region of the Iberian Peninsula.

The genetic structure of small semiaquatic animals may be influenced by dispersal across both rivers and land. The relative importance of these two modes of dispersal may vary across different species and with ecological conditions and evolutionary periods. The Pyrenean desman (Galemys pyrenaicus) is an endemic mammal of the Iberian Peninsula with a strong phylogeographic structure and semiaquatic habits, thus making it an ideal model to study the effects of river and overland dispersal on its genetic structure. Thanks to different types of noninvasive samples, we obtained an extensive sampling of the Pyrenean desman from the northwestern region of the Iberian Peninsula and sequenced two mitochondrial DNA fragments. We then analyzed, using an isolation‐by‐distance approach, the correlation between phylogenetic distances and geographical distances measured along both river networks and land to infer the relative importance of river and overland dispersal. We found that the correlations in the whole area and in a large basin were consistent with an effect of overland dispersal, which may be due to the postglacial colonization of new territories using terrestrial corridors and, possibly, a more extensive fluvial network that may have been present during the Holocene. However, in a small basin, likely to be less influenced by the impact of ancient postglacial dispersal, the correlations suggested significant overall effects of both overland and river dispersal, as expected for a semiaquatic mammal. Therefore, different scales and geographical regions reflect different aspects of the evolutionary history and ecology of this semiaquatic species using this isolation‐by‐distance method. The results we obtained may have crucial implications for the conservation of the Pyrenean desman because they reinforce the importance of interbasin dispersal for this species in the studied area and the need to protect the whole riverine ecosystem, including rivers, upland streams and terrestrial corridors between basins.

Using relatedness networks to infer contemporary dispersal: Application to the endangered mammal Galemys pyrenaicus.

Information about the degree of contemporary dispersal is important when trying to understand how populations interchange individuals and identify the specific barriers that prevent these movements. In the case of endangered species, this can represent crucial information when designing appropriate conservation strategies. Here we analyse relatedness between individuals from different localities and use these data to infer whether dispersal occurred in recent generations. We applied this approach to the Pyrenean desman (Galemys pyrenaicus), a semiaquatic and endangered species endemic to the Iberian Peninsula. We studied this species in four primary rivers in the Iberian Range, where two ancient mitochondrial lineages are separated by a strict contact zone, suggesting the existence of complex dispersal patterns. Using next-generation sequencing, we obtained 912 SNPs from each specimen and estimated relatedness values between them. While relatedness networks were dense within each river, we found surprisingly few relationships between individuals from different rivers despite their close proximity in some cases, indicating much lower dispersal between rivers compared to dispersal within a single river. In agreement with this result, the degree of inbreeding was exceedingly high in most individuals. These data show that relatedness information can be crucial to understand the contemporary dispersal patterns and conservation status of specific populations of endangered species.

Evidence of fine-scale genetic structure for the endangered Pyrenean desman (Galemys pyrenaicus) in the French Pyrenees

The Pyrenean desman (Galemys pyrenaicus) is a small, semiaquatic mammal endemic to the Pyrenean Mountains and the northern half of the Iberian Peninsula where it lives in cold and well-oxygenated flowing mountain streams. This species is currently classified as vulnerable on the IUCN Red List and has been undergoing habitat loss and fragmentation for decades, inevitably impacting its distribution. A recent genetic study, based on mitochondrial and intronic sequences, showed that the genetic variability of the Pyrenean desman is very low in the Pyrenees. In this study, we investigated the potential existence of genetic structure and gene flow at a smaller scale using 24 polymorphic microsatellite loci. As the Pyrenean desman is a very elusive species, we supplemented our tissue sample collection with samples of feces collected in the French range of this species. We successfully identified 70 individuals based on 355 fecal samples. Bayesian analyses revealed 3 genetic and geographic clusters (1 eastern, 1 central, and 1 western, including 3 genetic subclusters), with origins tracing back only 200 years. These clusters were characterized by low levels of genetic diversity and high inbreeding coefficients. Although gene flow among clusters appeared to be limited, populations seem to have exchanged alleles recently. Therefore, connectivity between watersheds should be enhanced to maintain genetic diversity and potentially improve the long-term survival of the Pyrenean desman in France. (Resume d'auteur)

Pleistocene cave hyenas in the Iberian Peninsula: New insights from Los Aprendices cave (Moncayo, Zaragoza

Instituto Universitario de Investigacion en Ciencias Ambientales de Aragon, Universidad de Zaragoza, Espana

Can Recent Global Changes Explain the Dramatic Range Contraction of an Endangered Semi-Aquatic Mammal Species in the French Pyrenees?

Species distribution models (SDMs) are the main tool to predict global change impacts on species ranges. Climate change alone is frequently considered, but in freshwater ecosystems, hydrology is a key driver of the ecology of aquatic species. At large scale, hydrology is however rarely accounted for, owing to the lack of detailed stream flow data. In this study, we developed an integrated modelling approach to simulate stream flow using the hydrological Soil and Water Assessment Tool (SWAT). Simulated stream flow was subsequently included as an input variable in SDMs along with topographic, hydrographic, climatic and land-cover descriptors. SDMs were applied to two temporally-distinct surveys of the distribution of the endangered Pyrenean desman (Galemys pyrenaicus) in the French Pyrenees: a historical one conducted from 1985 to 1992 and a current one carried out between 2011 and 2013. The model calibrated on historical data was also forecasted onto the current period to assess its ability to describe the distributional change of the Pyrenean desman that has been modelled in the recent years. First, we found that hydrological and climatic variables were the ones influencing the most the distribution of this species for both periods, emphasizing the importance of taking into account hydrology when SDMs are applied to aquatic species. Secondly, our results highlighted a strong range contraction of the Pyrenean desman in the French Pyrenees over the last 25 years. Given that this range contraction was under-estimated when the historical model was forecasted onto current conditions, this finding suggests that other drivers may be interacting with climate, hydrology and land-use changes. Our results imply major concerns for the conservation of this endemic semi-aquatic mammal since changes in climate and hydrology are expected to become more intense in the future.

Genomic diversity and geographical structure of the Pyrenean desman

The Pyrenean desman (Galemys pyrenaicus) is a small semi-aquatic mammal endemic to the Iberian Peninsula. The species has recently experienced a strong decline and some of its populations are severely threatened with extinction. To help in the preservation of this species, it is critical to understand its genetic structure and main evolutionary units, as these may have specific local adaptations and could be of great conservation value. Sequencing reduced representation libraries (ddRAD) from 26 specimens selected from across its entire range, we obtained around 45,000 loci per specimen and 1185 single nucleotide polymorphisms. Heterozygosity varied substantially among individuals from different areas. Interestingly, specimens from the southeastern Pyrenees had some of the lowest proportions of heterozygous positions inferred from genome-wide data in mammals so far. In addition, we estimated a tree reflecting genomic divergence, performed a principal component analysis, and carried out a Bayesian analysis of the population structure. Combined evidence supported the existence of five distinct genomic clusters largely coincident with the main mountain ranges where the species occurs, with few specimens presenting relevant admixture levels. There was good correspondence between these populations and the mitochondrial lineages detected in a previous study, yet substantial differences in some areas demonstrate the importance of performing genomic analysis to reveal the whole population history. Although the analysis of further specimens is necessary to better characterize the distribution of the different evolutionary units, the distinctive geographical structure of this species revealed by the genomic data should be considered in future conservation plans.

Spatial differences across the French Pyrenees in the use of local habitat by the endangered semi‐aquatic Pyrenean desman (Galemys pyrenaicus)

Abstract The implementation of effective and appropriate protection actions is frequently hindered by lack of thorough knowledge on species ecology especially in the case of endemic, vulnerable and elusive species. Using a recently updated and unpublished dataset describing the spatial distribution of the Pyrenean desman (Galemys pyrenaicus) in its northern range (French Pyrenees), an Ecological Niche Factor Analysis (ENFA) was conducted to provide a quantitative estimate of local habitat use by this endangered semi‐aquatic mammal. A comparative approach was used to investigate potential differences in habitat use among the three main hydrological regions of the French Pyrenees. The Pyrenean desman was identified as a marginal and specialist species concerning the selection of its local habitat in the French Pyrenees. Key habitat variables corresponded mainly to river‐bed characteristics (i.e. high heterogeneity of shelters and river substrates, fast flowing water facies, low amounts of fine sediment) and river‐bank characteristics (i.e. high proportion of rocks, low proportion of earth). A difference in habitat selection between the three hydrological regions of the French Pyrenees was also highlighted. A decrease in marginality and specialization from west to east as well as differences in habitat variables driving the ecological niche of the Pyrenean desman and its range suggested a spatial structure in desman populations regarding local ecological factors. These results stress the importance of effective and sustainable river management for the habitat quality of this endangered species and also demonstrate the importance of taking into account the variability in habitat preferences that can exist between geographically distinct populations. This finding has important implications for conservation planning that should thus be conducted at the population level instead of the traditional species level in order to target the specific needs of each hydrological region. Copyright © 2016 John Wiley & Sons, Ltd.

Evidencias de regresión local del desmán ibérico (Galemys pyrenaicus) en los Pirineos meridionales

We have studied the changes in the distribution and frequency of semiaquatic micromammals in the river network of Alt Pirineu Natural Park (southern Pyrenees, Iberian Peninsula) between 2000 and 2013-2014. The priority of this work has been the Iberian Desman (Galemys pyrenaicus) but we also evaluated the frequency in Water Shrews (Neomys fodiens and Neomys milleri) and Southern Water Vole (Arvicola sapidus), for which 2000 data were incomplete. It is the first time that a diachronic study on the relative frequency of Iberian Desman takes place at regional level and using an identical method in the two surveys. The methodology was the detection of faeces of these species in 66 river sections, prospected in the two periods considered. The most common semiaquatic mammals were Water Shrews, present in almost all river sections (94%), followed by the Desman (45%) and the Water Vole (34%). We found an intense regression of the Desman in a river basin where this species was common in 2000 (Noguera de Cardós) and it is extinct in the upper basin of this river. This local regression is probably attributable to a recent change in the model of hydroelectric management and we started a survey to evaluate this hypotesis.

A new method to identify the endangered Pyrenean desman (Galemys pyrenaicus) and to study its diet, using next generation sequencing from faeces

The Pyrenean desman (Galemys pyrenaicus) is a small endangered semi-aquatic mammal endemic to the Pyrenean Mountains and to the northern half of the Iberian Peninsula whose ecology and biology are still poorly known. The aim of this study was to identify Pyrenean desman faeces and to analyze its diet from this material using next-generation sequencing methods. We amplified and sequenced a small DNA minibarcode (133bp) of the COI gene in twenty-four putative faeces samples of Pyrenean desman and successfully identified the species in 16 samples. Other identified species were mammals, birds and amphibians, evidencing the potential application of our methods to a larger panel of taxa.In the Pyrenean desman faeces, we were able to identify nineteen prey species with a positive match (more than 98% of identity with a reference sequence) and eleven putative prey species with lower identity scores (90–96%). The nineteen species belonged to four orders and eleven families among which Trichoptera and Hydropsychidae were the most frequent, respectively. Future improvements could be obtained by extending the reference DNA sequence collection to reach precise identifications over the Desman's range and by increasing the sampling to gain a better knowledge of the local diet of this endangered species. Such information is of great importance to propose the best management measures for its conservation.

Integrating hydrological features and genetically validated occurrence data in occupancy modelling of an endemic and endangered semi-aquatic mammal, Galemys pyrenaicus, in a Pyrenean catchment

As freshwater habitats are among the most endangered, there is an urgent need to identify critical areas for conservation, especially those that are home to endangered species. The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal whose basic ecological requirements are largely unknown, hindering adequate conservation planning even though it is considered as a threatened species. Species distribution modelling is challenging for freshwater species. Indeed, the complexity of aquatic ecosystems (e.g., linear and hierarchical ordering) must be taken into account as well as imperfect sampling. High-quality and relevant hydrological descriptors should also be used. To understand the influence of environmental covariates on the occupancy and detection of the Pyrenean desman, we combine both a robust sign-survey data set (i.e. with genetic validation ensuring true presence information) and a hydrological model to simulate the flow regime across a whole catchment. Markovian site-occupancy analysis, taking into account sign detection and based on spatially adjacent replicates, indicated a positive influence of heterogeneity of substrate and shelters, and a negative influence of flow variability on Pyrenean desman detection. This valuable information should help to improve monitoring programs for this endangered species. Our results also highlighted a spatially clustered distribution and a positive influence of stream flow and number of tributaries on occupancy. Hence, modifications of flow regime (e.g. hydropower production, irrigation, climate change) and habitat fragmentation appear to be major threats for this species, altering the connectivity between tributaries and the mainstream river as well as between adjacent sub-catchments.

PCR-RFLP identification of the endangered Pyrenean desman, Galemys pyrenaicus (Soricomorpha, Talpidae), based on faecal DNA

AbstractThe Pyrenean desman is a vulnerable mammal species endemic to Pyrenees and the northern Iberian Peninsula. The presence of this elusive species can be most easily detected by sampling its faeces. However, these faecal samples can be confused with those of other vertebrate species living in the same habitats. This study provides two easy and reliable methods for the identification of the Pyrenean desman faeces based on genetic analyses. The first one consists of a nested PCR and sequencing of a mitochondrial cytochrome

Spatial replicates as an alternative to temporal replicates for occupancy modelling when surveys are based on linear features of the landscape

Summary Occupancy estimates can inform biodiversity managers about the distribution of elusive species, such as the Pyrenean desman Galemys pyrenaicus, a small semi‐aquatic mammal that lives along streams. Occupancy models rely on replication within a sampling site and provide estimates of the probability of detection. However, we still do not know how occupancy and detection estimates obtained from spatial vs. temporal replications differ or the appropriateness of using one or the other when cost and logistics make one approach prohibitive. Recently, the Markovian occupancy model has been developed to analyse adjacent spatial replicates and to test for spatial dependence between them. This model has already been applied to large and highly mobile mammals using trails, but never tested for any species with linear home ranges. We compared detection and occupancy estimates obtained from both temporal and spatial sampling designs that were subsequently organized into four data configurations (sites with both spatial and temporal replicates, adjacent spatial replicates only, temporal replicates only at the segment and site scales). From that, five occupancy models with different assumptions (the standard occupancy model, the standard multiscale model, the multiscale model with Markovian process for detection, the Markovian detection model and the Markovian occupancy model) were used. We also assessed which occupancy model was the most appropriate for each data configuration to determine whether it is necessary to incorporate correlation into models. We found that the estimated detection probabilities were relatively high (≥0·58) and similar when the same model was applied to each data configuration. Spatial replication weakly underestimated occupancy. But when using this design, the Markovian occupancy model was the most supported and minimized the underestimation of occupancy, highlighting a spatial dependence between adjacent replicates. Synthesis and applications. We show that a survey based on adjacent spatial replicates for a mammal living along linear features of the landscape is a good compromise between cost and occupancy estimates, while using the Markovian occupancy model to estimate detection and occupancy. Our finding may have wider applications for the monitoring of species especially when temporal replicates are difficult or unrealistic. Spatial design, for surveys based on sign detection, could thus be applied for species with linear home ranges or when surveys are constrained by linear habitats.

Activity and space patterns of Pyrenean desman (Galemys pyrenaicus) suggest non-aggressive and non-territorial behaviour

The Pyrenean desman is considered a flagship species for biodiversity and evolution. However, its scientific knowledge is still under development and currently on debate, particularly in relation to its behavioural ecology and social organization. Based on the previous hypothesis of individual desmans being solitary and territorial, activity and space patterns were considered to be arranged to avoid conspecifics. However, recent insights into the species’ social behaviour revealed non-interspecific avoidance. With this study, we provide novel insights into the activity and space patterns of the desman, and their relation to its social behaviour. A total of 30 individuals were trapped, 18 of which provided informative radiotracking data to study (1) activity behaviour, (2) the proportion of the home range utilized and the distances travelled, and (3) the dominant movement directionality. Activity and space use patterns were affected by daylight and seasonality, but not by sex, age or number of other conspecifics sharing the home range. In contrast to the previous observations, individuals did not show a pattern of directionality in their movements. Noticeably, we observed encounters between individuals without evidence of aggressive behaviour. Our results suggest that desmans do not alter their activity or their spatial behaviour to avoid encounters with conspecifics, as previously suggested. These novel findings provide more evidence of a social structure and organization with social interactions and non-aggressive behaviour. This is of relevance for management actions and for the conservation of this endemic mammal.

Phylogeography and postglacial expansion of the endangered semi-aquatic mammal Galemys pyrenaicus

BackgroundSpecies with strict ecological requirements may provide new insights into the forces that shaped the geographic variation of genetic diversity. The Pyrenean desman, Galemys pyrenaicus, is a small semi-aquatic mammal that inhabits clean streams of the northern half of the Iberian Peninsula and is endangered in most of its geographic range, but its genetic structure is currently unknown. While the stringent ecological demands derived from its aquatic habitat might have caused a partition of the genetic diversity among river basins, Pleistocene glaciations would have generated a genetic pattern related to glacial refugia.ResultsTo study the relative importance of historical and ecological factors in the genetic structure of G. pyrenaicus, we used mitochondrial and intronic sequences of specimens covering most of the species range. We show, first, that the Pyrenean desman has very low levels of genetic diversity compared to other mammals. In addition, phylogenetic and dating analyses of the mitochondrial sequences reveal a strong phylogeographic structure of a Middle Pleistocene origin, suggesting that the main lineages arose during periods of glacial isolation. Furthermore, both the spatial distribution of nuclear and mitochondrial diversity and the results of species distribution modeling suggest the existence of a major glacial refugium in the northwestern part of the Iberian Peninsula. Finally, the main mitochondrial lineages show a striking parapatric distribution without any apparent exchange of mitochondrial haplotypes between the lineages that came into secondary contact (although with certain permeability to nuclear genes), indicating incomplete mixing after the post-glacial recolonization. On the other hand, when we analyzed the partition of the genetic diversity among river basins, the Pyrenean desman showed a lower than expected genetic differentiation among main rivers.ConclusionsThe analysis of mitochondrial and intronic markers in G. pyrenaicus showed the predominant effects of Pleistocene glaciations on the genetic structure of this species, while the distribution of the genetic diversity was not greatly influenced by the main river systems. These results and, particularly, the discovery of a marked phylogeographic structure, may have important implications for the conservation of the Pyrenean desman.