|Understanding the origin and persistence of Microtus species in the Iberian Peninsula: the genetical, behavior and ecological forces|
CESAM Responsible researcher - Cristiane Bastos-Silveira
Programme - PTDC/BIA-BEC/103729/2008
Execution dates - 2010-01-01 - 2013-06-30 (42 Months)
Funding Entity - FCT - Portuguese Foundation for Science and Technology
Funding for CESAM - 130480 €
Total Funding - 130480 €
Proponent Institution - Fundação da Faculdade de Ciências da Universidade de Lisboa
Universidade de Aveiro
Speciation is the creative process leading to the build up of species diversity. Understanding the general patterns and processes of speciation is fundamental to explaining the diversity of life. The genus Microtus, which is thought to have originated 0.5–2 million years ago, is one of the best-known cases of rapid mammalian radiation with 65 extant species. If these numbers are taken at face value, then an average of 30 microtine speciation events have occurred every million years. A recent molecular phylogeny study, showed that the M. cabrerae lineage is very old and predating the radiation of the other European Microtus. In opposition, the sister species M. duodecimcostatus and M. lusitanicus presented the lowest cyt b divergence (4–5%) among all Microtus species analyses. The Cabrera vole is considered a ‘‘Vulnerable’’ species in Portugal and Spain, been the only endemic rodent of the Iberian Peninsula. Presents a fragmented range where subpopulations are small and subject to major inter-annual fluctuations. The subfossil remains found in France, outside the current distribution, suggests a range contraction. It is unknown which factors caused this contraction and to which level this process has affected its genetic variability. Microtus duodecimcostatus and M. lusitanicus are widespread across the Iberian Peninsula. Although widely accepted these species are of difficult taxonomic discrimination with diagnostic characteristics mainly based on the larger size of M. duodecimcostatus. Preliminary data from our research group show that neither M. lusitanicus individuals captured in the allopatric, nor in the sympatric areas, in Portugal, showed an agreement with the published putative molecular species differences. These findings raise questions regarding the actual allopatric area of each species, possible ongoing hybridization or the need of a species status review. The Iberian Peninsula was one of the most important Pleistocene glacial refugia in Europe. Its high physiographic complexity, and wide range of climates may favour survival throughout the Pleistocene. Hence, we aim to understand which genetic and ecological factors allowed the generation and persistence of these Microtus species on the this region. As a result of two decades of research on small mammals in Portugal, especially on M. cabrerae, M. duodecimcostatus and M. lusitanicus, we generated a unique dataset on several aspects of morphology and ecology in combination with a collection of biological material. The comprehensive nature of this dataset provides us with the opportunity to use integrated approaches including molecular genetic tools and geographic information system (GIS) based analyses. Because species boundaries are defined by characteristics pertaining to the abiotic environment, genetic composition of individuals as well as behavioral characteristics, we believe that tackling this issue is best done using a multidisciplinary approach. Therefore, a team of specialists will join in an enterprise to uncover the evolutionary history of these species. To achieve this goal we propose to: 1) perform sample field trips to Spain in order to cover as much as possible the entire range of these species; 2) unravel their genetic structure and variability by sequencing mtDNA (cyt b), Y chromosome (SMCY11) and nuclear (avpr1a) genes; 3) investigate the hypothesis of hybridisation between M. duodecimcostatus and M. lusitanicus, by testing whether pre-zygotic and/or post-zygotic reproductive isolation barriers exist and test whether males or females from one species avoid interspecific mates based on odours cues.; and 4) build up a GIS database containing species presence based on morphometric (museum collection records) and genetic identification (this project). These data will be combined with digital layers of several environmental variables for the entire Iberian Peninsula to generate predictive models. The integration these data will, at first, allow a straightforward approach to test if genetic diversity for each species is associated with significant divergence in the ecological niche. However we will also explore others venues as: 1) the impact of glacial refugia on the distribution of the study species, by using estimations of paleoclimatic variation, available through the Paleoclimatic Modeling Intercomparison Project; 2) the role of ecology in speciation, assuming that in the absence of geographical barriers, allopatry can sometimes be associated with specialization to relatively subtle differences in ecological conditions; and last but not least, 3) if our reproduction isolation tests confirm hybridization between M. duodecimcostatus and M. lusitanicus, possible patterns in environmental conditions at the hybrid zones will be investigated. With the present proposal we aim to contribute to reveal the factors influencing evolutionary processes in the Iberian Peninsula and the birth and persistence of species in this region.
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