Intraspecific variation in the energetics of the Cabrera vole.

Basal metabolic rate (BMR) is an intensively topic studied in ecophysiology for the purpose of understanding energy budgets of the species, variations of energy expenditure during their diary activities and physiological acclimatization to the environment. Establishing how the metabolism is assembled to the environment can provide valuable data to improve conservation strategies of endangered species. In this sense, metabolic differences associated to habitats have been widely reported in the interspecific level, however little is known about the intraspecific view of BMR under an environmental gradient. In this study, we researched the effect of the habitat on metabolic rate of an Iberian endemic species: Iberomys cabrerae. Animals were captured in different subpopulations of its altitudinal range and their MR was studied over a thermal gradient. MR was analyzed through a Linear Mixed Model (LMM) in which, in addition to thermal effects, the bioclimatic zone and sex also influenced the metabolism of the species. The beginning of thermoneutrality zone was set on 26.5°C and RMR was 2.3ml O2g(-1)h(-1), intermediate between both bioclimatic zones. Supramediterranean subpopulations started the Tlc earlier (24.9°C) and had higher RMR than the mesomediterranean ones (26.9°C). The thermal environment together with primary productivity conditions could explain this difference in the metabolic behaviour of the Cabrera voles.

Pleistocene history of Iberomys, an endangered endemic rodent from southwestern Europe.

The extant Cabrera's vole, Microtus cabrerae, differs in morphology and evolutionary history from the other species of Microtus. This arvicoline has unique derived features in the cranium, mandible and dentition. Probably its most conspicuous features are its large size, the high skull in lateral view, the long and distally broad nasals, and the triangle shape of the anteroconid complex, with a marked labio-lingual asymmetry of the occlusal surface of the first lower molars. In this study, we propose a phylogenetic lineage that includes Cabrera's vole in what until now has been the Microtus subgenus Iberomys. Paleontological information and several life history traits support the elevation of Iberomys to the rank of genus. Genus Iberomys comprises species that have appeared in succession during the Quaternary: in the Early Pleistocene, the extinct I. huescarensis in the Middle Pleistocene, the extinct I. mediterraneus and in the Late Pleistocene, the extant I. cabrerae. Interestingly, the extant species shows several biological singularities, such as multiple polymorphic copies of the SRY male-specific gene in both males and females, and the lowest basal metabolic rate in relation to weight among arvicoline species. Likewise, its habitat requirement is unique among the Iberian arvicolines. Accordingly, the biological and paleontological data that we present in this work support the elevation of its taxonomic rank to that of genus. This study also suggests a modification of nomenclature: Microtus (Iberomys) brecciensis is replaced with I. mediterraneus and the common name of the extant M. (I.) cabrerae changed from 'topillo' to 'iberon' to improve conservation and protection actions.