Pleistocene history ofIberomys, an endangered endemic rodent from southwestern Europe

Abstract

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.

A context for the last Neandertals of interior Iberia: Los Casares cave revisited

“…Concerning the microvertebrates, the presence of forest-dwelling taxa, such as Sciurus vulgaris and Apodemus , Mediterranean species such as Eliomys quercinus and Hystrix sp ., as well as species adapted to humid habitats such as Castor Fiber , Arvicola sapidus and Iberomys cabrerae , also suggest a warm and humid environment for level c [54, 101–102]. The absence of cold-indicator taxa in this level, such as the snow and tundra voles, is also of relevance here.…”

“…This is consistent with microfaunal evidence, as seen in the reduction in the number of taxa identified in level b with respect to c. Also, the disappearance of forest-dwelling taxa that were present in level c, such as Sciurus vulgaris and Apodemus species, and of Mediterranean indicators such as the dormice, Eliomys quercinus , or the wood mouse, most probably record an increasingly colder climate in layer b. In this context, survival of species such as Arvicola sapidus and Iberomys cabrerae , both related to humid habitats [101], is best explained considering that they were probably less affected by climatic stress than the Woodland-Mediterranean indicators [54, 102]. …”

Los micromamíferos (Lagomorpha, Eulipotyphla y Rodentia) del yacimiento del Pleistoceno Medio de Cuesta de la Bajada (Teruel, España): Estudio sistemático y consideraciones paleoambientales

“…M. (P.) gregaloides (HINTON, 1923). La nueva especie, denominada Iberomys huescarensis por Cuenca-Bescós & , se identificó en los niveles inferiores TD-3 a TD-6 de Gran Dolina de Atapuerca y en la Sima del Elefante (CuencaBescós et al, 2001;Made et al, 2003), y fue considerada como antecesora de Iberomys brecciensis (Cuenca-Bescós et al, 2014). Sin embargo, en un estudio realizado con anterioridad a estos trabajos por Gil (1986Gil ( y 1997 en los niveles inferiores mencionados de Gran Dolina, se documenta el registro M.…”

“…Garrido-García & Soriguer-Escofet (2012) apuntan a que su reducción en épocas recientes fue debida a otras causas como la influencia humana, al destruir los hábitats húmedos en los que vive por la expansión de la agricultura desde el periodo Subboreal. Ambas hipótesis, climática y antrópica, tal como señalan , y en nuestra opinión, no son excluyentes, ya que la retracción del área de distribución de Iberomys podría deberse, como se ha dicho, a causas climáticas, con la consecuente reducción de sus hábitats húmedos preferenciales, acelerada en tiempos recientes por la destrucción intensiva de los mismos por la acción humana que hacen necesaria la búsqueda de medidas para prevenir su extinción (GarridoGarcía & Soriguer-Escofet, 2012;Garrido-García et al, 2013;Fuentes et al, 2013;Pita et al, 2014;Cuenca-Bescós et al, 2014).…”

Paleontology and evolution‐part II

“…The revision of the taxomomic rank of Iberomys (to date regarded as a subgenus of Microtus) proposed by Cuenca-Bescós et al (2014) is also based on the fact that the extant Microtus cabrerae, an Iberoccitanian endemic vole, shows unique, derived features that on one hand make it different in morphology and evolutionary history from the other species of Microtus, and on the other suggest it could be included in the Iberomys phylogenetic lineage, known from the Middle Pleistocene onwards. Sometimes evidence from leaving taxa could be the starting point for revising previously established evolutionary models, phylogenetic schemes and/or taxonomy.…”