Agricultural intensification during the Late Holocene rather than climatic aridification drives the population dynamics and the current conservation status of Microtus cabrerae, an endangered Mediterranean rodent

Abstract

AbstractAimDisentangling the relative importance of climatic and anthropogenic factors is crucial in conservation biology but problematic using short‐term data only. Long‐term (palaeobiological) data are thus increasingly being used to understand taxon history and to identify potential status and baseline (pre‐anthropogenic) conditions, which in turn allows the optimization of species conservation plans. We combined species distribution models (SDMs) with current and palaeo‐occurrences of Microtus cabrerae, a threatened Mediterranean rodent, to circumvent the limitations of the palaeorecord (e.g. spatio‐temporal bias), to characterize this rodent's history (potential status and baseline conditions) since the Mid‐Holocene (~6,000 yr BP), and to determine the relative importance of climatic and anthropogenic factors in its decline.LocationHistoric distributional range of M. cabrerae (Iberian Peninsula and SE France).MethodsWe used generalized linear models (GLMs) to study the effects of four climatic (temperature and precipitation seasonality, minimum temperature, aridity) and four anthropogenic variables (human influence index, surface area of irrigated crops, rain‐fed crops and pastures) on the species’ current distribution. Then, we used an ensemble of SDMs to estimate its current and Mid‐Holocene potential distributions based only on climate variables, and validated model projections against current and palaeo records. Finally, suitability maps were analysed to study the species’ range dynamics during the Late Holocene.ResultsMicrotus cabrerae's current distribution is constrained by both climatic and anthropogenic variables. Temperature and precipitation seasonality—but not aridity or minimum temperature—play an important positive role in constraining its distribution, but agriculture is the main human activity that affects it negatively. Climatic changes during the Late Holocene probably led to an expansion of its distribution without fragmentating its range.Main conclusionsContrary to previous hypotheses, under natural conditions, M. cabrerae should be in an expansive phase of its taxon cycle. Yet, its potential and current conservation status is negatively affected by agricultural habitat destruction, suggesting that conservation strategies should aim to control agricultural intensification.