[Aim]: Lepus castroviejoi and Lepus corsicanus are sister species with allopatric distributions that share extensive phenotypic and genetic variation. Under the framework of niche conservatism, we assessed whether these species have similar ecological niches, which could provide insights into their mode of divergence, conservation, and taxonomic status. [Location]: The distribution range of L. castroviejoi in the northern Iberian Peninsula, and that of L. corsicanus in mainland Italy and Sicily. [Methods]: We developed spatially explicit ecological models to characterize the niches of the two species by modelling them separately and together. Individual models were transferred to the territory of the sister species to explore their niche relationships. Predictions were assessed for discrimination and calibration in a cross-assessment procedure. [Results]: The model trained with L. castroviejoi was not able to predict the range of L. corsicanus, whereas the model trained with L. corsicanus was able to discriminate the L. castroviejoi distribution better than by chance alone (AUC = 0.814), although the reliability of the predictions was limited. The model trained with L. corsicanus in Italy's mainland (excluding the range in Sicily), however, discriminated L. castroviejoi presences/absences (AUC = 0.788) and accurately predicted its probability of occurrence. Furthermore, a well-calibrated model, which was able to discriminate the species distributions (L. castroviejoi, AUC = 0.828; L. corsicanus, AUC = 0.956), was obtained when the species were considered together. [Main conclusions]: Our results suggest that L. castroviejoi and L. corsicanus share extensive niche properties, which reinforces their possible conspecific status. The ecological niche of their ancestor may have resembled the present occupied niche of L. corsicanus in mainland Italy, given that this model was able to accurately predict the distribution range of both species. Finally, ecological evidence suggests that niche conservatism may explain the fragmentation in the distribution range of their ancestor, which may have been the driver of the initial stages of divergence.P.A. received a José Castillejo fellowship (2010 –2011)in Portugal awarded by the Ministerio de Ciencia e Innovación to conduct this study, and was also partly supported bythe CGL2009-11316/BOS Spanish Government and FEDER project. P.A. and J.M.-F. currently hold postdoctoral grantsfrom the Fundaçao para a Ciência e a Tecnologia (FCT),funded by Programa Operacional Potencial Humano (POPH)– Quadro de Referência Estratégico Nacional (QREN) fromthe European Social Fund and by the Portuguese Ministério da Educaçao e Ciência (SFRH/BPD/90320/2012 and SFRH/BPD/43264/2008, respectively). Financial support was partly obtained from the research project grants PTDC/BIA-EVF/111931/2009 and PTDC/BIA-EVF/115069/2009, funded by FEDER through the COMPETE program and Portuguese national funds through the FCT.Peer Reviewe
