What story does geographic separation of insular bats tell? A case study on Sardinian Rhinolophids

Competition may lead to changes in a species’ environmental niche in areas of sympatry and shifts in the niche of weaker competitors to occupy areas where stronger ones are rarer. Although mainland Mediterranean (Rhinolophus euryale) and Mehely’s (R. mehelyi) horseshoe bats mitigate competition by habitat partitioning, this may not be true on resource-limited systems such as islands. We hypothesize that SardinianR. euryale(SAR) have a distinct ecological niche suited to persist in the south of Sardinia whereR. mehelyiis rarer. Assuming that SAR originated from other Italian populations (PES) – mostly allopatric withR. mehelyi– once on Sardinia the former may have undergone niche displacement driven byR. mehelyi. Alternatively, its niche could have been inherited from a Maghrebian source population. We: a) generated Maxent Species Distribution Models (SDM) for Sardinian populations; b) calibrated a model with PES occurrences and projected it to Sardinia to see whether PES niche would increaseR. euryale’s sympatry withR. mehelyi; and c) tested for niche similarity betweenR. mehelyiand PES, PES and SAR, andR. mehelyiand SAR. Finally we predictedR. euryale’s range in Northern Africa both in the present and during the Last Glacial Maximum (LGM) by calibrating SDMs respectively with SAR and PES occurrences and projecting them to the Maghreb.R. mehelyiand PES showed niche similarity potentially leading to competition. According to PES’ niche,R. euryalewould show a larger sympatry withR. mehelyion Sardinia than according to SAR niche. Such niches have null similarity. The current and LGM Maghrebian ranges ofR. euryalewere predicted to be wide according to SAR’s niche, negligible according to PES’ niche. SAR’s niche allowsR. euryaleto persist whereR. mehelyiis rarer and competition probably mild. Possible explanations may be competition-driven niche displacement or Maghrebian origin.