Long-interval monitoring reveals changes in the structure of a reptile community in a biogeographic transition zone

Abstract

Transition zones between biogeographical regions are natural scenarios to examine responses to local disturbances between species with contrasting biogeographic affinities. We compared absolute abundances of reptile species between fieldwork surveys carried out in 1999-2001 and 2012-2014 along a 1.5 km linear transect at the Peneda-Gerês National Park (NW Portugal), an area located in the transition zone between Mediterranean and Atlantic biogeographical regions. During the 13-year period, wildfires in 2007 and 2009 burnt two adjacent areas located on the southern part of the study area. Based on Landsat imagery, land cover analysis demonstrated significant differences between both periods, with an increase of open areas caused by the wildfires. We performed 99 surveys and detected 1774 reptiles belonging to five lizard and six snake species. There were changes in the reptile assemblage: Lacerta schreiberi (Atlantic lizard) showed a decrease in relative abundance from the first period, Podarcis sp (wall lizards) showed an increase, and Psammodromus algirus (Mediterranean lizard) colonized the study site in the second period. This field-based monitoring study confirms niche modelling predictions that forecasted range contraction for some Atlantic reptiles and expansion for some Mediterranean reptiles. Our results emphasize the importance of long-term monitoring to understand the magnitude of disturbance impacts on (reptile) communities.