Differences in chemical signals may explain species recognition between an island lizard, Podarcis atrata, and related mainland lizards, P hispanica

Chemical signals can be the basis of interspecific recognition and speciation in many animals The Columbretes Islands wall lizard Podarcis atrata is very close genetically to the mainland Iberian wall lizard Podarcis hispanica However a previous study suggested that chemosensory interspecific recognition would avoid reproductive interactions and hybridization between these two species These results suggested that chemicals used in intraspecific communication might differ in composition and/or proportions between these two species In this paper we used gas chromatography-mass spectrometry (GC-MS) to characterize the chemical composition of the lipophilic fraction from femoral gland secretions of male P atrata and P hispanica The analysis showed that chemicals found in femoral secretions varied in composition and proportions between species and between populations Seven steroids and two unidentified waxy esters were exclusive of P atrata lizards from the islands In contrast nine steroids and other six compounds were only found in mainland P hispanica There were also differences in proportions of shared compounds between species Moreover all these differences were higher between P atrata and P hispanica than between any population of P hispanica Chemical differences might be consequence of genetic differences but they could also be explained by adaptation to different habitats with different climatic conditions or diet resources Compounds that ale specific of each species or differences in the pattern of compounds could explain species recognition Therefore these results of chemical composition and previous studies of chemosensory recognition reinforce the fact that the genetic differences between P hispanica and P atrata may result in an effective reproductive isolation between these two taxa Crown Copyright (C) 2010 Published by Elsevier Ltd All rights reserved