The origin of island endemics provides outstanding opportunities to investigate evolutionary adaptation and diversification. This study focuses on a little-known yet remarkable radiation of deer from the Pleistocene of Malta. A large sample of teeth, bones and antlers from Għar Dalam Cave was subjected to detailed analysis of metric variables and qualitative morphological traits. Based on comparisons with variation in extant deer plus cluster analysis, a minimum of three size groups was identified, corresponding approximately in size to modern roe, fallow and small red deer. Analysis of morphological characters on skeletal elements strongly indicates that the ancestry of all three groups derives from red deer (Cervus elaphus). All groups demonstrate allometric grade shifts in limb bone proportions (progressively stockier with size reduction), plus likely differences in antler-base morphology. The inclusion of juvenile bones illustrates the ontogenetic trajectory for each of the three taxa. A small but critical sample of fossils collected in situ at Għar Dalam during the study demonstrates probable contemporaneity of the size groups, which together with the presence of only a single red deer size-class on Sicily (the likely source area), implies cladogenetic speciation on Malta itself. The stratigraphic context of in situ bones in relation to recent dating of speleothem within Għar Dalam reveals the origin of the Maltese deer to be much earlier than previously thought, pre-dating 160 ka, with the majority of finds in the region 116-80 ka; this roughly corresponds to age estimates for the Sicilian population. However, although the largest size category on Malta is similar in size to the Sicilian red deer, it differs from them in antler and postcranial proportions, and the medium-size category on Malta may be the progenitor of the radiation. The stratigraphic relations and degree of divergence among the three Maltese size-groups is suggestive of species status.
|Date of Award||1 Oct 2019|
- The University of Bristol
|Supervisor||David A Richards (Supervisor) & Adrian M. Lister (Supervisor)|