Defining the Island Dwarfing Rate of an Extinct Sicilian Elephant Using Ancient DNA

Abstract

Evolution on islands, and the often extreme phenotypic changes associated with it, has attracted much interest from evolutionary biologists. However, measuring the rate of change of a particular phenotypic trait of extinct animals can be challenging, due to the incompleteness of the fossil record. Here, we use combined molecular and fossil evidence to define the minimum and maximum rate of dwarfing in an extinct Mediterranean dwarf elephant from Puntali Cave (Sicily). Despite the challenges associated with recovering ancient DNA from warm climates, we successfully retrieved a mitogenome from a sample with an estimated age between 147,000 and 50,000 years. Our results suggest that this specific Sicilian elephant lineage evolved from one of the largest terrestrial mammals in the Pleistocene to a comparatively small-bodied island species, with an estimated average mass reduction of 0.79 - 18.45 kg and height reduction of 0.15 - 3.41 mm per generation. We show that combining ancient DNA, palaeontological and geochronological evidence can constrain the timing of phenotypic changes within narrower age boundaries than could be achieved using any source of evidence in isolation.