Insular mammalian fauna dynamics and paleogeography: A lesson from the Western Mediterranean islands

Abstract

Since the time of Darwin (1859) and Wallace (1869), islands have been regarded by scientists as a prime target for scrutinizing the forces that may influence evolution and diversification and important elements in biogeographic studies. This research aims to scrutinize whether and to what extent the composition and structure of past mammal insular faunas and their changes through time may provide sound clues for inferring the paleogeographical evolution of a region. As a case study, I critically analyzed the dynamics shown by the Plio-Pleistocene mammalian fauna of 3 Western Mediterranean insular districts, the Balearic Islands, Sardinia and Sicily, each characterized by its own peculiar paleobiogeographical evolutionary history. The revision of faunas and the critical analysis of the dispersal ability of the ancestors of island settlers have allowed hypothesizing on the time and mode of island colonization. The results obtained confirm that the early isolation of the Balearic Islands from the mainland led to the establishment of an endemic fauna since the pre-Messinian Miocene (?Astaracian European Land Mammal Age, MN7/8), and that Sardinia has definitely been isolated since the Pliocene, although dispersal events led to some faunal turnovers during the Pleistocene. In addition, the results suggest for Sicily a complex, still imperfectly disentangled history of alternate phases of complete separation and sporadic, more or less difficult connections with southern Italy.

Organization of Squamata (Reptilia) assemblages in Mediterranean archipelagos

“…Crete, Mallorca, and Sardinia were completely isolated by the end of the Messinian age and had impoverished and unbalanced faunas until the Late Pleistocene—Holocene (Krijgsman, Hilgen, Raffi, Sierro, & Wilson, ; Melis, Palombo, Ghaleb, & Meloni, ; Meulenkamp, Wortel, Wamel, Spakman, & Strating, ). Although currently situated very close to the continent, Sicily possibly had its colonization hindered by the fragmentation of Calabria into several islands until the mid‐Pleistocene, and the continuous persistence of the Strait of Messina throughout the Late Glacial (Marra, ; Palombo, ).…”

Genomic analyses of the extinct Sardinian dhole (Cynotherium sardous) reveal its evolutionary history

“…Given this complex scenario, a number of earlier studies considered the Sardinian dhole as a subgenus of Xenocyon, Cuon, or a derived form of Canis 3,10-12 that might have reached Sardinia and Corsica by sweepstake or passive dispersal at the transition between Early and Middle Pleistocene 4,20 . This phenomenon is especially feasible during periods of fluctuation of the sea level and have been known to contribute to the faunal turnover in Sardinia 4,18,20 .…”

“…Nevertheless, Pleistocene mammals of Sardinia are currently divided into two major faunal complexes, an older one (Nesogoral Faunal Complex) and a younger one (Tyrrhenicola Faunal Complex) divided by the end of the Early Pleistocene 18,19 . Given this complex scenario, a number of earlier studies considered the Sardinian dhole as a subgenus of Xenocyon, Cuon, or a derived form of Canis 3,10-12 that might have reached Sardinia and Corsica by sweepstake or passive dispersal at the transition between Early and Middle Pleistocene 4,20 . This phenomenon is especially feasible during periods of fluctuation of the sea level and have been known to contribute to the faunal turnover in Sardinia 4,18,20 .…”

Morphological divergence in giant fossil dormice

“…Nevertheless, the exceptional increase in body size associated with insular gigantism can result in unexpected morphologies, and evolutionary shifts to novel ecologies in context of the island setting might also be a powerful driver of evolutionary changes in morphology via functional adaptation. Dormice (Gliridae) are potent exemplars of the evolutionary 'island effect' of body size increase, having evolved extraordinary large sizes more frequently than other mammals -and on at least eight different islands since the beginning of the Miocene [26,27]. Furthermore, giant dormice are known from both the fossil record (e.g.…”