Islands are often regarded by scientists as living laboratories of evolution and an optimal context for the study of forces influencing evolution and diversification.Two main issues have been attentively scrutinized a...Islands are often regarded by scientists as living laboratories of evolution and an optimal context for the study of forces influencing evolution and diversification.Two main issues have been attentively scrutinized and debated:the loss of biodiversity and the peculiar changes undergone by island settlers,primarily changes in size of endemic vertebrates.Over time,several hypotheses have been formulated to explain the causal mechanism of body size modification.Faunas of those islands where mainland taxa migrate more than once provide the most interesting data to answer the question of whether or not trends of insular taxa result from a predictable response to differences in competition and availability of niches between insular and mainland environments.To contribute to the debate,the body size structure of the Pleistocene mammalian faunas from two Mediterranean islands,Sicily and Crete,were analyzed and compared with the structure of coeval mainland faunas.The results obtained suggest that:(i)size of endemic species does not directly depend on the area of islands;(ii)evolution and size of endemic species seems somewhat affected by the degree of isolation(constraining coloniza-tion from mainland)and physiography(sometimes permitting adaptive radiation);(iii)in unbalanced insular communities,the shift in size of non-carnivorous species largely depends on the nature of competing species;and(iv)body size of carnivorous species mainly depends on the size of the most available prey.Consequently,it is rational to suppose that the body size of insular mammals mainly results from the peculiar biological dynamics that characterizes unbalanced insular communities.Ecological interaction,particularly the intraguild competition,is the major driver behind the evolution of insular communities,leading towards an optimization of energy balance through a change in body size of endemic settlers.展开更多
Cenozoic terrestrial mammals from Sardinia contribute substantial information for reconstructing the complex his-tory of the western Mediterranean.The occurrence of endemic perissodactyls in Eocene marine and marsh de...Cenozoic terrestrial mammals from Sardinia contribute substantial information for reconstructing the complex his-tory of the western Mediterranean.The occurrence of endemic perissodactyls in Eocene marine and marsh deposits suggests the existence of ecological or physical barriers between the Corso-Sardinian massif and the Iberian-Occitanic area.At the end of the Oligocene,isolation of Sardinia was almost complete,although a migration from Europe occurred at the beginning of the Early Miocene,as indicated by the unbalanced endemic fauna from Oschiri.During the Late Miocene,the Tusco-Sardinian palaeobioprovince came into existence as an isolated region inhab-ited by the quite diversified,but notably endemic,Oreopithecus fauna.Sardinia was definitely isolated from Tuscany by the Messinian,but temporary connections with the European mainland possibly allowed the colonization of forerunners of some Sardinian Pliocene taxa.During the Plio-Pleistocene,Sardinia maintained permanent isolation.However,sea level drop,resulting in a relatively short distance between Sardinia and the European mainland,allowed different migratory events.From the Late Pliocene to the Late Pleistocene–Holocene,two main mammalian faunal complexes(FC)can be recognized:the Nesogoral FC(Late Pliocene-Early Pleistocene)and the Microtus(Tyrrhenicola)FC(late Early Pleistocene–Early Holocene).At the transition from Nesogoral to Microtus(Tyrrhenicola)FC,approximately 47%of the genera and 76%of the species disappeared,while approximately 58%of the genera and 71%of the species appeared.A noticeable turnover followed the arrival of Neolithic man and his accompanying fauna.Nonetheless,Praemegaceros was still present at about 7000 years BP,while Microtus(Tyrrhenicola)and Prolagus are respectively recorded in the Bronze and Iron Ages.展开更多
文摘Islands are often regarded by scientists as living laboratories of evolution and an optimal context for the study of forces influencing evolution and diversification.Two main issues have been attentively scrutinized and debated:the loss of biodiversity and the peculiar changes undergone by island settlers,primarily changes in size of endemic vertebrates.Over time,several hypotheses have been formulated to explain the causal mechanism of body size modification.Faunas of those islands where mainland taxa migrate more than once provide the most interesting data to answer the question of whether or not trends of insular taxa result from a predictable response to differences in competition and availability of niches between insular and mainland environments.To contribute to the debate,the body size structure of the Pleistocene mammalian faunas from two Mediterranean islands,Sicily and Crete,were analyzed and compared with the structure of coeval mainland faunas.The results obtained suggest that:(i)size of endemic species does not directly depend on the area of islands;(ii)evolution and size of endemic species seems somewhat affected by the degree of isolation(constraining coloniza-tion from mainland)and physiography(sometimes permitting adaptive radiation);(iii)in unbalanced insular communities,the shift in size of non-carnivorous species largely depends on the nature of competing species;and(iv)body size of carnivorous species mainly depends on the size of the most available prey.Consequently,it is rational to suppose that the body size of insular mammals mainly results from the peculiar biological dynamics that characterizes unbalanced insular communities.Ecological interaction,particularly the intraguild competition,is the major driver behind the evolution of insular communities,leading towards an optimization of energy balance through a change in body size of endemic settlers.
文摘Cenozoic terrestrial mammals from Sardinia contribute substantial information for reconstructing the complex his-tory of the western Mediterranean.The occurrence of endemic perissodactyls in Eocene marine and marsh deposits suggests the existence of ecological or physical barriers between the Corso-Sardinian massif and the Iberian-Occitanic area.At the end of the Oligocene,isolation of Sardinia was almost complete,although a migration from Europe occurred at the beginning of the Early Miocene,as indicated by the unbalanced endemic fauna from Oschiri.During the Late Miocene,the Tusco-Sardinian palaeobioprovince came into existence as an isolated region inhab-ited by the quite diversified,but notably endemic,Oreopithecus fauna.Sardinia was definitely isolated from Tuscany by the Messinian,but temporary connections with the European mainland possibly allowed the colonization of forerunners of some Sardinian Pliocene taxa.During the Plio-Pleistocene,Sardinia maintained permanent isolation.However,sea level drop,resulting in a relatively short distance between Sardinia and the European mainland,allowed different migratory events.From the Late Pliocene to the Late Pleistocene–Holocene,two main mammalian faunal complexes(FC)can be recognized:the Nesogoral FC(Late Pliocene-Early Pleistocene)and the Microtus(Tyrrhenicola)FC(late Early Pleistocene–Early Holocene).At the transition from Nesogoral to Microtus(Tyrrhenicola)FC,approximately 47%of the genera and 76%of the species disappeared,while approximately 58%of the genera and 71%of the species appeared.A noticeable turnover followed the arrival of Neolithic man and his accompanying fauna.Nonetheless,Praemegaceros was still present at about 7000 years BP,while Microtus(Tyrrhenicola)and Prolagus are respectively recorded in the Bronze and Iron Ages.
