Biogeography of Italy revisited: genetic lineages confirm major phylogeographic patterns and a pre-Pleistocene origin of its biota

Abstract

Warm-adapted species survived the cold stages of the past glacial-interglacial cycles in southern European peninsulas and recolonized major parts of Central and Northern Europe in the wake of postglacial warming. However, many of the genetic lineages which differentiated within these refugia predate even the Pleistocene. One of these refugia is the Italian Peninsula with its surrounding islands. In this meta-analysis, we compiled phylogeographic patterns of multiple species across this region. We transformed existing geographic information on 78 animal and plant species (with a total of 471 genetic lineages) within 17 predefined areas into presence/absence matrices. We elaborated three matrices: (i) only old lineages exclusively distinguished by deep splits, (ii) only young lineages distinguished by shallow (i.e. recent) splits, and (iii) presence/absence of the respective species. To infer biogeographic relationships between the predefined areas, we performed bootstrapped neighbour joining cluster analyses on these three matrices. In addition, we reviewed the geological history of Italy to identify causes of the observed biogeographic patterns. We found Sardinia and Corsica to be biogeographically closely linked with each other, and that they diverge strongly from all other regions. Sicily also diverges strongly from all other regions, while the intra-island differentiation was comparatively low. On the Italian mainland, Calabria exhibited the most pronounced biogeographic differentiation, often with several lineages present, resulting from old vicariance events within the region. Furthermore, southern Apulia and the Po Plain with adjoining areas of northern peninsular Italy displayed considerable distinctiveness. Admixture prevailed in the areas between these three regions. The ancient isolation of Sicily, as well as Sardinia plus Corsica, resulted in endemic lineages with only moderate recent exchange with adjacent mainland regions. Pronounced diversification occurs within the Italian Peninsula. The complex tectonic activities, such as shifting (micro)plates, submergence of major parts of peninsular Italy with the genesis of numerous Pliocene islands, in combination with the climatic cycles during the Pleistocene have most likely generated the current biogeographic pattern of species. Immigrations from the Balkan Peninsula into northern Italy partly accounted for the distinctiveness of this region.

The Endemic Vascular Flora of Sardinia: A Dynamic Checklist with an Overview of Biogeography and Conservation Status

“…These conditions are common in several Sardinian crystalline massifs such as Gennargentu [ 105 ], Sette Fratelli [ 106 ], or Limbara [ 107 ]. Taken together, these taxa represent the overwhelming majority of endemic vascular taxa and support the biogeographic scheme that characterises the independent Cyrno-Sardinian and Tuscan Archipelago province, already reported on the basis of faunistic and floristic approaches (e.g., [ 19 , 29 , 108 , 109 , 110 , 111 ]).…”

New distribution data and phylogenetic approach reveal bioregionalization of the western Palearctic ants

“…The biogeographic affinity of ant assemblages between the Tyrrhenian islands and the Iberian Peninsula suggests the evolutionary history shared by their fauna (Figures 2c-d and 3c-d). This may be due to the historical expansion of old lineages through land bridges (Senczuk et al, 2017; Dapporto et al, 2019; Schmitt et al, 2021), or to the legacy of more ancient geographic connections. Corsica and Sardinia islands were parts of the Tyrrhenian microplate which was separated from the Iberian Peninsula, and thus some lineages may persist with the same origins as the Iberian fauna (Ketmaier, Caccone & Silva-Opps, 2013; Schmitt et al, 2021).…”

“…Notably, delineations of regional lists highlight the biogeographic uniqueness of Sicily, Maltese and Cyprus islands (Figure 2). The SDMs we used to make range predictions do not correct for dispersal limitations, so the long-term isolation and complex geologic history of these islands (Poulakakis et al, 2013; Schmitt et al, 2021) and other regions with similar histories were not considered for the grid assemblage regionalization.…”

“…Moreover, the strong biogeographic affinities between some isolated regions also reveal the legacy of historical land connections. The high similarity in the fauna of the Apennine Peninsula and Adriatic Balkans, the Corsica and Sardinia islands, and the Sicilian and Maltese islands (Figures 2 and 3) can be explained by the biotic exchanges through land bridges during the period of partial disappearance of the Mediterranean Sea in late Miocene (i.e., Messinian salinity crisis) and Quaternary glacial periods (Randi, 2007;Schlick-Steiner et al, 2007;Schmitt, 2007;Dapporto et al, 2014;Schmitt et al, 2021). The biogeographic affinity of ant assemblages between the Tyrrhenian islands and the Iberian Peninsula suggests the evolutionary history shared by their fauna (Figures 2c-d and 3c-d).…”

Phylogeography of Sarmarutilus rubilio (Cypriniformes: Leuciscidae): Complex Genetic Structure, Clues to a New Cryptic Species and Further Insights into Roaches Phylogeny

“…In addition to past climatic fluctuations, freshwater fishes’ phylogeographic patterns and distribution in Italy were also driven by mountain ridges and the presence/lack of connections among drainages [ 14 , 27 , 95 ]; this is especially true for those taxa, such as Leuciscidae, that cannot disperse through the sea due to their little or no tolerance to brackish water [ 26 ] and references therein. Indeed, the Apennine chain, dividing peninsular Italy longitudinally from north to south, was found to influence the biogeographic structure even of semiaquatic vertebrate species but not that of the peninsular terrestrial ones (if not marginally) [ 96 ].…”