Plio-Pleistocene climatic change had a major impact on the assembly and disassembly processes of Iberian rodent communities

Comprehension of changes in community composition through multiple spatio-temporal scales is a prime challenge in ecology and palaeobiology. However, assembly, structuring and disassembly of biotic metacommunities in deep-time is insufficiently known. To address this, we used the extensively sampled Iberian Plio-Pleistocene fossil record of rodent faunas as our model system to explore how global climatic events may alter metacommunity structure. Through factor analysis, we found five sets of genera, called faunal components, which co-vary in proportional diversity over time. These faunal components had different spatio-temporal distributions throughout the Plio-Pleistocene, resulting in non-random changes in species assemblages, particularly in response to the development of the Pleistocene glaciations. Three successive metacommunities with distinctive taxonomic structures were identified as a consequence of the differential responses of their members to global climatic change: (1) Ruscinian subtropical faunas (5.3–3.4 Ma) dominated by a faunal component that can be considered as a Miocene legacy; (2) transition faunas during the Villafranchian–Biharian (3.4–0.8 Ma) with a mixture of different faunal components; and (3) final dominance of the temperate Toringian faunas (0.8–0.01 Ma) that would lead to the modern Iberian assemblage. The influence of the cooling global temperature drove the reorganisation of these rodent metacommunities. Selective extinction processes due to this large-scale environmental disturbance progressively eliminated the subtropical specialist species from the early Pliocene metacommunity. This disassembly process was accompanied by the organisation of a diversified metacommunity with an increased importance of biome generalist species, and finally followed by the assembly during the middle–late Pleistocene of a new set of species specialised in the novel environments developed as a consequence of the glaciations

Early adaptive radiations of Aplodontoidea (Rodentia, Mammalia) on the Holarctic region: systematics, and phylogenetic and paleobiogeographic implications

International audienceThe Aplodontoidea, now restricted to only oneNorth American species (Aplodontia rufa), have shown awide Holarctic extension since the Upper Eocene. As theirfossil record is poor, their phylogenetic relationships andthe origins of their successive radiations remain unclear.We perform here phylogenetic analyses, primarily based ondental evidence (94 dental of 97 characters), restricted toPaleogene and early Miocene taxa (46 taxa) in order toavoid biases introduced by substantially derived (divergent)taxa. We confirm the inclusion of some problematicgenera such as Cedromus or Douglassciurus withinSciuroidea rather than in Aplodontoidea. Ephemeromysand Lophallomys appear as the most basal members of theAplodontoidea, and Epeiromys is the closest outgroup ofthe Sciuroidea-Aplodontoidea clade. The relationshipsamong the ‘‘prosciurines’’ remain unclear, with paraphyleticgenera such as Prosciurus and Haplomys. Theirdiagnoses are reevaluated and a new genus is described.The Aplodontidae, including the clade of the latter, andHaplomys liolophus display a dichotomy betweenAnsomyinae and Aplodontinae, the two crown groups. Thefirst clade formed by the European species argoviensis anddescendens (referred to a new genus) can be proposed as asister group of the species of Ansomys. The second branchof the dichotomy includes the European Plesispermophilusand Sciurodon as basal groups. The species of Parallomysdo not form a clade, and the genus appears paraphyletic.The last dichotomy separates the Allomys clade from the‘meniscomyine’ clade. Comparisons of the selected speciesallow consideration of their patterns of dental evolution(e.g. enlargement of P4, development of a metaloph—protoloph disto-mesial connection, of crescentic shape inmain cusps and ectoloph, of a buccal protruding compressedmesostyle, of a metastylid crest or an anterior spurof the hypoconid, etc.). The split between sciuroids andaplodontoids occurred in North America, and then aplodontoidsdispersed rapidly throughout the whole Holarcticregion. The first aplodontid adaptive radiation took placeeither in North America or in Asia. Periodic exchangesoccurred between Europe, Asia and North America, andthe last radiations (meniscomyines) were restricted inNorth America