Phylogeny and evolution of body mass in didelphid marsupials (Marsupialia: Didelphimorphia: Didelphidae)

AMADOR, LUCILA INÉS; GIANNINI, NORBERTO PEDRO

ORGANISMS DIVERSITY & EVOLUTION

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2016 vol. 16 p. 641 - 657

1439-6092

Most extant New World marsupials belong in theDidelphidae, which comprises ca. 110 currently recognizedspecies of opossums. Didelphids are small mammals withtheir mean body mass, at species level, ranging from ca. 7 gto 2.2 kg. The largest species belong in a single clade, whilesubstantial variation remains scattered across the remaininggroups. We seek out to explore the details of this mass variationin an evolutionary framework. To this end, we first reconstructedthe phylogeny of didelphids based on an extensive,although fragmentary sample of sequences from ten genes.We recovered a fully resolved, highly robust phylogeny thattested and confirmed most previously reported groupings,providing a simultaneous depiction of phylogenetic relationshipsfor 81% of currently recognized species and all relevantsupra-specific clades. As much as 69 % of total body massvariation in didelphids was explained by this phylogenetichypothesis. Mapped on it, mass variation evolved as muchas 6.8 kg of total changes, starting from a reconstructed ancestralbody mass range of 22?33 g. No single, family-widepattern was evident; in fact, the dominant pattern for massvariation was that of increases in body mass along a few successivebranches, or phyletic giantism, followed byapomorphic nanism, i.e., decreases localized in single terminalbranches. Phyletic trends indicated the persistence of gradual,directional changes along considerable spans of geologicaltime and show that substantial variation of interest resides inthis and perhaps most groups of small mammals.