Evolution of post-weaning skull ontogeny in New World Opossums (Didelphidae)

FLORES, D.; GIANNINI, N.; ABDALA, F.

ORGANISMS DIVERSITY & EVOLUTION

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2018

1439-6092

Quantification of mammalian skull development has received much attention in therecent literature. Previous results in different lineages have shown an effect of historicallegacy on patterns of skull growth. In marsupials, the skull of adults exhibits highvariation across species, principally along a size axis. The development keys of themarsupial skull are fundamental to understanding the evolution of skull function in thisclade. Its generally well resolved phylogeny makes the group ideal for studyingmacroevolution of skull ontogeny. Here we tested the hypothesis that ontogeneticsimilarity is correlated with phylogeny in New World marsupials, so that developmentalpatterns are expected to be conserved from ancestral opossums. We concatenated ourpreviously published ontogenetic cranial data from several opossum species with newontogenetic sequences and constructed an allometric space on the basis of a set ofcomparable cranial linear measurements. In this ontogenetic space we determined thedegree of correspondence of developmental patterns and the phylogeny of the group. Inaddition we mapped ontogenetic trajectories onto the opossum phylogeny, treating thetrajectories as composite, continuously varying characters. Didelphids differed widelyin the magnitude of skull allometry across species. Splanchnocranial componentsexhibited all possible patterns of inter-specific variation, whereas mandibular variableswere predominantly allometrically ?positive? and neurocranial components werepredominantly allometrically ?negative?. The distribution of species in allometric spacereflected the compounded effect of phylogeny and size variation characteristic ofdidelphids. The terminal morphology of related species differed in shape so theirontogenetic trajectories deviated with respect to that of reconstructed common ancestorsin varying degree. Phylogeny was the main factor structuring the allometric space ofNew World marsupials. Didelphids inherited an ancestral constellation of allometrycoefficients without change 40 and retained much of it throughout their lineage history.Conserved allometric values on the nodes splitting placental outgroups and marsupialssuggests a developmental basis common to all therians.