Skull evolution and lineage diversification in endemic Malagasy carnivorans

Madagascar is one of the world’s foremost biodiversity hotspots with more
than 90% of its species endemic to the island. Malagasy carnivorans are
one of only four extant terrestrial mammalian clades endemic to
Madagascar. Although there are only eight extant species, these
carnivorans exhibit remarkable phenotypic and ecological diversity that is
often hypothesized to have diversified through an adaptive radiation.
Here, we investigated the evolution of skull diversity in Malagasy
carnivorans and tested if they exhibited characteristics of convergence
and an adaptive radiation. We found that their skull disparity exceeds
that of any other feliform family, as their skulls vary widely and
strikingly capture a large amount of the morphological variation found
across all feliforms. We also found evidence of shared adaptive zones in
cranial shape between euplerid subclades and felids, herpestids, and
viverrids. Lastly, contrary to predictions of adaptive radiation, we found
that Malagasy carnivorans do not exhibit rapid lineage diversification and
only marginally faster rates of mandibular shape evolution, and to a
lesser extent cranial shape evolution, compared to other feliforms. These
results reveal that exceptional diversification rates are not necessary to
generate the striking phenotypic diversity that evolved in carnivorans
after their dispersal to and isolation in Madagascar.