Genomic Support for a Moa–Tinamou Clade and Adaptive Morphological Convergence in Flightless Ratites

Abstract

One of the most startling discoveries in avian molecular phylogenetics is that the volant tinamous are embedded in the flightless ratites, but this topology remains controversial because recent morphological phylogenies place tinamous as the closest relative of a monophyletic ratite clade. Here, we integrate new phylogenomic sequences from 1,448 nuclear DNA loci totaling almost 1 million bp from the extinct little bush moa, Chilean tinamou, and emu with available sequences from ostrich, elegant crested tinamou, four neognaths, and the green anole. Phylogenetic analysis using standard homogeneous models and heterogeneous models robust to common topological artifacts recovered compelling support for ratite paraphyly with the little bush moa closest to tinamous within ratites. Ratite paraphyly was further corroborated by eight independent CR1 retroposon insertions. Analysis of morphological characters reinterpreted on a 27-gene paleognath topology indicates that many characters are convergent in the ratites, probably as the result of adaptation to a cursorial life style.

The Anatomy and Taxonomy of the Exquisitely Preserved Green River Formation (Early Eocene) Lithornithids (Aves) and the Relationships of Lithornithidae

“…By contrast, the nonmonophyly of Lithornithidae constraint added a significant number of steps (table 3). Constraining relationships to those obtained by Phillips et al, (2010), Baker et al (2014), and Mitchell et al (2014) led to an increase in the number of steps (41, 9% increase; 38, 8% increase; and 30, 6% increase, respectively) relative to the unconstrained tree. The number of MPTs was highest in the unconstrained "total" analysis.…”

“…Once tinamous are nested within a paraphyletic ratite assemblage in the constrained analyses, flight characters become ambiguously optimized (present in Neognathae, outgroups, and Palaeognathae). Recent phylogenies of extinct and extant palaeognaths (not sampling lithornithids) have painted a complex biogeographical picture largely inconsistent with a single loss of flight and rafting of already flightless taxa during Gondwanan breakup (e.g., Baker et al, 2014;Mitchell et al, 2014). Consistent placement of the volant Lithornithidae at the base of the clade suggests they could yield further insight into the plesiomorphic morphologies for a total group that has apparently lost flight repeatedly and dispersed broadly.…”

How do seemingly non-vagile clades accomplish trans-marine dispersal? Trait and dispersal evolution in the landfowl (Aves: Galliformes)

“…For example, large-bodied and flightless ratite birds (e.g. ostrich, emu) have seemingly colonized distant areas over evolutionary time despite severe dispersal constraints [5][6][7][8].…”

Comparative digesta retention patterns in ratites

“…), Kiwis (Apteryx spp. ), Moas, and Elephant birds; the debate is relevant to whether flightlessness in ratites evolved only once or several times independently (Harshman et al 2008, Phillips et al 2010, Baker et al 2014. Most recent results indicate a discrepancy between geographic location and phylogenetic relatedness among ratite species, suggesting that the major ratite lineages must have dispersed by flying before evolving converging anatomical characteristics and flightlessness (Mitchell et al 2014).…”