Morphology, Molecules, and the Phylogenetics of Cetaceans

Abstract

Recent phylogenetic analyses of cetacean relationships based on DNA sequence data have challenged the traditional view that baleen whales (Mysticeti) and toothed whales (Odontoceti) are each monophyletic, arguing instead that baleen whales are the sister group of the odontocete family Physeteridae (sperm whales). We reexamined this issue in light of a morphological data set composed of 207 characters and molecular data sets of published 12S, 16S, and cytochrome b mitochondrial DNA sequences. We reach four primary conclusions: (1) Our morphological data set strongly supports the traditional view of odontocete monophyly; (2) the unrooted molecular and morphological trees are very similar, and most of the conflict results from alternative rooting positions; (3) the rooting position of the molecular tree is sensitive to choice of artiodactyls outgroup taxa and the treatment of two small but ambiguously aligned regions of the 12S and 16S sequences, whereas the morphological root is strongly supported; and (4) combined analyses of the morphological and molecular data provide a well-supported phylogenetic estimate consistent with that based on the morphological data alone (and the traditional view of toothed-whale monophyly) but with increased bootstrap support at nearly every node of the tree.

Evolution of hyperphalangy and digit reduction in the cetacean manus

“…Here, we use a larger, taxonomically diverse sample of mysticetes and odontocetes. Although both studies optimize character states onto a phylogeny of odontocetes proposed by Messenger and McGuire (1998), the larger sample size of this study provided sufficient data to also trace characters onto a phylogeny of mysticetes (Rychel et al, 2004;Saski et al, 2005;Nikaido et al, 2006). This study also uses a different hypothesis of digital ray loss in tetradactylous mysticetes (i.e., loss of digital ray I).…”

“…Because the current published literature lacks a specieslevel cetacean phylogeny, two trees were used. For odontocetes, the combined morphological and molecular tree of Messenger and McGuire (1998) was used. For mysticetes, recent studies based on mtDNA and nuclear DNA sequences (Rychel et al, 2004;Sasaki et al, 2005), and insertions of transposons (Nikaido et al, 2006) yield generally consistent results among taxa.…”

Morfologia do sincrânio do boto-cinza, Sotalia guianensis (P.J. van Bénéden) (Cetacea, Delphinidae)

“…Cabe salientar aqui que as principais tendências evolutivas entre os odontocetos e a maior parte das modificações importantes neste grupo estão relacionadas ao topo do crânio, estejam elas associadas à anatomia facial das passagens nasais ou as condições encontradas nos ossos (exceção feita ao isolamento dos ossos periótico-timpânicos). Dentre estas estão a concavidade dorsal do cranium, a elevação e a assimetria do vértice craniano, a presença de forames nos pré-maxilares e a expansão da face com encurtamento da região intertemporal ("telescoping") (FORDYCE & BARNES 1994, MESSENGER & MCGUIRE 1998. Portanto, qualquer modificação na região do basicrânio é evidentemente importante e incomum, merecendo ser investigada numa amostra maior para detectar possíveis variações populacionais.…”

Phylogenetics of Australian Acacia thrips: the evolution of behaviour and ecology

“…The second reason for including our COI data in the combined analyses is that the ILD test has been shown to be very conservative and may be an unreliable guide to character incongruence (Davis et al, 1998;Messenger and Maguire, 1998;Yoder et al, 2001).…”