Aligning morphologies

RAMÍREZ, M. J.

Paris, Francia

Congreso; 23rd Annual Meeting of the Willi Hennig Society ‘‘Phylogenetics and Evolutionary Biology’’; 2004

Willi Hennig Society

The sequential application of first resolving primaryhomology, and second searching for optimal phylogenetictrees is not granted to produce optimal resultswhen there are more than one plausible primary homologyschemas. This problem is well known for the analysisof DNA sequence data, but has received little attentionin the case of more complex data, like morphology andbehavior. The interaction between comparative studiesand phylogenetic inference is most patent in the favoringof comparisons between close relatives at the time ofdeciding on homology. The traditional problem ofalternative anatomical interpretations affecting morphologicalcharacters is identified as belonging to the sameconceptual problem as the alternative alignments ofDNA sequences. Gains and losses are equivalent toinsertions and deletions, respectively, but not all homologyshifts in morphology structures are equally costly;homology shifts in anatomical interpretations must takeaccount of heterogeneous bounds in the number ofconditions observed in morphological characters (differingfrom the four possible states in nucleotide sequencedata); and transformations in anatomy are frequentlymultidimensional (differing from the one dimension ofsequence transformation events). I present an examplecase of 93 representative species of the spider familyAnyphaenidae. The homology of some sclerites in themale copulatory organ is disputed, and that regioninvolves phylogenetic information scored in more than20 characters (out of 200). The alternative interpretationsof the anatomy produce different optimal tree setsand different ancestral reconstructions of the structuresover the trees. I discuss the requisites, and present aproposal, for scoring and analyzing a morphologicaldataset for the simultaneous evaluation of alternativehomologies and phylogenetic hypotheses. The mostparsimonious trees are identified together with the mostparsimonious homology schemas.