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Phylogenetic Relationships among the Major Lineages of Modern Elasmobranchs
| Content Provider | Semantic Scholar |
|---|---|
| Author | Naylor, Gavin J. P. Ryburn, J. A. Fedrigo, Olivier Lopez, Andres Fernando Jimenez |
| Copyright Year | 2004 |
| Abstract | Modern elasmobranchs (sharks skates and rays) are the extant survivors of one of the earliest offshoots of the vertebrate evolutionary tree. Their basal placement on the tree has drawn attention from researchers interested in understanding features characterizing the ancestral vertebrate condition. While their basal placement has long been appreciated, most studies have adopted the stance that a single token elasmobranch is sufficient to represent the basal vertebrate condition. Usually, the exemplar chosen is the spiny dogfish Squalus acanthias, the stalwart of comparative anatomy classes. However, the use of a single taxon is valid only to the extent that it is representative of the basal condition. This is unlikely to be the case for all traits. Instead, it is more likely that only a few of the character states seen in the exemplar will actually reflect the basal condition while the majority will be uniquely derived for the exemplar itself. A quick survey of the unique and atypical traits seen in the model organisms Drosophila, Caenorhabditis, Danio and Mus attests to the fact that single representative “model” organisms are often more “atypical” than they are “representative”. To estimate the basal condition for any group we must use a phylogenetic tree. Trees allow us to distinguish traits that are likely common to the ancestral condition from those that are unique to particular lineages. In order to do this, it is important: (a) that the phylogenetic tree used be accurate, and (b) that the taxa compared provide an even, balanced and representative coverage of the evolutionary trajectory (Yang et al. 1995). In this paper we set out to establish a phylogenetic tree based on DNA sequence comparisons for the C H A P T E R 1 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://naylorlab.sc.fsu.edu/Publications/Elasmobranch_phylogeny.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
