For all these reasons, molecular phylogenies can contribute substantially to an updated view of evolutionary animation. To what extent do modern phylogenies confirm or reject the orderly animations suggested by Mayr’s analysis? Mayr’s ideas were shaped primarily from his studies of bird systematics, and, indeed, subsequent use of molecular phylogenies showed his insistence on the primacy of the allopatric mode of speciation to be correct for this group [Barraclough and Vogler, 2000; Edwards et al., “Speciation in Birds: Genes, Geography, and Sexual Selection” (Chapter 6)]. Mayr, however, was also interested in applying his view of speciation to all animals, both terrestrial and marine, and his evolutionary animations included more than bird species. Some of the nonavian genera that interested him have been examined extensively for phylogenetic relationships by using molecular tools.
In 1954, Mayr published a paper on the geographic speciation of marine taxa by focusing on the differentiation and geography of species in 20 genera of tropical sea urchins (Mayr, 1954). His goal was to examine the generality of his ideas about species formation by extending them to groups with ecology very different from that of birds. This goal was an important one for Mayr. In his view, even the most comprehensive recounting of speciation mechanisms was wanting if it applied to only a single taxon. Mayr’s conclusion at the end of this analysis was that geographic speciation applies equally well to marine species, such as sea urchins, as it does to birds, mammals, and insects.
Mayr took advantage of the publication of a complete monograph of sea urchin taxonomy by Mortensen (1928–1951) to examine the stages of speciation represented by each genus, restricting his attention to genera with species that inhabited the shallow seas in the West Indies. He divided the genera into four groups. Groups 1 and 2 included genera that had strictly allopatric species, the only difference between the groups being that group 2 genera included nontropical species. These two groups represented the earliest step in species formation, with a surfeit of polytypic species, and, presumably, low divergence among allopatric sister species. Group 3 represented the next step in speciation, in which congeneric species had sufficient time to develop genetic divergence, thereby allowing formerly allopatric sister species to invade each other’s ranges. Thus, these genera were presumed to show higher levels of divergence and the beginnings of sympatric overlap. Finally, group 4 genera were those in which the species were so old that current geographic ranges had nothing to do with speciation pattern. Whatever record of species formation there may have been among these ancient species was gone.
Although Mayr had the advantage of using the most comprehensive and up-to-date treatment of sea urchins provided by Mortensen’s monograph, this treatment was almost strictly taxonomic. Within genera, there