U nder the bsc successful and widely distributed

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Unformatted text preview: ia t he stringent application of the diagnosability criterion, virtually e very subspecies out there was promoted to the species level. A nd while the investigators involved in this wholesale splitting m ay not always have been aware of it, this stratagem involved a bandoning some very basic notions of evolutionary process. U nder the BSC, successful and widely - distributed species had b een actively expected to spawn subspecies: readily recog nizable local variants that were nonetheless reproductively c ompatible with their conspecifics living elsewhere. Indeed the B SC, and the corpus of evolutionary theory from which it was d erived (basically, the New Synthesis of the 1930s and 1940s: s ee Mayr 1982), saw subspecies as the engines of biodiversity, giving new species a place to start. Without subspecies, o r at least differentiated populations, there could be no new s pecies. And my contention here is that this simple proposition remains as valid now as it was twenty years ago, irrespective of w hether (or not) you accept the well-substantiated proposition t hat speciation and morphological divergence are not simply d ifferent sides of the same coin (Tattersall 1994). Saying this is not to deny the utility of the PSC perspec tive. Indeed, sophisticated applications of the approach in the s ystematics of a wide range of major taxa have permitted biolo gists (using both phenotypic and DNA criteria) to identify many c ases in which unrelated but phenotypically similar populations h ad been incorrectly lumped under the same bio - species. As a result, most investigators nowadays would demand data of s everal different kinds to confirm claims of population status, w hether specific or infraspecific. What is more, to acknowledge t hat subspecies exist as real entities, albeit elusive ones, also i nvolves accepting that the living world is a messy place. Nature i s not neatly packaged. At the lowest levels of the taxonomic h ierarchy, where divergence is minimal, and where even taxa d estined ultimately to be highly distinctive may be hard to d ifferentiate from their sisters, demarcations are often blurry. S ubspecies are, of course, diagnosable by definition. But even if f uture systematists will be able to look back and determine that d iagnosably differentiated populations had in fact embarked on s eparate historical trajectories, prior to the critical (and probably usually fairly short-term) event of speciation the only barri ers to genetic interchange among conspecific populations will meier et al. (1994) published the first edition of their field guide t o the lemurs, which has by now achieved canonical status, t hey listed 31 lemur species. By the time the second edition ( Mittermeier et al. 2006) was published a dozen years later, there w ere 68 species, plus some cryptic allusions to species as yet u nnamed. And in the third edition (Mittermeier et al. 2010), i ssued after an interval of only four years, the number of lemur s pecies had soared to 97. Now the total stands at well over 1 00 (see Tattersall 2013). Significantly, the number of polytypic l emur species simultaneou...
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This test prep was uploaded on 03/31/2014 for the course ARH 102 taught by Professor Leslie during the Fall '08 term at SUNY Stony Brook.

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