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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.
- Fall '08