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Unformatted text preview: sly underwent a marked decline:
t here were seven in 1994, but only two in 2006 and 2010.
SPECIES CONCEPTS, EVOLUTIONARY PROCESSES, AND
LEMURS. H ardly coincidentally, just as lemur species were
b urgeoning in Madagascar, the total number of different species
c oncepts on offer in the literature was similarly mushroom ing. At last count (Coyne and Orr 2004, Hausdorf 2011) there
w ere almost 30 such concepts. Most, however, fall into one
o f three classes. One large category consists of variants on
t he Biological Species Concept (BSC). A second contains
H ugh Paterson’s (1985) Recognition Concept of Species (RCS),
a s ignificant contribution that emphasizes the importance
o f shared common fertilization systems. But the idea of the
s pecies that is most closely identified with the recent prolifera tion of lemur species in Madagascar falls into the third. This
m ost importantly includes Joel Cracraft’s (1983) Phylogenetic
S pecies Concept (PSC), a derivative of G. G. Simpson’s (1961)
“ evolutionary” notion of the species.
In what was probably his most influential single articula tion of the PSC, Cracraft (1983: 170) defined the species as “an
i rreducible cluster of organisms that is diagnosably distinct from
o ther such clusters, and within which there is a parental pattern
o f ancestry and descent.” For operational as well as theoretical reasons, most subsequent practical applications of the PSC
h ave tended to overlook the last part of this definition, and to
f ocus instead solely upon the criterion of diagnosability (Tattersall 2007). Where it has been applied in vertebrate systematics,
t he PSC has by one estimate led to a multiplication of species
c ompared to the BSC of around 50 percent (Agapow et al. 2004). P AGE 8 M A DAG A SC A R CO NSERVAT I O N & D E V ELO PM EN T VOLUME 8 | I SSUE 1 — J ULY 2013 b e geographical ones. What is more, speciation itself is neither
a s imple process, nor even a unitary one. Indeed, there is a
g ood argument to be made that it is not usefully referred to as a
p rocess at all. After all, to do so would be to imply the action of
a s pecific mechanism (Tattersall 1986), whereas many different
m echanisms may in fact be involved, acting at anywhere from
t he molecular to the population levels (Tattersall 1994).
As useful as it may be to think of speciation as an event that
‘ happens’ at a point in time, the reality is that this fundamental
g enerator of biodiversity is something that we invariably infer
i n retrospect, and that we recognize only via its consequences.
S uch consequences most fundamentally involve the historical
i ndividualization of lineages (Ghiselin 1974), and the establish ment of the substantially impermeable reproductive barriers
t hat such individualization suggests. What is more, it is not easily
p redictable just how those consequences will be expressed,
n or even evident that they will be expressed in ways visible to
t he systematist. Closely related species may show considerable morphological divergence from one another, or they may
s how hardly any at all. This failure of newly - separated species
t o conform to a...
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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