Specialisation and extinction: Cope's law revisited
Titel:
Specialisation and extinction: Cope's law revisited
Auteur:
Kaiser, H. E. Boucot, A. J.
Verschenen in:
Historical biology
Paginering:
Jaargang 11 (1996) nr. 1-4 pagina's 247-265
Jaar:
1996-06
Inhoud:
Some lineages, specific and supraspecific, tend to be extinction-prone, others extinction-resistant in the face of environmental change. Recent attention to the theoretical causes of extinction has focused almost entirely on physical (exogenous) factors. In most higher taxa, species appearing first are commonly characterised by having small to average size, and relatively generalised morphology. Species appearing later in many groups frequently include forms characterised by significant morphologic departures from the early-appearing, but persistent norm. Such specialised features may include excessive ornamentation such as spinosity, and large, even giant size. Generalists within a genus occupy a considerable spectrum of environments (and communities), but specialists in the same genus tend to occur in a single environment and a single community. Particularly in the benthos, specialists tend to be biogeographically endemic and generalists cosmopolitan, unless the spectrum of environments is extensive and there are no barriers to reproductive communication. Not all forms becoming extinct show morphologic, ecologic or biogeographic evidence of specialisation; this is not surprising since specialisations are not restricted to the skeletal system alone, nor to ecologic and biogeographic characteristics. Specialised community types (e.g. the reef complex of communities, varied pelmatozoan and bryozoan thickets, and sponge forests) are far more extinction-prone than their more generalised level bottom antecedents. Such biological specialisations - connected with endogenous factors and characteristics of some species - may sometimes be recognised in the palaeontologic record.
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