Multivariate Morphometrics of Bottlenecked Populations

Abstract

In one way or another population bottlenecks and/or founder events have played critical roles in theories of speciation, including those of Mayr (1954, 1970, 1982), Carson (1968, 1975, 1982) and Templeton (1980a,b). In Mayr’s view (1954) the internal genetic change fostered by these founder events is “the most drastic change (except for polyploidy and hybridization) which may occur in a natural population, since it may affect all loci at once.” Basically, these speciation models envisage founder events as disruptive to established genetic relationships among polygenic traits, thereby creating opportunity for establishing new polygenic balances. In Carson’s founder flush theory, for example, he suggests that the genetic architecture can be viewed as containing “open” and “closed” portions. The “open” portion would largely have an additive genetic basis, be responsive to selection, and account for variation within species, while the “closed” portion would largely have a nonadditive genetic basis, be unresponsive to selection, and account for variation between species. Bottlenecks would then “unlock” the closed genetic system and allow for divergence of polygeneic traits in ways that would not normally occur within species.