Multivariate Phenotypic Differentiation Among Bottleneck Lines of the Housefly

Abstract

Abstract.-Multivariate phenotypic differentiation in eight morphometric traits was examined in bottleneck lines of the housefly initiated with one, four, or 16 pairs offties from a natural outbred population. Differentiation was assessed using a Mahalanobis' distance metric in units of additive genetic variance and covariance estimated from the ancestral population (i.e., generalized genetic distance). This distance metric was partitioned into contributions ofsize and shape to total distance. Bottleneck lines ofall sizes diverged significantly from the ancestral line, but the direction ofthese shifts differed among the lines of different initial founding size. Those populations founded with single pairs diverged from the ancestral line mostly in shape; the 16-pair lines differentiated almost entirely in size, and the four-pair lines were intermediate in the relative contribution of shape to differentiation from the control. Bottlenecks serve to alter the genetic relationships among traits within the derived populations and in doing so could promote speciation by permitting differentiation of the populations along evolutionary trajectories less accessible to the base population.

Large body size in an island‐dwelling bird: a microevolutionary analysis

“…A final caveat is that the G matrix itself may have changed during the past 4000 years, because of a founder effect occurring during colonization and/or selection associated with an island environment. Population bottlenecks are expected to affect G matrix structure, although in an unpredictable manner and only if the size of the founder population is very small (Bryant & Meffert, 1990;Phillips et al, 2001). A strong bottleneck is an unlikely scenario here because of the proximity of Heron Island to the mainland (Fig.…”

The reality and importance of founder speciation in evolution

“…This prediction has been tested and confirmed in a wide variety of organisms and experimental systems. (18,(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55) Recently, a rigorous molecular genetic study in yeast (56) has shown that the evolvability (ability to generate selectable phenotypic variation) of a gene depends upon the number of other genes whose activity affects it and the number of different regulatory sites that are associated with the gene. These molecular studies in yeast confirm the special importance of the new mutations or recombinants that accumulate in the flush phase in genes or gene complexes that are part of an epistatic system.…”

The biology of post-invasion events

“…Small populations of invading organisms may carry only a fraction of the genetic diversity of their source populations. Experimental studies with houseflies have shown that such 'bottlenecking' may alter genetic relationships among traits that could lead to differentiation along evolutionary trajectories less accessible to the original populations (Bryant & Meffert, 1990). Stone and Sunnucks (1993) conducted a survey of 39 populations of cynipid gallwasps that have tracked their oak host as it has been transplanted westward across Europe over the past 300400 years, in an increasingly patchy distribution.…”