Group size factors and geographic variation of morphometric correlation.

Abstract

Within-locality correlations among 8 morphological traits of the fundatrix and among 15 morphological traits of the alate fundatrigeniae of the aphid Pemphigus populicaulis were examined for among-locality variation. A jackknife procedure revealed highly significant differences among correlation matrices representing 34 local samples from eastern North America. Despite significant differences among localities, spatial autocorrelation tests failed to reveal any significant geographic pattern in correlations. Factor analyses of the pooled within-locality correlation matrices reveal appendage and body-size factors for both alates and stem mothers. It is hypothesized that the apparently random geographic differences in correlation are caused by change differences in the mode of response to short-term selection. Geographic patterns in trait means are established by selection, but, because local population sizes are finite, similar response to selection occurs by diverse physiological or developmental mechanisms in different populations.-from Author