Genecological variation in recently established populations of Abutilon theophrasti (velvetleaf)

Abstract

Life history and electrophoretic variation were examined in 39 populations of Abutilon theophrasti L., velvetleaf, collected from southern Ohio (39° N) to central Ontario (45° N). These collections represent a climatic gradient at the northern extreme of the distribution range of this weed species in North America. Plants from each of the 39 populations were grown from seed in a standard garden trial. A total of 51 growth, germination, and morphological characters were measured for each population. Significant among-population differences (p < 0.05) were found for 33 of the 51 characters. Many of these population differences were correlated with latitude and climate. These patterns of variation may well represent the first stages of differentiation in response to local environment. Of particular importance was the wide range of differences among populations in proportions of seeds exhibiting dormancy. Results from an electrophoretic survey of 16 enzyme systems provided evidence for very low levels of allozyme variation among the 39 populations of A. theophrasti. Only two enzymes were variable and only four multi-locus electrophoretic genotypes were evident among the 39 populations. Velvetleaf exhibited a number of genetic features characteristic of successful colonizers: high levels of fixed heterozygosity as a result of polyploidy, multilocus associations providing a reduced number of genotypes, and high levels of population differentiation in morphometric and life-history traits.