Genetic variation in continental and island populations of eichhornia paniculata (Pontederiaceae)

Abstract

Genetic variation was examined at 21 allozyme loci in 11 populations of Eichhornia paniculata (Pontederiaceae) from N.E. Brazil and Jamaica. Populations from Jamaica are genetically depauperate with respect to electrophoretically detectable variation, containing a significantly lower number of polymorphic loci, alleles per locus, mean observed heterozygosity and genetic diversity than Brazilian populations. These measures were significantly correlated with the outcrossing rate (t) of populations. The allozyme data were used to examine the patterns of genetic variation within and between populations by estimates of gene correlation and Nei’s gene diversity statistics. Populations within both regions are highly differentiated from one another, with those from Jamaica more strongly so. Brazilian populations contain more variation than is distributed among populations, while the reverse pattern occurs among Jamaican populations. The genetic distance between Jamaican populations is less than between Brazilian populations as a result of the low overall variability on the island. It is proposed that the founding of populations on Jamaica by longdistance dispersal, genetic drift and high levels of self-fertilisation all contribute to reducing levels of genetic variation in Jamaican populations. © 1987, The Genetical Society of Great Britain.