The successful founder: Genetics of introduced Carduelis chloris (greenfinch) populations in New Zealand

Abstract

The amount and distribution of genetic variation in seven introduced New Zealand populations of Carduelis chloris were assessed at 40 loci using starch gel electrophoresis and compared with those in native European populations. Fewer alleles (1.451 and fewer polymorphic loci (33 per cent) were detected across the introduced populations than across native populations (1.75, 55 per cent), reflecting the narrow geographical origin of the introduced populations. There was no evidence for severe inbreeding or genetic drift as the levels of average heterozygosity (H = 0.0251, percentage polymorphic loci (P = 16.91 and average number of alleles per locus (A = 1.221 were indistinguishable from levels observed within European populations (H = 0.025, P = 14.1, A = 1.191. Furthermore, introduced populations were genetically less weakly differentiated (F(ST) = 0.022) than native populations (F(ST) = 0.041), indicating that little genetic drift has been involved in the colonization of the new range. Similar levels of genetic variability in native and introduced greenfinch populations are consistent with theoretical expectations as the founder population size was relatively large (>60 individuals) and a rapid increase in population size directly after colonization was documented. A review of earlier studies on introduced birds also revealed that reductions in levels of genetic variability seem to be inversely proportional to the size of the founder population, and that less variation has been lost if the rate of population growth directly after introduction was fast.