Isozyme analysis of population structure and diversity in the puffball species Lycoperdon pyriforme

Isozyme analysis possesses predictive value and may reveal aspects of the natural history of a species that are not otherwise obvious. Working on this premise, isozyme analysis was performed on Lycoperdon pyriforme to shed light on the attributes of this species that most likely influence the distribution of genetic diversity observed among seven collection sites within the study region (i.e., central Arkansas, northeastern Kansas and northwestern Missouri). Forty-nine unique multilocus isozyme phenotypes were identified from cultures isolated from immature glebal tissue of 310 basidiocarps collected from the surface of decaying logs (~one isozyme phenotype per log). Numerical and cluster analyses to determine similarity of phenotypes indicated that these group out randomly and not according to collection site. Further analyses of isozyme data were performed, grouping phenotypes together into populations according to collection site. Isozyme bands were partitioned by locus based on the assumption that these represent alleles and interpreted on the assumption that the dikaryotic mycelia of this puffball species are physiologically diploid. Nine of the eleven putative loci examined were polymorphic, with a mean of 3.6 alleles/polymorphic locus. Mean heterozygosity for populations varied from 0.200 to 0.345, suggesting the possibility that outcrossing occurs in this species. Unweighted pair group method cluster analysis displayed marginal grouping of populations based on geographic proximity. Genetic diversity statistics indicate that genetic differentiation among populations is low (G ST = 0.122). Patterns of variation observed in this species suggest that gene flow has acted as a homogenizing force in this species within the region sampled.