Genetic relationships within and between populations of the endangered grass Lachnagrostis limitanea (Gramineae)

Allozyme electrophoresis was used to examine the genetic relationships within and between four naturally occurring populations of the endangered Spalding blown grass (Lachnagrostis limitanea (J.M.Black) S.W.L. Jacobs (syn. Agrostis limitanea)) from the mid north of South Australia. five polymorphic markers were detected during a screen of 34 putative allozyme loci, and used to assess population structure in the species. As karyotype analysis of seedlings derived from all populations confirmed that the species is polyploid (octoploid, with 2n = 8x = 56), allozymic interpretation and population genetic assessment were limited to the assignment of "whole genotypes" at each polymorphic marker for each plant. despite this restriction, the genetic data indicate that (1) sites displayed the low levels of allozymic divergence typical of conspecific populations, (2) each population was genetically distinct, (3) none of the three sites with small population sizes displayed any within-site genetic variability, and (4) most of the genetic diversity present in the species resides within the largest natural population (Yakkalo). Parent/progeny comparisons demonstrated an absence of apomixis and inferred that out-crossing was common in the Yakkalo population, suggesting that inbreeding rather than selfing perse is the most likely cause of the severe reduction in genetic variability observed at the other three sites. The implications of these results for conservation management of remnant L. limitanea populations are discussed.