Genetic Diversity in the Endangered Phebalium daviesii (Rutaceae) Compared to That in Two Widespread Congeners

Abstract

Genetic diversity in the rare and endangered Phebalium daviesii was compared to that in P. squamulosum subsp. squamulosum and P. glandulosum subsp. glandulosum using allozyme analysis. Phebalium daviesii was once presumed extinct, but 43 adult plants have so far been rediscovered. Phebalium squamulosum subsp. squamulosum and P. glandulosum subsp. glandulosum are widespread in the south-eastern part of the Australian mainland. Morphologically, these two taxa are the closest relatives of P. daviesii and share a similarity with P. daviesii in their ecological habitat. The level of genetic diversity and deviations from Hardy-Weinberg equiibrium were investigated using allozyme data with 18 enzyme systems. Nei's total genetic diversity, the proportion of polymorphic loci and the average number of alleles per locus were all slightly lower in P. daviesii than in P. squamulosum subsp. squamulosum and P. glandulosum subsp. glandulosum. Deviations from expected Hardy-Weinberg equilibrium were present in all three taxa and were more frequent in P. glandulosum subsp. glandulosum. This suggests that inbreeding may be occurring in all three Phebalium taxa and that P. daviesii does not suffer from increased inbreeding due to rarity. Phebalium daviesii has a high level of genetic diversity (H_t = 0.30) for such a rare species and should be able to recover from its population bottleneck with appropriate management.