Genetic diversity and hybridization in New Zealand’s endemic Lophomyrtus bullata (Myrtaceae): implications for conservation under myrtle rust threat
摘要
The conservation of threatened endemic species is vital to preserving regional biodiversity. Lophomyrtus bullata (Myrtaceae), also known as ramarama, is an endemic woody shrub or small tree species threatened by the arrival of the pathogenic fungus Austropuccinia psidii (myrtle rust) in New Zealand. The high susceptibility of L. bullata to myrtle rust has resulted in populations declining at an alarming rate, likely reducing genetic diversity and potentially increasing its extinction risk. To assess the current levels and distribution of genetic variation in L. bullata, twelve microsatellite markers were developed and screened across 18 locations. In addition, one site of the congener, L. obcordata (rōhutu), and two putative L. bullata x L. obcordata hybrid populations were also included in the analysis. Across populations of L. bullata, a total of 97 alleles were detected, with few private alleles. A moderately low expected heterozygosity (He = 0.44) and low genetic differentiation among locations (FST = 0.14) were additionally observed. Individuals were found to best cluster into five distinct genetic groups, largely corresponding to geographic regions. Among the strongest patterns observed was a north-south grade that coincides with a biogeographic pattern known as the Taupō line. In addition to providing insights into the evolutionary history of ramarama, these results also provide a practical guide for seed bank collections, population management, and re-vegetation projects, all of which will help contribute to the long-term conservation of L. bullata.