A preliminary conservation genetic study ofPittosporum obcordatum(Pittosporaceae), an endemic New Zealand species with a disjunct distribution

Abstract

Pittosporum obcordatum (Pittosporaceae; heart-leaved kōhūhū) is an endemic New Zealand plant species that is classified as Threatened-Nationally Vulnerable. It has a disjunct distribution and is only known from relatively few and small populations. Using 10 Inter-Simple Sequence Repeat markers (ISSRs), we studied patterns of genetic diversity and genetic differentiation among eight out of the c. 14 populations of this species to inform its conservation management. Pittosporum obcordatum has low genetic diversity at the population level (uH e = 0.169) compared to other longlived and outcrossing species, but genetic diversity is relatively high in comparison with several other threatened species. Spearman's Rank Correlation Coefficients suggest significant positive correlations between population size and genetic diversity as measured by the percentage of polymorphic loci and uH e. Pittosporum obcordatum also shows relatively high levels of genetic differentiation among populations (AMOVA-derived Φ' st = 0.508, P < 0.001; all pairwise Φ st values P < 0.05), indicating low genetic connectivity. Populations with relatively few plants are therefore prone to further reductions in genetic diversity through inbreeding and genetic drift. Of these, especially the Kaitaia, Owen Valley and Paengaroa populations are of conservation concern, because they contain private alleles, and therefore notably contribute to the genetic diversity of P. obcordatum.

Conservation Genetics of Four Critically Endangered Greek Endemic Plants: A Preliminary Assessment

“…Convolvulus argyrothamnos-a species endemic in Crete, the largest and most environmentally heterogeneous Greek island-occurs in a paleo-endemism hotspot [107], which implies that it might have had ample time and opportunities to accumulate genetic diversity [108]. As for Allium iatrouinum, which shows the second highest level of genetic diversity within the species studied here and similar to that reported for other palaeoendemic taxa occurring in the Mediterranean basin and elsewhere [40,96,109], this could be attributed to the fact that it belongs to a species group highly diversified in the Mediterranean, and its origin probably dates back in the Messinian [56].…”

“…By using ISSR markers, we were able to provide a first rough estimate of the genetic diversity patterns of four extremely rare and highly endangered Greek endemic plant taxa. All four of the studied taxa display moderate to high genetic diversity (uHe: 0.254-0.322; Table 3) compared to other plant taxa of conservation concern from the Mediterranean basin [32,33] or other parts of the world (e.g., the taxa mentioned in Table 3 by [96]) but within the range reported from other threatened plant taxa using ISSRs [33,41] (uHe: 0.029-0.400). Perennials usually are more genetically diverse than annuals ( [97] and references therein), while plants occurring on islands and in dry climates often exhibit higher levels of genetic diversity [97].…”