Population genetics of the threatened tree daisy Olearia gardneri (Asteraceae), conservation of a critically endangered species

Abstract

All known populations of the nationally critical tree daisy, Olearia gardneri, were studied using AFLP markers. With fewer than 160 individual plants, Olearia gardneri is the third-rarest tree in New Zealand and a good model with which to study evolutionary process in fragmented endangered plants. Genetic variation was at similar levels to other long-lived tree species in New Zealand and also as in other studies to date had poor correspondence between genetic and geographic distance. Genetic factors such as inbreeding depression and the loss of genetic diversity might lower fitness and have substantial consequences for evolution and survival of rare threatened plants. Due to the decline of this species in recent times it is imperative that conservation measures are undertaken, including revegetation. Despite considerable emphasis on ''eco-sourcing'' in plant recovery programmes there is strong evidence that this may not be the best strategy for O. gardneri due to breeding system and population size considerations.

Phylogeography and conservation perspectives of an endangered macaronesian endemic: Picconia azorica (Tutin) Knobl. (Oleaceae)

“…Ex situ conservation for reintroduction programs can be planned for the rare haplotype-bearing lineages, provided the necessary eco-physiological evaluation aimed at excluding the risk of reintroducing unsuitable-or less adapted-genotypes. The consequences of gene flow between differently adapted genotypes resulting from transplantations are unpredictable, but possible results include decreased fitness through outbreeding and reduction of local adaptation (Ellstrand and Elam 1993;Barnaud and Houliston 2009).…”

Genetic diversity and structure in fragmented populations of the endangered species Ranunculus cabrerensis (Ranunculaceae): implications for conservation

“…fragmented, endemic and rare) we had predicted that there should be low genetic diversity, but generally speaking, it seems that the total genetic diversity based on ISSR and AFLP markers is similar to, or slightly higher, than most of those described by different authors in other species. In fact, Nei's gene diversity estimates in other AFLP studies ranged from 0.07-0.26 (Gaudeul et al 2000;Rottenberg & Parker 2003;Barnaud & Houliston 2010;Chen et al 2010;Gong et al 2010) and in the case of ISSR analysis ranged from 0.10-0.28 (Qiu et al 2004;Xiao et al 2004;Wu et al 2004;Shao et al 2009;Jeong et al 2010). In addition, determining levels of diversity within species and populations, as well as ascertaining how species diversity is apportioned within and among populations, is useful in formulating strategies for conserving diversity within taxa (Hamrick et al 1991).…”

Inferring the late Quaternary phylogeography of Pseudopanax crassifolius using microsatellite analysis

“…In small populations there is more chance of inbreeding and inbreeding depression, which can contribute to a reduction of variability. The genetic diversity within New Zealand trees is often low (Hawkins & Sweet 1989;Billington 1991;Haase 1992;Barnaud & Houliston 2010), which might indicate population bottlenecks. However some New Zealand trees show greater diversity, a study of Pseudopanax ferox Kirk showed that small populations can harbour diversity (Shepherd & Perrie 2011).…”

“…How much structuring is present and why the structuring has formed are all part of the puzzle in trying to understand phylogeography. While the general trend is one of weak structure and diversity in New Zealand trees (Young et al 2001;Broadhurst et al 2008;Barnaud & Houliston 2010), Pseudopanax ferox shows strong structure (Shepherd & Perrie 2011). This contradictory pattern can be reasonably explained by the disjunct pattern of P.…”

“…There are other factors that can also contribute to the lack of genetic structure and differentiation. Barriers to gene flow such as human mitigated deforestation in New Zealand probably developed too recently to be detectable genetically (Barnaud & Houliston 2010).…”