Phylogeographic analyses for Kalloora (Podocarpus drouynianus) conservation management in the Southwest Australian Floristic Region.

BACKGROUND AND AIMS: In southwestern Australia, plants have persisted through significant climate shifts in ancient landscapes, and the evolutionary responses are apparent in their genetic signature. Kalloora (Podocarpus drouynianus) belongs to a genus typically found in wet, montane environments. It is unusual among its relatives in having developed mechanisms to survive in drought- and fire-prone mesic forests characterising the southwest corner of Australia, including post-fire flowering. A phylogeographic analysis of kalloora chloroplast genetic markers was undertaken to determine whether 1) kalloora persisted through historical climatic and geological shifts by contracting to refugial areas, and 2) there is extensive gene flow across its geographic range.

METHODS: Leaves were sampled from 10 P. drouynianus plants from 22 populations. The chloroplast and nuclear markers were sequenced and analysed. Chloroplast haplotypes were identified, and the resulting haplotype and nucleotide diversity parameters were calculated. A median-joining maximum parsimony network was generated, estimates of population differentiation and neutrality and expansion tests were calculated, and the distribution of haplotypes was mapped to visualise their geographic arrangement.

KEY RESULTS: Results indicated high haplotype diversity across the species' full distribution, a genetic patterning consistent with large population sizes and long-term persistence in the landscape. With the exception of a distinct haplotype assemblage within some outlier populations, phylogeographic structure was not evident across the species' distribution. These patterns suggest long term, localised persistence in the region. Moreover, extensive gene flow was indicated by the widespread distribution of shared haplotypes across its main range, which is consistent with wind pollination and presumed long-distance seed dispersal primarily by wetj (emus; Dromaius novaehollandiae).

CONCLUSIONS: Evolutionary and cultural understandings of landscape connectivity for both kalloora and wetj are important factors to consider in conservation approaches to support the ongoing demographic and evolutionary processes of kalloora to ensure its resilience and persistence into the future drying climate.