All Populations Matter: Conservation Genomics of Australia’s Iconic Purple Wattle, Acacia purpureopetala

Abstract

Maximising genetic diversity in conservation efforts can help to increase the chances of survival of a species amidst the turbulence of the anthropogenic age. Here, we define the distribution and extent of genomic diversity across the range of the iconic but threatened Acacia purpureopetala, a beautiful sprawling shrub with mauve flowers, restricted to a few disjunct populations in far north Queensland, Australia. Seed production is poor and germination sporadic, but the species occurs in abundance at some field sites. While several thousands of SNP markers were recovered, comparable to other Acacia species, very low levels of heterozygosity and allelic variation suggested inbreeding. Limited dispersal most likely contributed towards the high levels of divergence amongst field sites and, using a generalised dissimilarity modelling framework amongst environmental, spatial and floristic data, spatial distance was found to be the strongest factor explaining the current distribution of genetic diversity. We illustrate how population genomic data can be utilised to design a collecting strategy for a germplasm conservation collection that optimises genetic diversity. For this species, inclusion of all field sites will capture maximum genetic diversity for both in situ and ex situ conservation. Assisted cross pollination, within and between field sites and genetically structured groups, is recommended to enhance heterozygosity particularly at the most disjunct sites and further fragmentation should be discouraged to avoid loss of genetic connectivity.

Abundant post‐fire recruitment and rapid seedling maturity emphasise regular burning is beneficial for conserving the Vulnerable Purple‐flowered Wattle (Acacia purpureopetala)

“…(2018) and van der Merwe et al . (2021) that a Vulnerable rather than Critically Endangered EPBC Act status is more suitable for Purple‐flowered Wattle. This matches the current Queensland NC Act status.…”

“…Nearly half of Purple-flowered Wattle seedlings began producing flowers and seed in November 2021, almost 2 years after post-fire germination. As the peak months for flowering by Purple-flowered Wattle are December and January (Gleed & Franklin 2018;van der Merwe et al 2021), it is expected that well over half of the 2 year old seedlings would have begun flowering by January 2022. Surveys of woodlands burnt 3 years previously also found Purple-flowered Wattle plants with seed pods (Ford et al 2018).…”

Capturing Genetic Diversity in Seed Collections: An Empirical Study of Two Congeners with Contrasting Mating Systems

“…Lyophilised leaf tissues were randomized in 96-well tube racks and submitted to Diversity Arrays Technology Pty Ltd. (DArT) for DNA extraction and genotyping using the medium density DArTseq option. The DArT pipeline has successfully informed many studies across a wide range of model and non-model organisms (e.g., [ 47 , 48 ]) and is a cost- and time-efficient solution for generating genomic-scale data. Genotype data were provided as Single Nucleotide Polymorphism (SNP) matrices assembled through DArT’s proprietary analytical pipeline supplied with quality informing statistics for each bi-allelic marker and sample.…”

Molecular and morphological analyses support recognition ofProstanthera volucris(Lamiaceae), a new species from the Central Tablelands of New South Wales

“…To investigate admixture, individual ancestry coefficients were estimated using Sparse Non-Negative Matrix Factorisation (sNMF) in the R package LEA (Frichot & François 2015). The package uses cross-entropy values to infer the probable number of ancestral populations (K) in the data and assign individuals to genetic clusters and the optimal number of ancestral populations was selected based on the post-stabilisation of the steepest decline in cross-entropy values (Frichot & François 2015;van der Merwe et al 2021). The 'snmf' function was executed for values of K = 1-8 with 50 replicates for each value of K.…”