A range-wide analysis of population structure and genomic variation within the critically endangered spiny daisy (Acanthocladium dockeri)

Abstract

Understanding population structure and genetic diversity is important for designing effective conservation strategies. As a critically endangered shrub, the six remaining extant populations of spiny daisy (Acanthocladium dockeri) are restricted to country roadsides in the mid-north of South Australia, where the species faces many ongoing abiotic and biotic threats to survival. Currently the spiny daisy is managed by selecting individuals from the extant populations and translocating them to establish insurance populations. However, there is little information available on the genetic differentiation between populations and diversity within source populations, which are essential components of planning translocations. To help fill this knowledge gap, we analysed population structure within and among all six of its known wild populations using 7,742 SNPs generated by a genotyping-by-sequencing approach. Results indicated that each population was strongly differentiated, had low levels of genetic diversity, and there was no evidence of inter-population gene flow. Individuals within each population were generally closely related, however, the Melrose population consisted entirely of clones. Our results suggest genetic rescue should be applied to wild spiny daisy populations to increase genetic diversity that will subsequently lead to greater intra-population fitness and adaptability. As a starting point, we suggest focussing on improving seed viability via inter-population crosses such as through hand pollination experiments to experimentally assess their sexual compatibility with the hope of increasing spiny daisy sexual reproduction and long-term reproductive fitness.

Multi-gene insights into the taxonomy and conservation of Tasmania’s galaxiid fishes

“…Indeed, recent studies have now demonstrated that allozymes provide exceptional concordance with a companion SNP dataset for the delineation of all primary and admixed lineages in every group examined thus far (Gadopsis, Unmack et al 2017;Hypseleotris, Unmack et al 2019;Retropinna, Unmack et al 2022; Craterocephalus, Mogurnda and Rhadinocentrus, M. Adams and P. J. Unmack, unpubl. data), and can even provide comparable insights into fine-scale population structure (Jusaitis and Adams 2005;Brooks et al 2022).…”