Cycad Literature Database

Premise of research. Cycas candida (Cycadaceae) is an endangered species of cycad found in Queensland, Australia. The species faces risks because of habitat fragmentation, poaching for private collections, and changes in climate (such as increased fire frequency and higher temperatures), driving a need for an understanding of the genetic diversity and population structure of the species.

Methodology. Because of the large genome size of cycads, restriction site–associated DNA sequencing (RADseq), a next-generation sequencing method, was used for this population genomic study of C. candida to generate data representing the depth and coverage of the genome.

Pivotal results. The genomic assessment of C. candida revealed higher levels of observed heterozygosity than of expected heterozygosity and a low percentage of molecular variance between populations. The phylogenomic and structure analyses indicated high levels of genetic diversity within populations and little differentiation between populations. These results, coupled with the long generation time and limited dispersal of pollen and seed, suggest that the assessed populations were once part of a metapopulation that is currently experiencing limited gene flow and increasing fragmentation as a result of anthropogenic causes.

Conclusions. Based on our results, it is recommended to manage these populations as a single management unit to avoid inbreeding, encourage gene flow between the populations, and slow the effects of habitat fragmentation. Further conservation efforts should also focus on establishing ex situ collections for this species. We suggest that future studies employ genomic approaches such as RADseq for population genetics and conservation management of cycads.