Cycad species exist as small fragmented populations, therefore understanding their
genetic variation is imperative for their conservation to ensure their long-term
survival. Genetic data plays a fundamental role in identifying genotypes and
detecting populations with the highest genetic diversity. This project uses next
generation sequencing (NGS) and restriction associated DNA sequencing (RADseq)
to identify thousands of genome-wide polymorphisms from populations of selected
cycad species from the Northern Territory, Australia, namely: Cycas armstrongii,
Cycas calcicola, Cycas maconochiei ssp. maconochiei and the interspecific hybrid
C. armstrongii x maconochiei. RADseq was used to determine intra- and
interspecific genetic variation in populations, verify the putative hybrid, recognize
populations of conservation priority and determine if botanic garden collections
currently represent the genetic diversity inherent in the wild. Cycas calcicola showed
very low levels of genetic diversity and high inbreeding, and although there was
significant geographic partitioning between populations in the Katherine and
Litchfield National Park regions, which correlated with genetic differentiation.
Additionally, the results showed that C. calcicola was not genetically, well
represented in ex-situ collections. The genomic diversity of Cycas armstrongii, C.
maconochiei ssp. maconochiei and C. armstrongii x maconochiei differs from that of
C. calcicola and shows very low levels of genetic diversity yet generally with lower
levels of inbreeding. The results show little genetic distance between Cycas
armstrongii and C. maconochiei ssp. maconochiei, the most likely explanation is that
they represent morphological extremes of a single species. The results from
RADseq have far reaching significance for the conservation of cycads. In the case of
C. calcicola, a far more structured acquisition of genetic material will be required if
the full genetic diversity of this species is to be preserved in ex-situ collections
