Ongoing investigations into population genetics of cycads

Christy Powell, Brian Dorsey, San Diego Zoo Global, Huntington Botanical Garden

As the most endangered group of plants on the planet, cycads (Cycadales) face a number of threats to their continued existence. Efforts to preserve these iconic plants (in situ reserves and ex situ collections) could benefit greatly from a better understanding of population genetic dynamics and recent demographic history. We have shown that within the genus Dioon most species likely diverged between 30-80 kya. This very recent divergence along with long generation times suggests the possibility of shared polymorphisms across species and potentially incomplete speciation between accepted taxa. Conversely, the distribution of populations and the pollination/dispersal system suggests that migration rates may be quite low. Determining the relative influence of these processes will better inform conservation efforts. Given the nearly 50 Gb genomes of this group, we are using a hybrid of two RADseq methods to produce high coverage/highly multiplexed reduced representation data sets to assess connectivity, historical demography, and genetic diversity. While data for Dioon is still coming in, we have a pilot study using the same technique to assess the genetic diversity among Encephalartos latifrons plants held in botanical gardens in the USA, which we plan to extend to include wild populations with similar goals.

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