Evolution and Conservation at Multiple Scales in the Cycad Genus Dioon (Zamiaceae)

The cycad lineage (Cycadales) stretches back 300 million years. It has survived three mass extinctions and was once a widespread member of the world’s flora. Today there are 377 recognized species in ten genera restricted to tropical and subtropical regions. Despite the incredible longevity of the lineage, recent work suggests that the extant species are not “living fossils" but rather have diversified in the relatively recent past. This clade is perhaps the most threatened group of plants on the planet, with nearly 70% of species threatened with extinction due to loss of habitat and illegal collecting for enthusiasts. Prior to the last decade, relatively little phylogenetic work was done in most cycad genera and virtually no phylogeographic or population genetic study. These themes of lineage age, recent diversification, extinction risk, and lack of evolutionary study make cycad genera good study groups for many evolutionary questions and at the same time intersect to hamper efforts of conservation. My work on cycads has been focused on both macro- and microevolutionary processes, mainly in the genus Dioon, with the ultimate goals of understanding timing and mode of speciation and informing conservation. At one end of the macro/microevolutionary spectrum, we have tried to test the role of past climate change in the speciation process, and at the other, delimit species, and infer phylogeography and demographic history to identify evolutionary units of conservation concern. In this talk I will discuss previous studies in a broader context as well as ongoing projects.

‍