Abstract
Prioritizing conservation efforts based on phylogenetic tools is gaining momentum globally. However, these efforts are almost exclusively focused on animals, and particularly vertebrate, with no equivalent efforts on plants. The main objective of the present study is to use phylogeny to inform conservation efforts of cycads, the most threatened group in plant kingdom. Specifically, four questions are investigated: 1) What is the geographic pattern of richness and evolutionary distinctiveness (ED) of cycads? 2) Would protecting elevated habitats (e.g. mountains) – traditionally thought to be refuges for ancient lineages – safeguard an ancient lineage like cycads? 3) Would protecting threatened cycads prevent the loss of high-ED species? 4) If not, how can ED and threat data be combined to inform prioritization efforts for cycads globally? Cycads have a tropical and subtropical distribution with the highest richness in Central America, eastern Southern Africa and eastern Australia. Tropical richness is traditionally attributed to a more rapid speciation and lower extinction rate in the tropics vs. temperate regions, but the restriction of cycads distribution to tropics in particular, could be the result of the tropics being a ‘‘hot spot’’ for ancient or relictual lineages. To assess this hypothesis, the first ever complete phylogeny of cycad taxa was reconstructed and used to calculate ED values for each species – an approximate measure of how ancient or unique a species is – and analyse their geographic patterns. High-ED species are likely to correspond to non-random phenotypes and uniquely divergent genomes, and habitats or regions rich in high-ED species therefore deserve particular attention. ED scores range from 10.587 million years (MY) (Cycas micronesica and Cycas zeylanica) to 98.762 MY (Microcycas calocoma) (SD = ±12.62). High average ED values are observed across all known biogeographic regions of cycads, particularly in America and Southern Africa, making America (New World) and Southern Africa priority regions for cycad conservation. There is, however, no relationship between ED and altitude, and this has also been reported recently for birds, indicating that elevated regions are not refuges for ancient cycad lineages. Nonetheless, geographic origin correlates strongly with ED, with cycad of American origin being the most evolutionarily distinct and therefore deserves much conservation efforts. There is, however, a trend towards high-ED species being highly threatened, suggesting that efforts to preserve cycads based on IUCN threat categories would also contribute to...
M.Sc. (Environment Management)