Format: ORAL

Michael J. Moore1, Clare Muller2, Andreu Cera3, Norman A. Douglas4, Hilda Flores Olvera5, Helga Ochoterena5, Rebecca Drenovsky2, Pablo Tejero Ibarra6, Sara Palacio6

1 Oberlin College, Oberlin, OH, USA 2 John Carroll University, University Heights, OH, USA 3 Université de Caen-Normandie, Caen, France 4 University of Florida, Gainesville, FL, USA 5 Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad de México, México 6 Instituto Pirenaico de Ecología, CSIC, Jaca, Spain

Gypsum outcrops occur in arid and semi-arid regions around the globe, and present a significant barrier to plant growth due to challenging soil nutrient levels (excess sulfur and calcium, minimal nitrogen and phosphorus) and the presence of well-developed soil crusts. Nevertheless, these difficult soils host a wide variety of endemic plants. The Chihuahuan Desert region of Mexico and the USA has the largest known gypsum endemic flora in the world, with over 240 plant taxa known only from gypsum. Ongoing research into the diversification of this flora has revealed a number of repeated evolutionary patterns. For example, the dominant gypsum endemic taxa in the Chihuahuan Desert region typically belong to clades of gypsum endemics that likely originated in the Pliocene or latest Miocene, and that have survived the climatic oscillations of the Pleistocene. Likewise, the dominant gypsum endemic taxa of the Chihuahuan Desert belong to genera and families with many independent evolutionary origins of gypsum endemism, strongly suggesting that preadaptations to life on gypsum exist in these groups. One such preadaptation may be the ability to accumulate sulfur within leavesan abilitythat has now been documented in many of the dominant gypsum endemics of the Chihuahuan Desert. The presence of this trait in what are likely the oldest clades of gypsum endemics and some of their closest non-endemic relatives suggests that foliar sulfur accumulation may be one of the driving factors in explaining the historical assembly and evolution of the Chihuahuan Desert gypsum endemic flora. Similar patterns related to sulfur accumulation are also present in the independently derived Spanish gypsum flora, suggesting that this ecophysiological trait may be of global importance in understanding gypsum plant evolution.