Format: ORAL

Shannon Fehlberg1 Kevin Fehlberg1 Donna Dehn1 Marc Baker2 Paula Williamson3 James Beck4

1 Desert Botanical Garden, Phoenix, Arizona, USA 2 Arizona State University, Tempe, Arizona, USA 3 Texas State University, San Marcos, Texas, USA 4 Wichita State University, Wichita, Kansas, USA

Echinocereusis one of the most diverse genera of the Cactaceae family. ManyEchinocereusspecies display wide variation in stem, spine and floral morphology within and among populations. Such variation has resulted in the description of over 70 taxa, with a number of these considered rare, threatened, or endangered. While detailed morphological, cytological, and distributional studies have contributed greatly to our knowledge of species, subspecies, and varieties withinEchinocereus, the addition of genomic data are needed to enable understanding of evolutionary relationships and eliminate long-standing taxonomic confusion. Our recent work inEchinocereushas focused on three rare taxa:E. arizonicussubsp.arizonicus,E. fendlerisubsp.kuenzleri, andE. fitchiisubsp.albertii. For each of these taxa, population-level samples have been collected throughout the range and from a subset of close relatives. Population genetic and genomic, and flow cytometric data have been obtained and analyzed using standard population genetic, clustering, ordination, and phylogenetic approaches.Results indicate that genetic variation is high and typically geographically structured, sometimes supporting the rare taxon as a unique evolutionary lineage, but sometimes supporting stronger genetic affinity among geographically proximate populations and non-monophyly of the rare taxon. Detailed morphological studies for these same taxa have revealed that large sample sizes are critical for understanding the range of morphological variation within and among populations and reducing sampling error and phenological effects from environmental factors.Although most results from these genetic and morphological studies are in alignment with each other and support current taxonomy, some are not, which might be expected given the recent and rapid radiation of this genus and the potential for convergent evolution in characters that are typically used to define taxa.Information gained from these studies is actively being discussed with conservation managers to help prioritize and optimize conservation efforts.