Abstract Detail

Population Genetics/Genomics

Fehlberg, Shannon [1], Fehlberg, Kevin [1], Beck, James [2].

Population genomics reveals convergent evolution and informs conservation in the Echinocereus fendleri group (Cactaceae).

North America contains some of the most species-rich genera of cacti in the world with some of the family’s highest rates of evolutionary diversification. The genus Echinocereus exhibits particularly rapid radiation in the southwestern arid regions of the United States and displays wide variation in stem, spine and floral characters. Such variation has resulted in the description of over 70 taxa, with a number of these considered rare, threatened, or endangered. While careful morphological, cytological, and distributional studies have contributed greatly to our knowledge of species, subspecies, and varieties within Echinocereus, the addition of genetic and genomic data are needed to enable understanding of evolutionary relationships and eliminate long-standing taxonomic confusion. The goal of the present study is to examine phylogenomic variation in the Echinocereus fendleri group to determine relationships among three varieties primarily distributed in Arizona, New Mexico, and Texas, including the endangered and federally protected Kuenzler’s Hedgehog Cactus (Echinocereus fendleri var. kuenzleri). To accomplish this, more than 200 tissue samples were collected from 20+ sites representing all focal taxa and several outgroup taxa, and double‐digest restriction site-associated DNA sequence (ddRADseq) data were acquired. Measurements for key morphological traits used for distinguishing varieties were recorded for each sample at the time of collection. Analyses of these data indicate a well-supported, monophyletic E. fendleri clade, with strong geographic structuring. Within this clade, populations of E. fendleri var. rectispinus form a grade, with some sister to a well-supported clade containing all E. fendleri var. fendleri and E. fendleri var. kuenzleri, suggesting that the ‘rectispinus’ morphology of many, thin spines is ancestral in the group. Three subclades are apparent within the E. fendleri var. fendleri/kuenzleri clade- a northern clade comprising E. fendleri var. fendleri, a central clade comprising E. fendleri var. fendleri and E. fendleri var. kuenzleri from Lincoln Co., NM, and a southeastern clade comprising only E. fendleri var. kuenzleri. These results suggest two independent transitions to the extreme ‘kuenzleri’ morphology of very few, thick spines. This phylogeny further establishes that none of the three E. fendleri varieties correspond to evolutionary lineages, suggesting that a single, widespread, morphologically variable E. fendleri lineage should be recognized. Additionally, the non-monophyly of E. fendleri var. kuenzleri suggests that the approach to conservation of this taxon should be re-evaluated. Finally, with growing evidence for repeated instances of evolutionary convergence on extreme phenotypes, the genus Echinocereus could serve as an important model for future studies of the molecular basis of convergent evolution and adaptation in extreme environments.

1 - Desert Botanical Garden, Research Conservation and Collections, 1201 N. Galvin Pkwy., Phoenix, AZ, 85008, USA
2 - Wichita State University, Biology, 1845 Fairmount, Box 26, Wichita, KS, 67260, United States

convergent evolution.

Presentation Type: Oral Paper
Number: PGG4004
Abstract ID:459
Candidate for Awards:None

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