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Genetic analyses of Astragalus sect. Humillimi (Fabaceae) resolve taxonomy and enable effective conservation

September 24, 2018

Premise of the Study

Astragalus sect. Humillimi is distributed across the southwestern United States and contains two endangered taxa, A. cremnophylax var. cremnophylax and A. humillimus. The former was originally described from the South Rim of the Grand Canyon. Analysis of individuals discovered on the North Rim of the Grand Canyon yielded some evidence that the population represented a distinct species. To enable effective conservation, we clarify the group's taxonomy and characterize the genetic diversity of A. cremnophylax and A. humillimus.


We used AFLPs to genotype most species in sect. Humillimi, focusing on the two endangered forms. We examined patterns of genetic diversity using complementary analytical approaches.

Key Results

Our results demonstrate that North Rim populations group with A. c. var. cremnophylax. We found low levels of genetic diversity at certain localities and strong differentiation among populations. Astragalus humillimus, which has suffered recent and severe population declines, exhibits weak differentiation among and low diversity within populations.


Our results clarify the taxonomy of sect. Humillimi and define the boundaries of A. c. var. cremnophylax, which is shown to inhabit both rims of the Grand Canyon. This clarification, and detailed analysis of genetic variation within both endangered taxa, may advance ongoing efforts to conserve these taxa. Our results suggest that range‐wide genetic analysis of A. humillimus may inform recovery strategies for this taxon.

Citation Information

Publication Year 2018
Title Genetic analyses of Astragalus sect. Humillimi (Fabaceae) resolve taxonomy and enable effective conservation
DOI 10.1002/ajb2.1157
Authors Robert Massatti, Matthew Belus, Shahed Dowlatshahi, Gerard J. Allan
Publication Type Article
Publication Subtype Journal Article
Series Title American Journal of Botany
Index ID 70199620
Record Source USGS Publications Warehouse
USGS Organization Southwest Biological Science Center