Alllenrolfea Wetland Genetics Data

The hydrophyte Allenrolfea occidentalis (S. Watson) Kuntze (iodine bush) is a halophytic shrub of the arid southwest that is listed as a facultative wetland (FACW) species on the National Wetland Plant List. This rating means the species is usually a hydrophyte but occasionally is found in uplands. We tested for genetic (ecotypic) differences between plants sampled from wetlands versus uplands. We used genotyping-by-sequencing (ddRAD-seq) to generate data from 133 plants from 30 locations representing both wetland and upland occurrences for over 1300 loci. Analyses indicated that the strongest signal is differences in geographic distribution: samples that are in close geographic proximity tend to be more similar genetically regardless of whether they occur in wetland or upland locations. We detected no effect of habitat on overall genetic structure and we found only two (of the 1381) loci with a positive association between genotype and habitat. We infer that A. occidentalis occurrences near or in wetlands are not influenced by significant differences in genetics, but rather the rating for this species is a function of inadequate knowledge of its frequency of occurrence in wetlands.