Relative genetic diversity of the rare and endangered Agave shawii ssp. shawii and associated soil microbes within a southern California ecological preserve

Abstract

Shaw's Agave (Agave shawii ssp. shawii) is an endangered maritime succulent growing along the coast of California and northern Baja California. The population inhabiting Point Loma Peninsula has a complicated history of transplantation without documentation. The low effective population size in California prompted agave transplanting from the U.S. Naval Base site (NB) to Cabrillo National Monument (CNM). Since 2008, there are no agave sprouts identified on the CNM site, and concerns have been raised about the genetic diversity of this population. We sequenced two barcoding loci, rbcL and matK, of 27 individual plants from 5 geographically distinct populations, including 12 individuals from California (NB and CNM). Phylogenetic analysis revealed the three US and two Mexican agave populations are closely related and have similar genetic variation at the two barcoding regions, suggesting the Point Loma agave population is not clonal. Agave‐associated soil microbes used significantly more carbon sources in CNM soil samples than in NB soil likely due to higher pH and moisture content; meanwhile, soil type and soil chemistry analysis including phosphorus, nitrate nitrogen, organic matter, and metals revealed significant correlations between microbial diversity and base saturation (p < 0.05, r2 = 0.3676), lime buffer capacity (p < 0.01, r2 = 0.7055), equilibrium lime buffer capacity (p < 0.01, r2 = 0.7142), and zinc (p < 0.01, r2 = 0.7136). Soil microbiome analysis within the CNM population revealed overall expected richness (H′ = 5.647–6.982) for Agave species, while the diversity range (1 − D = 0.003392–0.014108) suggests relatively low diversity marked by high individual variation. The most prominent remaining US population of this rare species is not clonal and does not seem to be threatened by a lack of genetic and microbial diversity. These results prompt further efforts to investigate factors affecting Agave's reproduction and fitness.

Life Science Research Immersion Program Improves STEM-Specific Skills and Science Attitudes among Precollege Students

“…Students engaged in active learning by applying research skills to ongoing authentic research projects during the LSRIP. Among the four research themes, the AS project has resulted in a manuscript published in the journal Ecology and Evolution featuring two program participants as coauthors while two more were acknowledged for specific project contributions ( 41 ), a CT manuscript has been published in the journal Ecotoxicology and Environmental Safety ( 42 ), and two DM manuscripts are in preparation. Per consistent verbal feedback from most students during the program, collaborative student-instructor interactions minimized traditional student-teacher hierarchy and promoted active conversations instead of lecturing, establishing greater comfort among students.…”