Dissertations, Theses, and Capstone Projects

Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Dwight Kincaid

Subject Categories

Agricultural Science | Agriculture | Biodiversity | Genetics | Natural Resources and Conservation | Natural Resources Management and Policy | Plant Sciences

Keywords

Arctomecon, Development, Endangered, Markers, Microsatellite, Papaveraceae

Abstract

The genus Arctomecon (Papaveraceae) is comprised of three narrowly endemic rare species that are largely restricted to gypsum soils of the eastern Mojave Desert. The small, remaining populations of these species have become increasingly isolated by urban development and habitat fragmentation. Arctomecon humilis is federally listed as endangered due to its limited distribution within a ~15 km radius of an actively expanding city. Organizations involved with land management and conservation have called for greater insight into the genetic variation and population structure of the remaining subpopulations as they make important decisions regarding where to focus their efforts and resources.

The goal of this study was to provide answers to some of the remaining research gaps involving Arcotmecon species particularly conservation genetics by developing microsatellite markers and comparing community dynamics. First, a phylogenetic study using six gene regions (nrITS, cpDNA (matK, rbcL, trnH-psbA, rpl32-trnL, ndh-rpl32)) was conducted for members of the genus and three outgroup species. Thorough sampling throughout the geographic range of Arctomecon was conducted in order to obtain a complete representation of the genetic variability present across multiple populations. A total of 1176 plants were sampled from 35 locations with DNA extraction being performed on 949 of those, to be included in different stages of research. Outgroup taxa included a member of the sister genus Argemone, a Meconopsis species from within the subfamily, and an Eschscholzia from a separate subfamily. It was hypothesized that this increased sampling and number of gene regions would provide a more robust species tree, as compared to previous studies. Additionally, I hypothesized that new genetic markers could identify isolated populations that would be more informative to conservation management. The phylogenetic analysis did result in a well-supported species tree in addition to exhibiting broad structure among populations within each species. Notably, the population sampled in the Grand Canyon is genetically and morphologically divergent from all the other populations of A. californica that were sampled.

Polymorphic microsatellite markers revealed the micro-evolutionary structure from within and between populations of A. humilis. This was the first time that genetic markers of this type have been developed for any Arctomecon species. Sixteen markers with 2 to 31 alleles (mean=12) per marker were used to determine the level of variation and admixture among 341 individual plants from thirteen sampling localities. The number of individuals per locality ranged from 26 at Price Hills to 49 at Boomer Hill. Each marker was tested for amplification and variability within the sister species A. californica and A. merriamii where cross-amplification occurred with less success and fewer alleles than in A. humilis.

Population genetic analyses identified localities with greater amounts of admixture, as well as those more isolated and at risk of inbreeding depression. Through Bayesian analysis and genetic cluster assignment the overall trend suggests that populations are becoming more isolated. Analysis of Molecular Variance found 30% of the genetic variability between populations, and the FST analogues indicated substantial genetic differentiation (G'ST=0.427). A concern among land managers and conservation organizations concerned the effectiveness of the reserve system. An analysis of the allele frequencies located within the protected areas does indicate that the reserve system is effectively capturing genetic diversity. However, allele frequency data also suggest that a small number of new annual recruits represent only a subset of potential alleles. Due to the small effective population sizes and the already rare habitat supporting Arctomecon humilis the conservation efforts should continue to monitor and protect this unique species in all locations.

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