Conservation genetics of Butte County meadowfoam (Limnanthes floccosa ssp. californica Arroyo), an endangered vernal pool endemic

Abstract

The endangered annual plant Limnanthes floccosa ssp. californica Arroyo is restricted to vernal pools in Butte County, California. To identify populations with unique genetic resources, guide reintroduction efforts, and design seed collection scenarios for long-term ex situ seed storage we determined extant genetic diversity and structure by surveying 457 individuals from 21 distinct populations using nine polymorphic microsatellite markers. We found low within population genetic diversity: low allelic diversity (1.9 [0.06 SE] alleles/locus); low heterozygosity (H obs = 0.10 ± 0.018, H exp = 0.19 ± 0.015), and a high fixation index (0.556 ± 0.044). The number of polymorphic loci ranged between 11 and 89%. Bayesian ordination determined 20 distinct populations and we found high genetic structure among these (F st = 0.65, P \ 0.0001). We identified notable gene flow barriers across populations, confirming regional structuring between three previously defined population density centers and two outlying populations (F st = 0.21, P \ 0.0001). Population size estimates ranged between *50 and[5,000 extant plants per site. Our study confirms previous isozyme-based results and suggests that the loss of any population would represent a significant loss in the species' genetic diversity. Recovery requires active restoration of existing populations and permanent habitat protection. We recommend close comparison of microhabitats of declining populations with genetically similar populations, to determine the potential for human assisted gene flow via seed movement to recover declining populations.

Population-level genetic variation and climate change in a biodiversity hotspot

“…Conservation of vernal pool taxa requires the assessment of gene flow within and among populations to determine their degree of genetic isolation (Sloop et al, 2011) and their ability to persist under altered hydrological and climate change. An assessment of genetic variation in Neostapfia colusana, a federal threatened species endemic to vernal pools, found high levels of heterozygosity (H O ¼ 0Á68, H E ¼ 0Á71), but an F ST value of 0Á268 (P < 0Á0001) between northern and southern populations indicates that gene flow is very limited among the regions and likely due to the loss of geographically intermediate populations (Sloop et al, 2011).…”

“…An assessment of genetic variation in Neostapfia colusana, a federal threatened species endemic to vernal pools, found high levels of heterozygosity (H O ¼ 0Á68, H E ¼ 0Á71), but an F ST value of 0Á268 (P < 0Á0001) between northern and southern populations indicates that gene flow is very limited among the regions and likely due to the loss of geographically intermediate populations (Sloop et al, 2011). Some populations had lower than expected heterozygosity that was likely due to geographic isolation and increased inbreeding.…”

“…californica is a federal and state-listed endangered species endemic to vernal pools along the eastern edge of the Sacramento Valley and currently known from only 14 geographically isolated populations. The species has fairly low genetic diversity, with H O ¼ 0Á10 and H E ¼ 0Á19, and high among-population genetic structure, as measured by pairwise F ST values of 0Á12 -0Á79 (Sloop et al, 2011). Of particular concern for this species is its high rate of inbreeding and barriers to gene flow.…”

Chloroplast phylogeography of threatened aquatic Oxalis (Oxalidaceae): significant inter-population structure, divergent haplotypes and conservation implications

“…This provides baseline information on current and historic barriers to gene flow, effective population size, population breeding health and dispersal scenarios (Elam 1998;Karron 1987;Reed andFrankham 2003, Ramp et al 2006). Genetic diversity information helps identify populations that represent conservation priorities and thus directs better use of available resources (Millar and Libby 1991;Riggs 1990) to aid the persistence of this diversity (Balmford et al 1998;Cowling et al 1999;Sloop et al 2010). Conserving maximum genetic and habitat heterogeneity is therefore fundamental to species conservation, as it maximizes their evolutionary potential (Moritz 2002).…”