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1.  Genetic Diversity and Structure in Two Species of Leavenworthia With Self-incompatible and Self-compatible Populations 
Heredity  2010;106(2):310-318.
Self-fertilization is a common mating system in plants and is known to reduce genetic diversity, increase genetic structure, and potentially put populations at greater risk of extinction. In this study, we measured the genetic diversity and structure of two cedar glade endemic species, Leavenworthia alabamica and L. crassa. These species have self-incompatible (SI) and self-compatible (SC) populations and are therefore ideal for understanding how the mating system affects genetic diversity and structure. We found that L. alabamica and L. crassa had high species-level genetic diversity (He=0.229 and 0.183 respectively) and high genetic structure among their populations (FST=0.45 and 0.36 respectively), but that mean genetic diversity was significantly lower in SC compared to SI populations (SC vs. SI, He for L. alabamica was 0.065 vs. 0.206 and for L. crassa was 0.084 vs. 0.189). We also found significant genetic structure using maximum-likelihood clustering methods. These data indicate that the loss of SI leads to the loss of genetic diversity within populations. In addition, we examined genetic distance relationships between SI and SC populations to investigate possible population history and origins of self-compatibility. We find there may have been multiple origins of self-compatibility in L. alabamica and L. crassa. However, further work is required to test this hypothesis. Finally, given their high genetic structure and that individual populations harbor unique alleles, conservation strategies seeking to maximize species-level genetic diversity for these or similar species should protect multiple populations.
doi:10.1038/hdy.2010.59
PMCID: PMC2927727  PMID: 20485327
Leavenworthia; self-incompatibility; selfing; genetic diversity; mating system
2.  GENETIC FACTORS ASSOCIATED WITH MATING SYSTEM CAUSE A PARTIAL REPRODUCTIVE BARRIER BETWEEN TWO PARAPATRIC SPECIES OF LEAVENWORTHIA (BRASSICACEAE)1 
American journal of botany  2010;97(3):412-422.
Reproductive barriers play a major role in the origin and maintenance of biodiversity by restricting gene flow between species. Although both pre- and postzygotic barriers often isolate species, prezygotic barriers are thought to contribute more to reproductive isolation. We investigated possible reproductive barriers between Leavenworthia alabamica and L. crassa, parapatric species with high morphological and ecological similarity and the ability to hybridize. Using greenhouse and field experiments, we tested for habitat isolation and genetic incompatibilities. From controlled crosses, we identified unilateral incompatibility (a partial prezygotic barrier associated with the self-incompatibility system), but no evidence of other genetic incompatibilities. We found a small reduction in pollen viability of F1 hybrids and early germination of F1, F2, and BC hybrids relative to L. alabamica and L. crassa in a common garden experiment, but the effect on fitness was not tested. Field studies of hybrid pollen viability and germination are needed to determine if they contribute to reproductive isolation. In a reciprocal transplant, we found no evidence of habitat isolation or reduced hybrid survival (from seedling to adult stage) or reproduction. These data suggest unilateral incompatibility partially reproductively isolates L. alabamica and L. crassa, but no other reproductive barriers could be detected.
doi:10.3732/ajb.0900184
PMCID: PMC2879664  PMID: 20526457
Brassicaceae; genetic incompatibilities; hybrid fitness; habitat isolation; Leavenworthia alabamica; Leavenworthia crassa; reproductive barriers; unilateral incompatibility

Results 1-2 (2)