Mitchell McGlaughlin - Academia.edu (original) (raw)

Papers by Mitchell McGlaughlin

American journal of botany, 2015

Investigations of recently derived and edaphically (soil) defined plant systems have provided ins... more Investigations of recently derived and edaphically (soil) defined plant systems have provided insight into important mechanisms of ecological divergence. We investigated the impact of edaphic adaptation on recent divergence between two Colorado Plateau endemics: the gypsum facultative Oreocarya revealii (Boraginaceae) and its more generalist sister species O. paradoxa. We assessed morphological stability, genetic identity, and soil chemistry to determine whether O. revealii is a distinct lineage edaphically adapted from O. paradoxa, as has been described in the literature. We genotyped 21 populations throughout the ranges of both species using 11 microsatellite markers and three plastid regions (trnL-F, trnT-L, trnQ-rps16) for haplotype analysis. We compared these data with soil chemistry (Ca and S concentrations, indicating gypsum levels), location, and morphological identity of populations. Soil chemistry failed to explain genetic or morphological identity in either taxon. Haploty...

Applications in Plant Sciences, 2015

Microsatellite primers were designed for Calochortus gunnisonii (Liliaceae), a montane lily speci... more Microsatellite primers were designed for Calochortus gunnisonii (Liliaceae), a montane lily species of the central and southern Rocky Mountains, using next-generation DNA sequencing. The markers will be used to investigate population structure, genetic diversity, and demographic history. Thirteen polymorphic microsatellite loci were isolated from C. gunnisonii using Illumina MiSeq next-generation DNA sequencing and bioinformatic screening. The mean number of alleles per locus ranged from 4.15 to 5.92 (avg. = 4.97). Observed and expected heterozygosity ranged from 0.077 to 0.871 and 0.213 to 0.782, respectively. The primers were also tested for cross-species amplification value with C. flexuosus, C. nuttallii, C. kennedyi var. kennedyi, and C. subalpinus. These primers will be useful for genetic and evolutionary studies across C. gunnisonii's range within the southern and central Rocky Mountains. Furthermore, these markers have proven valuable for cross-species amplifications within Calochortus.

Bats (order Chiroptera) represent nearly one fourth of the approximately 5,000 known species of m... more Bats (order Chiroptera) represent nearly one fourth of the approximately 5,000 known species of mammals, yet many aspects of their biology are poorly understood. Bats of certain species are well known reservoirs of rabies virus but within the past few years bats also have been identified as reservoirs or potential reservoirs of several other important human and livestock pathogens. In some instances, these viruses may cause persistent infections without recognized pathology in the bat host. Even though these are medically important viruses, little is known as to how bat immune systems engage viruses or how these viruses may evade a sterilizing host immune response. We have recently initiated research on Seba's short-tailed fruit bat (Carollia perspicillata), which may be a reservoir for a newly discovered coronavirus. We cloned and characterized cDNAs of four cytokine genes; tumor necrosis factor, interleukin-10, interleukin-23a, and granulocyte macrophage stimulating factor. Ou...

Typescript (photocopy). Thesis (Ph. D.)--Claremont Graduate University, 2005. Includes bibliograp... more Typescript (photocopy). Thesis (Ph. D.)--Claremont Graduate University, 2005. Includes bibliographical references (leaves 115-129).

Conservation Genetics, 2014

Annals of Botany, 2010

Aims The Hawaiian silversword alliance (Asteraceae) is one the best examples of a plant adaptive ... more Aims The Hawaiian silversword alliance (Asteraceae) is one the best examples of a plant adaptive radiation, exhibiting extensive morphological and ecological diversity. No research within this group has addressed the role of geographical isolation, independent of ecological adaptation, in contributing to taxonomic diversity. The aims of this study were to examine genetic differentiation among subspecies of Dubautia laxa (Asteraceae) to determine if allopatric or sympatric populations and subspecies form distinct genetic clusters to understand better the role of geography in diversification within the alliance. † Methods Dubautia laxa is a widespread member of the Hawaiian silversword alliance, occurring on four of the five major islands of the Hawaiian archipelago, with four subspecies recognized on the basis of morphological, ecological and geographical variation. Nuclear microsatellites and plastid DNA sequence data were examined. Data were analysed using maximum-likelihood and Bayesian phylogenetic methodologies to identify unique evolutionary lineages. † Key Results Plastid DNA sequence data resolved two highly divergent lineages, recognized as the Laxa and Hirsuta groups, that are more similar to other members of the Hawaiian silversword alliance than they are to each other. The Laxa group is basal to the young island species of Dubautia, whereas the Hirsuta group forms a clade with the old island lineages of Dubautia and with Argyroxiphium. The divergence between the plastid groups is supported by Bayesian microsatellite clustering analyses, but the degree of nuclear differentiation is not as great. Clear genetic differentiation is only observed between allopatric populations, both within and among islands. † Conclusions These results indicate that geographical separation has aided diversification in D. laxa, whereas ecologically associated morphological differences are not associated with neutral genetic differentiation. This suggests that, despite the stunning ecological adaptation observed, geography has also played an important role in the Hawaiian silversword alliance plant adaptive radiation.

Conservation Genetics, 2014

ABSTRACT Sibara filifolia (Brassicaceae), Santa Cruz Island Rock Cress, an endangered annual plan... more ABSTRACT Sibara filifolia (Brassicaceae), Santa Cruz Island Rock Cress, an endangered annual plant endemic to the California Channel Islands which was presumed extinct for nearly 50 years, is currently known from only a few small patches on San Clemente Island (SCl) and Santa Catalina Island (SCa). In addition to protecting extant populations, recovery efforts have included ex situ seed collections to hedge against stochastic population losses. We examined genetic diversity and population structure in the wild and the effect of sampling intensity on the genetic diversity of ex situ seed collections using 13 species-specific microsatellite loci. Much of the genetic variation on each island consisted of rare alleles; 33% (SCl) or 59% (SCa) of the non-fixed alleles occurred at frequencies ≤ 0.05. Patches on SCl were genetically depauperate (mean HO = 0.002) compared to patches on SCa (mean HO = 0.344). One patch on SCl was genetically distinct, while the remaining four patches were genetically indistinguishable. The three patches on SCa were genetically distinct from those on SCl, but not from one another. Simulated sampling for the ex situ seed collections found that 10 individuals was sufficient to capture 90% of the diversity for normalized measures (NE, HO, and HE) in a depauperate (SCl) population, while 30 individuals was necessary in a diverse (SCa) population. However, sampling 125 (SCl) or 60 (SCa) individuals was necessary to capture 90% of all the alleles present. These findings indicate that theoretical guidelines for ex situ seed collections that recommend targeting 50 individuals per population overestimate the sampling effort required to adequately preserve common alleles, but may underestimate the effort necessary to capture most alleles in wild populations.

Botany, 2014

ABSTRACT GRAS proteins comprise a large family of genes that play important roles in regulating g... more ABSTRACT GRAS proteins comprise a large family of genes that play important roles in regulating gene expression throughout all stages of plant development. The physiological and phylogenetic breadth of GRAS proteins known among model species suggests that they may be useful as molecular genetic markers in non-model species. For example, GRAS genes involved in regulating legume–rhizobium symbioses may reveal ecological and evolutionary variation in these relationships. In this study, we collected sequences from Nodulation Signaling Protein 1 (NSP1), a gene involved in the development of an infection thread through which rhizobia enter roots, in five species of Acmispon Raf. to quantify genetic variation within and between closely related species and to compare sequence divergence in NSP1 from Acmispon with other legumes. We found a high degree of similarity of NSP1 from Acmispon with homologues in other angiosperms. Thirty-two unique alleles were identified within Acmispon, and much of this variation reflects spatial and geographic variation of sampled populations. There was no evidence of selection at the molecular level. Given the strong genetic structure found among Acmispon species, especially in a microsatellite region of the N-terminus, and the existence of homologues, NSP1 could be a useful phylogenetic marker across angiosperms.

Systematic Botany, 2008

Incongruence among different estimates of species relationships in plants, from different molecul... more Incongruence among different estimates of species relationships in plants, from different molecules, cytogenetic data, biogeographic data, morphological/anatomical data or other sources, has been used frequently as an indication of introgression, hybrid species origin, or chloroplast (cp) capture. In plants, these incongruences are most often seen between data derived from the nuclear vs. the cp genomes and the nuclear markers used for comparison usually have been from the nuclear ribosomal (nr) internal transcribed spacer region (ITS). The amount of genomic material shared between introgressing species can be highly variable. In some of these cases, other nuclear genomic regions have moved between species without leaving a signature on the nrITS. An example of well-supported phylogenetic incongruence is the placement of Dubautia scabra (DC.) D. D. Keck in the Hawaiian silversword alliance (HSA); evolutionary hypotheses for D. scabra based on molecular as opposed to cytogenetic data are strongly discordant. In this paper, we test these two conflicting phylogenetic hypotheses regarding the evolutionary relationships of Dubautia scabra using evidence from six low-copy nuclear genes, as well as multiple chloroplast noncoding regions and nrITS. The nrITS region is also examined for the presence of multiple copy types. Incongruence between inferred relationships based on nuclear chromosomal arrangements and molecular phylogenetic data from chloroplast DNA and nrITS is resolved in favor of a hypothesis of ancient hybridization rather than cytogenetic homoplasy involving dysploidy. Most single-copy nuclear genes track histories of D. scabra compatible with cytogenetic data whereas chloroplast and nrITS data track a common, different history that appears to reflect hybridization with a chromosomally distinct lineage that also occurs on Maui Nui and Hawai'i (the Big Island).

Plant Biology, 2014

The genus Rhinanthus L. is complex, containing many taxonomically unresolved taxa. In this paper ... more The genus Rhinanthus L. is complex, containing many taxonomically unresolved taxa. In this paper we studied genetic variation and species relationships in 15 populations of six Rhinanthus species from three sections. For this purpose, we developed new microsatellite primers for R. osiliensis and used them to investigate genetic variation in two narrow endemics (R. osiliensis, R. javorkae) and in four widespread species (R. rumelicus R. wagneri, R. angustifolius and R. minor). Species-specific private alleles were found in all species except R. osiliensis and R. angustifolius. The Bulgarian endemic R. javorkae showed the lowest genetic variation, followed by widespread R. minor and Estonian endemic R. osiliensis. Rhinanthus javorkae and R. minor were genetically most differentiated. Section Cleistolemus is weakly structured genetically, indicating close affinity between R. osiliensis, R. rumelicus, R. wagneri and R. angustifolius.

Molecular Ecology Resources, 2009

Molecular Ecology Resources, 2008

Sibara filifolia (Brassicaceae) is a federally endangered annual herb found on two of the Califor... more Sibara filifolia (Brassicaceae) is a federally endangered annual herb found on two of the California Channel Islands. Previous studies based on allozymes revealed little genetic variability on San Clemente Island. Nine polymorphic microsatellite loci were isolated from individuals on San Clemente Island. We found low levels of allelic variation (mean N A = 2.3), with seven loci exhibiting significant deviations from Hardy-Weinberg equilibrium (P < 0.01) and 10 pairs of loci exhibiting significant linkage disequilibrium (P < 0.01). Most of the observed variability (mean H O = 0.003) occurred among populations or in rare homozygous individuals.

Molecular Ecology, 2007

The relative roles of gene flow and natural selection in maintaining species differentiation have... more The relative roles of gene flow and natural selection in maintaining species differentiation have been a subject of debate for some time. The traditional view is that gene flow constrains adaptive divergence and maintains species cohesiveness. Alternatively, ecological speciation posits that the reverse is true: that adaptive ecological differentiation constrains gene flow. In this study, we examine gene flow and population differentiation among populations of two species of the Hawaiian silversword alliance, Dubautia arborea and D. ciliolata . We compare divergence in putatively neutral microsatellite markers with divergence in leaf morphometric traits, which may be selectively important or physiologically linked to selectively important traits. Gene flow between populations was found to be significant in only one of the two species, D. arborea . Leaf morphometric differentiation between species was significant, though not among populations within species. No evidence of effective genetic introgression was observed between apparently 'pure' populations of these species. Gene flow as measured by microsatellites was not correlated with geographic distance between populations, but was correlated with the linear placement of the widest part of the leaf. Because these two species are interfertile, as demonstrated by the presence of active hybrid zone, the lack of genetic introgression and the maintenance of species boundaries may be associated with natural selection on differential habitat.

Conservation Genetics Resources, 2013

ABSTRACT The genus Sclerocactus (Cactaceae) consists of 15 species, which have a confused taxonom... more ABSTRACT The genus Sclerocactus (Cactaceae) consists of 15 species, which have a confused taxonomic history due to morphological similarities and distribution overlap. Habitat loss and hybridization are of concern and have established cause for genetic investigations to further understand the genus and develop conservation strategies. Thirteen variable microsatellite loci were identified using S. glaucus and S. parviflorus and were tested in three additional species: S. wetlandicus, S. brevispinus and S. cloverii. The mean number of alleles per locus ranged from 2 to 11, with an average of 6.6. The observed and expected mean heterozygosity ranged from 0.00 to 0.90 and 0.26 to 0.90, respectively. These loci will aid in determining levels of hybridization, diversity and taxonomy of Sclerocactus.

Conservation Genetics Resources, 2011

Lotus subgenus Syrmatium is a group of 11 plant species that exhibit extensive ecological and mor... more Lotus subgenus Syrmatium is a group of 11 plant species that exhibit extensive ecological and morphological diversity throughout the California floristic province. Fifteen polymorphic microsatellite loci were isolated from two taxa, Lotus argophyllus var. adsurgens and L. dendroideus var. traskiae, and were screened for variability in 15 additional taxa within Lotus subgenus Syrmatium. Moderate levels of variability were observed with mean numbers of alleles per locus ranging from 1.3 to 7.3. The mean observed and expected heterozygosities ranged from 0.09 to 0.47 and 0.10 to 0.79, respectively. These new loci will be useful in conservation genetic and evolutionary studies within Lotus subgenus Syrmatium.

Conservation Genetics Resources, 2011

Rhamnus pirifolia Greene (Rhamnaceae), the island redberry, is a small evergreen tree endemic to ... more Rhamnus pirifolia Greene (Rhamnaceae), the island redberry, is a small evergreen tree endemic to the California Channel Islands and Guadalupe Island, Mexico. Nine polymorphic microsatellite loci were isolated from the taxon and were screened for variability in populations from three California Channel Islands. Moderate levels of variability were observed, with mean numbers of alleles per locus ranging from 1.3 to 4.7. The mean observed and expected heterozygosities ranged from 0.01 to 0.53 and 0.01 to 0.56, respectively. These new loci will be useful in conservation genetic and evolutionary studies within Rhamnus.

Conservation Genetics Resources, 2014

American journal of botany, 2015

Investigations of recently derived and edaphically (soil) defined plant systems have provided ins... more Investigations of recently derived and edaphically (soil) defined plant systems have provided insight into important mechanisms of ecological divergence. We investigated the impact of edaphic adaptation on recent divergence between two Colorado Plateau endemics: the gypsum facultative Oreocarya revealii (Boraginaceae) and its more generalist sister species O. paradoxa. We assessed morphological stability, genetic identity, and soil chemistry to determine whether O. revealii is a distinct lineage edaphically adapted from O. paradoxa, as has been described in the literature. We genotyped 21 populations throughout the ranges of both species using 11 microsatellite markers and three plastid regions (trnL-F, trnT-L, trnQ-rps16) for haplotype analysis. We compared these data with soil chemistry (Ca and S concentrations, indicating gypsum levels), location, and morphological identity of populations. Soil chemistry failed to explain genetic or morphological identity in either taxon. Haploty...

Applications in Plant Sciences, 2015

Microsatellite primers were designed for Calochortus gunnisonii (Liliaceae), a montane lily speci... more Microsatellite primers were designed for Calochortus gunnisonii (Liliaceae), a montane lily species of the central and southern Rocky Mountains, using next-generation DNA sequencing. The markers will be used to investigate population structure, genetic diversity, and demographic history. Thirteen polymorphic microsatellite loci were isolated from C. gunnisonii using Illumina MiSeq next-generation DNA sequencing and bioinformatic screening. The mean number of alleles per locus ranged from 4.15 to 5.92 (avg. = 4.97). Observed and expected heterozygosity ranged from 0.077 to 0.871 and 0.213 to 0.782, respectively. The primers were also tested for cross-species amplification value with C. flexuosus, C. nuttallii, C. kennedyi var. kennedyi, and C. subalpinus. These primers will be useful for genetic and evolutionary studies across C. gunnisonii&amp;amp;amp;amp;#39;s range within the southern and central Rocky Mountains. Furthermore, these markers have proven valuable for cross-species amplifications within Calochortus.

Bats (order Chiroptera) represent nearly one fourth of the approximately 5,000 known species of m... more Bats (order Chiroptera) represent nearly one fourth of the approximately 5,000 known species of mammals, yet many aspects of their biology are poorly understood. Bats of certain species are well known reservoirs of rabies virus but within the past few years bats also have been identified as reservoirs or potential reservoirs of several other important human and livestock pathogens. In some instances, these viruses may cause persistent infections without recognized pathology in the bat host. Even though these are medically important viruses, little is known as to how bat immune systems engage viruses or how these viruses may evade a sterilizing host immune response. We have recently initiated research on Seba's short-tailed fruit bat (Carollia perspicillata), which may be a reservoir for a newly discovered coronavirus. We cloned and characterized cDNAs of four cytokine genes; tumor necrosis factor, interleukin-10, interleukin-23a, and granulocyte macrophage stimulating factor. Ou...

Typescript (photocopy). Thesis (Ph. D.)--Claremont Graduate University, 2005. Includes bibliograp... more Typescript (photocopy). Thesis (Ph. D.)--Claremont Graduate University, 2005. Includes bibliographical references (leaves 115-129).

Conservation Genetics, 2014

Annals of Botany, 2010

Aims The Hawaiian silversword alliance (Asteraceae) is one the best examples of a plant adaptive ... more Aims The Hawaiian silversword alliance (Asteraceae) is one the best examples of a plant adaptive radiation, exhibiting extensive morphological and ecological diversity. No research within this group has addressed the role of geographical isolation, independent of ecological adaptation, in contributing to taxonomic diversity. The aims of this study were to examine genetic differentiation among subspecies of Dubautia laxa (Asteraceae) to determine if allopatric or sympatric populations and subspecies form distinct genetic clusters to understand better the role of geography in diversification within the alliance. † Methods Dubautia laxa is a widespread member of the Hawaiian silversword alliance, occurring on four of the five major islands of the Hawaiian archipelago, with four subspecies recognized on the basis of morphological, ecological and geographical variation. Nuclear microsatellites and plastid DNA sequence data were examined. Data were analysed using maximum-likelihood and Bayesian phylogenetic methodologies to identify unique evolutionary lineages. † Key Results Plastid DNA sequence data resolved two highly divergent lineages, recognized as the Laxa and Hirsuta groups, that are more similar to other members of the Hawaiian silversword alliance than they are to each other. The Laxa group is basal to the young island species of Dubautia, whereas the Hirsuta group forms a clade with the old island lineages of Dubautia and with Argyroxiphium. The divergence between the plastid groups is supported by Bayesian microsatellite clustering analyses, but the degree of nuclear differentiation is not as great. Clear genetic differentiation is only observed between allopatric populations, both within and among islands. † Conclusions These results indicate that geographical separation has aided diversification in D. laxa, whereas ecologically associated morphological differences are not associated with neutral genetic differentiation. This suggests that, despite the stunning ecological adaptation observed, geography has also played an important role in the Hawaiian silversword alliance plant adaptive radiation.

Conservation Genetics, 2014

ABSTRACT Sibara filifolia (Brassicaceae), Santa Cruz Island Rock Cress, an endangered annual plan... more ABSTRACT Sibara filifolia (Brassicaceae), Santa Cruz Island Rock Cress, an endangered annual plant endemic to the California Channel Islands which was presumed extinct for nearly 50 years, is currently known from only a few small patches on San Clemente Island (SCl) and Santa Catalina Island (SCa). In addition to protecting extant populations, recovery efforts have included ex situ seed collections to hedge against stochastic population losses. We examined genetic diversity and population structure in the wild and the effect of sampling intensity on the genetic diversity of ex situ seed collections using 13 species-specific microsatellite loci. Much of the genetic variation on each island consisted of rare alleles; 33% (SCl) or 59% (SCa) of the non-fixed alleles occurred at frequencies ≤ 0.05. Patches on SCl were genetically depauperate (mean HO = 0.002) compared to patches on SCa (mean HO = 0.344). One patch on SCl was genetically distinct, while the remaining four patches were genetically indistinguishable. The three patches on SCa were genetically distinct from those on SCl, but not from one another. Simulated sampling for the ex situ seed collections found that 10 individuals was sufficient to capture 90% of the diversity for normalized measures (NE, HO, and HE) in a depauperate (SCl) population, while 30 individuals was necessary in a diverse (SCa) population. However, sampling 125 (SCl) or 60 (SCa) individuals was necessary to capture 90% of all the alleles present. These findings indicate that theoretical guidelines for ex situ seed collections that recommend targeting 50 individuals per population overestimate the sampling effort required to adequately preserve common alleles, but may underestimate the effort necessary to capture most alleles in wild populations.

Botany, 2014

ABSTRACT GRAS proteins comprise a large family of genes that play important roles in regulating g... more ABSTRACT GRAS proteins comprise a large family of genes that play important roles in regulating gene expression throughout all stages of plant development. The physiological and phylogenetic breadth of GRAS proteins known among model species suggests that they may be useful as molecular genetic markers in non-model species. For example, GRAS genes involved in regulating legume–rhizobium symbioses may reveal ecological and evolutionary variation in these relationships. In this study, we collected sequences from Nodulation Signaling Protein 1 (NSP1), a gene involved in the development of an infection thread through which rhizobia enter roots, in five species of Acmispon Raf. to quantify genetic variation within and between closely related species and to compare sequence divergence in NSP1 from Acmispon with other legumes. We found a high degree of similarity of NSP1 from Acmispon with homologues in other angiosperms. Thirty-two unique alleles were identified within Acmispon, and much of this variation reflects spatial and geographic variation of sampled populations. There was no evidence of selection at the molecular level. Given the strong genetic structure found among Acmispon species, especially in a microsatellite region of the N-terminus, and the existence of homologues, NSP1 could be a useful phylogenetic marker across angiosperms.

Systematic Botany, 2008

Incongruence among different estimates of species relationships in plants, from different molecul... more Incongruence among different estimates of species relationships in plants, from different molecules, cytogenetic data, biogeographic data, morphological/anatomical data or other sources, has been used frequently as an indication of introgression, hybrid species origin, or chloroplast (cp) capture. In plants, these incongruences are most often seen between data derived from the nuclear vs. the cp genomes and the nuclear markers used for comparison usually have been from the nuclear ribosomal (nr) internal transcribed spacer region (ITS). The amount of genomic material shared between introgressing species can be highly variable. In some of these cases, other nuclear genomic regions have moved between species without leaving a signature on the nrITS. An example of well-supported phylogenetic incongruence is the placement of Dubautia scabra (DC.) D. D. Keck in the Hawaiian silversword alliance (HSA); evolutionary hypotheses for D. scabra based on molecular as opposed to cytogenetic data are strongly discordant. In this paper, we test these two conflicting phylogenetic hypotheses regarding the evolutionary relationships of Dubautia scabra using evidence from six low-copy nuclear genes, as well as multiple chloroplast noncoding regions and nrITS. The nrITS region is also examined for the presence of multiple copy types. Incongruence between inferred relationships based on nuclear chromosomal arrangements and molecular phylogenetic data from chloroplast DNA and nrITS is resolved in favor of a hypothesis of ancient hybridization rather than cytogenetic homoplasy involving dysploidy. Most single-copy nuclear genes track histories of D. scabra compatible with cytogenetic data whereas chloroplast and nrITS data track a common, different history that appears to reflect hybridization with a chromosomally distinct lineage that also occurs on Maui Nui and Hawai'i (the Big Island).

Plant Biology, 2014

The genus Rhinanthus L. is complex, containing many taxonomically unresolved taxa. In this paper ... more The genus Rhinanthus L. is complex, containing many taxonomically unresolved taxa. In this paper we studied genetic variation and species relationships in 15 populations of six Rhinanthus species from three sections. For this purpose, we developed new microsatellite primers for R. osiliensis and used them to investigate genetic variation in two narrow endemics (R. osiliensis, R. javorkae) and in four widespread species (R. rumelicus R. wagneri, R. angustifolius and R. minor). Species-specific private alleles were found in all species except R. osiliensis and R. angustifolius. The Bulgarian endemic R. javorkae showed the lowest genetic variation, followed by widespread R. minor and Estonian endemic R. osiliensis. Rhinanthus javorkae and R. minor were genetically most differentiated. Section Cleistolemus is weakly structured genetically, indicating close affinity between R. osiliensis, R. rumelicus, R. wagneri and R. angustifolius.

Molecular Ecology Resources, 2009

Molecular Ecology Resources, 2008

Sibara filifolia (Brassicaceae) is a federally endangered annual herb found on two of the Califor... more Sibara filifolia (Brassicaceae) is a federally endangered annual herb found on two of the California Channel Islands. Previous studies based on allozymes revealed little genetic variability on San Clemente Island. Nine polymorphic microsatellite loci were isolated from individuals on San Clemente Island. We found low levels of allelic variation (mean N A = 2.3), with seven loci exhibiting significant deviations from Hardy-Weinberg equilibrium (P < 0.01) and 10 pairs of loci exhibiting significant linkage disequilibrium (P < 0.01). Most of the observed variability (mean H O = 0.003) occurred among populations or in rare homozygous individuals.

Molecular Ecology, 2007

The relative roles of gene flow and natural selection in maintaining species differentiation have... more The relative roles of gene flow and natural selection in maintaining species differentiation have been a subject of debate for some time. The traditional view is that gene flow constrains adaptive divergence and maintains species cohesiveness. Alternatively, ecological speciation posits that the reverse is true: that adaptive ecological differentiation constrains gene flow. In this study, we examine gene flow and population differentiation among populations of two species of the Hawaiian silversword alliance, Dubautia arborea and D. ciliolata . We compare divergence in putatively neutral microsatellite markers with divergence in leaf morphometric traits, which may be selectively important or physiologically linked to selectively important traits. Gene flow between populations was found to be significant in only one of the two species, D. arborea . Leaf morphometric differentiation between species was significant, though not among populations within species. No evidence of effective genetic introgression was observed between apparently 'pure' populations of these species. Gene flow as measured by microsatellites was not correlated with geographic distance between populations, but was correlated with the linear placement of the widest part of the leaf. Because these two species are interfertile, as demonstrated by the presence of active hybrid zone, the lack of genetic introgression and the maintenance of species boundaries may be associated with natural selection on differential habitat.

Conservation Genetics Resources, 2013

ABSTRACT The genus Sclerocactus (Cactaceae) consists of 15 species, which have a confused taxonom... more ABSTRACT The genus Sclerocactus (Cactaceae) consists of 15 species, which have a confused taxonomic history due to morphological similarities and distribution overlap. Habitat loss and hybridization are of concern and have established cause for genetic investigations to further understand the genus and develop conservation strategies. Thirteen variable microsatellite loci were identified using S. glaucus and S. parviflorus and were tested in three additional species: S. wetlandicus, S. brevispinus and S. cloverii. The mean number of alleles per locus ranged from 2 to 11, with an average of 6.6. The observed and expected mean heterozygosity ranged from 0.00 to 0.90 and 0.26 to 0.90, respectively. These loci will aid in determining levels of hybridization, diversity and taxonomy of Sclerocactus.

Conservation Genetics Resources, 2011

Lotus subgenus Syrmatium is a group of 11 plant species that exhibit extensive ecological and mor... more Lotus subgenus Syrmatium is a group of 11 plant species that exhibit extensive ecological and morphological diversity throughout the California floristic province. Fifteen polymorphic microsatellite loci were isolated from two taxa, Lotus argophyllus var. adsurgens and L. dendroideus var. traskiae, and were screened for variability in 15 additional taxa within Lotus subgenus Syrmatium. Moderate levels of variability were observed with mean numbers of alleles per locus ranging from 1.3 to 7.3. The mean observed and expected heterozygosities ranged from 0.09 to 0.47 and 0.10 to 0.79, respectively. These new loci will be useful in conservation genetic and evolutionary studies within Lotus subgenus Syrmatium.

Conservation Genetics Resources, 2011

Rhamnus pirifolia Greene (Rhamnaceae), the island redberry, is a small evergreen tree endemic to ... more Rhamnus pirifolia Greene (Rhamnaceae), the island redberry, is a small evergreen tree endemic to the California Channel Islands and Guadalupe Island, Mexico. Nine polymorphic microsatellite loci were isolated from the taxon and were screened for variability in populations from three California Channel Islands. Moderate levels of variability were observed, with mean numbers of alleles per locus ranging from 1.3 to 4.7. The mean observed and expected heterozygosities ranged from 0.01 to 0.53 and 0.01 to 0.56, respectively. These new loci will be useful in conservation genetic and evolutionary studies within Rhamnus.

Conservation Genetics Resources, 2014