Mary Jo W. Godt

University of Georgia

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J. L. Hamrick

University of Georgia

J. L. Hamrick

University of Georgia

Ronald K. Chesser

Texas Tech University

Michael H. Smith

Savannah River National Laboratory

Susan L. Sherman‐Broyles

Juvenile Diabetes Research Foundation

Eva Gonzales

Saint Louis University

Florence E. Caplow

Washington Department of Natural Resources

Eric J. Baack

Luther College

Ilia J. Leitch

Royal Botanic Gardens, Kew

Kenneth Asbury

Cooperative Institutions

University of Georgia

University of California, Davis

Savannah River National Laboratory

University of Western Australia

Rutgers, The State University of New Jersey

Australian National University

Appalachian State University

Cornell University

University of California, Berkeley

University of British Columbia

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Genetic Diversity in the Endangered Lily Harperocallis flava and a Close Relative, Tofieldia racemosa

Conservation Biology (1997)

Mary Jo W. Godt Joan L. Walker J. L. Hamrick

We examined genetic diversity in 464 individuals of the monotypic lily Harperocallis flava in its two habitats (seepage bogs and a roadside right‐of‐way) and five populations of a co‐occurring related lily, Tofieldia racemosa. The endangered H. flava, endemic to the Apalachicola lowlands of the Florida panhandle, was monomorphic for the 22 loci scored. In contrast, T. racemosa had a high proportion of polymorphic loci ( P s = 68.2%; P p = 47.7%) with moderate genetic diversity ( H es = 0.134; H ep = 0.114). Estimated gene flow was moderately high ( Nm = 2.07) for T. racemosa, with most (93%) of the total genetic diversity found within populations. Despite the low level of genetic divergence, some isolation by distance was detected among T. racemosa populations. Harperocallis flava and other species without discernable genetic variation pose special problems for conservation biologists because genetic criteria are not available for the development of ex situ and in situ conservation and management strategies.

Genetic divergence

Conservation Genetics

In situ conservation

10.1046/j.1523-1739.1997.95439.x

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Citations (52)

Cryptocarya chinensis Spatial Distribution Patterns Caused by Human Disturbance in the Lower Subtropical Monsoon Evergreen broad-leaved Forest

生態學報 (2005)

Zhengfeng Wang Gao San-hong Mary Jo W. Godt Peng Shaolin Shenglei Fu

Lower subtropical monsoon evergreen broad leaved forests are of high conservation significance in Sooth China. Because of human activities, the forest has been largely destroyed; the remaining fragments are now mainly in several protected reserves. To further protect this forest outside the reserves and to study human influences on it, we analyzed the spatial pattern of Cryptocarya chinensis, a dominant tree in the forest near Changlong village, Guangzhou, China. Compared with low human disturbance forests, in which C. chinensis was clumped, we found that trees were randomly distributed, especially the young life stages. Human activities in this forest have also led to the decline of the C. chinensis seedling bank, suggesting that the population is regenerating badly.

Evergreen forest

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Genetic Diversity and Population Structure in Tradescantia hirsuticaulis (Commelinaceae)

American Journal of Botany (1993)

Mary Jo W. Godt J. L. Hamrick

Population fragmentation

10.2307/2445517

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Low levels of allozyme differentiation betweenPyxidanthera (pyxie-moss) taxa (Diapensiaceae)

Plant Systematics and Evolution (1995)

Mary Jo W. Godt J. L. Hamrick

10.1007/bf00989292

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Citations (6)

ATTERNS AND LEVELS OF POLLEN-MEDIATED GENE FLOW INLATHYRUS LATIFOLIUS

Evolution (1993)

Mary Jo W. Godt J. L. Hamrick

While gene flow can be an important force in evolution, few direct measures are available in the plant literature. Descriptions of gene movement within populations are more common, but have primarily involved crop species and artificially constructed populations. In this study, fractional paternity procedures were used to examine patterns of pollen movement over two years within two sites of Lathyrus latifolius, a bumblebee-pollinated, self-compatible perennial legume. Study sites consisted of 15 to 23 semi-discrete flowering patches that contained 1 to 29 distinct genotypes. Distributions of gene movement distances within the study sites differed significantly from that expected under random mating. Mean gene movement was 14 m. On average, 17.6% (range = 0-52%) of matings occurred within a flowering patch. Outcrossing rates, estimated from paternity analysis, ranged from 0.87 to 0.90 across sites and years. Significant heterogeneity occurred among maternal individuals with respect to outcrossing and immigration rates, indicating that mating patterns were idiosyncratic to each plant. Apparent rates of pollen flow into the sites ranged from 5 to 15%, while estimates of total pollen flow into sites ranged from 16 to 46%. Significant increases in immigration rates between years were associated with decreases in the density of flowering plants.

Outcrossing

10.1111/j.1558-5646.1993.tb01202.x

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Citations (61)

Genetic Variation in Lathyrus latifolius (Leguminosae)

American Journal of Botany (1991)

Mary Jo W. Godt J. L. Hamrick

10.2307/2444920

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Effects of life history traits on genetic diversity in plant species

Philosophical Transactions of the Royal Society B Biological Sciences (1996)

J. L. Hamrick Mary Jo W. Godt

Seven two-trait combinations (e.g. breeding system and seed dispersal mechanism) of five life history characteristics were used to analyse interspecific variation in the level and distribution of allozyme genetic diversity in seed plants. Highly significant differences were seen among categories for all seven comparisons. Life form and breeding system had highly significant influences on genetic diversity and its distribution. Regardless of other traits, outcrossing species tended to be more genetically diverse and had less genetic differentiation among their populations. Similarly, woody plants have less among population differentiation and somewhat more genetic diversity than non-woody species with similar life history traits. An analysis of twelve plant families indicated that species within families with predominately outcrossing, woody species had more genetic diversity and less interpopulation differentiation than species within families with predominately herbaceous species.

Outcrossing

Herbaceous plant

10.1098/rstb.1996.0112

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Citations (2,248)

Allozyme Diversity in Cultivated Crops

Crop Science (1997)

J. L. Hamrick Mary Jo W. Godt

Estimates of genetic diversity maintained by plant species and its distribution within and among populations allows plant geneticists to predict, in a general way, the evolutionary potential of species. Single‐gene markers, particularly allozymes, have been used to measure the genetic diversity of species. In this paper, the plant allozyme literature was reviewed to compare levels of genetic variation maintained by crop and non‐crop species. Crop species (plant species intentionally cultivated by humans) have more allozyme diversity as a whole than other seed plant species, although the mean genetic diversity partitioned within populations of crop species was similar to that of other plant species. Populations of crop species were more genetically heterogeneous, an observation that was probably due to the higher proportion of crops that reproduce by self fertilization. Dicotyledonous crops have much less genetic diversity than monocotyledonous crops at the species and the population level and exhibit more inter‐population genetic differentiation. Annual and perennial crop species had similar levels of genetic diversity and partitioned genetic diversity in similar ways. Predominantly selflng crops had somewhat less genetic diversity than outcrossing or mixed‐mating species. Selflng crops exhibited more population‐to‐population variation in genetic diversity and allele frequency differences were much greater among their populations. High population‐to‐population variation in genetic diversity increases the importance of empirical data for the design of sampling protocols.

Outcrossing

Genetic Variability

10.2135/cropsci1997.0011183x003700010004x

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Genetic Diversity in a Threatened Wetland Species, Helonias bullata (Liliaceae)

Conservation Biology (1995)

Mary Jo W. Godt J. L. Hamrick Susan Power Bratton

Genetic variation was examined in Helonias bullata , a threatened perennial plant species that occurs in isolated wetland habitats. Fifteen populations representing the species’ geographic range were sampled. Genetic diversity was low for the species ( H es = 0.053) as well as within populations ( H ep = 0.029). Of the 33 allozyme loci examined, 11 (33%) were polymorphic, while on average only 12.8% (4) of the loci were polymorphic within populations. The number of alleles per polymorphic locus was 2.36 for the species and averaged 2.09 across populations. For every genetic parameter calculated, variation in H. bullata was lower than that typically found for narrowly distributed plant species. The lowest levels of genetic diversity were found in northern areas that were colonized following the last glacial epoch. The number of genotypes detected per population ranged from three to 21, with a mean of 13 for this clonally reproducing species. We found a relatively high proportion of total genetic diversity (30.6%) among populations and a significant correlation (p < 0.002) between genetic distance and geographic distance. Genetic drift phenomena appear to play a major role in the population genetics of this species. Anomalously, several populations that appeared most limited in size and vigor were genetically most variable, perhaps because they represent older, relictual populations. Life‐history characteristics of H. bullata coupled with low levels of genetic diversity and the degradation and disappearance of wetlands threaten the existence of this species.

Genetic distance

10.1046/j.1523-1739.1995.09030596.x

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Citations (69)

Population genetic analysis of Elliottiaracemosa (Ericaceae), a rare Georgia shrub

Molecular Ecology (1999)

Mary Jo W. Godt J. L. Hamrick

Genetic and genotypic diversity found within populations of threatened plant species can have important implications for their conservation and management. In this study we describe genetic and genotypic diversity found within 10 populations of the endemic shrub Elliottia racemosa (Ericaceae), the Georgia plume. E . racemosa is a threatened species known from fewer than 50 locations, all within the state of Georgia, USA. Seedset is limited to nonexistent in some E . racemosa populations and sexual recruitment has not been documented. However, the species is known to spread vegetatively via root‐sprouts. Twenty‐one allozyme loci were resolved for E . racemosa , nine of which were polymorphic. Compared with other woody taxa, E . racemosa has low genetic (i.e. allelic) diversity within populations ( H ep = 0.063) and at the species level ( H es = 0.091). Most of the genetic variation (82%) was found within populations, and genetic identities between populations were high (mean I = 0.96). However, genotypic diversity (i.e. the number of multilocus genotypes) differed markedly among populations. Two of the 10 populations consisted almost entirely of single multilocus genotypes, whereas more than 20 multilocus genotypes (in samples of 48 stems) were detected at three sites. Sites in which few multilocus genotypes were detected have low seedset, suggesting that the lack of clonal diversity limits reproduction in some populations of this reportedly self‐incompatible species.

Sexual reproduction

10.1046/j.1365-294x.1999.00539.x

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Citations (28)