Effects of Habitat Fragmentation on Genetic Diversity in Cycas Balansae (Cycadaceae)
PDF

Keywords

Habitat fragmentation
Cycas balansae
genetic variation
allozymes
conservation

Abstract

Habitat fragmentation is a serious threat to species survival. In Vietnam, Cycas balansae has been considered as threatened species because of the reduction and fragmentation of its habitats and over-exploitation. We assessed genetic variability and the pattern of population structure among six populations sampled in four provinces: Hoa Binh, Ha Nam, Ninh Binh and Quang Ninh. Polyacrylamide gel electrophoresis was performed on leaf tissues from 152 individuals representing 6 populations of C. balansae. Six of twelve enzyme systems were used to estimate genetic diversity at population and species levels. Eleven loci were examined. The allozyme data showed high levels of genetic diversity within all populations, ranging from 0.538 in Ba Sao to 0.628 in Tan Dan (average 0.576). The maintenance of high levels of expected heterozygosity (average 0.571) and low in observed heterozygosity (average 0.347) might be related to great heterozygote deficiency and increased frequencies of rare alleles. Genetic differentiation among populations was low (Dst = 0.036 and Gst = 0.064), indicating high level of gene flow (Nm = 3.22). Isolation by geographical distance was observed, however, no significant relationship between genetic distances and geographical distances was recorded. Our studies suggest small population sizes of cycads brought about by fragmentation of its habitats, over-exploitation, and increasing number of inbred individuals within populations. 

https://doi.org/10.29037/ajstd.104
PDF

References

David, S.W., Charles, H.M., and Andrew, P.D. (1986), Habitat fragmentation in the temperate zone. Conservation biology, pp. 237-257.

Templeton, A.R. (1990), Off –site breeding of animals and implications for plant conservation strategies. In Falk D. A. and Holsinger K. E (eds.. Genetics and conservation of rare plants. Oxford Univ. pp. 182-194.

Barrett, S.C.H. and Köhn, J.R. (1991), Genetic and evolutionary consequences of small population size in plants: Implications for conservation. In Falk, D.A. and Holsinger, K.E. (eds.) Genetics and conservation of rare plants. pp. 3-30.

van Treuren, R., Bijlsma, R., van Delden, W., and Ouborg, N.J. (1991), The significance of genetic erosion in the process of extinction. 1. Genetic differentiation in Salvia pratensis and Scabiosa columbaria in relation to population size. Heredity, vol. 66, pp. 189-198.

Ellstrand, N.C. and Elam, R.D. (1991), Population genetic consequences of small population size: implications for plant conservation genetics, Conservation Biology, pp. 217-242.

Godt, M.J.W. and Hamrick, J.L. (1993) Genetic diversity and population structure in Tradescantia hirsuticaulis (Commelinacaeae). American Journal of Botany, vol. 80(8), pp. 959-966.

Cascante, A., Quesada, M., Lobo J.J., and Fuchs, E.A. (2002), Effects of dry tropical forest fragmentation on the reproductive success and genetic structure of the tree samanea saman. Conservation biology, vol. 16(1), pp. 137-147.

Young, A.G., Merriam, H.G., and Warwick, S.I. (1993), The effects of forest fragmentation on genetic variation in Acer saccbaram Marsk (sugar maple) populations. Heredity, vol. 71, pp. 277-289.

Hamilton, W.D. (1982), Pathogens as causes of genetic diversity in their host populations. In population biology of infections diseases, eds.: Anderson, R.M. and May, R.M, pp. 265296, New York.

Milligan, B.G., Leebens-Mack, J., and Strand, A.E (1994), Conservation genetics: beyond the maintenance of marker diversity. Molecular Ecology, vol. 3, pp. 423-435.

Huenneke, L.F. (1991), Ecological implications of variation in plant populations. In genetics and conservation of rare plants, eds.: Falk, D.A., Holsinger, K.E., New York, Oxford Univ. Press., pp. 31-44.

Falk, D.A. and Holsinger, K.E. (1991), Genetics and conservation of rare plants. New York, Oxford Univ. Press., p. 283.

Hiep, N.T. and Loc, P.K. (1997) The cycads of Vietnam (species composition, distribution, ecology, utilization, threatened status and conservation). Proceedings of the NCST of Vietnam, vol. 9(2), pp. 91-99.

Hill, K.D., Nguyen, H.T., and Phan, L.K. (2004), The genus Cycas (Cycadaceae) in Vietnam, Brittonia. In The botanical review 70(2), The New York Botanical Garden, pp. 134-193.

Triest, L. (1989), Electrophoretic polymorphism and divergence in Najas marina L. (Najadaceae): molecular markers for individuals, hybrids, cytodenmes, lower taxa, ecodemes and conservation of genetic diversity. Aquat. Bot., vol. 33, pp. 301-380.

Wright, S. (1969), Evolution and the genetics of populations, V.2. The theory and gene frequencies. Uni. of Chicago Press.

Nei, M. (1987), Molecular evolutionary genetics. Columbia University Press, New York

Nei, M. (1972), Genetic distance between populations. American Journal of Botany, vol.72, pp. 1590-1597.

Roger, J.S. (1972), Measures of genetic similarity and genetic distance studies in genetics, VII. Univ. Taxas, vol. 7213, pp. 145-153.

Goudet, J. (1995), A computer program to calculate F-statics. J. Heredity, vol. 86, pp. 485486.

Miller, M.P. (1997), Tools for population genetic analysis (TFPGA) 1. 3: A windows program for the analysis of allozyme and molecular population genetic data.

Wright, S. (1951), The genetical structure of populations Ann. Eugen, vol. 15, pp. 313-354.

Tam, N.M., Vinh, T.V., Giang, V.T.H., Trang, N.T., Hiep, N.T., and Triest, L. (2003), Population genetics of Cycas chevalieri and Cycas simplicipinna in tropical forests of Vietnam. Journal of Biotechnology, pp. 503-518.

Tam, N.M., Trang, N.T., Hiep, N.T., and Triest, L. (2005), Genetic diversity in Cycas ferruginea in Vietnam. Proceedings of the 1 st natioanl workshop on ecology and biological resources, pp. 227-231.

Schaal, B.A. (1975), Population structure and local differentiation in Liatris cylindracea. American Jour.of Botany, vol. 65, pp. 923-928.

Hichert, R.D. and Hamrick, J.L. (1983), Patterns and levels of genetic variation in Great Basin bristlecone pine, Pinus longaeva. Evolution, vol. 37(2), pp. 302-311.

Hamrick, J.L. (1990), The distribution of genetic variation within and among natural plant populations, Genetics and Conservation In Schenwald-Cox, C.M., Chamber, S.M., MacBryde, B., and Thomas, L. (eds.), pp. 335-348.

Schnabel, A. and Hamrick, J.L. (1990), Organization of genetic diversity within and among populations of Gleditsia triacanthos (Leguminosae), American Jour. of Botany, vol. 77, pp. 1060-1069.

Hamilton, W.D. (1982), Pathogens as causes of genetic diversity in their host populations. In population biology of infections diseases, eds.: Anderson, R.M. and May, R.M, pp. 265296, New York.

Milligan, B.G., Leebens-Mack, J., and Strand, A.E (1994), Conservation genetics: beyond the maintenance of marker diversity. Molecular Ecology, vol. 3, pp. 423-435.

Huenneke, L.F. (1991), Ecological implications of variation in plant populations. In genetics and conservation of rare plants, eds.: Falk, D.A., Holsinger, K.E., New York, Oxford Univ. Press., pp. 31-44.

Falk, D.A. and Holsinger, K.E. (1991), Genetics and conservation of rare plants. New York, Oxford Univ. Press., p. 283.

Hiep, N.T. and Loc, P.K. (1997) The cycads of Vietnam (species composition, distribution, ecology, utilization, threatened status and conservation). Proceedings of the NCST of Vietnam, vol. 9(2), pp. 91-99.

Hill, K.D., Nguyen, H.T., and Phan, L.K. (2004), The genus Cycas (Cycadaceae) in Vietnam, Brittonia. In The botanical review 70(2), The New York Botanical Garden, pp. 134-193.

Triest, L. (1989), Electrophoretic polymorphism and divergence in Najas marina L. (Najadaceae): molecular markers for individuals, hybrids, cytodenmes, lower taxa, ecodemes and conservation of genetic diversity. Aquat. Bot., vol. 33, pp. 301-380.

Wright, S. (1969), Evolution and the genetics of populations, V.2. The theory and gene frequencies. Uni. of Chicago Press.

Nei, M. (1987), Molecular evolutionary genetics. Columbia University Press, New York

Nei, M. (1972), Genetic distance between populations. American Journal of Botany, vol.72, pp. 1590-1597.

Roger, J.S. (1972), Measures of genetic similarity and genetic distance studies in genetics, VII. Univ. Taxas, vol. 7213, pp. 145-153.

Goudet, J. (1995), A computer program to calculate F-statics. J. Heredity, vol. 86, pp. 485486.

Miller, M.P. (1997), Tools for population genetic analysis (TFPGA) 1. 3: A windows program for the analysis of allozyme and molecular population genetic data.

Wright, S. (1951), The genetical structure of populations Ann. Eugen, vol. 15, pp. 313-354.

Tam, N.M., Vinh, T.V., Giang, V.T.H., Trang, N.T., Hiep, N.T., and Triest, L. (2003), Population genetics of Cycas chevalieri and Cycas simplicipinna in tropical forests of Vietnam. Journal of Biotechnology, pp. 503-518.

Tam, N.M., Trang, N.T., Hiep, N.T., and Triest, L. (2005), Genetic diversity in Cycas ferruginea in Vietnam. Proceedings of the 1 st natioanl workshop on ecology and biological resources, pp. 227-231.

Schaal, B.A. (1975), Population structure and local differentiation in Liatris cylindracea. American Jour.of Botany, vol. 65, pp. 923-928.

Hichert, R.D. and Hamrick, J.L. (1983), Patterns and levels of genetic variation in Great Basin bristlecone pine, Pinus longaeva. Evolution, vol. 37(2), pp. 302-311.

Hamrick, J.L. (1990), The distribution of genetic variation within and among natural plant populations, Genetics and Conservation In Schenwald-Cox, C.M., Chamber, S.M., MacBryde, B., and Thomas, L. (eds.), pp. 335-348.

Schnabel, A. and Hamrick, J.L. (1990), Organization of genetic diversity within and among populations of Gleditsia triacanthos (Leguminosae), American Jour. of Botany, vol. 77, pp. 1060-1069.

Downloads

Download data is not yet available.