DOI: 10.3724/SP.J.1003.2012.09083

Biodiversity Science (生物多样性) 2012/20:6 PP.676-684

Genetic diversity and the mating system in a fragmented population of Tsoongiodendron odorum

Habitat fragmentation is one of the most serious threats to plant diversity. In general, fragmentation negatively impacts the genetic variability of plant populations due to increased random genetic drift, inbreeding, and reductions in gene flow. To investigate the effect of habitat fragmentation on genetic diversity and the mating system of Tsoongiodendron odorum, in this study, we analyzed genetic diversity and the mating system in hierarchical levels at the population, stands, and the individual scales in a fragmented T. odorum population. We sampled and mapped 61 adult individuals from the population. Using eight microsatellite loci, we genotyped a total of 780 seeds from 15 maternal trees for the mating system analysis. The results revealed moderate levels of genetic diversity in both adults (HE = 0.522) and seeds (HE = 0.499) with no significant differences between the two ontogenic stages. In addition, we did not observe a significant increase in the seeds inbreeding coefficient. Results from the multilocus mating system analysis indicated that T. odorum was an outbreeding species with a multilocus outcrossing rate (tm) of 1.000. A small number of biparental inbreeding and correlated mating events were detected in this fragmented population. We found a small number of effective pollen donors (Nep is between 3.7 and 5.4), which seems to be a common character of insect-pollinated canopy trees. Minor differences in outcrossing rates were detected among stands, and more pollen donors were found in smaller stands. However, outcrossing rate was significantly different among individuals, and a few selfing events were detected in some seed trees. These results may provide fundamental information required to establish long term conservation strategies for this endangered tree which is endemic to China.

Key words:Tsoongiodendron odorum, habitat fragmentation, multilocus mating system analysis, conservation genetics, microsatellite

ReleaseDate:2014-07-21 16:28:35

Aguilar R, Ashworth L, Galetto L, Aizen MA (2006) Plant reproductive susceptibility to habitat fragmentation: review and synthesis through a meta-analysis. Ecology Letters, 9, 968-980.

Aguilar R, Quesada M, Ashworth L, Herrerias-Diego Y, Lobo J (2008) Genetic consequences of habitat fragmentation in plant populations: susceptible signals in plant traits and methodological approaches. Molecular Ecology, 17, 5177-5188.

Debout GDG, Doucet JL, Hardy OJ (2011) Population history and gene dispersal inferred from spatial genetic structure of a Central African timber tree, Distemonanthus benthamianus (Caesalpinioideae). Heredity, 106, 88-99.

DeLucas AI, Robledo-Arnuncio JJ, Hidalgo E, González-Martínez SC (2008) Mating system and pollen gene flow in Mediterranean maritime pine. Heredity, 100, 390-399.

Dick CW, Etchelecu G, Austerlitz F (2003) Pollen dispersal of tropical trees (Dinizia excelsa: Fabaceae) by native insects and African honeybees in pristine and fragmented Amazonian rainforest. Molecular Ecology, 12, 753-764.

Doyle JJ, Doyle JL (1987) A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochemical Bulletin, 19, 11-15.

Eckert CG, Kalisz S, Geber MA, Sargent R, Elle E, Cheptou PO, Goodwillie C, Johnston MO, Kelly JK, Moeller DA, Porcher E, Ree RH, Vallejo-Marín M, Winn AA (2010) Plant mating systems in a changing world. Trends in Ecology and Evolution, 25, 35-43.

El Mousadik A, Petit RJ (1996) High level of genetic differentiation for allelic richness among populations of the argan tree [Argania spinosa (L.) Skeels] endemic to Morocco. Theoretical and Applied Genetics, 92, 832-839.

Fu L (付琳), Xu FX (徐凤霞), Zeng QW (曾庆文) (2009) Studies on microsporogenesis and development of male gametophyte in Tsoongiodendron odorum Chun. Journal of Tropical and Subtropical Botany (热带亚热带植物学报), 17, 419-426. (in Chinese with English abstract)

Fu LK (傅立国), Jin JM (金鉴明) (1992) China Plant Red Data Book: Rare and Endangered Plants (中国植物红皮书: 稀有濒危植物). Science Press, Beijing. (in Chinese)

Goudet J (2001) FSTAT, a program to estimate and test gene diversities and fixation indices (Version 2. 9. 3).

He RK, Wang J, Huang HW (2012) Long-distance gene dispersal inferred from spatial genetic structure in Handeliodendron bodinieri, an endangered tree from karst forest in southwest China. Biochemical Systematics and Ecology, 44, 295-302.

Huang JX (黄久香), Zhuang XY (庄雪影) (2002) Genetic diversity of the populations of Tsoongiodendron odorum. Acta Phytoecologica Sinica (植物生态学报), 26, 413-419. (in Chinese with English abstract)

Hufford KM, Hamrick JL (2003) Viability selection at three early life stages of the tropical tree, Platypodium elegans (Fabaceae, Papilionoideae). Evolution, 57, 518-526.

Ishida K (2008) Effects of inbreeding on the magnitude of inbreeding depression in a highly self-fertilizing tree, Magnolia obovata. Ecology Resources, 23, 995-1003.

Jiang JH, Wang J, Kang M, Sun W, Huang HW (2011) Isolation and characterization of microsatellite loci in Tsoongiodendron odorum (Magnoliaceae). American Journal of Botany, 98, 284-286.

Kang M, Jiang MX, Huang HW (2005) Genetic diversity in fragmented populations of Berchemiella wilsonii var. pubipetiolata (Rhamnaceae). Annals of Botany, 95, 1145-1151.

Kikuchi S, Isagi Y (2002) Microsatellite genetic variation in small and isolated populations of Magnolia sieboldii ssp. japonica. Heredity, 88, 313-321.

Liu YH (刘玉壶) (1984) A preliminary study on the taxonomy of the family Magnoliaceae. Acta Phytotaxonomica Sinica (植物分类学报), 22, 89-109. (in Chinese with English abstract)

Luijten SH, Dierick A, Oostermeijer JGB, Raijmann LEL, Den Nijs HCM (2000) Population size, genetic variation, and reproductive success in a rapidly declining, self-incompatible perennial (Arnica montana) in the Netherlands. Conservation Biology, 14, 1776-1787.

Mathiasen P, Rovere AE, Premoli AC (2007) Genetic structure and early effects of inbreeding in fragmented temperate forests of a self-incompatible tree, Embothrium coccineum. Conservation Biology, 21, 232-240.

Nybom H (2004) Comparison of different nuclear DNA markers for estimating intraspecific genetic diversity in plants. Molecular Ecology, 13, 1143-1155.

Patterson B, Vaillancourt RE, Pilbeam DJ, Potts BM (2004) Factors affecting variation in outcrossing rate in Eucalyptus globulus. Australian Journal of Botany, 52, 773-780.

Rasmussen KK, Kollmann J (2008) Low genetic diversity in small peripheral populations of a rare European tree (Sorbus torminalis) dominated by clonal reproduction. Conservation Genetics, 9, 1533-1539.

Ritland K (1989) Correlated matings in the partial selfer Mimulus guttatus. Evolution, 43, 848-859.

Ritland K (2002) Extensions of models for the estimation of mating systems using n independent loci. Heredity, 88, 221-228.

Rousset F (2008) GENEPOP'007: a complete reimplementation of the GENEPOP software for Windows and Linux. Molecular Ecology Resources, 8, 103-106.

Sampson JF (1998) Multiple paternity in Eucalyptus rameliana (Myrtaceae). Heredity, 81, 349-355.

Schemske DW, Husband BC, Ruckelhaus MH, Goodwille C, Parker IM, Bishop JG (1994) Evaluating approaches to the conservation of rare and endangered plants. Ecology, 75, 584-606.

Silva CRS, Albuquerque PSB, Ervedosa FR, Mota JWS, Figueira A, Sebbenn AM (2011) Understanding the genetic diversity, spatial genetic structure and mating system at the hierarchical levels of fruits and individuals of a continuous Theobroma cacao population from the Brazilian Amazon. Heredity, 106, 973-985.

Sork VL, Smouse PE (2006) Genetic analysis of landscape connectivity in tree populations. Landscape Ecology, 21, 821-836.

Stoeckel S, Grange J, Fernandez-Manjarres JF, Bilger I, Frascaria-Lacoste N, Mariette S (2006) Heterozygote excess in a self-incompatible and partially clonal forest tree species-Prunus avium L. Molecular Ecology, 15, 2109-2118.

Sun M, Ritland K (1998) Mating system of yellow starthistle (Centaurea solstitialis), a successful colonizer in North America. Heredity, 80, 225-232.

Tamaki I, Setsuko S, Tomaru N (2009) Estimation of outcrossing rates at hierarchical levels of fruits, individuals, populations and species in Magnolia stellata. Heredity, 102, 381-388.

Wang R, Ai B, Gao BQ, Yu S, Li YY, Chen XY (2009) Spatial genetic structure and restricted gene flow in a functionally dioecious fig, Ficus pumila L. var. pumila (Moraceae). Population Ecology, 51, 307-315.

White GM, Boshier DH, Powel W (2002) Increased pollen flow counteracts fragmentation in a tropical dry forest: an example from Swietenia humilis Zuccarini. Proceedings of the National Academy of Sciences, USA, 99, 2038-2042.

Xu H (许涵), Huang JX (黄久香), Zhang H (张浩), Peng YS (彭逸生), He ZJ (何仲坚) (2007) Population structure and distribution pattern of Tsoongiodendron odorum on Nankunshan, Guangdong Province. Journal of South China Agricultural University (华南农业大学学报), 28, 73-77. (in Chinese with English abstract)

Zhang DY (张大勇), Jiang XH (姜新华) (2001) Mating system evolution, resource allocation, and genetic diversity in plants. Acta Phytoecologica Sinica (植物生态学报), 25, 130-143. (in Chinese with English abstract)

Zeng QW (曾庆文), Gao ZZ (高泽正), Xing FW (邢福武), Zhang DX (张奠湘), Gong X (龚洵) (2004) Pollination biology of an endangered species: Tsoongiodendron odorum (Magnoliaceae). In: Proceedings of the Fifth National Symposium on the Conservation and Sustainable Use of Biodiversity in China (第5届生物多样性保护和持续利用研讨会论文集) (ed. Biodiversity Committee, the Chinese Academy of Sciences), pp. 199-204. China Meteorological Press, Beijing. (in Chinese with English abstract)