Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 1: Spartina BiologyVARYING SUCCESS OF SPARTINA SPP. INVASIONS IN CHINA:GENETIC DIVERSITY OR DIFFERENTIATION?S. AN 1 , Y. XIAO 1 , H. QING 1 , Z. WANG 1 , C. ZHOU 1 , B. LI 2 , S. SHI 3 , D. YU 1 , Z. DENG 1 , AND L. CHEN 11School <strong>of</strong> Life Science, Nanjing University, Nanjing 210093, China; anshq@nju.edu.cn2Ministry Of Education Key Laboratory For Biodiversity Science And Ecological Engineering, Institute Of BiodiversityScience, Fudan University, Shanghai 200433, China; Bool@fudan.nju.edu.cn3School <strong>of</strong> Life Science, Zhongshan University, Guangzhou 510275, China; Sshlss@zsu.edu.cnBiological invasions are widely envisaged as a component <strong>of</strong> global change, which not only threatennative biodiversity but also cause a considerable economic loss to <strong>the</strong> invaded areas. However, forsome species little is known about why <strong>the</strong>y are successful invaders. At <strong>the</strong> molecular level, manyresearchers have reported that high genetic diversity contributes to <strong>the</strong> success <strong>of</strong> plant invasionswhereas o<strong>the</strong>r studies have shown that reduced genetic variation makes invasive species more successful.Obviously, <strong>the</strong>se are contradictory explanations. Our studies <strong>of</strong> Spartina in China showthat S. alterniflora with higher population differentiation (Fst) was more successful in invadingcoastal China than S. anglica which had low Fst, although <strong>the</strong> latter species, having fixed heterozygosity,had much higher genetic diversity than <strong>the</strong> former. Greater number <strong>of</strong> chromosomes orhigher genetic diversity (P and H) does not necessarily mean higher adaptability and more successfulinvasion for exotic species, while higher Fst was associated with higher invading ability in S.alterniflora. However, factors o<strong>the</strong>r than genetic variation and population genetic structure may bemore important in determining invasion success.Keywords: Average heterogeneity, genetic diversity, plant invasion, population differentiation,SpartinaInvasive plant species threaten <strong>the</strong> integrity <strong>of</strong> naturalecosystems and reduce <strong>the</strong> growth <strong>of</strong> economic cropsthroughout <strong>the</strong> world by displacing native plant communities(Kennedy et al. 2002), establishing monoculturesand competing with economic species in new habitats(Callaway 2002). At <strong>the</strong> population level, <strong>the</strong> leading <strong>the</strong>oriesfor <strong>the</strong> successful invasion <strong>of</strong> plants are <strong>the</strong>ir escapefrom <strong>the</strong> natural enemies that hold <strong>the</strong>m in check, freeing<strong>the</strong>m to utilize <strong>the</strong>ir full potential for resource competition(Keane & Crawley 2002); allelopathic effects, where <strong>the</strong>phytotoxins released by exotic plants damage native species(Callaway & Aschehoug 2000; Bais et al. 2003); and <strong>the</strong>occurrence <strong>of</strong> a suitable niche existing in <strong>the</strong> new location(Sakai et al. 2001). At <strong>the</strong> molecular level, most researchershave reported that high genetic diversity contributes to <strong>the</strong>success <strong>of</strong> plant invasions (Ellstrand & Schierenbeck 2000;Novak & Mack 2001), although reduced genetic variationcan make invasive species more successful (Tsutsui et al.2000). Here we suggest that <strong>the</strong> different molecular parametersare correlated with success or failure <strong>of</strong> Spartinainvasions in China.Historically, no native species <strong>of</strong> <strong>the</strong> genus Spartinaexisted in China. For <strong>the</strong> purpose <strong>of</strong> ecological engineering,two Spartina species, S. anglica and S. alterniflora, wereintroduced to China in <strong>the</strong> last century. However, <strong>the</strong>ir fatesdiffered. Spartina anglica originated in 1870s in east coastalEngland and is a hybrid between S. maritima as paternalspecies and S. alterniflora as <strong>the</strong> seed parent (Ferris et al.1997). In 1963, 44 individuals (actually ramets) <strong>of</strong> S. anglicawere produced by seed in China; 21 <strong>of</strong> <strong>the</strong>m were planted in<strong>the</strong> field and <strong>the</strong> o<strong>the</strong>rs were used to produce more <strong>of</strong>fspring,three <strong>of</strong> which had marvelous reproductive capacity (Chung1985). From 3 individuals, 9,100,000 clones were produced in1966, and were planted in 40 hectares (ha) <strong>of</strong> costal regionsin China. Thirteen years later, about 31,600 ha <strong>of</strong> S. anglicalow marshes were established in coastal China, and 36,000ha in 83 counties along coastal China (Fig. 1a) in 1985 (Qin& Chung 1992). Its sou<strong>the</strong>rn limit in China was at 21º27’Nwhereas <strong>the</strong> sou<strong>the</strong>rn limit in its native range is locatedbetween 42ºand 43º N in Europe (Chung 1993).The populations <strong>of</strong> S. anglica in China have generallylower height, lower biomass and lower net production (Chung1985) than <strong>the</strong>ir counterparts in its native range (Chater &Jones 1951; Gray & Benham 1991; Hubbard 1969) (Table 1).Starting in 1993, S. anglica became shorter in height, andlower in biomass and net biomass production. Pronounceddieback occurred in Chinese populations <strong>of</strong> S. anglica like<strong>the</strong> older populations in England (Gray et al. 1991). In 2000,S. anglica was found only in six counties (Fig. 1b). In 2002,<strong>the</strong> populations <strong>of</strong> S. anglica were found only in three counties,and <strong>the</strong> total area was less than 50 ha. Plant performancecontinued to be suppressed, e.g., height, biomass and netproduction were reduced; and <strong>the</strong> suppression still continues.Most <strong>of</strong> <strong>the</strong> S. anglica populations have been competitivelyreplaced by S. alterniflora, Phragmites australis, Typha spp.and Scirpus spp.-33-