长江中下游湖泊两种混生苦草属植物生活史特征与共存分布格局

 在对长江中下游流域湖南、湖北、江西和安徽4省25个湖泊苦草属(Vallisneria)植物种群进行广泛的取样调查、鉴定和查明种间共存格局的基 础上，结合同园种植实验，对该属两个混生近缘种刺苦草(V. spinulosa)和苦草(V. natans)有性和无性生活史特征进行了定量测定和比较研究 ，探讨了种间生活史差异对种间共存格局的影响。结果表明：1)刺苦草是长江中下游湖泊的优势物种，苦草为常见种，而密刺苦草(V. denseserrulata)仅有很少分布；2)苦草和刺苦草常混生于这些湖泊中，形成共存分布格局：刺苦草和苦草种间呈明显的的带状相间分布格局， 或苦草只零星分布于刺苦草群落中；3)刺苦草和苦草有性和无性生活史特征显著不同：刺苦草为多年生，主要以无性繁殖为主，只有有限的有 性繁殖投入；相反，苦草在调查的地区为一年生，以有性繁殖为主，只进行微弱的克隆生长，且不能产生克隆繁殖器官(冬芽)。刺苦草和苦草 在有性和无性繁殖生活史对策上的权衡，导致种间资源利用和竞争能力的分异而使这两个近缘种得以共存。

VALLISNERIA SPECIES IN LAKES OF THE MIDDLE-LOWER REACHES OF THE YANGTZE RIVER OF CHINA

Aims Vallisneria species are very common and important in shallow lakes of the middle-lower reaches of the Yangtze River of China.Our objectives were to:1) examine whether these co-existing Vallisneria species differ in sexual and clonal life-history traits,and 2) determine whether life-history traits explain the interspecific distribution pattern of these species.Methods Field investigations were carried out to determine the distribution and coexistence pattern of the three Vallisneria species(V.spinulosa,V.natans and V.denseserrulata) in lakes of the middle-lower reaches of the Yangtze River.Life-history traits of sexual reproduction and clonal propagation of V.spinulosa and V.natans were determined and compared under field condition and uniform glasshouse environment.Important findings V.spinulosa was the dominant species in these lakes,V.natans was very common and V.denseserrulata was rare in this region.V.spinulosa and V.natans widely coexisted in these lakes;they frequently displayed a clear interspecific zonation pattern,or V.natans individuals scarcely occurred in V.spinulosa communities.Field investigations and glasshouse experiments suggested great differences of sexual and clonal life-history traits between V.spinulosa and V.natans.V.spinulosa is perennial,and capable of extensive clonal propagation,while V.natans is annual and reproduces mainly by sexual seedling as well as limited clonal growth.Differences of resource-acquisition and competitive abilities,caused by trade-offs of resource allocation between sexual reproduction and clonal propagation,might determine the pattern of competitive coexistence of V.spinulosa and V.natans.