宁夏贺兰山斑子麻黄种群的性比及雌雄空间格局

Sex ratio and spatial pattern of Ephedra rhytidosperma in Helan Mountain of Ningxia

性比、空间分布格局及关联性对雌雄异株种群的繁殖、进化与发展具有重要影响。斑子麻黄是雌雄异株且狭域分布的国家二级保护植物,在维持贺兰山荒漠生态系统稳定性和多样性发挥着重要作用,但有关斑子麻黄种群性比的研究未见报道。研究分析了宁夏贺兰山4个不同海拔(S_(1)、S_(2)、S_(3)、S_(4))斑子麻黄天然种群性比、空间分布格局及关联性。结果表明:(1)斑子麻黄性比与生长环境条件密切相关。4个种群都偏雄,生长环境严酷的S_(3)、S_(4)种群性别显著偏雄(P<0.05);不同龄级分析显示由于环境的异质性,斑子麻黄种群偏雄发生在不同阶段,生境条件好的S_(1)、S_(2)种群在幼龄和成年阶段显著偏雌或有偏雌趋势,偏雄发生在老年阶段;而生长环境严酷的S_(3)、S_(4)种群偏雄发生在幼龄阶段,成年和老年阶段有偏雄的趋势。(2)雌雄种群的空间关联性会决定种群的发展。S_(1)、S_(3)、S_(4)雌雄空间关联性表现为“正关联→不关联”,但S_(1)种群雌雄之间空间关联性远远小于S_(3)、S_(4)种群,以致S_(1)种群雌雄之间空间关联性不够,导致S_(1)种群为衰退型;S_(3)、S_(4)种群为增长型种群,说明较大尺度的雌雄的空间关联有利于繁殖。而S_(2)种群在整个尺度上都表现为“无关联”,雌雄群体相互独立,各自发展,缺乏幼体,即衰退种群。研究结果揭示了斑子麻黄雌雄群体的组成、结构及空间分布特征,为其保育提供了理论依据。

The sex ratio,spatial distribution,as well as the correlation of Ephedra rhytidosperma have important effects on dioecious plants reproduction,evolution,and development.E.rhytidosperma is a national second-class protective plant with narrowly distribution,which is dioecious and plays an key role in maintaining the stability and diversity of Helan Mountain desert ecosystem.But research on the sex ratio of E.rhytidosperma populations has not been reported yet.In this paper,the sex ratio,spatial distribution and spatial correlation of E.rhytidosperma in the Helan Mountain were analyzed at four different elevations(S_(1),S_(2),S_(3),S_(4)).Our results showed that:(1)the sex ratio of E.rhytidosperma was closely related to its environmental conditions.The four populations at different altitudes were male-biased,S_(3)and S_(4)in harsh growing environment were significantly male-biased at younger period(P<0.05),and there also existed male tendency at the adult and old ages;Analysis of different age groups showed that male bias occurred at different stages due to environment.For S_(1)and S_(2)in favorable conditions,there was a significant or tendency of female-favoring in young and adult stage,while male-favoring occurred in an old stage.(2)The spatial correlation between male and female populations would determine the development.For S_(1),S_(3),S_(4),male and female spatial correlation showed a trend from“positive-correlation→to no-correlation”.But the spatial correlation of S_(1)was of insufficient relevance and far less than that in S_(3)and S_(4),so it was declining.While S_(3)and S_(4)were growing.It shows that the wider spatial correlation is good for reproducing.However,the populations of S_(2)were uncorrelated,the male and female populations developed separately and they were independent,and lack of larvae,so it was declining.The results of the study respectively revealed the composition,structure,spatial distribution of E.rhytidosperma,The paper also provided theoretical basis for E.rhytidosperma-conservation.