入侵植物黄花刺茄在新疆不同生境中的繁殖特性

Reproductive characteristics of the invasive species Solanum rostratum in different habitats of Xinjiang,China

外来植物的入侵与其繁殖特性密切相关,比较外来植物在不同生境中的繁殖特性将为揭示其入侵的最适生境及其入侵机制并制定合理的管理策略提供理论依据。黄花刺茄(Solanum rostratum)是一种原产新热带区和美国西南部、仅进行有性繁殖的一年生杂草,已在中国新疆等7个省/市成功入侵。本文对黄花刺茄在新疆绿洲、荒漠草原和砾质荒漠中的有性繁殖特性进行了研究,旨在比较该物种在不同生境中的繁殖能力,明确其在新疆入侵的最适生境。结果表明:(1)黄花刺茄单花开放持续时间为27–47 h。3种生境中植株每天开花时间和单花开放持续时间基本相同,但开花数/株表现为绿洲>荒漠草原>砾石荒漠,生境间存在极显著差异(P<0.01)。(2)3种生境中黄花刺茄的传粉昆虫均为四条隧蜂(Halictus quadricinctus)、隧蜂(Halictus sp.)和扁柄木蜂(Xylocopa latipes),且均为蜂振传粉。其中,扁柄木蜂的访花次数极少。(3)3种生境中传粉昆虫的总访花频率表现为绿洲>荒漠草原>砾石荒漠,彼此间均存在显著差异(P<0.05)。四条隧蜂喜好低温高湿环境,而隧蜂偏好高温低湿环境,四条隧蜂的日访花高峰期早于隧蜂。(4)3种生境中黄花刺茄的结实数/株、结籽数/果实、结籽数/株及种子千粒重表现为绿洲>荒漠草原>砾石荒漠,且结实数/株与开花数/株及传粉昆虫的总访花频率均呈极显著正相关,结籽数/果实和结籽数/株与总访花频率均呈显著正相关。这些结果说明:在新疆干旱区,绿洲是黄花刺茄入侵的最适生境。黄花刺茄在绿洲中可获得较多的资源,形成较多的花以吸引更多的传粉昆虫,并产生较多且千粒重较大的种子。

The invasiveness of alien plants is closely related to their reproductive characteristics. A comparison of reproductive characteristics of an alien species in different habitats will help to reveal its optimum habitat for invasion and the mechanism of invasion. Furthermore, it will provide a theoretical foundation for planning a reasonable management strategy. Solanum rostratum is a summer annual weed native to the neotropics and the southwestern USA that produces offspring only by sexual reproduction. This species has become established in seven provinces/cities of China, including Xinjiang. We compared reproductive characteristics of S. rostratum in oasis, desert grassland and gravel desert habitats in Xinjiang and determined the optimum habitat for its invasion. The results were as follows. （1） Single-flower duration of S. rostratum was between 27 and 47 hours. Daily flowering time and single-flower duration were similar among the three habitats. However, number of flowers per individual differed among habitats （P〈0.01=： oasis 〉 desert grassland 〉 gravel desert. （2） Halictus quadricinctus, Halictus sp. and Xylocopa latipes were the pollinators of S. rostratum, and all of them buzz-pollinated flowers. However, X. latipes visited flowers of S. rostratum, and all of them buzz-pollinated flowers. However, X. latipes visited flowers only occasionally. （3） Total visiting frequency of pollinators differed among habitats （P〈0.05）： oasis 〉 desert grassland 〉 gravel desert. Halictus quadricinctus preferred habitats with relatively low temperatures and high humidity, while another species of Halictus preferred relatively high temperatures and low humidity. Thus, the daily time of the peak of visiting frequency of H. quadricinctus was earlier than that of Halictus sp. （4） Order of number of fruits per individual, seed number per fruit and per individual and mass of 1,000 seeds was oasis 〉 desert grassland 〉 gravel desert. Fruit number per individual was highly significantly positively correlated with both number of flowers per individual and total visiting frequency of pollinators. Seed numbers per individual and per fruit were significantly positively correlated with total visiting frequency of pollinators. Our study indicates that S. rostratum can obtain more resources, produce more flowers that attract pollinators and produce more seeds with larger mass in oases than in desert grassland or gravel desert. Therefore, the oasis is the optimum habitat of S. rostratum in the arid region of Xinjiang, China.