冬虫夏草发生的影响因子

Factors influencing the occurrence of Ophiocordyceps sinensis

作为青藏高原高寒草甸特有的生物资源,冬虫夏草具有重要的药用和经济价值。特殊的生存环境决定了冬虫夏草的珍稀,外力的干扰和任何环境因子的变化都可能影响冬虫夏草的发生。钩蝠蛾属昆虫幼虫是冬虫夏草发生的营养和物质基础;高海拔分布决定了冬虫夏草发生所需的特殊气候和土壤条件;草甸植物为钩蝠蛾幼虫提供了丰富的食物资源;各种不同类型的天敌通过致病、捕食或寄生等作用对钩蝠蛾种群产生调节作用;过载放牧严重影响草甸植被的生长发育,并对冬虫夏草适生地草甸环境产生破坏作用;掠夺式采挖既破坏了环境也打断了冬虫夏草菌完成正常世代发育的链条。对影响冬虫夏草发生的各种因子进行了总结和分析,并指出了现有研究中存在的问题,为进一步开展冬虫夏草资源的可持续利用研究并拓展现有研究思路提供参考。

Ophiocordyceps sinensis,a unique entomophagous fungus parasitizing the larvae of the genus Thitarodes（Lepidoptera： Hepialidae） mainly distributed in the alpine meadow of the Tibetan Plateau,is known as a valuable invigorant of traditional Chinese medicine for centuries in China.It has become the most important source of cash income for the local farmers and herdsmen to collect O.sinensis.However,it is currently confronted with distribution shrink and output reduction,probably resulted from overexploitation,global warming and heavy grazing.The present paper reviewed the important factors influencing the occurrence of O.sinensis based on literatures published in past decades and analyzed the problems existing in the current research.As host,the larvae of Thitarodes spp.play a vital role in supplying nutritional materials for the occurrence of O.sinensis.More than 40 species of the genus Thitarodes have been recorded since 1958 in the Tibetan Plateau.The diverse habitats and terrains in the Tibetan Plateau accelerate the population differentiation and the formation of new species whose niche space and distribution area may become smaller and smaller.So the species of the genus Thitarodes are usually much more susceptive to environmental change.Due to the result of adaptive evolution for a long term,the development of O.sinensis and its host insects need the special climate and soil condition related with high-altitude distribution,such as subambient temperatures of atmosphere and soil,solar radiation,barometric pressure,hypoxic,etc..The snowline and the distribution altitude of O.sinensis have been raised gradually because of global warming,hence the distribution area and the output of O.sinensis has been drastically reduced.The environmental changes of subalpine meadow resulted from overexploitation and heavy grazing and other factors,such as global warming and rodent pests,also affect the occurrence of O.sinensis by influencing the food sources of host insects which feed on the roots of meadow plant.Natural enemies including pathogenic microbes,natural insect enemies,arachnid,birds,and rodents play important roles in regulating the population dynamics and maintaining the population balance of Thitarodes species through pathogeny,predation,and parasitism.Overexploitation not only damages the habitat,but also affects the reproduction and generation development of O.sinensis and its host insects.Although we have gotten more detailed information and some advances on the investigation and research of O.sinensis in past decades,some problems are required to unravel in the future.First,it is difficult to evaluate the effect of environmental factors on the occurrence and the developmental trends of O.sinensis because of the lack of systematic and detailed historical data.Second,the present environment data is limited in the habitat description or the simple weather record with larger scale.Third,the influence mechanism of environmental factors on the occurrence of O.sinensis is unclear.Fourth,most published data obtained usually by field investigation is not enough to reflect the true state of environmental effects on the occurrence of O.sinensis and its hosts.Therefore,understanding the effects of environmental factor on the occurrence of O.sinensis will be helpful to the further research and the sustainable utilization of O.sinensis.