西藏朗错秋季裸鲤属营养生态位及种间食物关系

西藏朗错海拔4300 m,是典型的高原湖泊之一。湖内具有兰格湖裸鲤和拉孜裸鲤共存的现象。本研究采用碳、氮稳定同位素技术分析了2018年秋季兰格湖裸鲤和拉孜裸鲤的食物组成和营养生态位,探讨了两种裸鲤的种间食物关系,包括饵料相似性和重叠系数。结果表明: 兰格湖裸鲤主要摄食蜉蝣类幼虫、摇蚊类幼虫、着生藻类、钩虾类和浮游生物;拉孜裸鲤主要摄食蜉蝣类幼虫、着生藻类、摇蚊类幼虫、钩虾类和水生维管束植物。两种裸鲤的营养生态位存在重叠,兰格湖裸鲤的δ¹³C值变幅(CR=1.60)、δ¹⁵N值变幅(NR=1.89)和凸多边形,总面积(TA=1.80)均小于拉孜裸鲤,差值分别为0.09、0.57和1.29。两种裸鲤的饵料相似性系数(94.2％)和重叠系数(91.5%)均较高,表明秋季西藏朗错两种裸鲤可能存在激烈的种间食物竞争关系。

Trophic niche and interspecific diet relationship of Gymnocypris in autumn from Langcuo Lake of Tibet,China.

Langcuo Lake is a typical plateau lake in the southern Tibet, with an altitude of 4300 m. Gymnocypris chui and Gymnocypris scleracanthus coexisted in this lake. In this study, we investigated the food composition and trophic niche of two Gymnocypris fishes in autumn by carbon and nitrogen stable isotopes technique in 2018. We further analyzed their interspecific diet relationship, including the diet similarity index and overlap coefficient. The results showed that G. chui mainly feed on ephemeroptera larvae, chironomidae larvae, periphytic algae, gammarus and plankton, while G. scleracanthus mainly feed on ephemeroptera larvae, periphytic algae, chironomidae larvae, gammarus and aquatic vascular plants. Two Gymnocypris fishes had trophic niche overlap. The δ¹³C range value (CR=1.60), δ¹⁵N range value (NR=1.89), and total area of convex hull (TA=1.80) of G. chui were lower than those of G. scleracanthus, with the difference values being 0.09, 0.57 and 1.29, respectively. The diet similarity index and overlap coefficient of those two species were higher, with a value of 94.2% and 91.5%, respectively. Our results suggested that the interspecific diet competition may be intense between the G. chui and G. scleracanthus in Langcuo Lake in autumn.