Diet variations of <i>Procambarus clarkii</i> and <i>Macrobrachium nipponense</i> in natural and modified wetlands at West Dongting Lake

Abstract

栖息地退化和外来物种入侵都是淡水生态系统中的主要威胁因素，因此，量化不同人类活动干扰强度下外来入侵生物和本土生物的食性组成差异，对于明确种间竞争强度，制定适合的管理对策至关重要.本研究应用碳、氮稳定同位素分析技术，比较了长江中下游西洞庭湖湿地受人类活动干扰程度不同的天然湿地和人工改造湿地中的入侵种克氏原螯虾（Procambarus clarkii）与本土种日本沼虾（Macrobrachium nipponense）的食性组成及差异.2017年8月8-18日在西洞庭湖区不同人类干扰强度的栖息地中采集了两种消费者和5种潜在食物来源样品，共计91个.测定碳氮稳定同位素含量后，使用贝叶斯混合模型，估算不同食物来源对消费者的贡献.研究发现：在两种栖息地中克氏原螯虾与日本沼虾食性均有重叠，且在改造湿地中重叠度更大.与克氏原螯虾相比，日本沼虾消费更多的动物性食物.与天然湿地相比，在改造湿地中由于克氏原螯虾数量更多，与本土种竞争食物资源，克氏原螯虾和日本沼虾δ¹³C比值都显著升高，食性组成均发生了变化，植物性食物来源比重增加.由于食性改变，在改造湿地中仅日本沼虾δ¹⁵N比值显著下降，克氏原螯虾在两种栖息地中δ¹⁵N比值无显著变化.本研究证明，随着人类干扰强度增大，受干扰湿地中外来入侵生物对本土生物的影响增大.;Habitat degradation and alien species invasion are the main threats for freshwater ecosystem. Therefore, quantifying the differences of diet composition between alien invasive and native species under different human disturbance intensities is very important for the understanding of the intensity of interspecific competition and determining appropriate management strategies. In this study, stable carbon and nitrogen isotope analysis technique was used to compare the diet composition and variations between the invasive species of Procambarus clarkii and the native species of Macrobrachium nipponense at open water (nature) and black poplar (Populus nigra) plantation (modified) wetlands in the West Dongting Lake. Ninety-one samples of consumers and potential food sources were collected between August 8 and 18, 2017. Bayesian mixture model were used to estimate diet composition of P. clarkii and M. nipponense at the two types of wetland. Result showed that compared with natural wetland, the number of P. clarkii in the modified wetland was larger and the diet overlap between invasive species (P. clarkii) and native species (M. nipponense) was greater in the modified wetland than in the natural wetland. Compared with P. clarkii, the native specie (M. nipponense) consumed more animal food in natural wetland. In the modified wetland, the δ¹³C for both P. clarkii and M. nipponense increased significantly, and their diet contained higher proportion of plant food sources. However, only M. nipponense showed significant changes in δ¹⁵N, while δ¹⁵N of P. clarkii showed no significant changes between the two habitats. This study suggested that with the increase of human disturbance, the impact of alien invasive organisms on local organisms increased.