Université Montpellier 2, Ecosystèmes Lagunaires, UMR CNRS - IFREMER - UMR 5119, CC 093, 34095 Montpellier Cedex 5, France.
Ecol Appl. 2010 Sep;20(6):1512-22. doi: 10.1890/09-1310.1.
Human activities have strong impacts on ecosystem functioning through their effect on abiotic factors and on biodiversity. There is also growing evidence that species functional traits link changes in species composition and shifts in ecosystem processes. Hence, it appears to be of utmost importance to quantify modifications in the functional structure of species communities after human disturbance in addition to changes in taxonomic structure. Despite this fact, there is still little consensus on the actual impacts of human-mediated habitat alteration on the components of biodiversity, which include species functional traits. Therefore, we studied changes in taxonomic diversity (richness and evenness), in functional diversity, and in functional specialization of estuarine fish communities facing drastic environmental and habitat alterations. The Terminos Lagoon (Gulf of Mexico) is a tropical estuary of primary concern for its biodiversity, its habitats, and its resource supply, which have been severely impacted by human activities. Fish communities were sampled in four zones of the Terminos Lagoon 18 years apart (1980 and 1998). Two functions performed by fish (food acquisition and locomotion) were studied through the measurement of 16 functional traits. Functional diversity of fish communities was quantified using three independent components: richness, evenness, and divergence. Additionally, we measured the degree of functional specialization in fish communities. We used a null model to compare the functional and the taxonomic structure of fish communities between 1980 and 1998. Among the four largest zones studied, three did not show strong functional changes. In the northern part of the lagoon, we found an increase in fish richness but a significant decrease of functional divergence and functional specialization. We explain this result by a decline of specialized species (i.e., those with particular combinations of traits), while newly occurring species are redundant with those already present. The species that decreased in abundance have functional traits linked to seagrass habitats that regressed consecutively to increasing eutrophication. The paradox found in our study highlights the need for a multifaceted approach in the assessment of biodiversity changes in communities under pressure.
人类活动通过对非生物因素和生物多样性的影响，对生态系统功能产生了强烈的影响。越来越多的证据表明，物种功能特征与物种组成的变化和生态系统过程的转变有关。因此，除了物种组成的变化外，量化人类干扰后物种群落功能结构的变化似乎至关重要。尽管如此，对于人类介导的生境改变对生物多样性组成部分（包括物种功能特征）的实际影响，仍然没有达成共识。因此，我们研究了特米诺斯泻湖（墨西哥湾）面临剧烈环境和生境变化的河口鱼类群落的分类多样性（丰富度和均匀度）、功能多样性和功能特化的变化。特米诺斯泻湖是一个热带河口，因其生物多样性、生境和资源供应而受到关注，这些都受到了人类活动的严重影响。我们在特米诺斯泻湖的四个区域进行了鱼类群落采样，两次采样时间相隔 18 年（1980 年和 1998 年）。通过测量 16 个功能特征，研究了鱼类的两种功能（食物获取和运动）。使用三个独立的组件来量化鱼类群落的功能多样性：丰富度、均匀度和发散度。此外，我们还测量了鱼类群落的功能特化程度。我们使用了一个零模型来比较 1980 年和 1998 年鱼类群落的功能和分类结构。在所研究的四个最大区域中，有三个区域没有表现出强烈的功能变化。在泻湖的北部，我们发现鱼类丰富度增加，但功能发散度和功能特化度显著下降。我们用一个衰退的特化物种（即那些具有特定组合的特征的物种）来解释这个结果，而新出现的物种与现有的物种是冗余的。那些丰度下降的物种具有与连续退化的海草生境相关的功能特征，同时伴随着富营养化的增加。我们的研究结果强调了在评估受到压力的群落的生物多样性变化时，需要采用多方面的方法。
