Severin Ina, Östman Örjan, Lindström Eva S
Department of Ecology and Genetics/Limnology, Uppsala University, Uppsala, Sweden.
PLoS One. 2013 Dec 4;8(12):e80825. doi: 10.1371/journal.pone.0080825. eCollection 2013.
Previous studies have shown variable relationships between dispersal rate and ecosystem functioning, but the reasons for and mechanisms behind variable dispersal rate-functioning patterns are currently unknown. In this study we used six bacterial lake water communities in a laboratory experiment in order to investigate how dispersal among communities influences community productivity by evaluating three different mechanisms: 1) changes in taxonomic diversity, 2) changes in phylogenetic diversity or 3) changes in the composition of functional traits. The experiment was conducted in two phases; (A) a dialysis bag experiment where the dispersal rate among six communities was manipulated and the subsequent change in bacterial diversity and growth rate was recorded, and (B) a regrowth experiment where we manipulated available resources to study how well a taxon grows on certain organic carbon resources, i.e. their functional traits. From experiment (B) we could thus estimate changes in functional traits in communities in experiment (A). Bacterial production was affected by dispersal, but not consistently among lakes. Neither change in taxonomic or phylogenetic diversity with dispersal could explain the observed dispersal-productivity relationships. Instead, changes in trait composition with dispersal, especially the communities' ability to use p-coumaric acid, an aromatic compound, could explain the observed dispersal-productivity relationships. Changes in this trait caused by dispersal seemed especially important for bacterial productivity in waters with a high aromaticity of the organic matter pool. We conclude that the effect of dispersal on bacterial communities can affect ecosystem functioning in different ways, through changes in functional key-traits which are important for the local environment.
以往的研究表明，扩散速率与生态系统功能之间的关系各不相同，但扩散速率-功能模式变化的原因和背后机制目前尚不清楚。在本研究中，我们在实验室实验中使用了六个细菌湖水群落，通过评估三种不同机制来研究群落间的扩散如何影响群落生产力：1）分类多样性的变化；2）系统发育多样性的变化；3）功能性状组成的变化。实验分两个阶段进行：（A）一个透析袋实验，其中操纵六个群落间的扩散速率，并记录随后细菌多样性和生长速率的变化；（B）一个再生长实验，其中我们操纵可利用资源，以研究一个分类单元在某些有机碳资源上的生长情况，即它们的功能性状。因此，从实验（B）中我们可以估计实验（A）中群落功能性状的变化。细菌生产力受扩散影响，但在不同湖泊间并不一致。分类或系统发育多样性随扩散的变化都无法解释观察到的扩散-生产力关系。相反，性状组成随扩散的变化，特别是群落利用对香豆酸（一种芳香化合物）的能力，可以解释观察到的扩散-生产力关系。扩散引起的这一性状变化对有机质库芳香度高的水体中的细菌生产力似乎尤为重要。我们得出结论，扩散对细菌群落的影响可以通过对当地环境重要的功能关键性状的变化，以不同方式影响生态系统功能。
