1. Water level and submerged macrophytes are critical players for the functioning of shallow lake ecosystems; understanding how waterbird communities respond to changes in both can have important implications for conservation and management. Here, we evaluated the effects of changes in water level and submerged macrophyte status on wintering waterbird community size, functional group abundances, functional diversity (FD), and community assembly by using a dataset compiled over 50 years.
2. We built generalised linear models to evaluate the effects of water level and submerged macrophyte status on the above‐listed attributes of the waterbird communities by using mid‐winter waterbird censuses, water level measurements, and submerged macrophyte surveys, along with submerged macrophyte macrofossil records from two shallow lakes in Turkey. Using a relevant set of functional traits, we defined functional groups, calculated four FD measures, and simulated null distributions of the FD measures for assessing assembly rules.
3. We found that macrophyte‐dominated years had significantly higher abundances of waterbirds in one of the study lakes, and had more diving herbivores and omnivores in both lakes, while diving/scooping fish‐eating waterbird abundance was lower in macrophyte‐dominated years. Community size in Lake Beyşehir exhibited a negative association with water level; surprisingly, however, none of the functional group abundances and FD indices were significantly related to water level.
4. In our study communities, standardised effect sizes of functional richness and functional dispersion—two indices that are particularly sensitive to community assembly processes—were mostly lower than those of randomly assembled communities, which implies functional clustering. Shifts to a scarce‐macrophyte state were associated with increases in these two indices, possibly due to either changes in the relative strength of environmental filtering and limiting similarity in community assembly or sampling of transitional communities. Further studies covering a wider range of the trophic/macrophyte status spectrum are needed to be certain.
5. The results of this study indicate that shifts between abundant and scarce‐macrophyte states can have significant effects on wintering waterbird abundances, FD and community assembly. The results also suggest that shallow lakes in macrophyte‐dominated states can support more wintering waterbirds, especially diving omnivores, some of which are globally threatened.

中文翻译：

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水鸟功能组成和多样性的变化：水位和淹没大型植物的作用

1. 水位和淹没的大型植物是浅湖生态系统功能的关键因素。了解水鸟社区如何应对两者的变化可能对保护和管理产生重要影响。在这里，我们使用50年来收集的数据集，评估了水位和淹没植物的状况变化对越冬水鸟群落规模，功能群丰度，功能多样性（FD）和群落聚集的影响。
2. 我们建立了广义线性模型，通过使用冬季水鸟普查，水位测量和淹没的大型植物调查以及来自沉没的大型植物的化石记录，评估了水位和淹没的大型植物的状况对上述水鸟群落的影响。在土耳其的两个浅湖。使用一组相关的功能性状，我们定义了功能组，计算了四个FD度量，并模拟了FD度量的空分布以评估装配规则。
3. 我们发现，在一个研究湖泊中，以大型植物为生的年份的水鸟丰度显着较高，两个湖泊中的潜水草食动物和杂食动物的数量更多，而以大型植物为主导的年份中，潜水/ sco食鱼的水鸟丰度较低。Beyşehir湖的社区规模与水位呈负相关。然而，令人惊讶的是，官能团的丰度和FD指数均与水位没有显着相关。
4. 在我们的研究社区中，功能丰富性和功能分散性的标准化效应量（这两个对社区组装过程特别敏感的指标）大多低于随机组装的社区，这意味着功能聚集。转变为稀缺的宏观植物状态与这两个指数的增加有关，这可能是由于环境过滤的相对强度发生了变化，并且限制了社区集会的相似性或过渡社区的采样。尚需进一步研究，涵盖更广泛的营养/宏观植物状态谱。
5. 这项研究的结果表明，丰富和稀有的宏观植物状态之间的转换可能对越冬水鸟的丰度，FD和群落组装产生重大影响。研究结果还表明，在以植物为主的各州中，浅水湖泊可以养活更多越冬的水鸟，尤其是潜水杂食动物，其中一些受到全球威胁。