Mathers Kate L, Armitage Patrick D, Hill Matthew, Bickerton Melanie, Mckenzie Morwenna, Pardo Isabel, Tickner David, Wood Paul J
Geography and Environment Loughborough University Loughborough UK.
Freshwater Biological Association, River Laboratory Wareham UK.
Ecol Evol. 2024 Aug 27;14(8):e70034. doi: 10.1002/ece3.70034. eCollection 2024 Aug.
Substrate composition has been widely recognised as a primary variable shaping lotic macroinvertebrate communities at the habitat unit level. However, fundamental understanding of how communities inhabiting mineralogical habitats (i.e., gravel, sand and silt) are structured across differing rivers is lacking. Moreover, research largely focusses on gravel beds and fine sediment in general (<2 mm) and as a result detailed field observations specifically of the sand and silt fractions are lacking. Using data from five UK streams collated from published studies, we assess taxonomic and functional biodiversity (alpha and beta diversity) at the habitat unit level (as defined by substrate composition of sand, silt and gravel). We found that the composition of taxonomic communities were clearly different in all habitat units for each individual stream (and at the landscape scale), with comparable, but less strong, distinctions between substrates for functional macroinvertebrate community composition. However, alpha diversity metrics and Local Contribution to Beta Diversity (LCBD) recorded among the different habitat units varied significantly across individual rivers, and the amount of variation explained by the habitat unit for taxonomic and functional composition demonstrated considerable differences suggesting strong context dependence. The depositional fine sediment habitats of sand and silt were found to support a discrete community composition and differing levels of alpha and beta diversity within and between rivers. We advocate that care should be taken when seeking to generalise biodiversity patterns at a landscape scale as our study highlights the high degree of context dependency when considering the role of the habitat template. Moreover, our results provide evidence that discriminating between the size fractions of fine sediment habitats (sand or silt) is important to fully elucidate the wider ecological importance of these habitats and the distinct taxonomic and functional biodiversity they support.
基质组成已被广泛认为是在栖息地单元层面塑造河流大型无脊椎动物群落的一个主要变量。然而，对于栖息在矿物学栖息地（即砾石、沙子和淤泥）中的群落如何在不同河流中构建，我们仍缺乏基本的了解。此外，研究主要集中在砾石床和一般的细颗粒沉积物（<2毫米）上，因此缺乏对沙子和淤泥部分的详细实地观察。利用从已发表研究中整理出的五条英国溪流的数据，我们在栖息地单元层面（由沙子、淤泥和砾石的基质组成定义）评估了分类和功能生物多样性（α和β多样性）。我们发现，对于每条单独的溪流（以及在景观尺度上），所有栖息地单元的分类群落组成明显不同，功能性大型无脊椎动物群落组成在不同基质之间的差异虽类似但不那么明显。然而，不同栖息地单元之间记录的α多样性指标和对β多样性的局部贡献（LCBD）在不同河流之间差异显著，栖息地单元对分类和功能组成的解释变异量也显示出相当大的差异，这表明存在很强的背景依赖性。我们发现，沙子和淤泥的沉积性细颗粒沉积物栖息地支持着离散的群落组成，以及河流内部和河流之间不同水平的α和β多样性。我们主张，在试图将生物多样性模式推广到景观尺度时应谨慎，因为我们的研究突出了在考虑栖息地模板的作用时背景依赖性的高度。此外，我们的结果提供了证据，表明区分细颗粒沉积物栖息地的粒度部分（沙子或淤泥）对于充分阐明这些栖息地的更广泛生态重要性以及它们所支持的独特分类和功能生物多样性很重要。
