Department of Zoology and Laboratory of Ornithology, Palacky University, Olomouc, Czech Republic.
J Anim Ecol. 2019 Nov;88(11):1766-1776. doi: 10.1111/1365-2656.13073. Epub 2019 Aug 7.
Ecological specialization enables the partitioning of resources and thus can facilitate the coexistence of species and promote higher species richness. Specialization and niche partitioning are expected to exert a decisive influence on local spatial scales, while species richness at regional scales should be shaped mostly by historical factors and abiotic conditions. Moreover, specialization is expected to be particularly important in communities that are exceptionally species rich for their environmental conditions. Concurrently, niche overlap in these communities should be minimized to enable species coexistence. We tested these hypotheses by studying specialization-richness relationship and niche overlap in assemblages of 298 species of songbirds (Passeriformes) across Australia. We used local (2-6 ha) to regional (bioregions) spatial scales and detailed data on habitat, diet and foraging behaviour (method, substrate and stratum). We expected the richness-specialization relationship to be particularly strong (a) on local spatial scales and (b) in communities exceptionally species rich for given environmental conditions (approximated by moisture and vegetation complexity). We also expected (c) low niche overlap in assemblages with specialized species. Only the third prediction was partly supported. First, while the specialization and species richness were often positively related, the strength and the direction of the relationship changed between traits and across spatial scales. The strength of the specialization-richness relationship was consistently positive only in foraging stratum, and it increased towards smaller spatial scales only in case of habitat and diet. Simultaneously, species in local communities demonstrated high overlap in habitat and diet. Second, we did not find particularly strong specialization-richness relationships in exceptionally species-rich communities. Third, we found the expected negative relationship between specialization and overlap in foraging stratum and substrate (in local communities), suggesting that species partition ecological space locally in terms of where they find food. Our expectations were only weakly supported. Specialization on foraging stratum was probably important in facilitating species coexistence. Conversely, although species were often specialized on habitat and diet, high overlap in these traits did not preclude their local coexistence. Overall, specialization and overlap in foraging traits were more important for species coexistence than habitat or diet.
生态特化使资源得以分割，从而促进物种共存并提高物种丰富度。特化和生态位分割预计会对局部空间尺度产生决定性影响，而物种丰富度在区域尺度上主要受到历史因素和非生物条件的影响。此外，在环境条件特别有利于物种丰富度的群落中，特化预计会特别重要。同时，为了实现物种共存，这些群落中的生态位重叠应该最小化。我们通过研究澳大利亚 298 种鸣禽（雀形目）组合的特化-丰富度关系和生态位重叠来检验这些假设。我们使用了局部（2-6 公顷）到区域（生物区）空间尺度以及有关栖息地、饮食和觅食行为（方法、基质和层）的详细数据。我们预计，丰富度-特化关系将特别强烈：（a）在局部空间尺度上，（b）在给定环境条件下（通过水分和植被复杂性来近似）物种特别丰富的群落中。我们还预计，（c）在特化物种组成的组合中，生态位重叠较低。只有第三个预测得到了部分支持。首先，虽然特化和物种丰富度通常呈正相关，但这种关系的强度和方向在性状和空间尺度上都发生了变化。只有在觅食层中，特化-丰富度关系的强度才始终为正，而且只有在栖息地和饮食方面，这种关系才会随着空间尺度的缩小而增强。同时，局部群落中的物种在栖息地和饮食方面表现出高度重叠。其次，我们在物种特别丰富的群落中没有发现特别强烈的特化-丰富度关系。第三，我们发现了在觅食层和基质中特化和重叠之间的预期负相关（在局部社区中），这表明物种在局部范围内根据食物来源分割生态空间。我们的预期仅得到了微弱的支持。在觅食层上的特化可能对促进物种共存很重要。相反，尽管物种在栖息地和饮食方面通常是特化的，但这些特征的高度重叠并不排除它们在当地共存。总的来说，觅食特征的特化和重叠对于物种共存比栖息地或饮食更为重要。
