Trophic resource partitioning drives fine-scale coexistence in cryptic bat species

Understanding the processes that enable species coexistence has important
implications for assessing how ecological systems will respond to global
change. Morphology and functional similarity increase the potential for
competition, and therefore, co-occurring morphologically similar but
genetically unique species are a good model system for testing coexistence
mechanisms. We used DNA metabarcoding and High Throughput Sequencing to
characterise for the first time the trophic ecology of two
recently-described cryptic bat species with parapatric ranges, Myotis
escalerai and Myotis crypticus. We collected faecal samples from
allopatric and sympatric regions and from syntopic and allotopic locations
within the sympatric region to describe the diets both taxonomically and
functionally and compare prey consumption with prey availability. The two
bat species had highly similar diets characterised by high arthropod
diversity, particularly Lepidoptera, Diptera and Araneae, and a high
proportion of prey that is not volant at night, which points to extensive
use of gleaning. Diet overlap at the prey-item level was lower in syntopic
populations, supporting trophic shift under fine-scale co-occurrence.
Furthermore, the diet of M. escalerai had a marginally lower proportion of
not nocturnally volant prey in syntopic populations, suggesting that the
shift in diet may be driven by a change in foraging mode. Our findings
suggest that fine-scale coexistence mechanisms can have implications for
maintaining broad-scale diversity patterns. This study highlights the
importance of including both allopatric and sympatric populations and
choosing meaningful spatial scales for detecting ecological patterns. We
conclude that a combination of high taxonomic resolution with a functional
approach helps identify patterns of niche shift.

阐明物种共存的实现机制，对于评估生态系统如何响应全球变化具有重要意义。形态与功能相似性会提升物种间的竞争潜力，因此，形态相似但遗传特征独特的同域共存物种，是检验共存机制的理想模型系统。本研究采用DNA宏条形码（DNA metabarcoding）与高通量测序（High Throughput Sequencing）技术，首次对两种新近被描述的邻域分布隐态蝙蝠物种——埃斯卡拉雷鼠耳蝠（Myotis escalerai）与隐纹鼠耳蝠（Myotis crypticus）的营养生态位展开了表征分析。我们分别从异域分布区、同域分布区，以及同域分布区内的同生境与异生境点位采集粪便样本，从分类学与功能学层面解析两种蝙蝠的食性，并对比猎物摄取量与猎物可获得性的差异。两种蝙蝠的食性高度相似，猎物类群均以节肢动物为主，且物种多样性丰富，尤其偏好鳞翅目（Lepidoptera）、双翅目（Diptera）与蜘蛛目（Araneae）；同时二者取食高比例的非夜间飞行猎物，这表明它们广泛采用拾食捕食策略。在猎物物种类群层面，同生境种群的食性重叠度更低，这验证了精细尺度共存下的营养生态位偏移现象。此外，在同生境种群中，埃斯卡拉雷鼠耳蝠的食谱中非夜间飞行猎物的占比略低，这表明其食性偏移可能由觅食模式的改变所驱动。本研究结果表明，精细尺度的共存机制对于维持大尺度的物种多样性格局具有重要意义。本研究强调，同时纳入异域与同域种群，并选取合理的空间尺度，对于探测生态格局至关重要。综上，结合高精度分类学鉴定与功能食性分析方法，有助于准确识别生态位偏移的相关格局。