Data from: Assessing feeding preferences of a consumer guild: partitioning variation among versus within species

Interspecific variation in resource use is critical to understanding species diversity, coexistence, and ecosystem functioning. A growing body of research describes analogous intraspecific variation and its potential importance for population dynamics and community outcomes. However, the magnitude of intraspecific variation relative to interspecific variation in key dimensions of consumer-resource interactions remains unknown, and is critical for understanding the importance of this variation for population and community processes. In this study, we examine feeding preference through repeated laboratory choice feeding assays of 444 wild-caught individuals of eight invertebrate grazer species on rocky reefs in northern California, USA. Between-species variation accounted for 25-33% of the total variation in preference for the preferred resource, while between-individual variation accounted for 4-5% of total variation. For two of the eight species, between-individual variation was significantly different from zero and contributed on-average 14% and 17% of the total diet variation, even after accounting for differences due to size and sex. Therefore, even with clearly distinguishable between-species differences in mean preference, diet variation between and within individuals can contribute to the dietary niche width of species and guilds, which may be overlooked by focusing solely on species' mean resource use patterns.

资源利用的种间变异（interspecific variation）是解析物种多样性、物种共存与生态系统功能的核心前提。日益增多的研究证实了类似的种内变异（intraspecific variation），及其对种群动态与群落结局的潜在重要性。然而，在消费者-资源相互作用（consumer-resource interactions）的关键维度上，种内变异相较于种间变异的量级仍未明确，而该信息对于理解此类变异在种群与群落过程中的重要性至关重要。本研究依托重复实验室选择性摄食实验（laboratory choice feeding assays），对美国加利福尼亚州北部岩礁生境中8种无脊椎草食动物（invertebrate grazer）的444个野生捕获个体的摄食偏好展开了分析。种间变异占对首选资源的偏好性总变异的25%~33%，而个体间变异仅占总变异的4%~5%。在8个物种类群中，有2个类群的个体间变异显著非零，即便校正了体型与性别带来的差异后，其平均贡献仍分别达到总饮食变异的14%与17%。因此，即便物种间的平均摄食偏好存在清晰可辨的差异，个体间与个体内的饮食变异仍可贡献物种乃至功能群的食性生态位宽度（dietary niche width）；若仅聚焦于物种的平均资源利用模式，这一贡献往往会被忽略。