Data from: Multichannel feeding by spider functional groups is driven by feeding strategies and resource availability

Multichannel feeding, whereby consumers feed across resource channels such as upon herbivore and detritivore resources, acts to link discrete compartments of a food web with implications for ecosystem functioning and stability. Currently however, we have little understanding which feeding strategies of consumers underlie multichannel feeding. We therefore link spider functional group and resource density-dependent or density-independent feeding strategies to multichannel feeding by quantifying not only consumer diet, but also the relative availability of resources. Here we analysed herbivore (green) and detritivore (brown) prey use by spider communities in grasslands, and tested if available prey biomass proportions were linked to observed spider dietary proportions. Different spider functional groups each linked green and brown resource channels, but while green prey were always consumed in proportion to their relative biomass, brown prey were consumed independently of proportion by some functional groups. Additionally, we found greater intraguild predation by cursorial spiders when green resources were relatively scarcer, suggesting green prey was preferred, and needed to be compensated for when rare. Overall, we observed a stronger consumer connection to the green than brown resource channel, yet this green connection was more variable due to greater range in green resource availability across grasslands and density-dependent consumption on green prey. Consequently, multichannel feeding by spiders was determined by density-dependent and density–independent feeding strategies that varied by spider functional group and across resources channels. Our results demonstrate that the role of multichannel feeding by spiders in linking separate food web compartments is a dynamic component of food web structure in these wild grasslands.多通道取食（Multichannel feeding）指消费者同时利用植食动物（herbivore）与腐食动物（detritivore）等多种资源通道获取食物，其可联结食物网中相互独立的功能隔间，并对生态系统功能与稳定性产生影响。然而目前学界对驱动消费者采取多通道取食行为的取食策略仍知之甚少。为此，我们不仅量化了消费者的食谱组成，还分析了资源的相对可获得性，以此将蜘蛛功能群（spider functional group）与依赖密度（density-dependent）或非依赖密度（density-independent）的取食策略和多通道取食行为关联起来。本研究针对草原生态系统中的蜘蛛群落展开分析，探究其对植食性（绿色）与腐食性（棕色）猎物的取食利用情况，并检验可获得猎物生物量占比是否与观测到的蜘蛛食谱占比存在关联。不同蜘蛛功能群均能联结绿色与棕色两类资源通道，但尽管蜘蛛对绿色猎物的取食比例始终与其相对生物量成正比，部分功能群对棕色猎物的取食则不受其生物量占比的影响。此外，我们发现当绿色资源相对匮乏时，游猎型蜘蛛（cursorial spiders）的集团内捕食（intraguild predation）行为更为频繁，这表明蜘蛛更偏好绿色猎物，在绿色猎物稀缺时需通过其他取食策略进行补偿。总体而言，消费者与绿色资源通道的联结强度整体强于棕色资源通道，但由于草原生态系统中绿色资源的可获得性波动范围更广，且蜘蛛对绿色猎物的取食存在密度依赖效应，这一绿色联结的波动也更为显著。综上，蜘蛛的多通道取食行为由依赖密度与非依赖密度的取食策略共同调控，这类策略因蜘蛛功能群以及资源通道的不同而存在差异。本研究结果表明，蜘蛛通过多通道取食联结不同食物网功能隔间的作用，是这类野生草原食物网结构中的一个动态组成部分。