Vaughan, I. P. | Search bioRxiv

bioRxiv2023

Sources of prey availability data alter interpretation of outputs from prey choice null networks

O_LINull models provide an invaluable baseline against which to test fundamental ecological hypotheses and highlight patterns in foraging choices that cannot be explained by neutral processes or sampling artefacts. In this way, null models can advance our understanding beyond simplistic dietary descriptions to identify drivers of interactions. This method, however, requires estimates of resource availability, which are generally imperfect representations of highly dynamic systems. Optimising method selection is crucial for study design, but the precise effects of different resource availability data on the efficacy of null models are poorly understood. C_LIO_LIUsing spider-prey networks as a model, we used prey abundance (suction sample) and activity density (sticky trap) data, and combinations of the two, to simulate null networks. We compared null diet composition, network properties (e.g., connectance and nestedness) and deviations of simulations from metabarcoding-based spider dietary data (to ascertain how different prey availability data alter ecological interpretation. C_LIO_LIDifferent sampling methods produced different null networks and inferred distinct prey selectivity. Null networks based on prey abundance and combined frequency-of-occurrence data more closely resembled the observed diet composition, and those based on prey abundance, activity density and proportionally combined data generated network properties most like dietary metabarcoding networks. C_LIO_LIWe show that survey method choice impacts all aspects of null network analyses, the precise effects varying between methods but ultimately altering ecological interpretation by increasing disparity in network properties or trophic niches between null and directly constructed networks. Merging datasets can generate more complete prey availability data but is not a panacea because it introduces different biases. The choice of method should reflect the research hypotheses and study system being investigated. Ultimately, survey methods should emulate the foraging mode of the focal predator as closely as possible, informed by the known ecology, natural history and behaviour of the predator. C_LI

ecology↗

bioRxiv2019

Recreational fisheries as a driver of salmonid population conservation

O_LIThe need to monitor and protect biodiversity has never been greater, yet resources are often constrained economically. The ecosystem service paradigm could promote nature conservation while sustaining economic activity and other societal benefits, but most efforts to assess biodiversity-ecosystem service (B-ES) links have focused on diversity measures, with little attention on how species abundance relates to the magnitude of ES provision.\nC_LIO_LIHere, we utilised four national scale, multi-decadal, Atlantic salmon (Salmo salar) datasets to investigate links between juvenile density, the abundance of returning adults, and two measures of recreational angling provision: rod catches and angling effort.\nC_LIO_LIRecreational rod catches only tracked juvenile density and returning adult numbers in catchments where juvenile and adult numbers were decreasing, implying important early-warning of ES decline. In contrast, angling effort declined consistently through time.\nC_LIO_LISynthesis and applications. These data illustrate i) the difficulty in measuring ES in ways that explicitly relate human resource use to nature conservation, and ii) the need for better quantification of populations at all life stages that determine ES provision, particularly in species where long-distance movements bring exposure to multiple global pressures. We suggest additional opportunities (e.g., monitoring of smolts, eDNA and citizen science initiatives) to facilitate conservation efforts and increase capacity to monitor ecosystem service sustainability.\nC_LI

ecology↗