Assessing multiple predator, diurnal and search area effects on predatory impacts by ephemeral wetland specialist copepods

Abstract

Predator-prey interaction strengths can be highly context-dependent. In particular, multiple predator effects (MPEs), variations in predator sex and physical habitat characteristics may affect prey consumption rates and thus the persistence of lower trophic groups. Ephemeral wetlands are transient ecosystems in which predatory copepods can be numerically dominant. We examine the interaction strengths of a specialist copepod Paradiaptomus lamellatus towards mosquito prey in the presence of conspecifics using a functional response approach. Further, we examine sex variability in predation rates of P. lamellatus under circadian and surface area variations. Then, we assess the influence of a cooccurring heterospecific predatory copepod, Lovenula raynerae, on total predation rates. We demonstrate MPEs on consumption, with antagonism between conspecific P. lamellatus predatory units evident, irrespective of prey density. Furthermore, we show differences between sexes in interaction strengths, with female P. lamellatus significantly more voracious than males, irrespective of time of day and experimental arena surface area. Predation rates by P. lamellatus were significantly lower than the heterospecific calanoid copepod L. raynerae, whilst heterospecific copepod groups exhibited the greatest Handling Editor: Télesphore Sime-Ngando.

Prey and predator density‐dependent interactions under different water volumes

“…However, the current sparsity of studies into multiple predator effects overall negates broader generalizations within or between such factors, particularly at the conspecific level. Recent works into another temporary pond specialist copepod, Paradiaptomus lamellatus Sars, 1985, has similarly found antagonistic interactions in calanoid copepods (Cuthbert, Dalu, Wasserman, Monaco, et al, 2020). This species is known to coexist with the focal species in the present study, L. raynerae, although it is less voracious (Wasserman, Alexander, Barrios-O'Neill, et al, 2016).…”

Anthropogenic noise does not strengthen multiple‐predator effects in a freshwater invasive fish

“…Conspecific presence did not change individual swimming distance and we did not compare the area covered between one and two fish, but the most likely explanation is that the time and attention devoted to the conspecific were not allocated to foraging. Many studies on MPEs have indeed found risk‐reducing effects on predation rates (Cuthbert et al ., 2020; Sih et al ., 1998), which could be the ‘null hypothesis’, simply because predators spend time in interactions instead of foraging.…”

Functional Responses and Additive Multiple Predator Effects of Two Common Wetland Fish

“…In ecological studies, it is fundamental to understand the biotic processes which impact floodplain wetlands ecosystem structure and functioning. Recent studies have recognized the need to examine individual consumer variability within wetland populations [61,62]. Despite the existing data on trophic interaction of single predator-prey dynamics, which is helpful in determining the strength of MPEs, further exploration studies of interspecific and conspecific interaction relationships are critical, especially regarding fish predation, because fish drive top-down cascades and shape the structure and functioning of invertebrate communities, including the presence of Chironomidae in floodplain wetlands.…”