Intraguild predation is increased in areas of low prey diversity in a generalist predator community

Aquatic ectotherms often attain smaller body sizes at higher temperatures. By analysing ~15,000 coastal‐reef fish surveys across a 15°C spatial sea surface temperature (SST) gradient, we found that the mean length of fish in communities decreased by ~5% for each 1°C temperature increase across space, or 50% decrease in mean length from 14 to 29°C mean annual SST. Community mean body size change was driven by differential temperature responses within trophic groups and temperature‐driven change in their relative abundance. Herbivores, invertivores and planktivores became smaller on average in warmer temperatures, but no trend was found in piscivores. Nearly 25% of the temperature‐related community mean size trend was attributable to trophic composition at the warmest sites, but at colder temperatures, this was <1% due to trophic groups being similarly sized. Our findings suggest that small changes in temperature are associated with large changes in fish community composition and body sizes, with important ecological implications.

Section: Discussionmentioning

confidence: 97%

Mean reef fish body size decreases towards warmer waters

Coghlan,

Blanchard,

Wotherspoon

et al. 2024

“…We estimated field foraging rates of wolf spiders (Lycosidae) using dietary metabarcoding data (N d and N s ) from Uiterwaal et al (2023), for which we caught 449 wolf spiders of various (morpho)species from 20 sites at Cedar Point Biological Station in Ogallala, Nebraska, United States. We used the six most collected (morpho) species here (H. baltimoriana, an unidentified morphospecies, Rabidosa rabida, Schizocosa mccooki, S. ocreata and S. saltatrix).…”

Section: At Er I a L S A N D M Et Hod S Estimating Foraging Rates Fro...mentioning

confidence: 99%

“…Foraging rates from Equation ( 8) can be paired with field prey densities to estimate the functional response. We used wolf spider prey density data from Uiterwaal et al (2023). In summary, we used box quadrats to collect arthropods at each spider collection site.…”

Section: Estimating Field Functional Responsesmentioning

confidence: 99%

“…In the field, such high taxonomic resolution may not always be possible. In Uiterwaal et al (2023), we grouped prey by family because this was the lowest resolution to which arthropods could be identified in both arthropod surveys and in spider diets. If field functional responses were assessed for individual prey species, we expect even starker contrasts to lab functional responses: prey densities -and foraging rates -would be even lower.…”

Section: Considerations For the Functional Response Researchmentioning

confidence: 99%

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Foraging rates from metabarcoding: Predators have reduced functional responses in wild, diverse prey communities

Uiterwaal,

DeLong

2024

Functional responses describe foraging rates across prey densities and underlie many fundamental ecological processes. Most functional response knowledge comes from simplified lab experiments, but we do not know whether these experiments accurately represent foraging in nature. In addition, the difficulty of conducting multispecies functional response experiments means that it is unclear whether interaction strengths are weakened in the presence of multiple prey types. We developed a novel method to estimate wild predators' foraging rates from metabarcoding data and use this method to present functional responses for wild wolf spiders foraging on 27 prey families. These field functional responses were considerably reduced compared to lab functional responses. We further find that foraging is sometimes increased in the presence of other prey types, contrary to expectations. Our novel method for estimating field foraging rates will allow researchers to determine functional responses for wild predators and address long‐standing questions about foraging in nature.

“…Given the potential ecological ramifications of IGP in P. pacificus (Quach & Chalasani, 2020), the direct link between mouth‐form plasticity and IGP provides an intriguing model to study how phenotypic plasticity might in this case promote coexistence, since ecological theory suggest that IGP, and cannibalism, could promote coexistence (Claessen et al., 2002; Holt & Polis, 1997; Rudolf, 2007). For instance, a recent study on a wolf spider community supports the role of IGP in coexistence (Uiterwaal et al., 2023).…”

Section: Introductionmentioning

confidence: 99%

The role of plasticity and stochasticity in coexistence

Kalirad,

Sommer

2024

Species coexistence in ecological communities is a central feature of biodiversity. Different concepts, i.e., contemporary niche theory, modern coexistence theory, and the unified neutral theory, have identified many building blocks of such ecological assemblies. However, other factors, such as phenotypic plasticity and stochastic inter‐individual variation, have received little attention, in particular in animals. For example, how resource polyphenisms resulting in predator–prey interactions affect coexistence is currently unknown. Here, we present an integrative theoretical–experimental framework using the nematode plasticity model Pristionchus pacificus with its well‐studied mouth‐form dimorphism resulting in cannibalism. We develop an individual‐based model that relies upon synthetic data based on our empirical measurements of fecundity and polyphenism to preserve demographic heterogeneity. We demonstrate how the interplay between plasticity and individual stochasticity result in all‐or‐nothing outcomes at the local level. Coexistence is made possible when spatial structure is introduced.