Intraspecific variation in body size does not alter the effects of mesopredators on prey

As humans continue to alter the species composition and size structure of marine food webs, it is critical to understand size-dependent effects of predators on prey. Yet, how shifts in predator body size mediate the effect of predators is understudied in tropical marine ecosystems, where anthropogenic harvest has indirectly increased the density and size of small-bodied predators. Here, we combine field surveys and a laboratory feeding experiment in coral reef fish communities to show that small and large predators of the same species can have similar effects. Specifically, surveys show that the presence of a small predator ( Paracirrhites arcatus ) was correlated with lower chances of prey fish presence, but these correlations were independent of predator size. Experimental trials corroborated the size-independent effect of the predator; attack rates were indistinguishable between small and large predators, suggesting relatively even effects of hawkfish in various size classes on the same type of prey. Our results indicate that the effects of small predators on coral reefs can be size-independent, suggesting that variation in predator size-structure alone may not always affect the functional role of these predators.

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Protection of large predators in a marine reserve alters size-dependent prey mortality

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.1936 ◽

2017 ◽

Vol 284 (1847) ◽

pp. 20161936 ◽

Cited By ~ 18

Author(s):

Rebecca L. Selden ◽

Steven D. Gaines ◽

Scott L. Hamilton ◽

Robert R. Warner

Keyword(s):

Size Structure ◽

Sea Urchins ◽

Marine Reserves ◽

Marine Reserve ◽

Mortality Rates ◽

Kelp Forests ◽

Size Dependent ◽

Predator Size ◽

Top Predators ◽

Large Predators

Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead ( Semicossyphus pulcher ). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorter-spined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.

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Clumpy coexistence in phytoplankton: The role of functional similarity in community assembly

10.1101/869966 ◽

2019 ◽

Cited By ~ 2

Author(s):

Caio Graco-Roza ◽

Angel M Segura ◽

Carla Kruk ◽

Patrícia Domingos ◽

Janne Soininen ◽

...

Keyword(s):

Body Size ◽

Community Assembly ◽

Species Coexistence ◽

Size Structure ◽

Species Abundance ◽

Functional Similarity ◽

Neutral State ◽

Functional Clustering ◽

Stochastic Fluctuations

AbstractEmergent neutrality (EN) suggests that species must be sufficiently similar or sufficiently different in their niches to avoid interspecific competition. Such a scenario results in a multimodal distribution of species abundance along the niche axis (e.g., body size), namely clumps. From this perspective, species within clumps should behave in a quasi-neutral state, and their abundance will show stochastic fluctuations. Plankton is an excellent model system for developing and testing ecological theories, especially those related to size structure and species coexistence. We tested EN predictions using the phytoplankton community along the course of a tropical river considering (i) body size structure, (ii) functional clustering of species in terms of morphology-based functional groups (MBFG), and (iii) the functional similarity among species with respect to their functional traits. Considering body size as the main niche axis, two main clumps (clump I and II) were detected in different stretches of the river and remained conspicuous through time. The clump I comprised medium-sized species mainly from the MBFG IV, while the clump II included large-bodied species from the groups V and VI. Pairwise differences in species biovolume correlated with species functional redundancy when the whole species pool was considered, but not among species within the same clump. Within-clump functional distinctiveness was positively correlated with species biovolume considering both seasons, and also at the upper course. These results suggest that species within clumps behave in a quasi-neutral state, but even minor shifts in trait composition may affect their biovolume. In sum, our findings point that EN belongs to the plausible mechanisms explaining community assembly in river ecosystems.

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The allometry of cannibalism in piscivorous fishes

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f03-051 ◽

2003 ◽

Vol 60 (5) ◽

pp. 594-602 ◽

Cited By ~ 45

Author(s):

Francis Juanes

Keyword(s):

Upper Bound ◽

Prey Size ◽

Trophic Niche ◽

Large Prey ◽

Predator Species ◽

Size Dependent ◽

Predator Size ◽

Large Databases ◽

Widespread Phenomenon ◽

Large Predators

Cannibalism is a widespread phenomenon that can have strong population and community effects. In this study, I compare the prey size predator size relationships of diets with and without cannibalized prey for four piscivorous species and five populations that are commonly cannibalistic and where large databases exist. I then examine the resultant trophic niche breadths (range of relative prey size consumed) to quantify whether inclusion of cannibalized prey in the diet slows down the decline in trophic niche breadth that many large predators exhibit as they grow. When comparing diets including cannibalized prey with those without, consistent differences were found among all predator species. In all cases, the slope of the upper bound of the predator size prey size scatters was larger for cannibal predators compared with noncannibals, suggesting selectivity for larger cannibal prey, which may be driven by higher rates of size-dependent capture success with familiar prey. The slopes of the upper bounds of the cannibal relative prey size vs. predator size scatter also tended to be larger than the upper-bound slopes for diets without conspecific prey. Finally, for all species, mean trophic breadth of diets including cannibalized prey were larger than those not including cannibal prey, suggesting that relatively large prey sizes may always be available for cannibals.

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Partitioning colony size variation into growth and partial mortality

Biology Letters ◽

10.1098/rsbl.2019.0727 ◽

2020 ◽

Vol 16 (1) ◽

pp. 20190727 ◽

Cited By ~ 4

Author(s):

Joshua S. Madin ◽

Andrew H. Baird ◽

Marissa L. Baskett ◽

Sean R. Connolly ◽

Maria A. Dornelas

Keyword(s):

Life History ◽

Body Size ◽

Life History Strategy ◽

Size Variation ◽

Partial Mortality ◽

Physical Damage ◽

Extrinsic Factors ◽

Intrinsic Factors ◽

Size Dependent

Body size is a trait that broadly influences the demography and ecology of organisms. In unitary organisms, body size tends to increase with age. In modular organisms, body size can either increase or decrease with age, with size changes being the net difference between modules added through growth and modules lost through partial mortality. Rates of colony extension are independent of body size, but net growth is allometric, suggesting a significant role of size-dependent mortality. In this study, we develop a generalizable model of partitioned growth and partial mortality and apply it to data from 11 species of reef-building coral. We show that corals generally grow at constant radial increments that are size independent, and that partial mortality acts more strongly on small colonies. We also show a clear life-history trade-off between growth and partial mortality that is governed by growth form. This decomposition of net growth can provide mechanistic insights into the relative demographic effects of the intrinsic factors (e.g. acquisition of food and life-history strategy), which tend to affect growth, and extrinsic factors (e.g. physical damage, and predation), which tend to affect mortality.

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Temperature alters food web body-size structure

Biology Letters ◽

10.1098/rsbl.2014.0473 ◽

2014 ◽

Vol 10 (8) ◽

pp. 20140473 ◽

Cited By ~ 29

Author(s):

Jean P. Gibert ◽

John P. DeLong

Keyword(s):

Body Size ◽

Food Web ◽

Size Structure ◽

Large Body ◽

Effect Of Temperature ◽

Food Web Structure ◽

Predator Prey ◽

Marine Predator ◽

Web Structure ◽

Predator Size

The increased temperature associated with climate change may have important effects on body size and predator–prey interactions. The consequences of these effects for food web structure are unclear because the relationships between temperature and aspects of food web structure such as predator–prey body-size relationships are unknown. Here, we use the largest reported dataset for marine predator–prey interactions to assess how temperature affects predator–prey body-size relationships among different habitats ranging from the tropics to the poles. We found that prey size selection depends on predator body size, temperature and the interaction between the two. Our results indicate that (i) predator–prey body-size ratios decrease with predator size at below-average temperatures and increase with predator size at above-average temperatures, and (ii) that the effect of temperature on predator–prey body-size structure will be stronger at small and large body sizes and relatively weak at intermediate sizes. This systematic interaction may help to simplify forecasting the potentially complex consequences of warming on interaction strengths and food web stability.

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Trophic position scales positively with body size within but not among four species of rocky reef predators

Marine Ecology Progress Series ◽

10.3354/meps13275 ◽

2020 ◽

Vol 640 ◽

pp. 189-200 ◽

Cited By ~ 1

Author(s):

AM Olson ◽

A Frid ◽

JBQ dos Santos ◽

F Juanes

Keyword(s):

Body Size ◽

Trophic Position ◽

Stomach Contents ◽

Rocky Reef ◽

Morphometric Traits ◽

Predator Species ◽

Predatory Fishes ◽

Average Size ◽

Interspecific Comparisons ◽

Large Predators

Intra- and interspecifically, larger-bodied predators generally occupy higher trophic positions (TPs). With widespread declines in large predators, there is a need to understand their size-based trophic roles to predict ecosystem-level responses. In British Columbia, Canada, we examined size-based trophic interactions between predatory fishes—3 rockfish species (genus Sebastes) and lingcod Ophiodon elongatus—and their prey, converting predator δ15N signatures to TP and analyzing stomach contents. Intraspecifically, TP scaled positively with predator length and gape width, but the rates of change varied by species. Interspecifically, TP did not scale positively with the observed mean sizes or known maximum sizes of species. Lingcod TP was lower than that of yelloweye and quillback rockfishes, which were 51 and 37%, respectively, smaller than lingcod. Yellowtail rockfish had the smallest average size, yet their mean TP did not differ significantly from that of lingcod. Neither species differences in some morphometric traits known to influence body size-TP relationships nor phylogenetic history explained these results. Most prey consumed were <20% of the predator’s size, which might partially explain the lack of a size-based trophic hierarchy among species. Currently, large size classes of rockfishes are being lost due to fisheries and perhaps climate-driven changes. Our findings on intraspecific size-TP relationships indicate that fishery removals of large individuals may diminish trophic structures. Interspecific comparisons of TP suggest that, along with size, species remain an important factor in understanding trophic dynamics. In addition, smaller-bodied predator species may have significant ecological roles to be considered in ecosystem-based fisheries management.

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The role of rough surface in the size-dependent behavior upon nano-indentation

Mechanics of Materials ◽

10.1016/j.mechmat.2021.103836 ◽

2021 ◽

pp. 103836

Author(s):

Ding Tang ◽

Leilei Zhao ◽

Huamiao Wang ◽

Dayong Li ◽

Yinghong Peng ◽

...

Keyword(s):

Rough Surface ◽

Nano Indentation ◽

Size Dependent ◽

Dependent Behavior

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Richness of Rhizosphere Organisms Affects Plant P Nutrition According to P Source and Mobility

Agriculture ◽

10.3390/agriculture11020157 ◽

2021 ◽

Vol 11 (2) ◽

pp. 157

Author(s):

Jean Trap ◽

Patricia Mahafaka Ranoarisoa ◽

Usman Irshad ◽

Claude Plassard

Keyword(s):

Careful Consideration ◽

Soil Conditions ◽

Organic P ◽

P Nutrition ◽

Soil P ◽

P Acquisition ◽

Complex Interactions ◽

Experimental Trials ◽

The Relationship

Plants evolve complex interactions with diverse soil mutualist organisms to enhance P mobilization from the soil. These strategies are particularly important when P is poorly available. It is still unclear how the soil P source (e.g., mineral P versus recalcitrant organic P) and its mobility in the soil (high or low) affect soil mutualist biological (ectomycorrhizal fungi, bacteria and bacterial-feeding nematodes) richness—plant P acquisition relationships. Using a set of six microcosm experiments conducted in growth chamber across contrasting P situations, we tested the hypothesis that the relationship between the increasing addition of soil mutualist organisms in the rhizosphere of the plant and plant P acquisition depends on P source and mobility. The highest correlation (R2 = 0.70) between plant P acquisition with soil rhizosphere biological richness was found in a high P-sorbing soil amended with an organic P source. In the five other situations, the relationships became significant either in soil conditions, with or without mineral P addition, or when the P source was supplied as organic P in the absence of soil, although with a low correlation coefficient (0.09 < R2 < 0.15). We thus encourage the systematic and careful consideration of the form and mobility of P in the experimental trials that aim to assess the role of biological complexity on plant P nutrition.

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