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Predation is ubiquitous on coral reefs. Among the most charismatic group of reef predators are the top predatory fishes, including sharks and large-bodied bony fishes. Despite the threat presented by top predators, data describing their realized effects on reef community structure and functioning are challenging to produce. Many innovative studies have capitalized on natural experimental conditions to explore predator effects on reefs. Gradients in predator density have been created by spatial patterning of fisheries management. Evidence of prey release has been observed across some reefs, namely that potential prey increase in density when predator density is reduced. While such studies search for evidence of prey release among broad groups or guilds of potential prey, a subset of studies have sought evidence of release at finer population levels. We find that some groups of fishes are particularly vulnerable to the effects of predators and more able to capitalize demographically when predator density is reduced. For example, territorial damselfish appear to realize reliable population expansion with the reduction in predator density, likely because their aggressive, defensive behavior makes them distinctly vulnerable to predation. Relatedly, individual fishes that suffer from debilitating conditions, such as heavy parasite loads, appear to realize relatively stronger levels of prey release with reduced predator density. Studying the effects of predators on coral reefs remains a timely pursuit, and we argue that efforts to focus on the specifics of vulnerability to predation among potential prey and other context-specific dimensions of mortality hold promise to expand our knowledge.
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How can we avoid the extinction of any species naturally? A mathematical model
A large number of herbivorous mammals and reptiles in many terrestrial ecosystems across the globe are presently in the receiving end of extinction. Over-exploitation by its immediate predator and anthropogenic actions is one of the main reasons. Reintroduction of apex predator or top predator at some instances has proven to be a successful strategy in restoring ecological balance. In this paper, we conceptualize the role of top predator in enriching the density of vulnerable species of lower trophic level, with the help of mathematical modeling. First, the dynamical behavior of two species system (prey and mesopredator) is studied, where growth of prey is subject to strong Allee effect. Also, the cost of predation induced fear is incorporated in the growth term. Parametric regions, for which the species perceive extinction risk are analyzed and depicted numerically. We consider that whenever density of the vulnerable species reach a certain threshold, minimum viable population, top predator is introduced in the habitat. Our obtained results show that a species population can be restored from the verge of extinction to a stable state with much higher population density with the introduction of top predator and even it stabilizes an oscillatory system.
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- PAR ID:
- 10647008
- Publisher / Repository:
- World Scientific Publishing Company
- Date Published:
- Journal Name:
- International Journal of Biomathematics
- ISSN:
- 1793-5245
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Predator–prey coupling can result in oscillations of predator–prey densities. These oscillations in predator–prey densities correspond to oscillations in intraspecific competition where a high population density causes high intraspecific competition. Strong coupling of native species can however be disrupted by the introduction of invasive species into food webs. Here, we investigated how the body condition (body mass relative to body length) of a predator, lake trout, and its primary prey, cisco, changed as their respective population densities shifted. We found that the body condition of lake trout and cisco was strongly influenced by their respective population densities, that is, density dependence. The body conditions of lake trout and cisco were also inversely related, which highlights strong predator–prey coupling. Further, we were able to detect the impacts of a recent invasive species,Bythotrephes, as we saw size‐specific shifts in the body condition of prey following the invasion. Overall, this study highlights how the long‐term study of a simple measure, body condition, can reveal predator–prey coupling and yield new insights into the impacts of an invasive species.more » « less
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Abstract Keystone predation can be a determinant of community structure, including species diversity, but factors underlying “keystoneness” have been minimally explored. Using the system in which the original keystone, the sea starPisaster ochraceus, was discovered, we focused on two potential (but overlapping) determinants of keystoneness: intrinsic traits or state variables of the species (e.g., size, density), and extrinsic environmental parameters (e.g., prey productivity) that may provide conditions favorable for keystone predator evolution. Using a comparative‐experimental approach, with repeated field experiments at multiple sites across a variable coastal environment, we tested predation rates, or how quickly predators consumed prey, and predation effects, or community response to predator presence or absence. We tested five hypotheses: (H1) predation rates and effects will vary in space but not time; (H2) per population predation rates will vary primarily with individual traits and population variables; (HJHH3) per capita predation rates will vary only with individual traits; (H4) predation effects will vary with traits, variables, and external drivers; and (H5) as predicted by the keystone predation hypothesis, diversity will vary unimodally with predation pressure. As hypothesized, predation rates differed among sites but not over time (H1), and in caging exclusion experiments, predation effect varied with both intrinsic and extrinsic factors (H4). Unexpectedly, predation rates varied with both intrinsic and extrinsic (H2, per population), or only with extrinsic (H3, per capita) factors. Further, in large‐plot exclusion experiments, predation effect was most closely associated with individual traits (contraH4). Finally, taxon diversity varied unimodally with proxies of predation pressure (sessile prey abundance) and was sensitive to extrinsic factors (mussel growth, temperature, and upwelling,H5). Hence, keystoneness depended on predator individual traits, predator population variables, and environmental parameters. However, temporal differences in caging experiments suggested that environmental characteristics underlying prey dynamics may be preeminent. Compared to prior experiments, predation was weaker with low prey input compared to periods with high prey input. Collectively, our results suggest that keystone predator evolution depends on the coalescence of species‐specific characteristics, and environmental parameters favoring high prey productivity. Our approach may be a model for future studies exploring the generality of keystoneness.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1142/S1793524524500682
