Culling of overabundant and invasive species to manage their ecological impacts on target species is widely practised but outcomes are unpredictable and monitoring of effectiveness often poor. ...Culling must improve ecosystem function, so clear, measurable goals, such as improved breeding potential of target species, are necessary. Many overabundant and invasive species are also nest predators and nest predation is the principal cause of breeding failure of many birds of conservation concern. It is important for managers to know the likely effects on nest predation when culling one species among a suite of nest predatory species.
We tested the effect of culling a hyperaggressive, overabundant bird and known nesting disruptor, the noisy miner (Manorina melanocephala), on artificial nest predation rates in remnant eucalypt woodlands in a highly fragmented agricultural landscape of eastern Australia. Culling of noisy miners is already practised to manage this key threatening process, but evidence of improved breeding outcomes for target species is lacking.
We found no significant change in artificial nest predation rates following the treatment, despite a 28% reduction in noisy miner abundance in treatment compared to control sites. We identified five other nest predatory bird species, the noisy miner being responsible for 18.3% of total predation.
Our findings suggest a compensatory nest predation model, which is problematic for management. It means that, where culling is done with a view to improving breeding potential of target species by reducing nest predation, removing one nest predatory species may not result in a commensurate reduction in nest predation.
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•Culling noisy miners did not reduce artificial nest predation rates.•Noisy miners were responsible for 18% of artificial nest predation.•Five other bird species were recorded predating nests.•Compensatory nest predation seems to be operating in this landscape.•Culling noisy miners may not improve breeding potential of target species.
The consequences of plant–animal interactions often transcend the mere encounter stage, as those encounters are followed by a chain of subsequent stages on the plant's reproductive cycle that ...ultimately determine fitness. Yet, the dissemination and recruitment stages of animal‐mediated seed dispersal are seldom analysed jointly, hindering a full understanding of the ecology of seed dispersal.
We analyse the dispersal and recruitment of a fleshy‐fruited plant (Pistacia lentiscus), from fruit production to seedling survival up to their second year. We link early reproductive investment of individual plants to seedling recruitment and explore the role played by seed viability, the coterie of frugivores and microhabitat seed deposition.
The proportion of viable seeds was generally low (mean = 34%) but highly variable among individual plants (range: 0%–95%). Seed viability did not seem to have a direct effect on individual plant's recruitment.
We recorded 28 bird species feeding on P. lentiscus fruits or seeds. Their contribution to plant recruitment was mainly determined by their intensity of fruit consumption and probability to disperse viable seeds. Most frugivores presented non‐random microhabitat preferences, delivering uneven seed contributions to different sites.
Post‐dispersal seed predation by rodents was the most limiting phase in P. lentiscus recruitment. Yet, microhabitats showing the lowest predation rates received the lowest seed rain. Hence, we found a decoupling of the dissemination and recruitment stages: most seeds do not arrive at the most suitable microhabitats.
We estimate P. lentiscus plants need to produce c. 5 × 105 fruits to recruit a single seedling that survives to its second summer in our study site. Its success as a prevalent species in Mediterranean lowland landscapes relies on its high fecundity and thorough fruit removal and dispersal by a diversified frugivore assemblage, which compensates for the high seed unviability characteristic of this genus.
Synthesis: Measuring the delayed, post‐dispersal outcomes of animal frugivory interactions may overturn inferences based on consumption observations only. Seed rain patterns are often decoupled from microhabitats' suitability for seedling recruitment. Hence, more integrative studies that encompass the entire plant reproductive cycle (from fruit production to seedling recruitment) are needed to fully understand frugivores' lasting contribution to plant regeneration in natural populations.
Resumen
Las consecuencias de las interacciones de frugivoría entre plantas y animales a menudo trascienden la mera fase de encuentro, ya que estos encuentros van seguidos de una cadena de etapas posteriores en el ciclo demográfico de la planta que, en última instancia, determinan su éxito reproductivo. Sin embargo, las etapas de diseminación de semillas y reclutamiento mediada por animales rara vez se analizan conjuntamente, lo que dificulta una comprensión completa de las implicaciones que tiene la dispersión de semillas.
Analizamos la dispersión y el reclutamiento de una planta de fruto carnoso (Pistacia lentiscus), desde la producción de frutos hasta la supervivencia de las plántulas de dos años de edad. Relacionamos la inversión reproductiva de plantas individuales con el reclutamiento de plántulas y exploramos el papel que desempeñan la viabilidad de las semillas, la cohorte de frugívoros y la deposición de semillas en diferentes microhábitats.
La proporción de semillas viables fue generalmente baja (media = 34%) pero muy variable entre plantas individuales (rango: 0%–95%). La viabilidad de las semillas no pareció tener un efecto directo sobre el reclutamiento de plantas individuales.
Se registraron 28 especies de aves alimentándose de frutos o semillas de P. lentiscus. Su contribución al reclutamiento de plantas estuvo determinada principalmente por la intensidad en el consumo de frutos y la probabilidad de dispersar semillas viables. La mayoría de los frugívoros presentaron preferencias de microhábitat no aleatorias, aportando contribuciones desiguales de semillas a diferentes sitios.
La depredación post‐dispersiva de semillas por roedores fue la fase más limitante en el reclutamiento de P. lentiscus. No obstante, los microhábitats con tasas menores de depredación recibieron una menor lluvia de semillas. Por lo tanto, encontramos un desacoplamiento entre las fases de diseminación y reclutamiento: la mayoría de las semillas no llegan a los microhábitats más adecuados.
Estimamos que las plantas de P. lentiscus necesitan producir unos 5 × 105 frutos para reclutar una sola plántula que sobreviva hasta su segundo verano en nuestro lugar de estudio. Su éxito como especie predominante en matorrales mediterráneos a baja altitud se basa en su alta fecundidad y en el abundante consumo de frutos y dispersión de semillas por parte de un conjunto diversificado de frugívoros, lo que compensa la baja viabilidad de las semillas característica en este género.
Síntesis—Medir los resultados aplazados (post‐dispersivos) de las interacciones de frugivoría por parte de animales puede modificar las inferencias basadas únicamente en observaciones de consumo. Los patrones de lluvia de semillas están a menudo disociados de la idoneidad de los microhábitats para el reclutamiento de plántulas. Por lo tanto, se necesitan estudios más integradores que abarquen todo el ciclo reproductivo de la planta (desde la producción de frutos hasta el reclutamiento de plántulas) para poder comprender plenamente la contribución de los frugívoros a la regeneración de las plantas en las poblaciones naturales.
Measuring post‐dispersal outcomes of animal frugivory interactions may overturn inferences based on consumption observations only. We show how abundant seed dispersal (high consumption) is required for the successful recruitment of Pistacia lentiscus. Nevertheless, we found a decoupling between microhabitats' suitability and seedling recruitment. More integrative studies encompassing the entire plant reproductive cycle (from fruit production to seedling recruitment) are needed to fully understand frugivores' lasting contribution to plant regeneration in natural populations.
Predation risk varies on a moment-to-moment basis, through day and night, lunar and seasonal cycles, and over evolutionary time. Hence, it is adaptive for prey animals to exhibit environment-specific ...behaviour, morphology, and (or) life-history traits. Herein, the effects of temporally varying predation risk on growth, behaviour, morphology, and life-history traits of larval Indian Skipper Frogs (Euphlyctis cyanophlyctis (Schneider, 1799)) were studied by exposing them to no risk, continuous, predictable, and unpredictable risks at different time points. Our results show that larval E. cyanophlyctis could learn the temporal pattern of risk leading to weaker behavioural responses under predictable risk and stronger responses to unpredictable risk. Temporally varying predation risk had a significant impact on tadpole morphology. Tadpoles facing continuous risk had narrow tail muscles. Tadpoles facing predictable risk during the day were heavy with wide and deep tail muscles, whereas those facing predictable risk at night had long tails. Tadpoles facing unpredictable risk were heavy with narrow tail muscles. Metamorphic traits of E. cyanophlyctis were also affected by the temporal variation in predation risk. Tadpoles facing predictable risk during the day emerged at the largest size. However, tadpoles facing predictable risk at night and unpredictable risk metamorphosed earlier, whereas those facing continuous risk metamorphosed later.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sclerodermus sp. (Hymenoptera: Bethylidae) is one of the few known natural enemies of pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae). An experiment was carried out on controlling the ...larva of M. alternatus by using a parasitoid, Sclerodermus sp. The results are as follows. Laboratory experiment indicated that the parasitoid could kill 95.66% of the 1st instar larvae, 85.91% of the 2nd instar larvae, and 57.88% of the 3rd instar larva of pine sawyer by stinging and host-feeding (by predation). In addition, the bethylid could parasitize its host and complete a generation on the 2nd-3rd instar of its host larvae (by parasitism); the response of this parasitoid to its host, in field and indoor mesh, showed to be highly variable and unpredictable and between 2.3% and 14.9% of all parasitoids released and entered a target pine sawyer-infested cutlog. The parasitoid did not respond differently to aggregations of 1, 3, or 6 pine sawyer-infested cutlogs. However, the efficiency of Sclerodermus sp. relea
Despite theoretical advances, the ecological factors and functional traits that enable species varying in seed size and fecundity to coexist remain unclear. Given inherent fecundity advantages, why ...don't small‐seeded species dominate communities?
In perennial grasslands, we evaluated whether small‐seeded species are less tolerant of competition from the community dominant bunchgrass than large‐seeded species, but also less vulnerable to seed predation by mice. We also explored whether trade‐offs involving competitive tolerance include two other functional traits, height and leaf mass per area (LMA). We added seeds of 17 forb species to plots where bunchgrass competition and rodent seed predation were manipulated across sites varying in bunchgrass productivity and thus competitive intensity. Seeds were added at densities mimicking interspecific variation in fecundity among target species.
Standardizing for differences in fecundity (i.e. seed input, which enabled us to evaluate inherent interspecific differences in susceptibility to biotic interactions), bunchgrass competition more greatly reduced recruitment and establishment of small‐ versus large‐seeded species, whereas rodent seed predation more greatly reduced the recruitment of large‐ versus small‐seeded species. Plant height and LMA were unrelated to the competition effect size.
Small‐seeded species abundance decreased across sites increasing in bunchgrass productivity, whereas this was not the case for large‐seeded species. For adult plants but not seedlings, community‐weighted functional trait means (CWM) for seed size, height and LMA increased in plots with versus without bunchgrass competition and the CWM for seed size and height also increased at sites with greater bunchgrass productivity (for adults only). In contrast, rodent seed predation had no significant effects on CWM seed size.
At the end of the experiment, adult abundance positively correlated with plant fecundity in plots lacking bunchgrass, indicating the inherent advantages accrued to high fecundity small‐seeded species. However, with bunchgrass competition, abundances were equalized across species due to reduced competitive tolerance of high fecundity small‐seeded species.
Synthesis. Our results suggest that coexistence among subordinate forb species varying in seed size and fecundity is in‐part due to a trade‐off involving competitive tolerance and fecundity, mediated by seed size and associated functional traits.
Our results suggest that coexistence among subordinate forb species varying in seed size and fecundity is in part due to a trade‐off involving competitive tolerance and fecundity, mediated by seed size and associated functional traits.
Predation risk, the probability that a prey animal will be killed by a predator, is fundamental to theoretical and applied ecology. Predation risk varies with animal behavior and environmental ...conditions, yet attempts to understand predation risk in natural systems often ignore important ecological and environmental complexities, relying instead on proxies for actual risk such as predator–prey spatial overlap. Here we detail the ecological and environmental complexities driving disconnects between three stages of the predation sequence that are often assumed to be tightly linked: spatial overlap, encounters and prey capture. Our review highlights several major sources of variability in natural predator–prey systems that lead to the decoupling of spatial overlap estimates from actual encounter rates (e.g. temporal activity patterns, predator and prey movement capacity, resource limitations) and that affect the probability of prey capture given encounter (e.g. predator hunger levels, temporal, topographic and other environmental influences on capture success). Emerging technologies and statistical methods are facilitating a transition to a more spatiotemporally detailed, mechanistic understanding of predator–prey interactions, allowing for the concurrent examination of multiple stages of the predation sequence in mobile, free‐ranging animals. We describe crucial applications of this new understanding to fundamental and applied ecology, highlighting opportunities to better integrate ecological contingencies into dynamic predator–prey models and to harness a mechanistic understanding of predator–prey interactions to improve targeting and effectiveness of conservation interventions.
The landscape of fear is an important driver of prey space use. However, prey can navigate the landscape of fear by exploiting temporal refuges from predation risk. We hypothesized that diel patterns ...of predator and prey movement and space use would be inversely correlated due to temporal constraints on predator habitat domain. Specifically, we evaluated habitat selection and activity of the vicuña and its only predator, the puma, during three diel periods: day, dawn/dusk, and night. Pumas selected the same habitats regardless of diel period—vegetated and rugged areas that feature stalking cover for pumas—but increased their activity levels during dawn/dusk and night when they benefit from reduced detection by prey. Vicuñas avoided areas selected by pumas and reduced activity at night, but selected vegetated areas and increased activity by day and dawn/dusk. Vicuña habitat selection and movement strategies appeared to reduce the risk of encountering pumas; movement rates of pumas and vicuñas were negatively correlated across the diel cycle, and habitat selection was negatively correlated during dawn/dusk and night. Our study shows that an ambush predator’s temporal activity and space use patterns interact to create diel refugia and shape the antipredator behaviors of its prey. Importantly, it is likely the very nature of ambush predators’static habitat specificity that makes predator activity important to temporally varying perceptions of risk. Prey which depend on risky habitats for foraging appear to mitigate risk by feeding when they can more easily detect predators and when predators are least active.
The very presence of predators can strongly influence flexible prey traits such as behavior, morphology, life history, and physiology. In a rapidly growing body of literature representing diverse ...ecological systems, these trait (or “fear”) responses have been shown to influence prey fitness components and density, and to have indirect effects on other species. However, this broad and exciting literature is burdened with inconsistent terminology that is likely hindering the development of inclusive frameworks and general advances in ecology. We examine the diverse terminology used in the literature, and discuss pros and cons of the many terms used. Common problems include the same term being used for different processes, and many different terms being used for the same process. To mitigate terminological barriers, we developed a conceptual framework that explicitly distinguishes the multiple predation-risk effects studied. These multiple effects, along with suggested standardized terminology, are risk-induced trait responses (i.e., effects on prey traits), interaction modifications (i.e., effects on prey–other-species interactions), nonconsumptive effects (i.e., effects on the fitness and density of the prey), and trait-mediated indirect effects (i.e., the effects on the fitness and density of other species). We apply the framework to three well studied systems to highlight how it can illuminate commonalities and differences among study systems. By clarifying and elucidating conceptually similar processes, the framework and standardized terminology can facilitate communication of insights and methodologies across systems and foster cross-disciplinary perspectives
Many ecosystems contain sympatric predator species that hunt in different places and times. We tested whether this provides vacant hunting domains, places and times where and when predators are least ...active, that prey use to minimize threats from multiple predators simultaneously. We measured how northern Yellowstone elk (Cervus elaphus) responded to wolves (Canis lupus) and cougars (Puma concolor), and found that elk selected for areas outside the high‐risk domains of both predators consistent with the vacant domain hypothesis. This enabled elk to avoid one predator without necessarily increasing its exposure to the other. Our results demonstrate how the diel cycle can serve as a key axis of the predator hunting domain that prey exploit to manage predation risk from multiple sources. We argue that a multi‐predator, spatiotemporal framework is vital to understand the causes and consequences of prey spatial response to predation risk in environments with more than one predator.
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