Nest predation is the leading cause of reproductive mortality in oviparous tetrapods and can limit population growth in some species. Rates of nest predation could be influenced through modification ...of the cues used to find nests, but this requires a clear understanding of how nests are located. Here, we used a buffet-style choice experiment to test the relative role of three cue types (visual, tactile, and chemosensory) on the detection and depredation of Snapping Turtle (Chelydra serpentina (L., 1758)) nests by a suite of predators dominated by raccoons (Procyon lotor (L., 1758)). We created sets of artificial nests along an authentic nesting site, presenting single or multiple cues. We interspersed artificial nests with authentic nests and monitored predation rates on both. Predators used all three cues to locate potential nests for investigation. However, nests with tactile cues were significantly more likely to be depredated than nests with only visual and chemosensory cues. Multiple cues had additive effects on predation probability. Addition of chemosensory cues to tactile treatments increased the probability of predation. The importance of tactile cues in this system supports the use of nest cages to protect nests in early stages of development, but cannot explain the recently described late-stage peak in predation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Top‐order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been ...identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the ecological function of top predators is a critical global imperative. Here we review studies of the ecological effects of the dingo Canis lupus dingo, Australia's largest land predator, using this as a case study to explore the influence of a top predator on biodiversity at a continental scale. The dingo was introduced to Australia by people at least 3500 years ago and has an ambiguous status owing to its brief history on the continent, its adverse impacts on livestock production and its role as an ecosystem architect. A large body of research now indicates that dingoes regulate ecological cascades, particularly in arid Australia, and that the removal of dingoes results in an increase in the abundances and impacts of herbivores and invasive mesopredators, most notably the red fox Vulpes vulpes. The loss of dingoes has been linked to widespread losses of small and medium‐sized native mammals, the depletion of plant biomass due to the effects of irrupting herbivore populations and increased predation rates by red foxes. We outline a suite of conceptual models to describe the effects of dingoes on vertebrate populations across different Australian environments. Finally, we discuss key issues that require consideration or warrant research before the ecological effects of dingoes can be incorporated formally into biodiversity conservation programs.
The critically endangered bivalve species, the pen shell Pinna nobilis, has been suffering from an epidemic disease in the Mediterranean Sea, and its populations have totally disappeared in many ...areas across the basin. The Sea of Marmara’s populations of the pen shell, which were previously assumed to have remained unaffected by the epidemic disease because of the special hydrographical condition of the sea (brackish water), have been devastated after the catastrophic mucilage event suddenly outburst in November 2020 in the region. The settlement of healthy juvenile specimens of the species was frequently observed in the area after the mucilage event. However, an unexpected predator of juvenile specimens of the pen shell, the spiny sea star Marthasterias glacialis, was encountered in the area in January 2023. Two cases were observed and the spiny sea star has a capability of crashing one valve of the sea-pen through which it consumes its flesh. This predation might have the potential to affect populations of P. nobilis, which has been struggling to survive in the region after its mass mortality due to the mucilage event. Such data are of utmost importance to imply effective conservation planning for the sustainability of the remaining populations of the pen shell in the region.
Community ecology can link habitat to disease via interactions among habitat, focal hosts, other hosts, their parasites, and predators. However, complicated food web interactions (i.e., trophic ...interactions among predators and their impacts on host density and diversity) often obscure the important pathways regulating disease. Here, we disentangle community drivers in a case study of planktonic disease, using a two-step approach. In step one, we tested univariate field patterns linking community interactions directly to two disease metrics. Density of focal hosts (Daphnia dentifera) was related to density but not prevalence of fungal (Metschnikowia bicuspidata) infections. Both disease metrics appeared to be driven by selective predators that cull infected hosts (fish, e.g., Lepomis macrochirus), sloppy predators that spread parasites while feeding (midges, Chaoborus punctipennis), and spore predators that reduce contact between focal hosts and parasites (other zooplankton, especially small-bodied Ceriodaphnia sp.). Host diversity also negatively correlated with disease, suggesting a dilution effect. However, several of these univariate patterns were initially misleading, due to confounding ecological links among habitat, predators, host density, and host diversity. In step two, path models uncovered and explained these misleading patterns, and grounded them in habitat structure (refuge size). First, rather than directly reducing infection prevalence, fish predation drove disease indirectly through changes in density of midges and frequency of small spore predators (which became more frequent in lakes with small refuges). Second, small spore predators drove the two disease metrics through fundamentally different pathways: they directly reduced infection prevalence, but indirectly reduced density of infected hosts by lowering density of focal hosts (likely via competition). Third, the univariate diversity–disease pattern (signaling a dilution effect) merely reflected the confounding direct effects of these small spore predators. Diversity per se had no effect on disease, after accounting for the links between small spore predators, diversity, and infection prevalence. In turn, these small spore predators were regulated by both size-selective fish predation and refuge size. Thus, path models not only explain each of these surprising results, but also trace their origins back to habitat structure.
One of the main assumed impacts of invasive gobies is predation on benthic macroinvertebrates. Despite numerous dietary studies, however, quantitative evaluations of impact in European river systems ...are scarce. Here, we investigate the impact of tubenose (Proterorhinus semilunaris, Heckel 1837) and round (Neogobius melanostomus, Pallas 1814) gobies on macroinvertebrates in a lowland river (River Dyje, Czech Republic) by allowing and preventing gobiid access to rip-rap substrate naturally colonised by invertebrates at two sites (Site 1-tubenose goby only, Site 2-tubenose and round gobies). Gobies had a negative impact on invertebrates at both sites, with overall invertebrate density reduced by 15% (ca. 17.9 g m.sup.-2 per year) at Site 1 and 36% (ca. 23.6 g m.sup.-2 per year) at Site 2. Both species showed increased impact in summer and ingested larger invertebrates preferentially, resulting in an overall reduction in invertebrate body size. Tubenose gobies had a significant impact on Annelida, Gastropoda, Crustacea and Ephemeroptera nymphs, while tubenose and round goby together impacted Annelida, Bivalvia (Dreissena), Gastropoda, Crustacea, Ephemeroptera nymphs, Odonata nymphs and Chironomidae larvae. Our results confirm that round and tubenose gobies can have a significant negative impact on aquatic invertebrate density and community composition.
Predation is the most common cause of nest failure in birds. While nest predation is relatively well studied in general, our knowledge is unevenly distributed across the globe and taxa, with, for ...example, limited information on shorebirds breeding in subtropics. Importantly, we know fairly little about the timing of predation within a day. Here, we followed 444 nests of the red‐wattled lapwing (Vanellus indicus), a ground‐nesting shorebird, for a sum of 7,828 days to estimate a nest predation rate, and continuously monitored 230 of these nests for a sum of 2,779 days to reveal how the timing of predation changes over the day and season in a subtropical desert. We found that 312 nests (70%) hatched, 76 nests (17%) were predated, 23 (5%) failed for other reasons, and 33 (7%) had an unknown fate. Daily predation rate was 0.95% (95%CrI: 0.76% – 1.19%), which for a 30‐day long incubation period translates into ~25% (20% – 30%) chance of nest being predated. Such a predation rate is low compared to most other avian species. Predation events (N = 25) were evenly distributed across day and night, with a tendency for increased predation around sunrise, and evenly distributed also across the season, although night predation was more common later in the season, perhaps because predators reduce their activity during daylight to avoid extreme heat. Indeed, nests were never predated when midday ground temperatures exceeded 45℃. Whether the diel activity pattern of resident predators undeniably changes across the breeding season and whether the described predation patterns hold for other populations, species, and geographical regions await future investigations.
The diel timing of nest predation in birds is mostly unknown. Here, incubating red‐wattled lapwings faced a low chance of nest predation (20%–30%), but night predation was more common later in the season, perhaps because predators reduce their activity during daylight to avoid extreme heat. Indeed, nests were never predated when midday ground temperatures exceeded 45℃. These results highlight the need for continuous monitoring to reveal the temporal pattern of predation on multiple time scales.
The role of vegetated habitats such as seagrass and macroalgal beds as nurseries is essential for the survival of larval and juvenile fish, although quantitative evaluation of the contribution of ...these habitats to nursery function is limited. Moreover, growth–survival relationships of larvae and juveniles associated with vegetated habitats have rarely been examined. To quantitatively and qualitatively evaluate the processes affecting juvenile survival in vegetated habitats, we investigated whether there is a correlation between the degree of selection for bigger and faster‐growing fish and mortality rates for three cohorts by birth date of post‐settlement black rockfish (Sebastes cheni) in a macroalgal bed. We also analyzed relationships between growth rate and experienced temperature by age class to examine the effects of temperature on growth. The latest cohort, which grew under lower vegetation coverage due to a seasonal increase in water temperature, showed higher mortality with evidence of strong selection for survival of bigger and faster‐growing fish. The growth–temperature relationships showed that positive effects of temperature on growth weakened after settlement. Therefore, we suggest that macroalgal coverage has a critical role in controlling the growth–mortality relationship of post‐settlement S. cheni. Furthermore, the negative effects of high temperature on juvenile survival through loss of vegetation may be greater than the positive effects on juvenile growth. These findings would contribute to the management of fisheries resources by increasing the understanding of relationships between survival mechanisms in fish early life stages and vegetation phenology of their habitat under the increasing effects of global warming.
Numerous studies report proximity to land cover edges decreases avian nesting success, yet variation among species, sites, and nesting guilds obscures overall patterns. Nest success is a key ...demographic parameter, and edges are often created from anthropogenic disturbance; therefore, further understanding of nest success and edges should inform bird conservation efforts. We performed a meta-analysis to examine effects of edges on mature forest and shrubland bird nest survival in eastern North America. Sixteen studies fit our inclusion criteria, comprising data for 11 mature forest and 9 shrubland species. Nest success for mature forest birds declined with proximity to edges. Additionally, random effects of species and study explained a relatively large amount of variance in nest survival. We did not find a significant edge effect for shrubland birds, but only two data points (averaged within studies) were greater than 100 meters from an edge. Thus, in studies we compiled, an impact of edges was only apparent for forest species that nested far from edges. An interactive effect of distance-to-edge and nest placement (low vs. higher nesting height) did not significantly influence nest survival. Single-species analyses showed a relationship between distance-to-edge and nesting success for Hermit Thrush ( Catharus guttatus ), though small sample sizes may have limited our ability to detect relationships for other species. Overall, core areas greater than 250 m from edges tend to have higher nest success for mature forest birds, information that will help managers and conservationists when maintaining habitat for both forest and shrubland bird communities.
Summary
Annually variable and synchronous seed production by plant populations, or masting, is a widespread reproductive strategy in long‐lived plants. Masting is thought to be selectively beneficial ...because interannual variability and synchrony increase the fitness of plants through economies of scale that decrease the cost of reproduction per surviving offspring. Predator satiation is believed to be a key economy of scale, but whether it can drive phenotypic evolution for masting in plants has been rarely explored.
We used data from seven plant species (Quercus humilis, Quercus ilex, Quercus rubra, Quercus alba, Quercus montana, Sorbus aucuparia and Pinus pinea) to determine whether predispersal seed predation selects for plant phenotypes that mast.
Predation selected for interannual variability in Mediterranean oaks (Q. humilis and Q. ilex), for synchrony in Q. rubra, and for both interannual variability and reproductive synchrony in S. aucuparia and P. pinea. Predation never selected for negative temporal autocorrelation of seed production.
Predation by invertebrates appears to select for only some aspects of masting, most importantly high coefficient of variation, supporting individual‐level benefits of the population‐level phenomenon of mast seeding. Determining the selective benefits of masting is complex because of interactions with other seed predators, which may impose contradictory selective pressures.
See also the Commentary on this article by Kelly, Kelly, 229: 1829–1831.
1. Local plant community assembly is influenced by a series of filters that affect the recruitment and establishment of species. These filters include regional factors that limit seeds of any given ...species from reaching a local site as well as local interactions such as post-dispersal seed predation and disturbance, which dictate what species actually establish. How these filters interact to influence recruitment into local assemblages, and whether they act differentially on individual species based on traits such as seed size or their provenance (i.e. native vs. exotic), has not been well examined. Such studies, however, are crucial for understanding community assembly and for making predictions about what species might be favoured under specific ecological circumstances. 2. We added 20 native and 19 exotic species that varied in seed size to undisturbed or experimentally disturbed subplots in and out of larger rodent exclusion plots at ten grassland sites across the Blackfoot River drainage in western Montana, USA. 3. Individually, exclusion of rodent seed predators and disturbance substantially increased cumulative (summed across all species) seedling recruitment. Exclusion of rodent seed predators enhanced recruitment to a greater extent in disturbed rather than undisturbed plots and for native species compared with exotics, while disturbance enhanced recruitment to a greater extent for exotics compared with natives. Examination of individual species responses indicated that results were generalizable across species within each group and not driven by the response of a few species. 4. Seed size mediated these patterns. Notably, the positive effect of rodent exclusion on recruitment was greater for large- versus small-seeded species, while the impact of disturbance on recruitment was more pronounced for small-seeded exotics relative to other groups. 5. Synthesis. These results reveal that local 'filters' such as post-dispersal seed predation and disturbance can individually and collectively impose strong limitation on seedling recruitment into local assemblages. Seed size importantly predicts how strongly individual species are influenced by these local filters. Interestingly, in situ community filters have differential effects on native versus exotic species, suggesting that processes that limit native recruitment may not have the same inhibitory influence on exotics.
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