Increased Predation Pressure Research Articles

Wing coloration patterns in the Early Jurassic dragonflies as potential indicator of increasing predation pressure from insectivorous reptiles

Wing coloration is a very ancient feature among insects. Even the wings of the oldest known Pterygota showed transverse colored bands involved in a putative disruptive function. However, no evidence of wing coloration in the representatives of the superorder Odonatoptera is recorded before the latest Triassic. These were the only insect flying-predators until the pterosaurs began their diversification. Here we argue that the situation dramatically changed in the Early Jurassic, with the simultaneous appearance of Odonata with patterns of coloration in phylogenetically distant clades. It is especially the case in the Heterophlebiidae, a small family closely related to the Anisoptera, in which we could record no less than five different patterns of coloration in the same rather small area of North-Western Europe. At the same time and in the same area, small potentially insectivorous pterosaurs greatly diversified. The increase of the predation pressure on the Odonata is the most probable cause of the appearance of patterns of colored spots and bands on the dragonfly wings at that time. In the period between the Middle Jurassic to Early Cretaceous, the number of Odonata with spots and bands of color on wings dramatically increased, we assume in relation to the predation pressure due to an increasing diversification of insectivorous pterosaurs, but also small feathered dinosaurs and birds.

Modeling total predation to avoid perverse outcomes from cat control in a data-poor island ecosystem.

Data hungry, complex ecosystem models are often used to predict the consequences of threatened species management, including perverse outcomes. Unfortunately, this approach is impractical in many systems, which have insufficient data to parameterize ecosystem interactions or reliably calibrate or validate such models. Here we demonstrate a different approach, using a minimum realistic model to guide decisions in data- and resource-scarce systems. We illustrate our approach with a case-study in an invaded ecosystem from Christmas Island, Australia, where there are concerns that cat eradication to protect native species, including the red-tailed tropicbird, could release meso-predation by invasive rats. We use biophysical constraints (metabolic demand) and observable parameters (e.g. prey preferences) to assess the combined cat and rat abundances which would threaten the tropicbird population. We find that the population of tropicbirds cannot be sustained if predated by 1607 rats (95% credible interval (CI) [103, 5910]) in the absence of cats, or 21 cats (95% CI [2, 82]) in the absence of rats. For every cat removed from the island, the bird's net population growth rate improves, provided that the rats do not increase by more than 77 individuals (95% CI [30, 174]). Thus, in this context, one cat is equivalent to 30-174 rats. Our methods are especially useful for on-the-ground predator control in the absence of knowledge of predator-predator interactions, to assess whether 1) the current abundance of predators threatens the prey population of interest, 2) managing one predator species alone is sufficient to protect the prey species given potential release of another predator, and 3) control of multiple predator species is needed to meet the conservation goal. Our approach demonstrates how to use limited information for maximum value in data-poor systems, by shifting the focus from predicting future trajectories, to identifying conditions which threaten the conservation goal. This article is protected by copyright. All rights reserved.

The Biological Roots of Music and Dance : Extending the Credible Signaling Hypothesis to Predator Deterrence.

After they diverged from panins, hominins evolved an increasingly committed terrestrial lifestyle in open habitats that exposed them to increased predation pressure from Africa's formidable predator guild. In the Pleistocene, Homo transitioned to a more carnivorous lifestyle that would have further increased predation pressure. An effective defense against predators would have required a high degree of cooperation by the smaller and slower hominins. It is in the interest of predator and potential prey to avoid encounters that will be costly for both. A wide variety of species, including carnivores and apes and other primates, have therefore evolved visual and auditory signals that deter predators by credibly signaling detection and/or the ability to effectively defend themselves. In some cooperative species, these predator deterrent signals involve highly synchronized visual and auditory displays among group members. Hagen and Bryant (Human Nature, 14(1), 21-51, 2003) proposed that synchronized visual and auditory displays credibly signal coalition quality. Here, this hypothesis is extended to include credible signals to predators that they have been detected and would be met with a highly coordinated defensive response, thereby deterring an attack. Within-group signaling functions are also proposed. The evolved cognitive abilities underlying these behaviors were foundations for the evolution of fully human music and dance.

Lowering the rate of timber harvesting to mitigate impacts of climate change on boreal caribou habitat quality in eastern Canada

Many boreal populations of woodland caribou (Rangifer tarandus caribou) have declined in Canada, a trend essentially driven by the increasing footprint of anthropogenic disturbances and the resulting habitat-mediated apparent competition that increases predation pressure. However, the influence of climate change on these ecological processes remains poorly understood. We evaluated how climate change will affect boreal caribou habitat over the 2030–2100 horizon and in a 9.94 Mha study area, using a climate-sensitive simulation ensemble that integrates climate-induced changes in stand dynamics, fire regime, and different levels of commercial timber harvesting. We assessed the relative importance of these three drivers under projections made using different radiative forcing scenarios (RCP 2.6, 4.5, 8.5). Habitat quality was estimated from resource selection functions built with telemetry data collected from 121 caribou between 2004 and 2011 in 7 local populations. At the beginning of our simulations, caribou habitat was already structured along a south-to-north increasing quality gradient. Simulations revealed changes in forest cover that are driven by climate-induced variations in fire regime and scenarios of harvesting levels, resulting in the loss of older coniferous forests and an increase in deciduous stands. These changes induced a generalized decrease in the average habitat quality and in the percentage of high-quality habitat for caribou, and in a northward recession of suitable habitat. Timber harvesting was the most important agent of change for the 2030–2050 horizon, although it was slowly replaced by changes in fire regime until 2100. Our results clearly showed that it is possible to maintain the current average habitat quality for caribou in future scenarios that consider a reduction in harvested volumes, the only lever under our control. This suggests that we still have the capacity to conciliate socioeconomic development and caribou conservation imperatives in the face of climate change, an important issue debated throughout the species distribution range.

Integrated population modeling identifies low duckling survival as a key driver of decline in a European population of the Mallard

Abstract Europe’s highest densities of breeding Mallards (Anas platyrhynchos) are found in the Netherlands, but the breeding population there has declined by ~30% since the 1990s. The exact cause of this decline has remained unclear. Here, we used an integrated population model to jointly analyze Mallard population survey, nest survey, duckling survival, and band-recovery data. We used this approach to holistically estimate all relevant vital rates, including duckling survival rates for years for which no explicit data were available. Mean vital rate estimates were high for nest success (0.38 ± 0.01) and egg hatch rate (0.96 ± 0.001), but relatively low for clutch size (8.2 ± 0.05) compared to populations in other regions. Estimates for duckling survival rate for the three years for which explicit data were available were low (0.16–0.27) compared to historical observations, but were comparable to rates reported for other regions with declining populations. Finally, the mean survival rate was low for ducklings (0.18 ± 0.02), but high and stable for adults (0.71 ± 0.03). Population growth rate was only affected by variation in duckling survival, but since this is a predominantly latent state variable, this result should be interpreted with caution. However, it does strongly indicate that none of the other vital rates, all of which were supported by data, was able to sufficiently explain the population decline. Together with a comparison with historic vital rates, these findings point to a reduced duckling survival rate as the likely cause of the decline. Candidate drivers of reduced duckling survival are increased predation pressure and reduced food availability, but this requires future study. Integrated population modeling can provide valuable insights into population dynamics even when empirical data for a key parameter are partly missing.

Changing patterns of conflict between humans, carnivores and crop-raiding prey as large carnivores recolonize human-dominated landscapes

Large carnivores are making remarkable comebacks in Europe, but how this affects human-wildlife conflict remains unclear. Rebounding carnivore populations lead to increasing livestock depredation, which in turn leads to greater economic losses for farmers. However, returning carnivores could also influence the behavior of wild ungulates, which are themselves responsible for major crop damage and associated economic losses. Here, we exploit the natural experiment of a rebounding wolf population in the Italian Apennines to study how this affected both types of human-wildlife conflic. We used large datasets of wolf occurrences (n = 351), livestock depredation events (n = 165), and crop damage events by wild boar (n = 3442) to independently model the determinants of livestock depredation and crop damage distribution in relation to wolf habitat suitability over a ten-year period of increasing wolf numbers. These analyses yielded two major insights. First, livestock depredations were mainly related to insufficient prevention measures (e.g. lacking fencing) rather than landscape context, providing a clear pathway to conflict mitigation. Second, crop damage decreased in areas of higher wolf habitat suitability and became more likely in areas of lower wolf habitat suitability, closer to settlements. This suggests increasing predation pressure forces wild boars to avoid the most suitable wolf habitat, leading to a redistribution of crop damage in the landscape. More generally, our study highlights complex human-wildlife interactions as large carnivores recover in human-dominated landscapes, suggesting that multiple, co-occurring conflicts need to be assessed jointly and adaptively in order to foster coexistence between humans and wildlife.

Genetic analyses are more sensitive than morphological inspection at detecting the presence of threatened Mojave desert tortoise (Gopherus agassizii) remains in canid scat and raven pellets

AbstractSubsidization of predator populations increases predation pressure on prey species, which is exacerbated when natural resources are scarce. Estimating the frequency of predation by subsidized predators on vulnerable species, especially low‐density, long‐lived species such as the federally threatened Mojave desert tortoise (Gopherus agassizii), allows landscape managers to evaluate the need for actions like reducing subsidies, discouraging predation by taste aversion, or predator removal. Most studies of Mojave desert tortoise predation have relied on morphological analysis to identify hard parts in predator scat. Here, we developed and validated a qPCR assay to test for the presence of Mojave desert tortoise in DNA extracted from scat and pellets. We used the assay to detect tortoise DNA in scat and pellets collected in a conservation easement adjacent to Boulder City, Nevada, from three Mojave desert tortoise predators: coyotes (Canis latrans), desert kit foxes (Vulpes macrotis arsipus), and common ravens (Corvus corax)—all of which consume anthropogenic resources. We compared the results of our qPCR assay to results from morphological analysis of the same samples and found that the qPCR method is much more sensitive at detecting the presence of tortoise remains. Although neither method can determine whether consumption was the result of predation or scavenging, nor how many individual tortoises were consumed, our findings indicate that conservation managers may benefit from focusing efforts on reducing subsidies that attract and support predators and on reducing tortoise mortality from predation.

Experimental repatriation of snowshoe hares along a southern range boundary reveals historical community interactions

AbstractClimate change is altering interspecific interactions globally, yet community‐level responses are difficult to predict due to both the direct and indirect effects of changing abiotic and biotic conditions. Snowshoe hares (Lepus americanus) are particularly vulnerable to decreasing snow cover and resultant camouflage mismatch. This species shares a suite of predators with alternative prey species including porcupines (Erethizon dorsatum) and ruffed grouse (Bonasa umbellus), and all three species historically exhibited synchronized population dynamics. Recently, the community has become partially disassembled, notably with the loss of snowshoe hares and associated enemy‐mediated indirect interactions resulting from declining snow duration. Specifically, we hypothesized that the extirpation of hares in the early 1990s indirectly increased predation pressure on ruffed grouse and porcupines. To test our hypothesis, we experimentally translocated 96 snowshoe hares to a site within a regional ecotone between northern and southern forests where snowshoe hares were recently extirpated and monitored community members before, during, and after translocation. Ruffed grouse were only loosely associated with the biotic interactions that linked porcupines and snowshoe hares, likely due to predation occurring from avian predators and strong negative direct effects of declining winter snow depths. In contrast, predation of neonate porcupines was virtually non‐existent following repatriation, compared with periods without hares. This abrupt attenuation of predation did not increase overall survival due to increased non‐predation mortality from cold, early spring weather. Porcupines directly benefited from warming winters: decreased snow cover increased adult survival and warmer temperatures around parturition increased maternal condition and reduced non‐predation causes of mortality for neonates. Our experimental manipulation suggests that enemy‐mediated indirect interactions were likely to be important features of this community; however, climate change has disrupted these interactions, resulting in extirpation of a central prey species (snowshoe hare) and increased predation of an alternative prey species (porcupine). We show complex effects from climate change with some species directly and negatively affected, while others benefited from direct effects of warming winters, but suffered negative effects from indirect interactions. Due to absent snowshoe hares and associated biotic interactions, continued persistence of this community module is unlikely, potentially resulting in altered no‐analog communities along trailing edge distributions.

Niche partitioning in a guild of invasive mammalian predators.

Predators compete aggressively for resources, establishing trophic hierarchies that influence ecosystem structure. Competitive interactions are particularly important in invaded ecosystems where introduced predators can suppress native prey species. We investigated whether niche partitioning exists within a guild of invasive mammalian predators and determined the consequences for native species. Over 4405 camera‐trap days, we assessed interactions among three invasive predators: two apex predators (feral cats Felis catus and ferrets Mustela furo) and a mesopredator (stoats Mustela erminea), in relation to their primary prey (lagomorphs, rodents and birds) and habitat use. Further, we tested for mesopredator release by selectively removing cats and ferrets in a pulse perturbation experiment. We found compelling evidence of niche partitioning; spatiotemporal activity of apex predators maximized access to abundant invasive prey, with ferrets targeting lagomorphs and cats targeting rodents. Mesopredators adjusted their behavior to reduce the risk of interference competition, thereby restricting access to abundant prey but increasing predation pressure on diurnal native birds. Stoats were only recorded at the treatment site after both larger predators were removed, becoming the most frequently detected predator at 6 months post‐perturbation. We suggest there is spatial and resource partitioning within the invasive predator guild, but that this is incomplete, and avoidance is achieved by temporal partitioning within overlapping areas. Niche partitioning among invasive predators facilitates coexistence, but simultaneously intensifies predation pressure on vulnerable native species.

Effects of Population Declines on Habitat Segregation and Activity Patterns of Rabbits and Hares in Doñana National Park, Spain

Competition, predation, and diseases are key factors shaping animal communities. In recent decades, lagomorphs in Europe have been impacted by virus-borne diseases that have caused substantial declines in their populations and, subsequently, in many of their predators. We examined activity and habitat-use patterns of sympatric European rabbits (Oryctolagus cuniculus L.) and Iberian hares (Lepus granatensis R.) in Doñana National Park, Spain, (DNP) during two periods of disease outbreak. In the first period (1984–1985), fecal pellet counts and roadside counts indicated that lagomorph species were segregated, with rabbits occurring in scrublands and hares in marshlands. Both species also occupied rush and fern belt ecotones. Roadside counts at sunrise, midday, sunset, and midnight revealed that rabbits and hares had the same activity patterns (crepuscular and nocturnal) in the zone of sympatry. During the second period (2005–2016), roadside counts showed that rabbits and hares were mainly nocturnal in scrublands and border marshlands. Hares occupied scrublands; a habitat previously occupied only by rabbits. These results are interpreted in light of the competition theory and predation pressure. The disease-caused decline of rabbits has likely favored hares that moved into scrublands, a vegetation type previously occupied exclusively by rabbits. The decline of rabbits in DNP has also caused the almost disappearance of this area of the Iberian lynx (Lynx pardinus), a rabbit specialist, thus enabling generalist predators to increase. Generalist predators have subsequently increased predation pressure on both rabbits and hares, causing them to switch to nocturnal activity.

Impacts of spruce budworm defoliation on the habitat of woodland caribou, moose, and their main predators.

Forest logging has contributed to the decline of several woodland caribou populations by causing the fragmentation of mature coniferous stands. Such habitat alterations could be worsened by spruce budworm (SBW) outbreaks. Using 6201 vegetation plots from provincial inventories conducted after the last SBW outbreak (1968–1992) in boreal forests of Québec (Canada), we investigated the influence of SBW‐caused tree defoliation and mortality on understory vegetation layers relevant to woodland caribou and its main predators. We found a positive association between severe outbreaks and the cover of most groups of understory plant species, especially in stands that were dominated by balsam fir before the outbreak, where a high canopy openness particularly benefited relatively fast‐growing deciduous plants. Such increases in early successional vegetation could provide high‐quality forage for moose, which is likely to promote higher wolf densities and increase predation pressure on caribou. SBW outbreaks may thus negatively affect woodland caribou by increasing predation risk, the main factor limiting caribou populations in managed forests. For the near future, we recommend updating the criteria used to define critical caribou habitat to consider the potential impacts of spruce budworm defoliation.

From crypsis to masquerade: Ontogeny changes the colour defences of a crab spider hiding as bird droppings

Abstract Selection imposed by visually hunting predators has driven the evolution of colour‐based antipredator defence strategies such as crypsis, masquerade, mimicry and aposematism. Individuals of many animals are generally considered to rely on a single type of defence strategy, but individuals of some species use multiple colour‐based defences. Many animals switch between colour‐based defences against visually hunting predators during ontogeny. However, why this occurs remains poorly understood. The crab spider Phrynarachne ceylonica is an often‐cited example of a bird dropping masquerade. It has recently been demonstrated that P. ceylonica crab spiders gain protection from their predators by being misidentified as bird droppings by their predators. P. ceylonica females show an ontogenetic shift in colour defences: early instars possess a dark and cryptic form, while at later instars and as adults, the spiders resemble bird droppings. We hypothesised that this shift may be driven by differential changes in predation risk of two defence strategies with increasing body size due to ontogeny. We tested this hypothesis by presenting naïve domestic chicks with 3D printed artificial spiders of two different sizes (small, large) and two colours (dark, bird dropping‐like), and determined whether larger bird dropping‐like spiders are more readily found and attacked than cryptic forms by chicks. We found that small cryptic spiders were more difficult to detect than small bird dropping masquerading spiders, but large cryptic spiders were attacked much more quickly and more frequently than large bird dropping masquerading spiders. Increasing predation pressure on larger, cryptic spiders during ontogeny suggests that switching to bird dropping masquerade may be a more effective defence as spiders increase in size. We thus conclude that the ontogenetic shift from crypsis to masquerade is adaptive.

Amphipod assemblages associated with native habitat-forming seaweeds of the Alboran Sea: influence by environmental protection and biogeographical patterns

Context Despite the key ecological role played by epifaunal communities associated with macroalgae in temperate coastal rocky shores worldwide, biodiversity and ecological patterns of their associated invertebrate communities are still poorly known. Aims The present study aims to compare the amphipod assemblages associated with the dominant canopy-forming macroalgae in shallow subtidal habitats of the Alboran Sea, as well as to explore its biogeographical patterns and the influence of protection measures. Methods Replicate samples of both Ericaria selaginoides (=Cystoseira tamariscifolia) and Halopteris scoparia were collected at two different bioregions within the Alboran Sea and both inside and outside marine protected areas. Key results Amphipoda was the dominant taxon within the mobile epifaunal community, both in terms of number of species (47 different species were recorded) and individuals (>70% of the total abundance). Assemblages associated with E. selaginoides and H. scoparia differed and showed a marked response to the Mediterranean–Atlantic gradient in this region; species related to warmer waters become increasingly dominant towards the east. However, there were no significant differences in amphipod assemblage composition, abundance or species richness between protected and non-protected areas. Conclusions Obtained results highlighted the relevance of these native macroalgae as habitat for epifauna, as well as the influence of macroalgal identity and regional biogeographical patterns on amphipod distribution. Implications This study provides valuable baseline information to monitor human-induced changes such as coastal pollution, invasive species, and climate change. It also draws attention about the uncertain response of epifaunal communities to management strategies (such as marine protected areas) and ecological processes (e.g. increasing predation pressure).

Cladoceran community succession and identification of anthropogenic signals since 1950s in Lake Tianchi in Yunlong County, northwest Yunnan

从1950s开始, 云南地区部分湖泊受到了水文调控(如筑坝)和鱼类引入等流域开发活动的直接影响, 湖泊水环境与生态系统结构已出现明显改变. 开展浮游动物群落的长期生态响应评价有助于认识气候波动和人为胁迫的影响模式. 本文选取云龙天池进行了沉积物记录分析, 在重建过去100年环境变化历史的基础上开展了枝角类群落的多指标分析(物种组成、个体大小、生物量等), 进一步结合多变量分析识别了枝角类群落构建的关键驱动因子. 结果显示, 云龙天池在过去100年间经历了明显的水位波动, 约1962年以前水位较低, 1950s起的水文调控(筑坝)导致湖泊水位波动上升, 2006年以来略有下降. 枝角类群落随水位波动呈现由底栖种向浮游种占优转变的模式, 并在2006年以来底栖种略有增加. 总体上, 低水位时期底栖枝角类占优, 高水位时期浮游枝角类占优. 水体营养水平也对枝角类群落产生了较为显著的影响. 在沉积物总氮和有机质通量上升时, 长额象鼻溞(Bosmina longirostris)相对丰度和枝角类浓度都明显上升. 枝角类象鼻溞个体大小表明, 1969年鱼类引入后象鼻溞的壳长、壳刺长度、触角长度显著减小, 反映了鱼类捕食压力上升的影响. 本研究进一步揭示了水文调控和鱼类引入对湖泊环境和生物群落结构的驱动影响. 其中, 1960s以前云龙天池处于自然波动的状态, 湖泊环境和枝角类群落变化主要受气候(如降水、气温)的影响; 1960s以来人类活动的影响强度已经掩盖了气候变化的信号, 成为影响湖泊生态演化轨迹的主要因素. 为了开展有效的湖泊保护与生态治理, 有必要综合评估水文调控、鱼类引入等人类活动对湖泊生态健康的长期影响.;Since the 1950s, many lakes in Yunnan have been directly impacted by watershed development activities such as hydrological regulation (such as damming) and fish introduction, and thus lake environment and ecosystem structure have changed significantly. Investigation on the long-term response of zooplankton communities to limnological changes is vital for understanding the effects of climate change and anthropogenic stresses on lakes. In this study, Lake Tianchi from Yunlong County, northwest Yunnan, was selected for reconstructing environmental change history over the past 100 years, with a focus on the succession of the cladoceran community and the identification of its environmental drivers. The results showed that Lake Tianchi has experienced significant fluctuations in water level over the past 100 years, which was relatively low before about 1962, gradually rose during 1962-2006 due to hydrological regulation (damming), and slightly declined from about 2006 onward. The dominant taxa of cladoceran community shifted from littoral species to planktonic ones while benthic taxa slightly increased after 2006. In brief, benthic cladocerans were generally dominant during the low water-level period, while planktonic taxa predominated when water level rose. The percentage of Bosmina longirostris and the cladoceran concentration were both increased when the sedimentary TN and LOI₅₅₀ increased since the 1960s, suggesting that the influence of nutrients on the compositional change and production of cladocerans. After planktivorous fish was introduced in 1969, the carapace, carapace mucro and antennule lengths of Bosmina were all significantly decreased, suggesting the influence of increasing predation pressure by zooplanktivorous fish. This study highlights the long-term impacts of hydrological regulation and fish introduction on the lake environment and biological community structure. Before the 1960s, the lake was generally in natural conditions, lake environment and cladoceran communities were mainly affected by climate (precipitation, temperature), while, after the 1960s, the influence of human activities has overridden the role of climate change and become the main factor in affecting the ecological structure of Lake Tianchi. For lake protection and ecological remediation, it is necessary to comprehensively assess the impact of multiple human activities (i.e. hydrological regulation and fish introduction) on lake ecosystem health for generating appropriate restoration strategies.

What factors relate with the activity synchronization intensity among big cats and their ungulate prey in Northeast China?

The activity synchronization rhythm is an important aspect of measuring interspecific interactions between predators and prey, and crucial for large carnivores conservation. However, little is known about what factors relate their activity synchronization dynamics. With the climate change and human society development, the spatial-temporal distribution and activity synchronized rhythm of large carnivores and their prey would inevitably be affected, which would further affect the adaptability of large carnivores and bring new challenges to their conservation. In this study, we hypothesized the ambient temperature and human activity would influence the activity synchronization intensity among Amur tiger, Amur leopard and ungulates (roe deer, sika deer and wild boar) through cross-correlation function and temporal niche overlap model based on the camera traps data. The result show that the activity rhythms of the five target species showed species and seasonal differences, the temporal niche overlaps between ungulates were normally higher than that between the cats and prey, the weakest overlap was observed between the two big cat species, and time-lags of similar rhythmic activity can reduce the temporal overlap pressures of species. Furthermore, we found that ambient temperature relate interspecific synchrony of roe deer-sika deer and roe deer-wild boar pairs at the daily scale. And at hourly scale, temperature and human activities exerted significantly positive or negative stresses on the interspecific activity synchronization of all target species, observed in all three seasons. Our study provides new insights on our understanding of the mechanisms by which sympatric predators and ungulate prey coexist and interact in view of temporal niche overlap, as well as how wildlife managers can manage the mammal assembly effectively. As the Amur tiger and leopard populations in China are being recovered quickly, the rapidly increasing predation pressure and limited environmental resources could have profound implications for the interaction and coexistence among these two large carnivores and their ungulate prey. Managers should strengthen the monitoring, and understand its causes and consequences, so as to develop effective protective measures.

Decade changes of the food web structure in tropical seagrass meadow: Implication of eutrophication effects

Seagrass meadows are experiencing worldwide declines mainly because of nutrient enrichment. However, knowledge about how eutrophication affects its food web structure is still limited. Based on decade-scale observations in a tropical seagrass meadow, we analysed primary producer structures, isotopic niche, and the diets of consumers respond to the decade nutrient enrichment. Through decades of nutrient enrichment, the biomass of epiphytes, particulate organic matter (POM), and macroalgae significantly increased. Correspondingly, the contribution of seagrass to the entire food web decreased significantly. Meanwhile, the isotopic niches of consumers have also become more shrinking, which reflects a more concentrated diet and higher predation pressure for consumers. These findings suggest that eutrophication leads to a significant shift in the structure of primary producers, which has changed food source availability and increased predation pressure, leading to a dietary shift in consumers and a simplified food web structure.

A twig-like insect stuck in the Permian mud indicates early origin of an ecological strategy in Hexapoda evolution

Full body impressions and resting traces of Hexapoda can be of extreme importance because they bring crucial information on behavior and locomotion of the trace makers, and help to better define trophic relationships with other organisms (predators or preys). However, these ichnofossils are much rarer than trackways, especially for winged insects. Here we describe a new full-body impression of a winged insect from the Middle Permian of Gonfaron (Var, France) whose preservation is exceptional. The elongate body with short prothorax and legs and long wings overlapping the body might suggests a plant mimicry as for some extant stick insects. These innovations are probably in relation with an increasing predation pressure by terrestrial vertebrates, whose trackways are abundant in the same layers. This discovery would possibly support the recent age estimates for the appearance of phasmatodean-like stick insects, nearly 30 million years older than the previous putative records. The new exquisite specimen is fossilized on a slab with weak ripple-marks, suggesting the action of microbial mats favoring the preservation of its delicate structures. Further prospections in sites with this type of preservation could enrich our understanding of early evolutionary history of insects.

Scavenging patterns of generalist predators in forested areas: The potential implications of increase in carrion availability on a threatened capercaillie population

AbstractThe increases in ungulate populations and hunting bags throughout Europe and North America have resulted in higher carcass numbers available for mesocarnivore species in temperate and boreal forests. The increase in food resources can sustain denser predator populations, potentially affecting prey species such as the threatened western capercaillie Tetrao urogallus. We investigated the ungulate population trends in recent decades and the carrion use by facultative scavengers in areas of the Pyrenees occupied by capercaillie to assess the potential effects on predation of nests and adult birds, and on its population trend. We found a significant increase in the number of ungulates harvested during the period of sharp capercaillie population decline. Carrion was provided experimentally in forested areas occupied by capercaillie showing that remains were mainly consumed by red fox Vulpes vulpes, followed by wild boar Sus scrofa and marten species (Martes sp.). Season (cold or warm) was the most important factor determining scavenging activity in most species. Main predators of capercaillie nests and adults were martens and red fox, with no predation by wild boar. Our data show that main predators of capercaillie are the same species that mainly consume carrion, especially in winter, and that plentiful carrion resources could maintain higher populations of these species, potentially increasing predation pressure on the capercaillie population. This study shows that managing carrion arising from hunting activity in areas of capercaillie distribution is a necessary management action to reduce the available carrion biomass and so reduce the impact of mesocarnivores on capercaillie conservation.

New invasive predator reduces the abundance of native prey in a cold‐temperate marine fouling community

Abstract Invasive species threaten the conservation of marine environments, and urgent management strategies are needed to prevent their introduction, establishment and spread. Specifically, marine invasive predators destabilize ecological interactions and alter community structure and function. However, most of the evidence showing the effect of these predators is restricted to a few species and regions, while for others the information remains scarce. This study experimentally evaluated the ecological effects of the sea slug Pleurobranchaea maculata, a recently introduced invasive predator, on the fouling communities of a cold‐temperate port in the South‐western Atlantic. The results show that increasing predation pressure reduces significantly the abundance of sea anemones, which are among the preferred prey items. This study reveals new evidence to help better understand the effects of P. maculata on the biological communities of a recently invaded region. Furthermore, it provides the first experimental evidence supporting the hypothesis that marine invasive predators can induce a significant decrease in the abundance of native species in benthic communities of cold‐temperate marine environments in the South‐western Atlantic.

Intra‐population variation in reproductive timing covaries with thermal plasticity of offspring performance in perch Percafluviatilis

Life history theory posits that organisms should time their reproduction to coincide with environmental conditions that maximize their fitness. Population-level comparisons have contributed important insights on the adaptive value of reproductive timing and its association to environmental variation. Yet, despite its central role to ecology and evolution, the causes and consequences of variation in reproductive timing among individuals within populations are poorly understood in vertebrates other than birds. Using a combination of observational field studies and a split-brood experiment, we investigated whether differences in breeding time were associated with changes in hatching success, reproductive allocation and reaction norms linking offspring performance to temperature within an anadromous Baltic Sea population of perch Perca fluviatilis. Field observations revealed substantial variation in reproductive timing, with the breeding period lasting almost 2months and occurring in temperatures ranging from 10 to 21℃. The hatching success of perch decreased as the reproductive season progressed. At the same time, the reproductive allocation strategy changed over the season, late breeders (the offspring of which were introduced into a high resource environment and increased predation pressure) produced more and smaller eggs that resulted in smaller larvae, compared with early breeders. The split-brood experiment in which eggs were incubated in different temperatures (10, 12, 15, 18°C) showed that differences in reproductive timing were associated with a change in the shape of the reaction norm linking offspring performance to water temperature indicative of adaptive phenotypic plasticity, with the offspring of early breeders performing best in low temperatures and the offspring of late breeders performing best in high temperatures. The seasonal changes in reproductive traits and the shape of the thermal performance suggest time-dependent adaptive differences among individuals within the population. Management actions aimed at preserving and restoring variation in the timing of reproductive events will thus likely also influence variation in associated life history traits and thermal performance curves, which could safeguard populations against environmental challenges and changes associated with exploitation and global warming.