Coexistence of carnivores in a heterogeneous landscape: habitat selection and ecological niches

Understanding distributional patterns and mechanisms used by species for habitat selection is crucial to adopt effective land management policies in terms of biodiversity conservation. A heterogeneous landscape may allow coexistence of species. That coexistence will be dependent on the availability of the resources in the habitat that has to be sufficient to fulfil their basic needs. The present study aimed to investigate habitat selection, niche breadth and niche overlap of three sympatric carnivore species (Vulpes vulpes, Genetta genetta and Martes foina) in a typically fragmented landscape from Central Portugal, using camera-trapping techniques. The results obtained revealed that the investigated species use the available habitats differently and in a non-random way. The red fox showed the most specialized behaviour, positively selecting coniferous forests. The common genet preferred eucalyptus, avoiding old-growth mixed woodland, in contrast with stone marten that exhibited a strong preference for this late habitat, avoiding eucalyptus. Concerning the niche breadth, the genet had the highest value while the red fox had the lowest one. The results obtained at the camera-trap level showed that the highest niche overlap occurred between the genet and the stone marten which suggests that these species can coexist and share the available resources. Regarding the habitat level, the greatest niche overlap was found for the stone marten and the red fox, indicating the exploration of the same general habitat conditions by both species. The results obtained in the present study support the concept that landscape complexity allows coexistence between species within the same trophic level.     

Chemical cues modify species interactions: the ecological consequences of predator avoidance by freshwater snails

Chemical signals released by predators or injured prey often induce shifts in the traits of prey species, which may in turn affect species interactions. Here we investigate the role that chemical cues play in mediating species interactions in the littoral food web of lakes. Previous studies have shown that predators induce shifts in the morphology, life history, and behavior of the freshwater snail Physella, but the ecological consequences of developing these inducible defenses are not well documented. We observed habitat use of the freshwater snail Physella gyrina along a depth gradient in a natural lake, and found they increased their use of covered habitats with increasing depth. We hypothesized that this habitat shift was due to changes in the level and type of predation risk, and that the habitat shift would affect periphyton standing crops. These hypotheses were tested in a mesocosm experiment in which we manipulated the presence of molluscivorous fish and crayfish. Predators were confined to cages and snail density was identical in all treatments, so any effects of predators were mediated through trait shifts induced by chemical cues. In the presence of fish, Physella moved under cover, but in the presence of crayfish, Physella avoided cover and moved to the water surface. These non‐lethal effects of predators on snail habitat use influenced the interaction between snails and their periphyton resources. In the presence of fish, periphyton standing crop in covered habitats was reduced to just 8% of periphyton in the absence of fish. Crayfish had no significant effect on periphyton in covered habitats, but they reduced periphyton in near‐surface habitats to 39% of the standing crop in the absence of crayfish. The combined effects of fish and crayfish were generally intermediate to their individual effects. We conclude that because chemical cues often have strong effects on individual traits and trophic interactions are sensitive to trait values, chemical cues may play an important role in shaping the structure and dynamics of food webs.     

The ecological consequences of unpalatable prey: phytoplankton response to nutrient and predator additions

Thermoregulation is thought to be the most important factor influencing habitat selection by terrestrial ectotherms, at least in temperate climates. The cost-benefit model of thermoregulation predicts that ectotherms should invest more in thermoregulation when the costs of doing so are low (when the thermal quality of the habitat is high). However, the extent to which ectotherms vary their thermoregulatory behaviour according to the thermal quality of habitats is currently unknown. We studied the relationship between habitat use and thermoregulation in 53 black rat snakes using temperature-sensitive radio-transmitters. Among the habitats available to black rat snakes, edges had the highest thermal quality, retreat sites and forest were intermediate, and open habitats had the lowest thermal quality. Black rat snakes experienced more favourable body temperatures while in barns (retreat sites) than in edges, and in edges than in forest. During the day, the effectiveness and the extent of thermoregulation by the snakes were equal in barns and forest, but much lower in edges. In fact, black rat snakes selected thermally favourable microhabitats less than their availability while in edges. Therefore, more favourable body temperatures were not necessarily achieved in thermally superior habitats by increased thermoregulation, but simply because favourable temperatures were encountered more often in those habitats. This result is contrary to the central prediction of the cost-benefit model of thermoregulation and we suggest that this model should be modified to put more emphasis on other costs of thermoregulation, such as increased predation risk or lost foraging opportunities.     

Heavy-metal adaptation in terrestrial invertebrates: A review of occurrence,genetics, physiology and ecological consequences

1. The occurrence of genetic adaptation to heavy metals in natural populations of terrestrial invertebrates is evaluated from literature data. Five criteria for adaptation evidence are applied, with concepts from ecotoxicology, ecology, life-history theory and quantitative genetics.2. There is strong evidence for the occurrence of adaptation in natural populations of the isopod Porcellio scaber (Isopoda), the springtails Isotoma notabilis, Onychiurus armatus and Orchesella cincta (Collembola), the blowfly Lucilia cuprina and the fruit fly Drosophila melanogaster (Diptera). Adaptation to metal-containing pesticides has been demonstrated in ticks (Acarina). Population divergence indicates acclimation or adaptation in many other species.3. Metal adaptation has been achieved within a few generations under laboratory conditions in some species; adapted populations occur at field sites that have been polluted for decades, or longer.4. Genetic variation for tolerance and life-history characteristics, allowing for adaptation, was quantified in a reference population of Orchesella cincta. Tolerance and life-history patterns in exposed field populations matched predictions from genetic variation.5. Adaptation involves modification and intensification of existing physiological mechanisms for metal assimilation, excretion, immobilization or compartmentalized storage. There are indications ofinter-population divergence in metal-binding proteins in a snail. In the fruit fly Drosophila melanogaster metal adaptation is achieved by duplication of the metallothionein gene.6. An altered life-history is often part of the complex adaptation syndrome. Metal-adapted invertebrates have a shorter life-cycle and a higher reproductive effort.7. Possible consequences of adaptation, consisting of costs of tolerance determined by genetic correlations, and probably of reduced genetic variation for tolerance and other features, are discussed. Reduced genetic variation is suggested by results for the springtail Orchesella cincta.8. The distinction between “costs of tolerance” on the one hand and linkage disequilibrium or direct selection for altered life-history patterns on the other hand is discussed.9. Species with high sensitivity (i.e. a low NOEC), that do not have populations maintaining sufficient genetic variation to evolve tolerance or modified life-history characteristics, or that have costly tolerance mechanisms, or both, are most at risk for extinction at sites with increasing metal pollution.10. Metal adaptation in terrestrial invertebrates appears to be of degree rather than of kind: indications for a specific metal-fauna, equivalent to metal-vegetation, are lacking.     

Use of plant resources by an omnivorous predator and the consequences for effective predation

Plant-provided food may enhance survival and establishment of omnivorous predators on target crops but on the other hand they may adversely affect predation rates and thus their potential for biological control of target pests. However, it is not known how predation is affected by plant food quality and prey density. The omnivorous predator Macrolophus pygmaeus is commonly used in augmentative releases in greenhouse crops. Experiments have shown its ability to utilize plant resources; eggplant and pepper plant leaves are the most and least suitable, respectively. In this study we searched the effects of floral resources (pollen or flower) of eggplant or pepper plant on the predation rate of M. pygmaeus. We used experiments in dishes (leaves) and cages (plants) under a range of densities of its prey, the aphid Myzus persicae. We did not find evidence that the consumption rates and the type of the functional responses of M. pygmaeus were affected by the plant leaf (eggplant vs pepper plant) or the increase in the spatial scale (leaf vs plant). However, the presence of pollen or a flower of eggplant and to a lesser extent of pepper plant reduced the plateau of the functional response to aphid density and increased the handling time per prey. The extent of prey feeding replacement by flower resources was dependent on the interaction between plant species and prey density. It seems that there is a constant rate of prey consumption replacement at intermediate and high prey densities on eggplant but only at intermediate prey densities on pepper plant. These results indicate the interactions between plant and prey resources in diets of omnivores and may be useful for its efficacy in pest control on eggplant and pepper plant.     

The results of computerization of studies of ecological consequences of the accident on the Chernobyl Nuclear Power Plant for terrestrial ecosystems

In the paper some results of application of information and calculation technologies in researches of ecological consequences of accident on Chernobyl NPP are brought. The effectiveness of a computerization of investigations is scored. Technical and information component isselected. The singularities of application of the methodology of computerization in radioecological researches are considered. The special attention is given to integration of knowledge accumulated in the form of information materials, databases, mathematical models. The browse of the series of radioecological information and of informational-prognostic systems constructed from the moment of accident is made. As an example of successful usage of a computerization in radioecological researches provided by small scientific collectives experience of MSU division of radioecology and ecotoxicology are considered.     

Uptake of Bt-toxin by herbivores feeding on transgenic maize and consequences for the predator Chrysoperla carnea

Abstract  1. Chrysoperla carnea is an important predatory insect in maize. To assess the ecological effects of Bt-maize, expressing the Cry1Ab protein, on larvae of this predator, the following factors were examined: (1) the performance of three prey herbivores ( Rhopalosiphum padi , Tetranychus urticae , and Spodoptera littoralis ) on transgenic Bt and non‐transgenic maize plants; (2) the intake of the Cry1Ab toxin by the three herbivores; and (3) the effects on C. carnea when fed each of the prey species.
2. The intrinsic rate of natural increase (r_m) was used as a measure of performance for R. padi and T. urticae . No difference in this parameter was observed between herbivores reared on Bt or non‐transgenic plants. In contrast, a higher mortality rate and a delay in development were observed in S. littoralis larvae when fed Bt-maize compared with those fed the control maize plants.
3. The ingestion of Cry1Ab toxin by the different herbivores was measured using an immunological assay (ELISA). Highest amounts of Cry1Ab toxin were detected in T. urticae , followed by S. littoralis , and only trace amounts detected in R. padi .
4. Feeding C. carnea with T. urticae , which were shown to contain the Cry1Ab toxin, or with R. padi , which do not ingest the toxin, did not affect survival, development, or weight of C. carnea . In contrast, a significant increase in mortality and a delay in development were observed when predators were fed S. littoralis larvae reared on Bt-maize.
5. A combined interaction of poor prey quality and Cry1Ab toxin may account for the negative effects observed on C. carnea when fed S. littoralis . The relevance of these findings to the ecological risks of Bt-maize on C. carnea is discussed.     

Gene flow from genetically modified rice to its wild relatives: Assessing potential ecological consequences

Pollen-mediated gene flow is the major pathway for transgene escape from GM rice to its wild relatives. Transgene escape to wild Oryza species having AA-genome will occur if GM rice is released to environments with these wild Oryza species. Transgenes may persist to and spread in wild populations after gene flow, resulting unwanted ecological consequences. For assessing the potential consequences caused by transgene escape, it is important to understand the actual gene flow frequencies from GM rice to wild relatives, transgene expression and inheritance in the wild relatives, as well as fitness changes that brought to wild relatives by the transgenes. This article reviews studies on transgene escape from rice to its wild relatives via gene flow and its ecological consequences. A framework for assessing potential ecological consequences caused by transgene escape from GM rice to its wild relatives is discussed based on studies of gene flow and fitness changes.     

Considerations for the development of a terrestrial index of ecological integrity

Ecological systems are composed of complex biological and physical components that are difficult to understand and to measure. However, effective management actions and policy decisions require information on the status, condition, and trends of ecosystems. Multiple levels of information are needed to make effective decisions and the ideal indicators for measuring ecosystem integrity will incorporate information from multiple dimensions of the ecosystem. A terrestrial index of ecological integrity would be a useful tool for ecosystem managers and decision makers. The ideal requirements of the terrestrial index of ecosystem integrity (TIEI) are that it be comprehensive and multi-scale, grounded in natural history, relevant and helpful, able to integrate concerns from aquatic and terrestrial ecology, and that it be flexible and measurable.The objective of this research is to investigate if an index, or indices, could be developed that would summarize the condition of ecosystems so that changes can be tracked over time and this information utilized as a tool to support environmental decision making.     

面向居民生态福祉的国土空间生态网络构建——以临沂市为例

构建面向居民福祉的生态安全体系,统筹考虑生态安全格局中的生态系统要素连通关系和生态系统服务供需关系,是强化国土空间生态修复规划成果,提升居民生态福祉的重要途径。研究基于"源-汇"理论,构建景观生态安全维育网络与生态系统服务亲近网络。结果显示：（1）45%的生态系统服务保护目标是实现高生态系统服务供给和低机会成本的合理阈值,基于此识别的生态供给源地面积为1230.89km²,中心城区及部分主要街道的生态系统服务供需关系呈现高需求-低供给现象;（2）共识别景观生态安全维育廊道75条,其中重要廊道1054km,次重要廊道1154km,一般廊道1366km;（3）生态系统服务亲近廊道分为10个组团,网络化程度低,西北部主要由森林构成,中东部主要由沿河湿地提供服务;（4）构建临沂市"三区两带五廊多组团"的国土空间生态安全格局,在保障景观生态安全的同时有效协调区域生态系统服务供求关系,促进生态-社会协同可持续发展。     

Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: new linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters

Sea otters in California are commonly infected with Toxoplasma gondii. A unique Type X strain is responsible for 72% of otter infections, but its prevalence in terrestrial animals and marine invertebrates inhabiting the same area was unknown. Between 2000 and 2005, 45 terrestrial carnivores (lions, bobcats, domestic cats and foxes) and 1396 invertebrates (mussels, clams and worms) were screened for T. gondii using PCR and DNA sequencing to determine the phylogeographic distribution of T. gondii archetypal I, II, III and Type X genotypes. Marine bivalves have been shown to concentrate T. gondii oocysts in the laboratory, but a comprehensive survey of wild invertebrates has not been reported. A California mussel from an estuary draining into Monterey Bay was confirmed positive for Type X T. gondii by multilocus PCR and DNA sequencing at the B1 and SAG1 loci. This mussel was collected from nearshore marine waters just after the first significant rainfall event in the fall of 2002. Of 45 carnivores tested at the B1, SAG1, and GRA6 typing loci, 15 had PCR-confirmed T. gondii infection; 11 possessed alleles consistent with infection by archetypal Type I, II or III strains and 4 possessed alleles consistent with Type X T. gondii infection. No non-canonical alleles were identified. The four T. gondii strains with Type X alleles were identified from two mountain lions, a bobcat and a fox residing in coastal watersheds adjacent to sea otter habitat near Monterey Bay and Estero Bay. Confirmation of Type X T. gondii in coastal-dwelling felids, canids, a marine bivalve and nearshore-dwelling sea otters supports the hypotheses that feline faecal contamination is flowing from land to sea through surface runoff, and that otters can be infected with T. gondii via consumption of filter-feeding marine invertebrates.     

Selection of hibernation sites by Anthonomus pomorum: preferences and ecological consequences

The apple blossom weevil, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), has a long period of aestivo-hibernation in the adult stage lasting from summer to early spring of the following year. Potential hibernation sites within an apple orchard consist of high-stem rough-bark trees or dwarf smooth-bark trees. Field release-recapture experiments in 2 consecutive years showed that 64 and 47% of the weevils remained in the vicinity of the release sites in an area of high-stem trees and dwarf trees, respectively. The dispersing weevils moved over an average distance of 5.5 m in the dwarf tree area, as compared to 3.8 m in the high-stem tree area. The prevalent direction of dispersal was along tree rows in both areas. Some weevils displayed, after release in mid-July, a directional dispersal to the adjacent forests. Others, released in the dwarf tree area, dispersed towards the area of high-stem rough-bark apple trees. Experiments simulating various hibernation sites demonstrated that the litter of dry leaves was the most preferred overwintering shelter, yielding a relatively high survival rate. Branches with rough bark ranked second, while branches with smooth bark, grass and pure soil were not favourable for overwintering. Flight tendency in newly emerged weevils of summer generation was significantly higher in June/July than in August/September. This corresponds to the dispersal behaviour in the field. The timing of spring colonisation of apple trees was similar for weevils overwintering within the orchard and for those from outside. These results suggest that modern, dwarf apple orchards offer unfavourable conditions for overwintering, but that the relatively small proportion of weevils which manage to reach the adjacent forests find optimal hibernation sites there.     

The evolution of viviparity in holocene islands: ecological adaptation versus phylogenetic descent along the transition from aquatic to terrestrial environments

Species that contain populations with different reproductive modes offer excellent opportunities to study the transition between such strategies. Salamandra salamandra (Linnaeus, 1758) is one of two species within the Salamandra – Lyciasalamandra clade which displays two reproductive modes simultaneously. Along the S. salamandra distribution, the common reproductive mode is ovoviviparity although the species also has viviparous populations in the northern Iberian Peninsula. The occurrence of viviparity has recently been reported in two small offshore island populations on the Atlantic coast (NW Iberia), which originated after the last glacial period (8000–9000 years ago). In this paper, we analysed ovoviviparous, hybrid and viviparous populations (inland and mainland) from 17 localities across the northern Iberian Peninsula using two mitochondrial markers (Cyt b and COI , c . 1100 bp). Phylogenetic and phylogeographic analyses highly support that viviparity arose as an evolutionary novelty in the S. salamandra island populations and that viviparous populations are therefore not monophyletic. The recent insularity of Atlantic island populations leads us to conclude that the transition from ovoviviparity to viviparity can happen in a very short-time span. Additionally, to determine the likely source of this evolutionary transition, we discuss how ecological pressures could have an effect on the maintenance of the ovoviviparous reproductive mode. Hence, taking into account the results of this study, we propose the consideration of the island populations as an evolutionary unit for conservation purposes.     

Reproductive consequences of the terrestrial habit in Orchestia (Crustacea: Amphipoda)

The reproductive bionomics of four species of British littoral Orchestia are compared and contrasted. Three of the marine species studied form a series which occupy successively higher positions on the shore and demonstrate increasing degrees of preadaptation to terrestrial life.

The fundamental adaptations of primitive terrestrial Orchestia are: adoption of a cryptozoic habit, and a reduced growth rate and adult body size. As a consequence of slow growth and small body size, the number of eggs/brood and number of broods/year is markedly reduced. Commonly associated adaptations are: female larger than the male, sex ratio bias to the female, and a tendency to endemism.     

Consumptive emasculation: the ecological and evolutionary consequences of pollen theft

Many of the diverse animals that consume floral rewards act as efficient pollinators; however, others 'steal' rewards without 'paying' for them by pollinating. In contrast to the extensive studies of the ecological and evolutionary consequences of nectar theft, pollen theft and its implications remain largely neglected, even though it affects plant reproduction more directly. Here we review existing studies of pollen theft and find that: (1) most pollen thieves pollinate other plant species, suggesting that theft generally arises from a mismatch between the flower and thief that precludes pollen deposition, (2) bees are the most commonly documented pollen thieves, and (3) the floral traits that typically facilitate pollen theft involve either spatial or temporal separation of sex function within flowers (herkogamy and dichogamy, respectively). Given that herkogamy and dichogamy occur commonly and that bees are globally the most important floral visitors, pollen theft is likely a greatly under-appreciated component of floral ecology and influence on floral evolution. We identify the mechanisms by which pollen theft can affect plant fitness, and review the evidence for theft-induced ecological effects, including pollen limitation. We then explore the consequences of pollen theft for the evolution of floral traits and sexual systems, and conclude by identifying key directions for future research.     

Nonantagonistic interactions between the sexes revealed by the ecological consequences of reproductive traits

In addition to the obvious role reproductive traits play in mating-system evolution, reproductive characters can also have critical ecological or life history consequences. In this study we examine the ecological consequences of mating for female cactophilic Drosophila to test different hypotheses about the processes driving divergence in reproductive characters. Comparisons between intra- and interpopulation matings suggest that population differences in mating benefits, namely increased desiccation resistance in mated females, is not solely attributable to either a male or female-specific reproductive trait. Instead, the results indicate that increased desiccation resistance is a product of a male-female postmating-prezygotic interactions. The results underscore that postmating-prezygotic interactions can serve as an arena for the evolution of male characters that confer substantial benefits to females, not just costs arising from sexual conflict. Variation in the relative benefits conferred by mating between intra- and interpopulation matings also suggests that the relationship between speciation and divergence in reproductive characters via male-female interaction will be difficult to predict.