To understand host-parasite interactions, it is necessary to quantify variation and covariation in defence traits. We quantified parasite resistance and fitness tolerance of a polymorphic damselfly ...(Ischnura elegans), an insect with three discrete female colour morphs but with monomorphic males. We quantified sex and morph differences in parasite resistance (prevalence and intensity of water mite infections) and morph-specific fitness tolerance in the females in natural populations for over a decade. There was no evidence for higher parasite susceptibility in males as a cost of sexual selection, whereas differences in defence mechanisms between female morphs are consistent with correlational selection operating on combinations of parasite resistance and tolerance. We suggest that tolerance differences between female morphs interact with frequency-dependent sexual conflict, which maintains the polymorphism locally. Host-parasite interactions can therefore shape intra- and intersexual phenotypic divergence and interfere with sexual selection and sexual conflict.
Caudal autotomy in lizards has intrigued scientists for more than 100 years. Because of the relative lack of literature under natural conditions, the complicated association among field autotomy ...rate, real prédation pressure, the long-term cost of tail loss, and the benefit of regeneration remains equivocal. In this study, we conducted a 7-year capture-mark-recapture (CMR) programme with a wild population of a sexually dichromatic lizard, Takydromus vindipunctatus. We used autotomy indexes and a contemporary bird census mega-dataset of four predatory birds as predictors to examine the association between tail loss and predation pressure. We further estimated the survival cost of tail loss and alleviation by regeneration under natural conditions through CMR modelling. We found that large and small avian predators affect lizard survival through the following two routes: the larger-sized cattle egret causes direct mortality while the smaller shrikes and kestrels are the major causes of autotomy. Following autotomy, the survival rate of tailless individuals over the next month was significantly lower than that of tailed individuals, especially males during the breeding season, which showed a decline of greater than 30%. This sex-related difference further demonstrated the importance of reproductive costs for males in this sexually dichromatic species. However, the risk of mortality returned to baseline after the tails were fully grown. This study indicates the benefit of tail regeneration under natural conditions, which increases our understanding of the cost–benefit dynamics of caudal autotomy and further explains the maintenance of this trait as an evolutionarily beneficial adaption to long-term predator–prey interactions.
The responses of lowland tropical communities to climate change will critically influence global biodiversity but remain poorly understood. If species in these systems are unable to tolerate warming, ...the communities—currently the most diverse on Earth—may become depauperate ('biotic attrition'). In response to temperature changes, animals can adjust their distribution in space or their activity in time, but these two components of the niche are seldom considered together. We assessed the spatio-temporal niches of rainforest mammal species in Borneo across gradients in elevation and temperature. Most species are not predicted to experience changes in spatio-temporal niche availability, even under pessimistic warming scenarios. Responses to temperature are not predictable by phylogeny but do appear to be trait-based, being much more variable in smaller-bodied taxa. General circulation models and weather station data suggest unprecedentedly high midday temperatures later in the century; predicted responses to this warming among small-bodied species range from 9% losses to 6% gains in spatio-temporal niche availability, while larger species have close to 0% predicted change. Body mass may therefore be a key ecological trait influencing the identity of climate change winners and losers. Mammal species composition will probably change in some areas as temperatures rise, but full-scale biotic attrition this century appears unlikely.
Demographic connectivity is vital to sustaining metapopulations yet often changes dramatically through time due to variation in the production and dispersal of offspring. However, the relative ...importance of variation in fecundity and dispersal in determining the connectivity and dynamics of metapopulations is poorly understood due to the paucity of comprehensive spatio-temporal data on these processes for most species. We quantified connectivity in metapopulations of a marine foundation species (giant kelp Macrocystis pyrifera) across 11 years and approximately 900 km of coastline by estimating population fecundity with satellite imagery and propagule dispersal using a high-resolution ocean circulation model. By varying the temporal complexity of different connectivity measures and comparing their ability to explain observed extinction-colonization dynamics, we discovered that fluctuations in population fecundity, rather than fluctuations in dispersal, are the dominant driver of variation in connectivity and contribute substantially to metapopulation recovery and persistence. Thus, for species with high variability in reproductive output and modest variability in dispersal (most plants, many animals), connectivity measures ignoring fluctuations in fecundity may overestimate connectivity and likelihoods of persistence, limiting their value for understanding and conserving metapopulations. However, we demonstrate how connectivity measures can be simplified while retaining utility, validating a practical solution for data-limited systems.
There are many examples of apparent manipulation of host phenotype by parasites, yet few examples of hypermanipulation—where a phenotype-manipulating parasite is itself manipulated by a parasite. ...Moreover, few studies confirm manipulation is occurring by quantifying whether the host's changed phenotype increases parasite fitness. Here we describe a novel case of hypermanipulation, in which the crypt gall wasp Bassettia pallida (a phenotypic manipulator of its tree host) is manipulated by the parasitoid crypt-keeper wasp Euderus set, and show that the host's changed behaviour increases parasitoid fitness. Bassettia pallida parasitizes sand live oaks and induces the formation of a 'crypt' within developing stems. When parasitized by E. set, B. pallida adults excavate an emergence hole in the crypt wall, plug the hole with their head and die. We show experimentally that this phenomenon benefits E. set, as E. set that need to excavate an emergence hole themselves are about three times more likely to die trapped in the crypt. In addition, we discuss museum and field data to explore the distribution of the crypt-keeping phenomena.
How animals locate nutritious but camouflaged prey items with increasing accuracy is not well understood. Olfactory foraging is common in vertebrates and the nutritional desirability of food should ...influence the salience of odour cues. We used signal detection analysis to test the effect of nutritional value relative to the conspicuousness of food patches on rates of foraging improvement of wild house mice Mus musculus searching for buried food (preferred peanuts or non-preferred barley). Olfactory cues were arranged to make food patches conspicuous or difficult to distinguish using a novel form of olfactory camouflage. Regardless of food type or abundance, mice searching for conspicuous food patches performed significantly better than mice searching for camouflaged patches. However, food type influenced how mice responded to different levels of conspicuousness. Mice searching for peanuts improved by similar rates regardless of whether food was easy or hard to find, but mice searching for barley showed significant differences, improving rapidly when food was conspicuous but declining in accuracy when food was camouflaged. Our results demonstrate a fundamental tenet of olfactory foraging that nutritional desirability influences rates of improvement in odour discrimination, enabling nutritious but camouflaged prey to be located with increasing efficiency.
Human activity alters natural habitats for many species. Understanding variation in animals' behavioural responses to these changing environments is critical. We show how signal detection theory can ...be used within a wider framework of state-dependent modelling to predict behavioural responses to a major environmental change: novel, exotic species. We allow thresholds for action to be a function of reserves, and demonstrate how optimal thresholds can be calculated. We term this framework 'state-dependent detection theory' (SDDT). We focus on behavioural and fitness outcomes when animals continue to use formerly adaptive thresholds following environmental change. In a simple example, we show that exposure to novel animals which appear dangerous—but are actually safe—(e.g. ecotourists) can have catastrophic consequences for 'prey' (organisms that respond as if the new organisms are predators), significantly increasing mortality even when the novel species is not predatory. SDDT also reveals that the effect on reproduction can be greater than the effect on lifespan. We investigate factors that influence the effect of novel organisms, and address the potential for behavioural adjustments (via evolution or learning) to recover otherwise reduced fitness. Although effects of environmental change are often difficult to predict, we suggest that SDDT provides a useful route ahead.
Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern ...California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead (Semicossyphus pulcher). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorterspined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.
1. Nitrogen and phosphorus supply influences the rate of litter decomposition and nutrient dynamics during decomposition. Besides the total amount of N and P available to decomposers, their relative ...supply (N : P ratio) might be important, e.g. through an influence on the composition and activity of microbial communities. 2. We carried out two experiments using laboratory microcosms to test that (i) N : P ratios (in either litter or the environment) determine whether N or P limits the rate of decomposition, (ii) the 'critical' N : P ratio between N and P limitation depends on overall nutrient availability, (iii) litter colonization by fungi and bacteria depends on the N : P ratio, and (iv) N : P ratios determine if proportionately more N or P is retained or immobilized by the litter. 3. In one experiment, cellulose as a nutrient-free litter analogue was incubated on sand fertilized with varying N : P supply ratios, whereas in a second experiment, Carex leaf litter with varying N : P ratios was incubated on nutrient-free sand. 4. Results essentially support our hypotheses. Cellulose decomposition was N- or P-limited depending on the N : P supply ratio. The shift from N to P limitation occurred at N : P supply ratios of 1·7-45, depending on overall nutrient supply. Bacteria were most abundant on cellulose at low N : P supply ratios, when decomposition was N-limited, while fungi were relatively more important at high N : P ratios, when decomposition was P-limited. The amounts of mineral N and P immobilized on cellulose and those released from litter, both in absolute terms and relative to supply, depended on the type of nutrient limitation (N vs. P). 5. The N : P ratio of nutrients available to decomposers appears to be an important determinant of plant litter decomposition, the relative importance of fungi and bacteria in litter-associated microbial communities, and litter nutrient dynamics.
Seascape ecology of coastal biogenic habitats Boström, Christoffer; Pittman, Simon J.; Simenstad, Charles ...
Marine ecology. Progress series (Halstenbek),
04/2011, Letnik:
427
Journal Article
Recenzirano
Odprti dostop
We review the progress made in the emerging field of coastal seascape ecology, i.e. the application of landscape ecology concepts and techniques to the coastal marine environment. Since the early ...1990s, the landscape ecology approach has been applied in several coastal subtidal and intertidal biogenic habitats across a range of spatial scales. Emerging evidence indicates that animals in these seascapes respond to the structure of patches and patch mosaics in different ways and at different spatial scales, yet we still know very little about the ecological significance of these relationships and the consequences of change in seascape patterning for ecosystem functioning and overall biodiversity. Ecological interactions that occur within patches and among different types of patches (or seascapes) are likely to be critically important in maintaining primary and secondary production, trophic transfer, biodiversity, coastal protection, and supporting a wealth of ecosystem goods and services. We review faunal responses to patch and seascape structure, including effects of fragmentation on 5 focal habitats: seagrass meadows, salt marshes, coral reefs, mangrove forests, and oyster reefs. Extrapolating and generalizing spatial relationships between ecological patterns and processes across scales remains a significant challenge, and we show that there are major gaps in our understanding of these relationships. Filling these gaps will be crucial for managing and responding to an inevitably changing coastal environment. We show that critical ecological thresholds exist in the structural patterning of biogenic ecosystems that, when exceeded, cause abrupt shifts in the distribution and abundance of organisms. A better understanding of faunal–seascape relationships, including the identifications of threshold effects, is urgently needed to support the development of more effective and holistic management actions in restoration, site prioritization, and forecasting the impacts of environmental change.
PDF