Factors Influencing Site Abandonment and Site Selection in a Sit-and-Wait Predator: A Review of Pit-Building Antlion Larvae

There is a large body of evidence indicating that predator behavior may strongly influence patterns and processes at the population and community level. Site selection is a major component of fitness in sit-and-wait predators, especially when relocation is rare. Although several review articles dealt with these issues in web-building spiders, this is the first attempt to summarize the effects of biotic and abiotic factors on site selection and relocation in another group of sit-and-wait predators, the pit-building antlions (Neuroptera: Myrmeleontidae). Our synthesis shows that prey abundance may have relatively little effect on pit relocation and that physical properties of the habitat or competition often override its effect. We suggest that owing to a variety of constraints such as physiological constraints or difficulties in assessing site quality, site selection and relocation are not necessarily optimal and thus food intake rate is not maximized. We call for a multi-factorial study on a single species in order to pinpoint the dominant factors and to assess to what extent they influence site selection and relocation. We conclude by proposing new research directions, such as studying whether pit relocation is an adaptive response, when controlling for possible phylogenetic effects.     

Do Predators Condition the Distribution of Prey within Micro Habitats? An Experiment with Stoneflies (Plecoptera)

The selection of habitat by macroinvertebrates living in running waters may be influenced by the physical characteristics of the substratum, as well as by the presence of other species. In this study, an artificial river with three different substrata (pebbles, detritus, and leaves) was utilized to analyze the microhabitat preference of two Plecoptera prey species (Amphinemura sulcicollis and Brachyptera risi), both in absence and in presence of a Plecoptera predator species (Perla marginata). In the absence of predators, both prey species showed a clear preference for the leaf microhabitat. When the predators were present, only Brachyptera risi showed a change of microhabitat selection, with a decrease of leaves and an increase of pebbles and detritus utilization. Amphinemura sulcicollis did not change their substratum utilization. This study demonstrates that the presence of a predator may affect microhabitat selection through a switch from the preferred to the less preferred substrata, although not all species change their habitat utilization in response to predator presence. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

红尾伯劳的巢址选择与营巢行为

2003年4-9月通过焦点动物取样法(focalanimal sampling)和完全记录法(all-occurrence recording)对红尾伯劳的营巢行为进行了研究。结果表明：凌晨选巢,巢多位于7—15m的高大乔木冠部分叉处。对19个巢址主成分分析表明：前6个主成分特征值均大于1,累积贡献率达83．74％,基本包含了16个参数的总信息量。营巢活动自5月下旬至7月中旬,两性参与筑巢,营巢期间有求偶交配行为,营巢期6～8d。衔材主由雄鸟担任,达72．16％,衔材高峰出现于营巢第2d和第4d,每日高峰在7～8时和15-17时。理巢基本全由雄鸟承担。护巢性强。     

Does habitat heterogeneity affect the diversity of epigaeic arthropods in vineyards?

1. The aims of this research performed in vineyards within the Douro Demarcated Region were to determine the species composition of vineyard epigaeic arthropods assemblages and to determine the influence of certain factors on their activity densities and diversity: (i) landscape composition in buffers (125, 250, 500 and 750 m) around each study site; (ii) adjacent vegetation; and (iii) vineyards' ground cover. Arthropods' were assessed using pitfall traps located inside the vineyards at three distances from adjacent vegetation (5, 50 and 100 m).
2. Activity densities and diversity increased from spring to summer for all the studied trophic groups (omnivores, detritivores, predators, phytophages), thus showing them to be affected by season.
3. The activity densities of phytophages were always higher at a distance of 5 m from the adjacent vegetation, which suggests that, although they could originate from these habitats, they do not move too far into the vineyard. Predators reported higher activity densities at 5 m during spring. Meanwhile, in summer, no significant differences were found with the increasing distance from the edge. This result suggests that these habitats could serve both as a refuge and a hibernation habitat, from which predators could colonize the vineyard.

     

How the type of anthropogenic change alters the consequences of ecological traps

Understanding altered ecological and evolutionary dynamics in novel environments is vital for predicting species responses to rapid environmental change. One fundamental concept relevant to such dynamics is the ecological trap, which arises from rapid anthropogenic change and can facilitate extinction. Ecological traps occur when formerly adaptive habitat preferences become maladaptive because the cues individuals preferentially use in selecting habitats lead to lower fitness than other alternatives. While it has been emphasized that traps can arise from different types of anthropogenic change, the resulting consequences of these different types of traps remain unknown. Using a novel model framework that builds upon the Price equation from evolutionary genetics, we provide the first analysis that contrasts the ecological and evolutionary consequences of ecological traps arising from two general types of perturbations known to trigger traps. Our model suggests that traps arising from degradation of existing habitats are more likely to facilitate extinction than those arising from the addition of novel trap habitat. Importantly, our framework reveals the mechanisms of these outcomes and the substantial scope for persistence via rapid evolution that may buffer many populations from extinction, helping to resolve the paradox of continued persistence of many species in dramatically altered landscapes.