The variations in the niches of species within a clade depend on the complex interplay among geography, climatic history, and species-specific factors. For the first time, we investigated the ...evolutionary patterns in the climate and habitat niches of 50 species in the order Squamata and a nested subclade (family Lacertidae) in southwest Europe. The habitats of species were characterized at three spatial levels: 1 km
2
(macrohabitat), 2830 m
2
(mesohabitat), and 100 m
2
(microhabitat). We compared three evolutionary models Brownian motion, Ornstein-Uhlenbeck, and Early Burst and fitted Pagel models (lambda, kappa, and delta) to the niche variations to assess the strength of the phylogenetic signal, tempo, and mode of evolution. We expected: (i) that the habitat niche would be more labile than the climate niche; and (ii) variability in the rate of niche evolution as a response to recent climate cycles. The Ornstein-Uhlenbeck model provided a better fit for the different dimensions of the niche, implying evolutionary attraction towards the niche optimum. In the climatic niches for both groups of taxa, a model with an accelerated rate of evolution was preferred to alternative Pagel’s models. We found a greater degree of phylogenetic signal in the climatic niche than in the habitat niche. Overall, squamates exhibited evolutionary lability according to the variation in the habitat structure, thereby suggesting that none of the major subclades is specialized for any specific habitat component.
Continuous availability of food resources, such as pollen, is vital for many insects that provide pollination and pest control services to agriculture. However, there is a lack of knowledge about the ...shared or complementary use of floral resources by such species, which hampers more effective landscape management to simultaneously promote them in agroecosystems.
Here, we simultaneously quantified pollen use by a bumblebee (Bombus terrestris) and a mason bee (Osmia bicornis), two bee species recognized as important crop pollinators, as well as a lacewing (Chrysoperla carnea) and a ladybeetle species (Harmonia axyridis), both common predators of crop aphids, throughout the season in 23 agricultural landscapes in Germany and Switzerland.
Pollen diets were more diverse and similar among C. carnea and H. axyridis compared to the two bee species, but all four species shared key pollen types early in the season such as Acer, Quercus, Salix and Prunus. All species exhibited a pronounced shift in pollen sources from primarily woody plants (mainly trees) in spring to primarily herbaceous plants in summer. The majority of pollen (overall ≥64%) came from non‐agricultural plants even in crop‐dominated landscapes.
Synthesis and applications. Our results highlight the importance of trees as pollen sources for many insect species, particularly early in the season. Our findings support incentives that promote heterogeneous agricultural landscapes including both woody and herbaceous semi‐natural habitats, ensuring phenological complementarity of floral resources for insect species that can provide pollination and pest control services to agriculture. The identified key plant species can help to design and optimize agri‐environment schemes to promote these functionally important insects.
The Mediterranean peninsulas host rich assemblages of lizards, but little is known about the factors that limit their habitat use on large spatial scales. In this study, we investigated the variation ...in habitat use of 29 species of lacertid lizards on the Iberian and Italian peninsulas and the transitional region of southeastern France. We investigated whether the types of habitat used were phylogenetically determined or, in contrast, were more influenced by spatial or climatic effects. We characterized the vegetal composition of 483 habitats used by lacertids and estimated the contribution of each component to habitat variability using distance‐based redundancy analysis. We showed that overall turnover patterns were determined similarly in both peninsulas, despite differences in the composition of the lacertid assemblages. The aridity‐related component dominated over the phylogenetic one, which has a weak influence in both regions. The species showed different turnover patterns, being low in those present in cold alpine habitats and shrub‐steppe specialists. In some Iberian endemics, habitat turnover occurs within relatively homogeneous climatic bands. However, in the Italian species, habitat turnover has a comparatively stronger climatic component, suggesting lower climatic specialization. This study shows that species distributions across habitats provide information to assess community properties and can be applied to explore differences among faunal assemblages over large geographic areas. Our results provide evidence that beta diversity can play a key role in structuring patterns of habitat turnover.
Elucidating the diets of insect predators is important in basic and applied ecology, such as for improving the effectiveness of conservation biological control measures to promote natural enemies of ...crop pests. Here, we investigated the aphid diet of two common aphid predators in Central European agroecosystems, the native Coccinella septempunctata (Linnaeus) and the invasive Harmonia axyridis (Pallas; Coleoptera: Coccinellidae) by means of high throughput sequencing (HTS). For acquiring insights into diets of mobile flying insects at landscape scale minimizing trapping bias is important, which imposes methodological challenges for HTS. We therefore assessed the suitability of three field sampling methods (sticky traps, pan traps and hand-collection) as well as new aphid primers for identifying aphid prey consumption by coccinellids through HTS. The new aphid primers facilitate identification to species level in 75% of the European aphid genera investigated. Aphid primer specificity was high in silico and in vitro but low in environmental samples with the methods used, although this could be improved in future studies. For insect trapping we conclude that sticky traps are a suitable method in terms of minimizing sampling bias, contamination risk and trapping success, but compromise on DNA-recovery rate. The aphid diets of both field-captured ladybird species were dominated by Microlophium carnosum, the common nettle aphid. Another common prey was Sitobion avenae (cereal aphid), which got more often detected in C. septempunctata compared to H. axyridis. Around one third of the recovered aphid taxa were common crop pests. We conclude that sampling methodologies need constant revision but that our improved aphid primers offer currently one of the best solutions for broad screenings of coccinellid predation on aphids.
Predation is an interaction during which an organism kills and feeds on another organism. Past and current interest in studying predation in terrestrial habitats has yielded a number of methods to ...assess invertebrate predation events in terrestrial ecosystems. We provide a decision tree to select appropriate methods for individual studies. For each method, we then present a short introduction, key examples for applications, advantages and disadvantages, and an outlook to future refinements. Video and, to a lesser extent, live observations are recommended in studies that address behavioral aspects of predator–prey interactions or focus on per capita predation rates. Cage studies are only appropriate for small predator species, but often suffer from a bias via cage effects. The use of prey baits or analyses of prey remains are cheaper than other methods and have the potential to provide per capita predation estimates. These advantages often come at the cost of low taxonomic specificity. Molecular methods provide reliable estimates at a fine level of taxonomic resolution and are free of observer bias for predator species of any size. However, the current PCR‐based methods lack the ability to estimate predation rates for individual predators and are more expensive than other methods. Molecular and stable isotope analyses are best suited to address systems that include a range of predator and prey species. Our review of methods strongly suggests that while in many cases individual methods are sufficient to study specific questions, combinations of methods hold a high potential to provide more holistic insights into predation events. This review presents an overview of methods to researchers that are new to the field or to particular aspects of predation ecology and provides recommendations toward the subset of suitable methods to identify the prey of invertebrate predators in terrestrial field research.
We present a decision tree and overview of methods to measure invertebrate predation in terrestrial ecosystems. Major method are addressed with an introduction, examples for applications, a discussion of advantages and disadvantages, and an outlook to future refinements.
Biodiversity is fundamental for ecosystem functioning, but little is known about how function responds to biodiversity loss following habitat disturbance in natural systems. Due to the global decay ...of veteran trees, many associated saproxylic (i.e. deadwood-dependent) insects are considered threatened. Nevertheless, the role of habitat spatial configuration on saproxylic insect biodiversity and dead wood decomposition is poorly understood. We performed a six-year landscape-scale colonization experiment on saproxylic beetles inhabiting hollow oaks, using boxes filled with wood mould as standardized habitat patches. We placed boxes either on a hollow tree or on another tree 61–324 m from the hollows, thereby creating two habitat isolation levels. We quantified wood mould decay and biodiversity in the boxes, measuring species richness, total abundances and community-weighted mean of body mass (CWM) as an index of community functional composition. Isolation had a persistent negative effect on primary consumer biodiversity, but it only impaired decay at the beginning of the experiment. All effects were independent of landscape-level (500-m radius) habitat amount surrounding the boxes. Wood mould decay was mediated by CWM of primary consumers. Therefore function was driven by the body masses of the dominant primary consumer species but not by species numbers (richness) or individual numbers (abundance). Our experiment shows that small-scale habitat isolation leads to biodiversity loss and reduced function and indicates that habitats created by conservation efforts will be used by more saproxylic species if located within sites with a high density of veteran trees.
Predator non‐consumptive effects (NCE) are a suite of phenotypic responses of prey to avoid predation that cascade down food webs and can have a stronger impact than predation itself. However, the ...role of NCE in intraguild interactions remains understudied. Thus, multi‐species experiments based on species traits are needed to improve our understanding of the impact of NCE on community structure.
We investigated NCE of ants on 17 spider species as intraguild prey (8 cursorial and 9 sedentary) to test the influence of spider hunting mode on the strength of NCE. Sedentary spiders select a habitat patch and wait for prey, whereas cursorial spiders roam around searching for prey. Because actively foraging organisms have higher encounter rates with predators, cursorial spiders should show stronger reactions to ant presence.
We collected cues (footprint hydrocarbons) of the black garden ant Lasius niger on filter papers. Then, we placed spiders individually on the papers and filmed their behaviour once on a paper with cues and once on a cue‐free one. We used the increase in walking activity in the presence of cues as an indicator of avoidance behaviour towards ants.
Cursorial spiders spent a longer time moving and being mobile, and had a higher overall mean mobility when exposed to ant cues compared with blank filter papers, whereas sedentary spider species did not react to ant cues at all.
The avoidance of ant cues by cursorial spiders corresponds to their higher risk of encountering ants compared with sedentary species, in accordance with the threat‐sensitivity hypothesis. Our multi‐species study shows the relevance of NCE for intraguild interactions and highlights the importance of experimental trait‐based approaches to improve predictability of species interactions and the role of NCE in ecological communities.
Non‐consumptive effects shape entire ecological communities but their context dependence is poorly understood, limiting their predictive power. The authors present a multi‐species experiment using ants (predators) and spiders (intraguild prey), showing that prey traits (spider foraging mode: (C)ursorial, (S)edentary) explain the strength of their anti‐predator behaviour towards ant cues.
•Spider densities in semi-natural habitats are three times as high as in crops.•As an exception, Oedothorax apicatus overwinters almost entirely in crops.•Most spiders emerge prior to the arrival of ...pests in crop fields.•Woody SNH have the highest spider species richness.•Herbaceous SNH have the highest potential as source habitat for agrobionts.
Semi-natural habitats (SNH) support biodiversity and associated ecosystem services on farmland, thereby contributing to sustainable agriculture. However, little is known about the specific suitability of different types of SNH as overwintering habitat for predatory arthropods, despite the crucial role of such knowledge for conservation biological control. We used ground photoeclectors to sample spiders in 65 habitats comprising crop fields and four major SNH types (herbaceous areal, herbaceous linear, woody areal, woody linear) across two study regions in Switzerland and Germany to identify the most important overwintering habitats for spiders. Spider emergence started in February and over half of the individuals of the most common spiders had already emerged by late April. SNH supported on average 146% higher species richness and 194% higher densities of spiders than crop fields. Woody and herbaceous SNH supported distinct spider communities, with individual species exhibiting marked preferences for either woody or herbaceous SNH. Habitat shape (areal or linear) had no significant effects on spider overwintering. Woody SNH hosted more species, whereas herbaceous SNH had higher densities of agrobiont species (i.e. species known to reach high densities in crops in the growing season). Given the higher number of overwintering agrobionts in herbaceous SNH, this habitat type has potential to promote pest control by spill-over of spiders into nearby crops early in the season. In contrast, woody SNH seem to be more important for the conservation of diverse spider communities that are highly distinct from those inhabiting open land. Hence, creating and preserving a variety of SNH is key to provide suitable overwintering sites for species in agricultural landscapes.
Mate preference based on relatedness may evolve in response to costs and benefits of inbreeding avoidance. Whereas mating with closely related individuals can have negative fitness consequences due ...to inbreeding depression, it may simultaneously be favoured by inclusive fitness benefits. Variation in the fitness payoff shaped by benefits of inbreeding may even lead to preference for mating with kin. We investigated this hypothesis in the social spider Stegodyphus dumicola, a cooperative species in which reproduction occurs among siblings within the group, premating dispersal is lacking and infrequent encounters with unrelated individuals result in homozygous genetic lineages. We tested whether female mate choice is influenced by male relatedness by pairing females with males that differ in the degree of genetic relatedness, namely nest members, non-nest members from the same population and non-nest members from allopatric populations. We recorded premating (male rejections, latency to mating) and mating (copulation duration and interruptions) behaviours. Females showed no preference for partners on the basis of their relatedness during the premating phase, as frequencies of rejections and successful matings did not differ markedly in encounters with nest and non-nest members. This suggests that selection on discriminatory mechanisms may be weakened or lost in species with inbreeding tolerance and in which relatedness between interacting individuals is very high and variance in relatedness extremely low. Unrelated males from the geographically distant population experienced longer copulations than males from the same population. We interpret this finding as depicting a possible scenario of a between-population reproductive barrier or functional incompatibility, which may be the mechanism causing lower fitness in between-population crosses previously documented in these populations.
•Benefits of inbreeding may lead to mate preference for kin.•Social spiders inbreed due to lack of dispersal and within nest matings.•Our study shows that females do not prefer partners based on their relatedness.•Selection on kin recognition mechanisms may be relaxed in this system.
ABSTRACT
Understanding distribution patterns and multitrophic interactions is critical for managing bat‐ and bird‐mediated ecosystem services such as the suppression of pest and non‐pest arthropods. ...Despite the ecological and economic importance of bats and birds in tropical forests, agroforestry systems, and agricultural systems mixed with natural forest, a systematic review of their impact is still missing. A growing number of bird and bat exclosure experiments has improved our knowledge allowing new conclusions regarding their roles in food webs and associated ecosystem services. Here, we review the distribution patterns of insectivorous birds and bats, their local and landscape drivers, and their effects on trophic cascades in tropical ecosystems. We report that for birds but not bats community composition and relative importance of functional groups changes conspicuously from forests to habitats including both agricultural areas and forests, here termed ‘forest‐agri’ habitats, with reduced representation of insectivores in the latter. In contrast to previous theory regarding trophic cascade strength, we find that birds and bats reduce the density and biomass of arthropods in the tropics with effect sizes similar to those in temperate and boreal communities. The relative importance of birds versus bats in regulating pest abundances varies with season, geography and management. Birds and bats may even suppress tropical arthropod outbreaks, although positive effects on plant growth are not always reported. As both bats and birds are major agents of pest suppression, a better understanding of the local and landscape factors driving the variability of their impact is needed.
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