A global consistent positive effect of urban green area size on bird richness

Background: Although the species-urban green area relationship (SARu) has been analyzed worldwide, the global consistency of its parameters, such as the fit and the slope of models, remains unexplored. Moreover,the SARu can be explained by 20 different models. Therefore, our objective was to evaluate which models provide a better explanation of SARus and, focusing on the power model,to evaluate the global heterogeneity in its fit and slope. Methods: We tested the performance of multiple statistical models in accounting for the way in which species richness increases with area, and examined whether variability in model form was associated with various methodological and environmental factors. Focusing on the power model, we analyzed the global heterogeneity in the fit and slope of the models through a meta-analysis. Results: Among 20 analyzed models, the linear model provided the best fit to the most datasets, was the top ranked model according to our efficiency criterion, and was the top overall ranked model.The Kobayashi and power models were the second and third overall ranked models, respectively.The number of green areas and the minimum number of species within a green area were the only significant variables explaining the variation in model form and performance, accounting for less than 10% of the variation. Based on the power model,there was a consistent overall fit (r2=0.50) and positive slope of 0.20 for the species richness increase with area worldwide.Conclusions:The good fit of the linear model to our SARu datasets contrasts with the non-linear SAR frequently found in true and non-urban habitat island systems;however, this finding may be a result of the small sample size of many SARu datasets. The overall power model slope of 0.20 suggests low levels of isolation among urban green patches, or alternatively that habitat specialist and area sensitive species have already been extirpated from urban green areas.

Effects of firewood harvesting intensity on biodiversity and ecosystem services in shrublands of northern Patagonia

Background: Forest management has historically focused on provisioning of goods (e.g. timber, biomass), butthere is an increasing interest to manage forests also to maintain biodiversity and to provide other ecosystemservices (ES).Methods: We evaluated the effects of firewood harvesting intensity on biodiversity and different ES in threecontrasting shrubland sites in northern Patagonia (Argentina). At each site, four harvesting treatments, representingvarious levels of harvest intensity, were randomly assigned to eight permanent sample plots of 31.5m× 45 mduring 2013–2014.Results: We found that the effects of increasing harvesting intensity on plant diversity changed from negative topositive (and from nonlinear to more linear responses) with increasing site productivity. Harvesting intensityshowed contrasting effects on variables related to fire protection ecosystem service, since it reduced fuel amount(potentially reducing fire spread) but also reduced live fuel moisture content (potentially increasing flammability) atthe three sites. Two variables related to soil formation and protection ES, leaf litter cover and aerial soil cover,decreased with harvesting intensity at the three sites.Conclusions: We conclude that shrubland management for firewood production may enhance biodiversity withoutcompromising certain important ES. The intensity of harvesting should be determined according to site conditionsand forecasted impacts on biodiversity, fire and soil formation and protection.

Foraging behavior related to habitat characteristics in the invasive wasp Vespula germanica

When foraging on carrion resources, the wasp Vespula germanica usually makes repeated visits to the feeding site until depleting the resource. In the present study we analyzed how environmental cues affect wasps＇ behavior when re-locating a protein food source. We studied this behavior in two different natural habitats： closed and open habitats. As closed habitats have more references to orient wasps to the feeding site than open habitats, we hypothesized that they would return to the foraging site more frequently in closed habitats than in open ones. We tested this hypothesis by studying wasp behavior in three different natural habitat conditions： （i） closed habitats, （ii） open habitats, and （iii） open habitats artificially modified by adding five sticks with flagging. Experiments consisted of training individual wasps to feed from a certain array, and at the testing phase we removed food and displaced the array by 60 cm. Therefore, we recorded wasps＇ choices when returning to the training area, by counting both the wasps＇ first approaches and the number of visits to the original feeding site and the displaced array. Wasps＇ behavior while re-locating a protein food source was different if foraging at open or closed habitats. Wasps more frequently re- visited a previous feeding location when foraging in closed habitats than when foraging in open ones. Furthermore, wasps more frequently visited the displaced array than the original feeding site in all three treatments. Nevertheless, when wasps were trained in closed habitats, they returned to the original feeding site more frequently than if trained in open ones. Interestingly, when five sticks with flagging were added in open habitats, wasps responded similarly as in closed habitats without these references. The results show that foraging behavior in V. germanica seems to be different in closed and open habitats, probably associated with the existence of references that guide foragers when re-locating undepleted resources

How behavioral plasticity enables foraging under changing environmental conditions in the social wasp Vespula germanica (Hymenoptera: Vespidae)

The foraging strategy at abundant resources of the social wasp Vespula germanica includes scanning in the direction of the nest while memorizing resource-specific landmarks and contextual cues.In the present study,we sought to explore wasps'behavioral plasticity on foraging trips to resources whose location and composition changed after a single visit.We evaluated how contextual modifications of food displacement and replacements 60 cm apart from the original site,affect re-orientation for re-finding previously memorized food resources.The results showed that wasps detected and collected the resource faster when more changes were introduced on the following visit.If returning foragers discovered several modifications on both the location and the kind of resource,they collected food more rapidly from the displaced dish,than if only a single parameter in the environment had been changed.These findings illustrate the grade of behavioral plasticity in V.germanica while foraging on abundant resources,which may contribute to the understanding of the prodigious invasive success of this species in anthropized environments.

Cattle change plant reproductive phenology,promoting community changes in a post-fire Nothofagus forest in northern Patagonia,Argentina

Aims Variations in rates and length of flowering and fruiting not only affect the reproduction of a given plant species but also the behavior and reproduction of associated taxa.Flowering and fruiting variations may be influenced by herbivory,especially by large mammals.The aim of this study was to determine the effects of cattle browsing on the reproductive phenology of understory species in a subalpine post-fire Nothofagus forest in Patagonia.Methods The effects of herbivory on plant reproductive phenology were studied in a set of experimental exclosures(fenced plots)installed since 2001 in a post-fire N.pumilio forest,located in Nahuel Huapi National Park(NHNP),Argentina.We monitored the beginning and duration of each reproductive phenological stage:floral bud,open flower,immature fruit and mature fruit.We also counted the number of flowers,fruits,seeds and viable seeds of the dominant plants to assess whether browsing modifies temporal patterns of the flowering and fruiting periods.Important Findings Cattle reduced the total number of species flowering and fruiting and changed the reproductive phenology of some species.We found that palatable species seem to be negatively affected by browsing in terms of reduced fitness due to changes in flowering and fruiting periods.In contrast,cattle benefitted the reproduction of non-palatable species and could promote the invasion of shade-intolerant exotic forbs such as Cirsium vulgare.The effects of livestock reported in this study are important to understanding how browsing could alter native species establishment and possibly alter successional trajectories during recolonization after fire.

Evidence of associative blocking during foraging in the social wasp Vespula germanica

While foraging,Vespula germanica usually return to abundant food sites.During this relocation behavior,these wasps learn to identify contextual cues associated with food position.We analyzed associative blocking in this species,that is,how an association with a conditioned stimulus(CS1)blocks subsequent learning when a novel stimulus(CS2)is added on a second foraging visit.Three groups of wasps(A,B,and C;total 74 individual wasps)were observed while collecting meat during one or two consecutive visits.In group A,an environmental cue(CS1)was paired with food placed at a specific site,and on the second visit,a second cue(CS2)was added while food remained in the same position.In a subsequent testing phase,CS1 was removed and the food source displaced nearby.We then recorded the number of hovers performed over the empty dish(previously baited).Group A wasps appeared to ignore the addition of CS2 on their second visit because they performed fewer hovers over the learned site.For group A,the duration of the decision-making process to finally fly toward the baited dish was shorter than when CS1 and CS2 were presented together on their first visit(group B).This is the first study to demonstrate the occurrence of associative blocking in vespids,confirming that a prior foraging experience influences subsequent food relocation in V.germanica.Our findings reveal that first learning episodes block further associations with novel contextual cues,contributing to understanding of complex cognitive processes involved in V.germanica´s foraging behavior.

Phenotypic plasticity in Drosophila cactophilic species the effect of competition, density, and breeding sites

Changes in the environmental conditions experienced by naturally occurring populations are frequently accompanied by changes in adaptive traits allowing the organ- ism to cope with environmental unpredictability. Phenotypic plasticity is a major aspect of adaptation and it has been involved in population dynamics of interacting species. In this study, phenotypic plasticity （i,e., environmental sensitivity） of morphological adap- tive traits were analyzed in the cactophilic species Drosophila buzzatii and Drosophila koepferae （Diptera： Drosophilidae） considering the effect of crowding conditions （low and high density）, type of competition （intraspecific and interspecific competition） and cacti hosts （Opuntia and Columnar cacti）. All traits （wing length, wing width, thorax length, wing loading and wing aspect） showed significant variation for each environmental factor considered in both Drosophila species. The phenotypic plasticity pattern observed for each trait was different within and between these cactopbilic Drosophila species depending on the environmental factor analyzed suggesting that body size-related traits respond almost independently to environmental heterogeneity. The effects of ecological factors analyzed in this study are discussed in order to elucidate the causal factors investigated （type of com- petition, crowding conditions and alternative host） affecting the election of the breeding site and/or the range of distribution of these cactophilic species.