Reproductive trait differences drive offspring production in urban cavity‐nesting bees and wasps

The contrasting and idiosyncratic changes in biodiversity that have been documented across urbanization gradients call for a more mechanistic understanding of urban community assembly. The reproductive success of organisms in cities should underpin their population persistence and the maintenance of biodiversity in urban landscapes. We propose that exploring individual‐level reproductive traits and environmental drivers of reproductive success could provide the necessary links between environmental conditions, offspring production, and biodiversity in urban areas. For 3 years, we studied cavity‐nesting solitary bees and wasps in four urban green space types across Toronto, Canada. We measured three reproductive traits of each nest: the total number of brood cells, the proportion of parasite‐free cells, and the proportion of non‐emerged brood cells that were parasite‐free. We determined (a) how reproductive traits, trait diversity and offspring production respond to multiple environmental variables and (b) how well reproductive trait variation explains the offspring production of single nests, by reflecting the different ways organisms navigate trade‐offs between gathering of resources and exposure to parasites. Our results showed that environmental variables were poor predictors of mean reproductive trait values, trait diversity, and offspring production. However, offspring production was highly positively correlated with reproductive trait evenness and negatively correlated with trait richness and divergence. This suggests that a narrow range of reproductive traits are optimal for reproduction, and the even distribution of individual reproductive traits across those optimal phenotypes is consistent with the idea that selection could favor diverse reproductive strategies to reduce competition. This study is novel in its exploration of individual‐level reproductive traits and its consideration of multiple axes of urbanization. Reproductive trait variation did not follow previously reported biodiversity‐urbanization patterns; the insensitivity to urbanization gradients raise questions about the role of the spatial mosaic of habitats in cities and the disconnections between different metrics of biodiversity.     

Preliminary assessment of cavity‐nesting Hymenopterans in a low‐intensity agricultural landscape in Transylvania

In this study, our aim was to assess several traits of cavity‐nesting Hymenopteran taxa in a low‐intensity agricultural landscape in Transylvania. The study took place between May and August 2018 at eight study sites in the hilly mountainous central part of Romania, where the majority of the landscape is used for extensive farming or forestry. During the processing of the trap nest material, we recorded several traits regarding the nests of different cavity‐nesting Hymenopteran taxa and the spider prey found inside the nests of the spider‐hunting representatives of these taxa. We also evaluated the relationship between the edge density and proportion of low‐intensity agricultural areas surrounding the study sites and some of these traits.The majority of nests were built by the solitary wasp genus Trypoxylon, followed by the solitary wasp taxa Dipogon and Eumeninae. Solitary bees were much less common, with Hylaeus being the most abundant genus. In the nests of Trypoxylon, we mostly found spider prey from the family of Araneidae, followed by specimens from the families of Linyphiidae and Theridiidae. In the nests of Dipogon, we predominantly encountered spider prey from the family of Thomisidae. We found significant effects of low‐intensity agricultural areas for the genera of Auplopus, Megachile, Osmia, and the Thomisid prey of Dipogon. We also found that the spider prey of Trypoxylon was significantly more diverse at study sites with higher proportions of low‐intensity agricultural areas.Our results indicate that solitary bees seem to be more abundant in areas, where the influence of human activities is stronger, while solitary wasps seem to rather avoid these areas. Therefore, we suggest that future studies not only should put more effort into sampling in low‐intensity agricultural landscapes but also focus more on solitary wasp taxa, when sampling such an area.     

Trait coordination and environmental filters shape functional trait distributions of forest understory herbs

1. Understanding the drivers of trait selection is critical for resolving community assembly processes. Here, we test the importance of environmental filtering and trait covariance for structuring the functional traits of understory herbaceous communities distributed along a natural environmental resource gradient that varied in soil moisture, temperature, and nitrogen availability, produced by different topographic positions in the southern Appalachian Mountains.
2. To uncover potential differences in community‐level trait responses to the resource gradient, we quantified the averages and variances of both abundance‐weighted and unweighted values for six functional traits (vegetative height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, and leaf δ¹³C) using 15 individuals of each of the 108 species of understory herbs found at two sites in the southern Appalachians of western North Carolina, USA.
3. Environmental variables were better predictors of weighted than unweighted community‐level average trait values for all but height and leaf N, indicating strong environmental filtering of plant abundance. Community‐level variance patterns also showed increased convergence of abundance‐weighted traits as resource limitation became more severe.
4. Functional trait covariance patterns based on weighted averages were uniform across the gradient, whereas coordination based on unweighted averages was inconsistent and varied with environmental context. In line with these results, structural equation modeling revealed that unweighted community‐average traits responded directly to local environmental variation, whereas weighted community‐average traits responded indirectly to local environmental variation through trait coordination.
5. Our finding that trait coordination is more important for explaining the distribution of weighted than unweighted average trait values along the gradient indicates that environmental filtering acts on multiple traits simultaneously, with abundant species possessing more favorable combinations of traits for maximizing fitness in a given environment.

     

Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas,India

1. We investigated some aspects of hawkmoth community assembly at 13 elevations along a 200‐ to 2770‐m transect in the eastern Himalayas, a little studied biodiversity hot spot of global importance. We measured the morphological traits of body mass, wing loading, and wing aspect ratio of 3,301 free‐ranging individuals of 76 species without having to collect or even constrain them. We used these trait measurements and T‐statistic metrics to assess the strength of intracommunity (“internal") and extra‐community (“external”) filters which determine the composition of communities vis‐a‐vis the regional pool of species.
2. The trait distribution of constituent species turned out to be nonrandom subsets of the community‐trait distribution, providing strong evidence for internal filtering in all elevational communities. The external filter metric was more ambiguous. However, the elevational dependence of many metrics including that of the internal filter provided evidence for external (i.e., environmental) filtering. On average, a species occupied as much as 50%–75% of the total community‐trait space, yet the T‐statistic metric for internal filter was sufficiently sensitive to detect a strong nonrandom structure in the trait distribution.
3. We suggest that the change in T‐statistic metrics along the environmental gradient may provide more clues to the process of community assembly than previously envisaged. A large, smoothly varying and well‐sampled environmental span would make it easier to discern them. Developing T‐statistics for combined analysis of multiple traits will perhaps provide a more accurate picture of internal/filtering and niche complementarity. Moths are a hyperdiverse taxon and a very important component of many ecosystems. Our technique for accurately measuring body and wing dimensions of free‐ranging moths can generate trait database for a large number of individuals in a time‐ and resource‐efficient manner for a variety of community assembly studies using this important taxon.

     

Differences in functional trait responses to elevation among feeding guilds of Aculeata community

The response of communities to environmental change is expected to vary among feeding guilds. To evaluate the response of guilds to environmental factors without considering the taxonomic specificities, it is useful to examine Aculeata bees and wasps, which consist of closely related taxa including different guilds, pollinators, predators, and parasitoids. In this study, we evaluated changes in species diversity (SD) and functional traits of each feeding guild along an elevational gradient in a boreal forest in northern Japan. We used yellow pan traps to collect Aculeata bees and wasps at 200–1600 m above sea level. We investigated six functional traits (trophic level, seasonal duration, body size, elevational range, nesting position, and soil dependency) and the horizontal distribution of the species. The SD of all Aculeata, predators, and parasitoids decreased with an increase in elevation; however, the SD of pollinators did not show any specific trend. Although the functional trait composition of all Aculeata species did not show any trend, that of each feeding guild responded to elevation in different ways. Pollinators increased in body size and showed a decrease in seasonal duration with increasing elevation, suggesting that tolerance and seasonal escape from physical stress at high elevations are important for shaping pollinator communities. Predators increased their elevational range and the proportion of above‐ground nesting species increased with increasing elevation, suggesting that the ability to live in a wider range of environments and avoid unsuitable soil environments at high elevations might be important. Parasitoids changed their hosts and displayed variable traits with increasing elevation, suggesting that brood parasitoids have difficulty in surviving at high elevation. The traits for each guild responded in different ways, even if they were dominated by the same environmental factors. Our findings imply that differences in the responses of functional traits would produce different community assembly patterns in different guilds during further climate change.     

Trait hierarchies are stronger than trait dissimilarities in structuring spatial co‐occurrence patterns of common tree species in a subtropical forest

1. The dissimilarity and hierarchy of trait values that characterize niche and fitness differences, respectively, have been increasingly applied to infer mechanisms driving community assembly and to explain species co‐occurrence patterns. Here, we predict that limiting similarity should result in the spatial segregation of functionally similar species, while functionally similar species will be more likely to co‐occur either due to environmental filtering or due to competitive exclusion of inferior competitors (hereafter hierarchical competition).
2. We used a fully mapped 50‐ha subtropical forest plot in southern China to explore how pairwise spatial associations between saplings and between adult trees were influenced by trait dissimilarity and hierarchy in order to gain insight into assembly mechanisms. We assessed pairwise spatial associations using two summary statistics of spatial point patterns at different spatial scales and compared the effects of trait dissimilarity and trait hierarchy of different functional traits on the interspecific spatial associations. These comparisons allow us to disentangle the effects of limiting similarity, environmental filtering, and hierarchical competition on species co‐occurrence.
3. We found that trait dissimilarity was generally negatively related to interspecific spatial associations for both saplings and adult trees across spatial scales, meaning that species with similar trait values were more likely to co‐occur and thus supporting environmental filtering or hierarchical competition. We further found that trait hierarchy outweighed trait dissimilarity in structuring pairwise spatial associations, suggesting that hierarchical competition played a more important role in structuring our forest community than environmental filtering across life stages.
4. This study employed a novel method, by offering the integration of pairwise spatial association and trait dissimilarity as well as trait hierarchy, to disentangle the relative importance of multiple assembly mechanisms in structuring co‐occurrence patterns, especially the mechanisms of environmental filtering and hierarchical competition, which lead to indistinguishable co‐occurrence patterns. This study also reinforced the importance of trait hierarchy rather than trait dissimilarity in driving neighborhood competition.

     

Size‐dependent and environment‐mediated shifts in leaf traits of a deciduous tree species in a subtropical forest

AimsUnderstanding the joint effects of plant development and environment on shifts of intraspecific leaf traits will advance the understandings of the causes of intraspecific trait variation. We address this question by focusing on a widespread species Clausena dunniana in a subtropical broad‐leaved forest.MethodsWe sampled 262 individuals of C. dunniana at two major topographic habitat types, the slope and hilltop, within the karst forests in Maolan Nature Reserve in southwestern China. We measured individual plant level leaf traits (i.e., specific leaf area (SLA), leaf area, leaf dry‐matter content (LDMC), and leaf thickness) that are associated with plant resource‐use strategies. We adopted a linear mixed‐effects model in which the plant size (i.e., the first principal component of plant basal diameter and plant height) and environmental factors (i.e., topographic habitat, canopy height, and rock‐bareness) were used as independent variables, to estimate their influences on the shifts of leaf traits.Key ResultsWe found that (1) plant size and the environmental factors independently drove the intraspecific leaf trait shifts of C. dunniana, of which plant size explained less variances than environmental factors. (2) With increasing plant size, C. dunniana individuals had increasingly smaller SLA but larger sized leaves. (3) The most influential environmental factor was topographic habitat; it drove the shifts of all the four traits examined. Clausena dunniana individuals on hilltops had leaf traits representing more conservative resource‐use strategies (e.g., smaller SLA, higher LDMC) than individuals on slopes. On top of that, local‐scale environmental factors further modified leaf trait shifts.ConclusionsPlant size and environment independently shaped the variations in intraspecific leaf traits of C. dunniana in the subtropical karst forest of Maolan. Compared with plant size, the environment played a more critical role in shaping intraspecific leaf trait variations, and potentially also the underlying individual‐level plant resource‐use strategies.     

Bee Tracker—an open‐source machine learning‐based video analysis software for the assessment of nesting and foraging performance of cavity‐nesting solitary bees

The foraging and nesting performance of bees can provide important information on bee health and is of interest for risk and impact assessment of environmental stressors. While radiofrequency identification (RFID) technology is an efficient tool increasingly used for the collection of behavioral data in social bee species such as honeybees, behavioral studies on solitary bees still largely depend on direct observations, which is very time‐consuming. Here, we present a novel automated methodological approach of individually and simultaneously tracking and analyzing foraging and nesting behavior of numerous cavity‐nesting solitary bees. The approach consists of monitoring nesting units by video recording and automated analysis of videos by machine learning‐based software. This Bee Tracker software consists of four trained deep learning networks to detect bees that enter or leave their nest and to recognize individual IDs on the bees’ thorax and the IDs of their nests according to their positions in the nesting unit. The software is able to identify each nest of each individual nesting bee, which permits to measure individual‐based measures of reproductive success. Moreover, the software quantifies the number of cavities a female enters until it finds its nest as a proxy of nest recognition, and it provides information on the number and duration of foraging trips. By training the software on 8 videos recording 24 nesting females per video, the software achieved a precision of 96% correct measurements of these parameters. The software could be adapted to various experimental setups by training it according to a set of videos. The presented method allows to efficiently collect large amounts of data on cavity‐nesting solitary bee species and represents a promising new tool for the monitoring and assessment of behavior and reproductive success under laboratory, semi‐field, and field conditions.     

Urban living influences the nesting success of Darwin’s finches in the Galápagos Islands

Urbanization is expanding worldwide with major consequences for organisms. Anthropogenic factors can reduce the fitness of animals but may have benefits, such as consistent human food availability. Understanding anthropogenic trade‐offs is critical in environments with variable levels of natural food availability, such as the Galápagos Islands, an area of rapid urbanization. For example, during dry years, the reproductive success of bird species, such as Darwin''s finches, is low because reduced precipitation impacts food availability. Urban areas provide supplemental human food to finches, which could improve their reproductive success during years with low natural food availability. However, urban finches might face trade‐offs, such as the incorporation of anthropogenic debris (e.g., string, plastic) into their nests, which may increase mortality. In our study, we determined the effect of urbanization on the nesting success of small ground finches (Geospiza fuliginosa; a species of Darwin''s finch) during a dry year on San Cristóbal Island. We quantified nest building, egg laying and hatching, and fledging in an urban and nonurban area and characterized the anthropogenic debris in nests. We also documented mortalities including nest trash‐related deaths and whether anthropogenic materials directly led to entanglement‐ or ingestion‐related nest mortalities. Overall, urban finches built more nests, laid more eggs, and produced more fledglings than nonurban finches. However, every nest in the urban area contained anthropogenic material, which resulted in 18% nestling mortality while nonurban nests had no anthropogenic debris. Our study showed that urban living has trade‐offs: urban birds have overall higher nesting success during a dry year than nonurban birds, but urban birds can suffer mortality from anthropogenic‐related nest‐materials. These results suggest that despite potential costs, finches benefit overall from urban living and urbanization may buffer the effects of limited resource availability in the Galápagos Islands.     

Identifying the sister group to the bees: a molecular phylogeny of Aculeata with an emphasis on the superfamily Apoidea

Debevec, AH., Cardinal, S & Danforth, BN. Identifying the sister group to the bees: a molecular phylogeny of Aculeata with an emphasis on the superfamily Apoidea. —Zoologica Scripta, 41, 527–535. The hymenopteran superfamily Apoidea includes the bees (Anthophila) as well as four predatory wasp families (Heterogynaidae, Ampulicidae, Sphecidae and Crabronidae) collectively referred to as the “sphecoid” or “apoid” wasps. The most widely cited studies suggest that bees are sister to the wasp family Crabronidae, but alternative hypotheses have been proposed based on both morphological and molecular data. We combined DNA sequence data from previously published studies and newly generated data for four nuclear genes (28S, long‐wavelength rhodopsin, elongation factor‐1α and wingless) to identify the likely sister group to the bees. Analysis of our four‐gene data set by maximum likelihood and Bayesian methods indicates that bees most likely arise from within a paraphyletic Crabronidae. Possible sister groups to the bees include Philanthinae, Pemphredoninae or Philanthinae + Pemphredoninae. We used Bayesian methods to explore the robustness of our results. Bayes Factor tests strongly rejected the hypotheses of crabronid monophyly as well as placement of Heterogynaidae within Crabronidae. Our results were also stable to alternative rootings of the bees. These findings provide additional support for the hypothesis that bees arise from within Crabronidae, rather than being sister to Crabronidae, thus altering our understanding of bee ancestry and evolutionary history.     

Potential local adaptation in populations of invasive reed canary grass (Phalaris arundinacea) across an urbanization gradient

Urban stressors represent strong selective gradients that can elicit evolutionary change, especially in non‐native species that may harbor substantial within‐population variability. To test whether urban stressors drive phenotypic differentiation and influence local adaptation, we compared stress responses of populations of a ubiquitous invader, reed canary grass (Phalaris arundinacea). Specifically, we quantified responses to salt, copper, and zinc additions by reed canary grass collected from four populations spanning an urbanization gradient (natural, rural, moderate urban, and intense urban). We measured ten phenotypic traits and trait plasticities, because reed canary grass is known to be highly plastic and because plasticity may enhance invasion success. We tested the following hypotheses: (a) Source populations vary systematically in their stress response, with the intense urban population least sensitive and the natural population most sensitive, and (b) plastic responses are adaptive under stressful conditions. We found clear trait variation among populations, with the greatest divergence in traits and trait plasticities between the natural and intense urban populations. The intense urban population showed stress tolerator characteristics for resource acquisition traits including leaf dry matter content and specific root length. Trait plasticity varied among populations for over half the traits measured, highlighting that plasticity differences were as common as trait differences. Plasticity in root mass ratio and specific root length were adaptive in some contexts, suggesting that natural selection by anthropogenic stressors may have contributed to root trait differences. Reed canary grass populations in highly urbanized wetlands may therefore be evolving enhanced tolerance to urban stressors, suggesting a mechanism by which invasive species may proliferate across urban wetland systems generally.     

Monitoring of tube‐nesting bees and wasps with bamboo tube nest traps of different types in two types of forests in temperate Japan

Tube‐nesting bees and wasps were collected with bamboo tube nest traps in a cherry blossom forest and an old secondary forest in Tama Forest Science Garden in the western suburbs of Tokyo. Curtain type traps, in which bamboo tubes were vertically arranged, attracted more bees and wasps to nests than bundle type traps, in which bamboo tubes were bundled haphazardly. The attractiveness of small tubes was similar between small tube traps, which were only composed of small tubes (about 4 mm in diameter), and size mixture traps, which set small tubes together with larger tubes, indicating that the presence of the larger species did not affect the nesting of small species. In the cherry forest, which was characterized by the sparse distribution of deciduous cherry trees with a thin canopy layer and rich growth of weeds, Megachilidae, Colletidae, Sphecidae and Eumenidae were common. In the shady secondary forest, where evergreen trees (Abies firma Sieb. et Zucc., Quercus glauca Thunb.) and shrubs (Aucuba japonica Thunb., Eurya japonica Thunb., Camellia japonica L.) were prevalent, Pompilidae was abundant. Among five species of Crabronidae recorded in this study, four were collected mostly in the cherry forest, whereas the most abundant, Trypoxylon malaisei Gussakovskij, was also common in the secondary forest. Likewise, Auplopus carbonarius (Scopoli) (Pompilidae) was common in the secondary forest and not rare in the cherry forest. These results suggest that the tube‐nesting bees and wasps can be a good bioindicator for monitoring environment.     

Individual variation in feeding morphology,not diet,can facilitate the success of generalist species in urban ecosystems

Generalist species dominate urban ecosystems. The success of urban generalists is often related to a plastic diet and feeding traits that allow them to take advantage of a variety of food resources provided by humans in cities. The classification of a species as a generalist is commonly based on mean estimates of diet‐ and feeding‐related traits. However, there is increasing evidence that a generalist population can consist of individual specialists. In such cases, estimates based on mean can hide important individual variation that can explain trophic ecology and the success of urban dwellers. Here, we focus on guppies, Poecilia reticulata, a widespread alien fish species which has invaded both urban and non‐urban systems, to explore the effect of urbanization on individual diet and feeding morphology (cranium shape). Our results show that guppies in urban and non‐urban populations are not individual specialists, having a similar generalist diet despite the high population density. However, there is important individual variation in cranium shape which allow urban guppies to feed more efficiently on highly nutritious food. Our data suggest that individual variation in feeding efficiency can be a critical overlooked trait that facilitates the success of urban generalists.     

Enhancing flowering plant functional richness improves wild bee diversity in vineyard inter‐rows in different floral kingdoms

Wild bees are threatened by multiple interacting stressors, such as habitat loss, land use change, parasites, and pathogens. However, vineyards with vegetated inter‐rows can offer high floral resources within viticultural landscapes and provide foraging and nesting habitats for wild bees. Here, we assess how vineyard management regimes (organic vs. conventional; inter‐row vegetation management) and landscape composition determine the inter‐row plant and wild bee assemblages, as well as how these variables relate to functional traits in 24 Austrian and 10 South African vineyards. Vineyards had either permanent vegetation cover in untilled inter‐rows or temporary vegetation cover in infrequently tilled inter‐rows. Proportion of seminatural habitats (e.g., fallows, grassland, field margins) and woody structures (e.g., woodlots, single trees, tree rows) were used as proxies for landscape composition and mapped within 500‐m radius around the study vineyards. Organic vineyard management increased functional richness (FRic) of wild bees and flowering plants, with woody structures marginally increasing species richness and FRic of wild bees. Wild bee and floral traits were differently associated across the countries. In Austria, several bee traits (e.g., lecty, pollen collection type, proboscis length) were associated with flower color and symmetry, while in South African vineyards, only bees’ proboscis length was positively correlated with floral traits characteristic of Asteraceae flowers (e.g., ray–disk morphology, yellow colors). Solitary bee species in Austria benefitted from infrequent tillage, while ground nesting species preferred inter‐rows with undisturbed soils. Higher proportions of woody structures in surrounding landscapes resulted in less solitary and corbiculate bees in Austria, but more aboveground nesting species in South Africa. In both countries, associations between FRic of wild bees and flowering plants were positive both in organic and in conventional vineyards. We recommend the use of diverse cover crop seed mixtures to enhance plant flowering diversity in inter‐rows, to increase wild bee richness in viticultural landscapes.     

Remotely sensed between‐individual functional trait variation in a temperate forest

1. Trait‐based ecology holds the promise to explain how plant communities work, for example, how functional diversity may support community productivity. However, so far it has been difficult to combine field‐based approaches assessing traits at the level of plant individuals with limited spatial coverage and approaches using remote sensing (RS) with complete spatial coverage but assessing traits at the level of vegetation pixels rather than individuals. By delineating all individual‐tree crowns within a temperate forest site and then assigning RS‐derived trait measures to these trees, we combine the two approaches, allowing us to use general linear models to estimate the influence of taxonomic or environmental variation on between‐ and within‐species variation across contiguous space.
2. We used airborne imaging spectroscopy and laser scanning to collect individual‐tree RS data from a mixed conifer‐angiosperm forest on a mountain slope extending over 5.5 ha and covering large environmental gradients in elevation as well as light and soil conditions. We derived three biochemical (leaf chlorophyll, carotenoids, and water content) and three architectural traits (plant area index, foliage‐height diversity, and canopy height), which had previously been used to characterize plant function, from the RS data. We then quantified the contributions of taxonomic and environmental variation and their interaction to trait variation and partitioned the remaining within‐species trait variation into smaller‐scale spatial and residual variation. We also investigated the correlation between functional trait and phylogenetic distances at the between‐species level. The forest consisted of 13 tree species of which eight occurred in sufficient abundance for quantitative analysis.
3. On average, taxonomic variation between species accounted for more than 15% of trait variation in biochemical traits but only around 5% (still highly significant) in architectural traits. Biochemical trait distances among species also showed a stronger correlation with phylogenetic distances than did architectural trait distances. Light and soil conditions together with elevation explained slightly more variation than taxonomy across all traits, but in particular increased plant area index (light) and reduced canopy height (elevation). Except for foliage‐height diversity, all traits were affected by significant interactions between taxonomic and environmental variation, the different responses of the eight species to the within‐site environmental gradients potentially contributing to the coexistence of the eight abundant species.
4. We conclude that with high‐resolution RS data it is possible to delineate individual‐tree crowns within a forest and thus assess functional traits derived from RS data at individual level. With this precondition fulfilled, it is then possible to apply tools commonly used in field‐based trait ecology to partition trait variation among individuals into taxonomic and potentially even genetic variation, environmental variation, and interactions between the two. The method proposed here presents a promising way of assessing individual‐based trait information with complete spatial coverage and thus allowing analysis of functional diversity at different scales. This information can help to better understand processes shaping community structure, productivity, and stability of forests.

     

Functional assembly of tropical montane tree islands in the Atlantic Forest is shaped by stress tolerance,bamboo presence,and facilitation

AimsAmidst the Campos de Altitude (Highland Grasslands) in the Brazilian Atlantic Forest, woody communities grow either clustered in tree islands or interspersed within the herbaceous matrix. The functional ecology, diversity, and biotic processes shaping these plant communities are largely unstudied. We characterized the functional assembly and diversity of these tropical montane woody communities and investigated how they fit within Grime''s CSR (C—competitor, S—stress‐tolerant, R—ruderal) scheme, what functional trade‐offs they exhibit, and how traits and functional diversity vary in response to bamboo presence/absence.MethodsTo characterize the functional composition of the community, we sampled five leaf traits and wood density along transects covering the woody communities both inside tree islands and outside (i.e., isolated woody plants in the grasslands community). Then, we used Mann–Whitney test, t test, and variation partitioning to determine the effects of inside versus outside tree island and bamboo presence on community‐weighted means, woody species diversity, and functional diversity.ResultsWe found a general SC/S strategy with drought‐related functional trade‐offs. Woody plants in tree islands had more acquisitive traits than those within the grasslands. Trait variation was mostly taxonomically than spatially driven, and species composition varied between inside and outside tree islands. Leaf thickness, wood density, and foliar water uptake were unrelated to CSR strategies, suggesting independent trait dimensions and multiple drought‐coping strategies within the predominant S strategy. Islands with bamboo presence showed lower Simpson diversity, lower functional dispersion, lower foliar water uptake, and greater leaf thickness than in tree islands without bamboo.ConclusionsThe observed functional assembly hints toward large‐scale environmental abiotic filtering shaping a stress‐tolerant community strategy, and small‐scale biotic interactions driving small‐scale trait variation. We recommend experimental studies with fire, facilitation treatments, ecophysiological and recruitment traits to elucidate on future tree island expansion and community response to climate change.     

Adjustments in physiological and morphological traits suggest drought‐induced competitive release of some California plants

Drought and competition affect how morphological and physiological traits are expressed in plants. California plants were previously found to respond less negatively to resource limitation compared to invasive counterparts. In a glasshouse in Santa Cruz, CA, USA, we exposed five native California C₃ grassland species to episodic drought and competition (via five locally invasive species). We hypothesized that leaf morphology would be more affected by competition, and leaf photosynthetic gas exchange more so by drought, consistent with optimal partitioning and environmental filter theories. We expected that traits would exhibit trade‐offs along a spectrum for resource conservatism versus acquisition. Bromus carinatus had greater photosynthetic recovery, while Diplacus aurantiacus had lower percent loss of net assimilation (PLA) and intrinsic water‐use efficiency (iWUE) during drought and competition simultaneously compared to just drought. Stipa pulchra and Sidalcea malviflora gas exchange was unaffected by drought, and leaf morphology exhibited drought‐related adjustments. Lupinus nanus exhibited trait adjustments for competition but not drought. Functional traits sorted onto two principal components related to trade‐offs for resource conservatism versus acquisition, and for above‐ versus belowground allocation. In summary, morphological traits were affected by competition and drought, whereas physiological traits, like leaf gas exchange, were primarily affected by drought. The grassland plants we studied showed diverse responses to drought and competition with trait trade‐offs related to resource conservatism versus acquisition, and for above‐ versus belowground allocation consistent with optimal partitioning and environmental filter theories. Diplacus aurantiacus experienced competitive release based on greater iWUE and lower PLA when facing drought and competition.     

Use of human-made nesting structures by wild bees in an urban environment

Most bees display an array of strategies for building their nests, and the availability of nesting resources plays a significant role in organizing bee communities. Although urbanization can cause local species extinction, many bee species persist in urbanized areas. We studied the response of a bee community to winter-installed human-made nesting structures (bee hotels and soil squares, i.e. 0.5 m deep holes filled with soil) in urbanized sites. We investigated the colonization pattern of these structures over two consecutive years to evaluate the effect of age and the type of substrates (e.g. logs, stems) provided on colonization. Overall, we collected 54 species. In the hotels, two gregarious species, Osmia bicornis L. and O. cornuta Latr. dominated the community (over 87 % of the data). Over 2 years, the age of the soil squares did not affect their level of colonization and the same was true for the hotels with respect to O. bicornis and ‘other species’. However, O. cornuta occurred less often and raised fewer descendants in 1-year old hotels than in new ones. Bee nesting was not affected by the soil texture and, among above-ground nesting bees, only O. bicornis showed a preference for some substrates, namely Acer sp. and Catalpa sp. In a context of increasing urbanization and declining bee populations, much attention has focused upon improving the floral resources available for bees, while little effort has been paid to nesting resources. Our results indicate that, in addition to floral availability, nesting resources should be taken into account in the development of urban green areas to promote a diverse bee community.     

Depicting the phenotypic space of the annual plant Diplotaxis acris in hyperarid deserts

The phenotypic space encompasses the assemblage of trait combinations yielding well‐suited integrated phenotypes. At the population level, understanding the phenotypic space structure requires the quantification of among‐ and within‐population variations in traits and the correlation pattern among them. Here, we studied the phenotypic space of the annual plant Diplotaxis acris occurring in hyperarid deserts. Given the advance of warming and aridity in vast regions occupied by drylands, D. acris can indicate the successful evolutionary trajectory that many other annual plant species may follow in expanding drylands. To this end, we conducted a greenhouse experiment with 176 D. acris individuals from five Saudi populations to quantify the genetic component of variation in architectural and life history traits. We found low among‐population divergence but high among‐individual variation in all traits. In addition, all traits showed a high degree of genetic determination in our study experimental conditions. We did not find significant effects of recruitment and fecundity on fitness. Finally, all architectural traits exhibited a strong correlation pattern among them, whereas for life history traits, only higher seed germination implied earlier flowering. Seed weight appeared to be an important trait in D. acris as individuals with heavier seeds tended to advance flowering and have a more vigorous branching pattern, which led to higher fecundity. Population divergence in D. acris might be constrained by the severity of the hyperarid environment, but populations maintain high among‐individual genetic variation in all traits. Furthermore, D. acris showed phenotypic integration for architectural traits and, to a lesser extent, for life history traits. Overall, we hypothesize that D. acris may be fine‐tuned to its demanding extreme environments. Evolutionary speaking, annual plants facing increasing warming, aridity, and environmental seasonality might modify their phenotypic spaces toward new phenotypic configurations strongly dominated by correlated architectural traits enhancing fecundity and seed‐related traits advancing flowering time.     

Adult insect personality in the wild—Calopteryx splendens as a model for field studies

Animal personality has received increasing interest and acknowledgment within ecological research over the past two decades. However, some areas are still poorly studied and need to be developed. For instance, field studies focused on invertebrates are currently highly underrepresented in the literature. More studies including a wider variety of traits measured and species tested are needed to improve our understanding of trait‐correlation patterns and generalities. We studied nine behavioral traits, in the damselfly Calopteryx splendens, from an array of three experiments: (i) courtship, (ii) aggressiveness, and (iii) boldness, and calculated their repeatability. The behaviors were measured twice in two different contexts: (i) undisturbed territory and (ii) partially deteriorated territory. Traits related to courtship and boldness were all repeatable across the two contexts. Among aggressive behaviors, only one trait (number of hits) was repeatable. This work demonstrates, for the first time, the presence of within‐population personality differences in an adult damselfly in the wild. We further propose C. splendens as a promising model species for testing personality in the wild under highly controlled environmental conditions.