Altitudinal, temporal and trophic partitioning of flower-visitors in Alpine communities

Strong habitat and seasonal phenology effects on the evolution of self-compatibility, clonality and pollinator shifts in Lachenalia (Asparagaceae: Scilloideae)

Plants employ a diversity of reproductive safeguarding strategies to circumvent the challenge of pollen limitation. Focusing on southern African Lachenalia (Asparagaceae: Scilloideae), we test the hypothesis that the evolution of reproductive safeguarding traits (self-compatibility, autonomous selfing, bird pollination and clonal propagation) is favoured in species occupying conditions of low insect abundance imposed by critically infertile fynbos heathland vegetation and by flowering outside the austral spring insect abundance peak. We trace the evolution of these traits and selective regimes on a dated, multi-locus phylogeny of Lachenalia and assess their evolutionary associations using ordinary and phylogenetic regression. Ancestral state reconstructions identify an association with non-fynbos vegetation and spring flowering as ancestral in Lachenalia, the transition to fynbos vegetation and non-spring flowering taking place multiple times. They also show that self-compatibility, autofertility, bird pollination and production of multiple clonal offsets have evolved repeatedly. Regression models suggest that bird pollination and self-compatibility are selected for in fynbos and in non-spring flowering lineages, with autofertility being positively associated with non-spring flowering. These patterns support the interpretation of these traits as reproductive safeguarding adaptations under reduced insect pollinator abundance. We find no evidence to support the interpretation of clonal propagation as a reproductive safeguarding strategy.

Elevational shifts in reproductive ecology indicate the climate response of a model chasmophyte, Rainer's bellflower (Campanula raineri)

BACKGROUND AND AIMS

Elevation gradients provide 'natural experiments' for investigating plant climate change responses, advantageous for the study of protected species and life forms for which transplantation experiments are illegal or unfeasible, such as chasmophytes with perennial rhizomes pervading rock fissures. Elevational climatic differences impact mountain plant reproductive traits (pollen and seed quality, sexual vs. vegetative investment) and pollinator community composition; we investigated the reproductive ecology of a model chasmophyte, Campanula raineri Perp. (Campanulaceae), throughout its current elevational/climatic range to understand where sub-optimal conditions jeopardise survival. We hypothesised that: 1) reproductive fitness measures are positively correlated with elevation, indicative of the relationship between fitness and climate; 2) C. raineri, like other campanulas, is pollinated mainly by Hymenoptera; 3) potential pollinators shift with elevation.

METHODS

We measured pollen and seed quality, seed production, the relative investment in sexual vs. vegetative structures and vegetative (Grime's CSR) strategies at different elevations. Potential pollinators were assessed by combining molecular and morphological identification.

KEY RESULTS

Whereas CSR strategies were not linked to elevation, pollen and seed quality were positively correlated, as was seed production per fruit (Hypothesis 1 is supported). The main pollinators of C. raineri were Apidae, Andrenidae, Halictidae (Hymenoptera) and Syrphidae (Diptera), probably complemented by a range of occasional pollinators and visitors (Hypothesis 2 partially supported). Potential pollinator communities showed a taxonomic shift towards Diptera with elevation (particularly Anthomyiidae and Muscidae) and away from Hymenoptera (Hypothesis 3 was supported).

CONCLUSIONS

Pollinator availability is maintained at all elevations by taxon replacement. However, reduced pollen quality and seed production at lower elevations suggest an impact of climate change on reproduction (especially <1200 m a.s.l., where seed germination was limited). Aside from guiding targeted conservation actions for C. raineri, our results highlight problems that may be common to mountain chasmophytes worldwide.

The Sequential Direct and Indirect Effects of Mountain Uplift, Climatic Niche, and Floral Trait Evolution on Diversification Dynamics in an Andean Plant Clade

Why and how organismal lineages radiate is commonly studied through either assessing abiotic factors (biogeography, geomorphological processes, and climate) or biotic factors (traits and interactions). Despite increasing awareness that both abiotic and biotic processes may have important joint effects on diversification dynamics, few attempts have been made to quantify the relative importance and timing of these factors, and their potentially interlinked direct and indirect effects, on lineage diversification. We here combine assessments of historical biogeography, geomorphology, climatic niche, vegetative, and floral trait evolution to test whether these factors jointly, or in isolation, explain diversification dynamics of a Neotropical plant clade (Merianieae, Melastomataceae). After estimating ancestral areas and the changes in niche and trait disparity over time, we employ Phylogenetic Path Analyses as a synthesis tool to test eleven hypotheses on the individual direct and indirect effects of these factors on diversification rates. We find strongest support for interlinked effects of colonization of the uplifting Andes during the mid-Miocene and rapid abiotic climatic niche evolution in explaining a burst in diversification rate in Merianieae. Within Andean habitats, later increases in floral disparity allowed for the exploitation of wider pollination niches (i.e., shifts from bee to vertebrate pollinators), but did not affect diversification rates. Our approach of including both vegetative and floral trait evolution, rare in assessments of plant diversification in general, highlights that the evolution of woody habit and larger flowers preceded the colonization of the Andes, but was likely critical in enabling the rapid radiation in montane environments. Overall, and in concert with the idea that ecological opportunity is a key element of evolutionary radiations, our results suggest that a combination of rapid niche evolution and trait shifts was critical for the exploitation of newly available niche space in the Andes in the mid-Miocene. Further, our results emphasize the importance of incorporating both abiotic and biotic factors into the same analytical framework if we aim to quantify the relative and interlinked effects of these processes on diversification.

Rhamphempis, a New Genus of Empidini (Diptera: Empididae: Empidinae) of the New World, with Descriptions of Five New Species from French Guiana and the Eastern United States

The genus Rhamphempisgen. nov. (Diptera: Empididae: Empidinae: Empidini) is described and includes the following five new species from French Guiana and the USA: Rhamphempis concavasp. nov. (France: French Guiana, Roura); R. distinctasp. nov. (France: French Guiana, Roura); R. mirificasp. nov. (France: French Guiana, Régina); R. montreuilisp. nov. (Type species, France: French Guiana, Mitaraka, Roura, St-Georges-de-l'Oyapock); and R. septentrionalissp. nov. (USA: Maryland, College Park). The genus differs from other empidine genera by the following combination of characters: scape and postpedicel lengthened, proboscis long, strongly sclerotised with labella as long as prementum bearing annulations, wing with R2+3 somewhat shortened, more or less recurved at pterostigma, R4+5 unforked, base of abdomen yellowish in male, brownish to blackish in female, male pregenital segments strongly modified and postabdomen more or less downcurved, presence of large surstylus, very fine and long phallus. The genus is fully illustrated and keyed along with a discussion of its peculiar disjunct geographic distribution and its phylogenetic relationship within the tribe Empidini.

Contradistinctive floral attributes, pollination guilds and their consequence on the outcrossing rate in two elevational morphs of Rhododendron arboreum Sm

Infraspecific floral trait variations may appear in response to elevational differences in alpine plant species. There is enormous information on the selection of such morphs mediated by biotic and/or abiotic variables. Whether such differences contribute to differences in reproductive strategy and mating outcomes is rarely investigated. We investigated these aspects in two distinct elevational floral morphs (Red and Pink) of Rhododendron arboreum Sm. in Western Himalaya. The red morphs occupy the lower elevations while pink morphs the higher elevations. The two morphs differ in floral traits like phenology, dimension, display, quality of floral rewards, and pollinators that happen to influence interaction with available pollinator pool at each elevation. The pink morph exhibits entomophily, while the red ones show ornithophily. Although experimental pollinations established that both the morphs are self-compatible, selfing results in significantly lower fruit-set than either cross- or open-pollinations. The outcrossing rate in the red morph, as determined by using simple sequence repeat (SSR) markers, was higher (tm=0.82) than that in the pink morph (tm=0.76), with a tendency of the latter to be shifting towards mixed-mating strategy. However, the extent of biparental inbreeding was comparable among the two morphs. It is inferred that the differences in the mating outcomes among the morphs in the tree species are linked to those emerging from floral traits and the pollination by different functional groups of floral visitors.

Discussion: Harnessing microbiome-mediated adaptations in insect pollinators to mitigate climate change impact on crop pollination

Insect pollinators, vital for agriculture and biodiversity, face escalating threats from climate change. We argue and explore the pivotal role of the microbiomes in shaping adaptations of insect pollinator resilience amid climate-induced challenges (climate change and habitat alteration). Examining diverse taxonomic groups, we unravel the interplay between insect physiology, microbiomes, and adaptive mechanisms. Climate-driven alterations in microbiomes impact insect health, behavior, and plant interactions, posing significant effects on agricultural ecosystems. We propose harnessing microbiome-mediated adaptations as a strategic approach to mitigate climate change impacts on crop pollination. Insights into insect-pollinator microbiomes offer transformative avenues for sustainable agriculture, including probiotic interventions (use of EM PROBIOTIC) and microbiome engineering (such as engineering gut bacteria) to induce immune responses and enhanced pollination services. Integrating microbiome insights into conservation practices elucidates strategies for preserving pollinator habitats, optimizing agricultural landscapes, and developing policies to safeguard pollinator health in the face of environmental changes. Finally, we stress interdisciplinary collaboration and the urgency of understanding pollinator microbiome dynamics under climate change in future research.

Tropicohilara, a New Genus of Hilarini (Diptera: Empididae: Empidinae) from Brazil, with Descriptions of Six New Species

The genus Tropicohilaragen. nov. (Diptera: Empididae: Empidinae: Hilarini) is described and includes the following six new species from Brazil: Tropicohilara amazonensissp. nov. (type species, Brazil: Amazonas, Manaus); T. bahiensissp. nov. (Brazil: Bahia, Camacan); T. bellasp. nov. (Brazil: Pernambuco, Jaqueira); T. mineirasp. nov. (Brazil: Minas Gerais, Itamonte); T. paranaensissp. nov. (Brazil: Paraná, Piraquara); and T. sinclairisp. nov. (Brazil: Paraná, Morretes). The genus is presently recorded from the Amazonian and Atlantic Forest biomes. It differs from other hilarine genera by the following combination of characteristics: predominantly yellowish specimens; occiput somewhat conical in dorsal view; postpedicel elongate, male first fore tarsomere unmodified; hind tibia slightly shorter than hind femur; wing vein R2+3 with setae on ventral surface; male tergite 7 with a sclerotized band at posterior margin, tergite 8 reduced and upwardly directed so that terminalia can be flexed forward. A key to the species is provided.

Elevational homogenization of mountain parasitoids across six decades

Elevational gradients are characterized by strong environmental changes within small geographical distances, providing important insights on the response of biological communities to climate change. Mountain biodiversity is particularly sensitive to climate change, given the limited capacity to colonize new areas and the competition from upshifting lowland species. Knowledge on the impact of climate change on mountain insect communities is patchy, but elevation is known to influence parasitic interactions which control insect communities and functions within ecosystems. We analyzed a European dataset of bristle flies, a parasitoid group which regulates insect herbivory in both managed and natural ecosystems. Our dataset spans six decades and multiple elevational bands, and we found marked elevational homogenization in the host specialization of bristle fly species through time. The proportion of specialized parasitoids has increased by ca. 70% at low elevations, from 17 to 29%, and has decreased by ca. 20% at high elevations, from 48 to 37%. As a result, the strong elevational gradient in bristle fly specialization observed in the 1960s has become much flatter over time. As climate warming is predicted to accelerate, the disappearance of specialized parasitoids from high elevations might become even faster. This parasitoid homogenization can reshape the ecological function of mountain insect communities, increasing the risk of herbivory outbreak at high elevations. Our results add to the mounting evidence that symbiotic species might be especially at risk from climate change: Monitoring the effects of these changes is urgently needed to define effective conservation strategies for mountain biodiversity.

Opposing Patterns of Altitude-Driven Pollinator Turnover in the Tropical and Temperate Americas

AbstractAbiotic factors (e.g., temperature, precipitation) vary markedly along elevational gradients and differentially affect major groups of pollinators. Ectothermic bees, for example, are impeded in visiting flowers by cold and rainy conditions common at high elevations, while endothermic hummingbirds may continue foraging under such conditions. Despite the possibly far-reaching effects of the abiotic environment on plant-pollinator interactions, we know little about how these factors play out at broad ecogeographic scales. We address this knowledge gap by investigating how pollination systems vary across elevations in 26 plant clades from the Americas. Specifically, we explore Cruden's 1972 hypothesis that the harsh montane environment drives a turnover from insect to vertebrate pollination at higher elevations. We compared the elevational distribution and bioclimatic attributes for a total of 2,232 flowering plants and found that Cruden's hypothesis holds only in the tropics. Above 30°N and below 30°S, plants pollinated by vertebrates (mostly hummingbirds) tend to occur at lower elevations than those pollinated by insects. We hypothesize that this latitudinal transition is due to the distribution of moist, forested habitats favored by vertebrate pollinators, which are common at high elevations in the tropics but not in the temperate Americas.

Phenological variations in relation to climatic variables of moist temperate forest tree species of western Himalaya, India

Phenology, an important ecological attribute, deals with the development of vegetative and reproductive parts of trees called "phenophases", which are important determinants of primary productivity and sensitive to climate change. The present study recorded various phenophases of major tree species (i.e., Quercus leucotrichophora, Rhododendron arboreum, and Myrica esculenta) as per the two-digit numerical system of Biologische Bundesanstalt, Bundessortenamt, Chemische Industrie (BBCH) scale. A total of 72 individual trees, twenty-four from each species, distributed between 1400 and 1980 m. a.s.l elevations were tagged and measured fortnightly for two consecutive years (2019-2021) in the moist temperate forest of Western Himalaya and compared with earlier existing records. Various phenophases were correlated with climatic factors along with duration and thermal time for each phenological growth stage. We found 24 growth stages for Q. leucotrichophora and M. esculenta and 28 for R. arboreum distributed across seven principal growth stages (e.g. bud development, 0; leaf development, 1; shoot development, 3; inflorescence development, 5; flower development, 6; fruit development, 7; and fruit maturation, 8) of trees as per BBCH scale. Maximum growing degree was 748.87 and 627.95 days recorded for R. arboreum and M. esculenta during leaf development, and 796.17 days for Q. leucotrichophora during fruit development. Flower emergence was observed pre, during, and post-emergence of new leaves for R. arboreum, M. esculenta, and Q. leucotrichophora, respectively, which varied at spatial scale with previous findings. Longevity of fruit development to ripening took 17, 4, and 2 months, respectively in Q. leucotrichophora, R. arboreum and M. esculenta. Duration of leaf initiation and flowering was positively correlated with climatic variables, whereas, the reverse was observed for fruiting in the studied tree species. The study concludes that the variations in phenophases of the three species were strongly influenced by climatic variations, especially minimum temperature. The result of the present study would be important in enabling us to formulate efficient forest management strategies by understanding the short-term adaptation of the climate-sensitive important tree species in the western Himalaya.

Intraspecific variation in morphology of spiny pollen grains along an altitudinal gradient in an insect-pollinated shrub

Intraspecific variations in pollen morphological traits are poorly studied. Interspecific variations are often associated with pollination systems and pollinator types. Altitudinal environmental changes, which can influence local pollinator assemblages, provide opportunities to explore differentiation in pollen traits of a single species over short distances. The aim of this study is to examine intraspecific variations in pollen traits of an insect-pollinated shrub, Weigela hortensis (Caprifoliaceae), along an altitudinal gradient. Pollen spine phenotypes (length, number and density), pollen diameter, lipid mass (pollenkitt) around pollen grains, pollen production per flower and pollinator assemblages were compared at four sites at different altitudes. Spine length and the spine length/diameter ratio of pollen grains were greater at higher altitudes but not correlated with flower or plant size. Spine number and density increased as flower size increased, and pollen lipid mass decreased as plant size increased. Bees were the predominant pollinators at low-altitude sites whereas flies, specifically Oligoneura spp. (Acroceridae), increased in relative abundance with increasing altitude. The results of this study suggest that the increase in spine length with altitude was the result of selection favouring longer spines at higher-altitude sites and/or shorter spines at lower-altitude sites. The altitudinal variation in selection pressure on spine length could reflect changes in local pollinator assemblages with altitude.

Biopesticides and insect pollinators: Detrimental effects, outdated guidelines, and future directions

As synthetic pesticides play a major role in pollinator decline worldwide, biopesticides have been gaining increased attention to develop more sustainable methods for pest management in agriculture. These biocontrol agents are usually considered as safe for non-target species, such as pollinators. Unfortunately, when it comes to non-target insects, only the acute or chronic effects on survival following exposure to biopesticides are tested. Although international boards have highlighted the need to include also behavioral and morphophysiological traits when assessing risks of plant protection products on pollinators, no substantial concerns have been raised about the risks associated with sublethal exposure to these substances. Here, we provide a comprehensive review of the studies investigating the potential adverse effects of biopesticides on different taxa of pollinators (bees, butterflies, moths, beetles, flies, and wasps). We highlight the fragmentary knowledge on this topic and the lack of a systematic investigation of these negative effects of biopesticides on insect pollinators. We show that all the major classes of biopesticides, besides their direct toxicity, can also cause a plethora of more subtle detrimental effects in both solitary and social species of pollinators. Although research in this field is growing, the current risk assesment approach does not suffice to properly assess all the potential side-effects that these agents of control may have on pollinating insects. Given the urgent need for a sustainable agriculture and wildlife protection, it appears compelling that these so far neglected detrimental effects should be thoroughly assessed before allegedly safe biopesticides can be used in the field and, in this view, we provide a perspective for future directions.

Insect Visitors of Specialty Cut Flowers in High Tunnels

Various strategies incorporate floral resources into agricultural landscapes to support beneficial insects. Specialty cut flower production offers a rarely explored approach to offer floral resources while yielding a marketable product for growers. We characterized insect visitation to six species of specialty cut flowers. Due to Wyoming's growing conditions, the flowers were grown in high tunnels, thus offering insight into insect abundance in this unique semi-controlled environment. The flower species tested were Calendula officinalis, Celosia argentea, Daucus carota, Helichrysum bracteatum, Matthiola incana, and a Zinnia elegans-Zinnia hybrida mixture. At least four species were in bloom from early June through late September. The flowers attracted diverse pollinator groups including Diptera, Hymenoptera, Coleoptera, and Lepidoptera. Bees most often visited Ca. officinalis, H. bracteatum, and Celosia spicata whereas flies most often visited D. carota. Bombus were the most oft-collected bees from the flowers and were found on all six cut flower species. Wasp abundance varied little across the cut flowers, but wasp community composition was distinct. The highest diversity of wasp families was collected from the Zinnia mixture (seven families) in contrast to less diverse collections from Ce. spicata (two families). The most abundant wasp families collected were Crabronidae and Sphecidae. Our experiment documented that ornamental cut flower species attract pollinator insects into high tunnel environments. All cut flower species tested were visited by multiple types of beneficial insects. Planting a mixture of specialty cut flowers can support insect diversity while also diversifying on-farm agricultural products through sale of cut flower stems.

The Early Season Community of Flower-Visiting Arthropods in a High-Altitude Alpine Environment

In mountain ecosystems, climate change can cause spatiotemporal shifts, impacting the composition of communities and altering fundamental biotic interactions, such as those involving flower-visiting arthropods. On of the main problems in assessing the effects of climate change on arthropods in these environments is the lack of baseline data. In particular, the arthropod communities on early flowering high-altitude plants are poorly investigated, although the early season is a critical moment for possible mismatches. In this study, we characterised the flower-visiting arthropod community on the early flowering high-altitude Alpine plant, Androsace brevis (Primulaceae). In addition, we tested the effect of abiotic factors (temperature and wind speed) and other variables (time, i.e., hour of the day, and number of flowers per plant) on the occurrence, abundance, and diversity of this community. A. brevis is a vulnerable endemic species growing in the Central Alps above 2000 m asl and flowering for a very short period immediately after snowmelt, thus representing a possible focal plant for arthropods in this particular moment of the season. Diptera and Hymenoptera were the main flower visitors, and three major features of the community emerged: an evident predominance of anthomyiid flies among Diptera, a rare presence of bees, and a relevant share of parasitoid wasps. Temperature and time (hour of the day), but not wind speed and number of flowers per plant, affected the flower visitors' activity. Our study contributes to (1) defining the composition of high-altitude Alpine flower-visiting arthropod communities in the early season, (2) establishing how these communities are affected by environmental variables, and (3) setting the stage for future evaluation of climate change effects on flower-visiting arthropods in high-altitude environments in the early season.

Flower Color as Predictor for Nectar Reward Quantity in an Alpine Flower Community

Entomophilous plants have evolved colorful floral displays to attract flower visitors to achieve pollination. Although many insects possess innate preferences for certain colors, the underlying proximate and ultimate causes for this behavior are still not well understood. It has been hypothesized that the floral rewards, e.g., sugar content, of plants belonging to a particular color category correlate with the preference of the flower visitors. However, this hypothesis has been tested only for a subset of plant communities worldwide. Bumble bees are the most important pollinators in alpine environments and show a strong innate preference for (bee) “UV-blue” and “blue” colors. We surveyed plants visited by bumble bees in the subalpine and alpine zones (&gt;1,400 m a.s.l.) of the Austrian Alps and measured nectar reward and spectral reflectance of the flowers. We found that the majority of the 105 plant samples visited by bumble bees fall into the color categories “blue” and “blue-green” of a bee-specific color space. Our study shows that color category is only a weak indicator for nectar reward quantity; and due to the high reward variance within and between categories, we do not consider floral color as a reliable signal for bumble bees in the surveyed habitat. Nevertheless, since mean floral reward quantity differs between categories, naïve bumble bees may benefit from visiting flowers that fall into the innately preferred color category during their first foraging flights.

Variation in Plant-Pollinator Network Structure along the Elevational Gradient of the San Francisco Peaks, Arizona

The structural patterns comprising bimodal pollination networks can help characterize plant-pollinator systems and the interactions that influence species distribution and diversity over time and space. We compare network organization of three plant-pollinator communities along the altitudinal gradient of the San Francisco Peaks in northern Arizona. We found that pollination networks become more nested, as well as exhibit lower overall network specialization, with increasing elevation. Greater weight of generalist pollinators at higher elevations of the San Francisco Peaks may result in plant-pollinator communities less vulnerable to future species loss due to changing climate or shifts in species distribution. We uncover the critical, more generalized pollinator species likely responsible for higher nestedness and stability at the higher elevation environment. The generalist species most important for network stability may be of the greatest interest for conservation efforts; preservation of the most important links in plant-pollinator networks may help secure the more specialized pollinators and maintain species redundancy in the face of ecological change, such as changing climate.

Distribution and pollination services of wild bees and hoverflies along an altitudinal gradient in mountain hay meadows

Extensively managed and flower-rich mountain hay meadows, hotspots of Europe's biodiversity, are subject to environmental and climatic gradients linked to altitude. While the shift of pollinators from bee- to fly-dominated communities with increasing elevation across vegetation zones is well established, the effect of highland altitudinal gradients on the community structure of pollinators within a specific habitat is poorly understood. We assessed wild bee and hoverfly communities, and their pollination service to three plant species common in mountain hay meadows, in eighteen extensively managed yellow oat grasslands (Trisetum flavescens) with an altitudinal gradient spanning approx. 300 m. Species richness and abundance of pollinators increased with elevation, but no shift between hoverflies and wild bees (mainly bumblebees) occurred. Seedset of the woodland cranesbill (Geranium sylvaticum) increased with hoverfly abundance, and seedset of the marsh thistle (Cirsium palustre) increased with wild bee abundance. Black rampion (Phyteuma nigrum) showed no significant response. The assignment of specific pollinator communities, and their response to altitude in highlands, to different plant species underlines the importance of wild bees and hoverflies as pollinators in extensive grassland systems.

Temporal organization among pollination systems in a tropical seasonal forest

Temporal constancy of pollination systems is essential for the maintenance of pollinators through time. Community-level assessment of flowering phenology allows understanding variations across seasons and years and the risks of decoupling flowering and pollinators' activity. We evaluated flowering patterns and temporal diversity of pollination systems in a tropical seasonal forest. We asked whether the temporal organization of flowering times differs among pollination systems; if there is a constancy of pollination systems through the year, since climate and phylogenies constraint flowering time; if there is a prevalent flowering pattern by pollination system, and if the temporal organization of pollination systems by modularity analyses is coherent with grouping by pre-defined seasons. We characterized 10 pollination systems, examined flowering strategies, climate cues and phylogenetic constraints. Pollination by large-to-medium bees dominated (49.2%), followed by diverse insects (22.1%) and flies (14.7%). The remaining systems represented 14% of species. Flowering occurred year-round for most pollination systems, predominating the seasonal flowering strategy. Flowering patterns ranged from aggregated to nested, and random. Climate affected the flowering of most pollination systems, but there was no phylogeny constraint. Modularity grouped pollination systems differently than rainfall seasonality. Contrasting the expectations of reduced temporal constancy, most systems were present year-round, facilitating the exploitation of floral resources by pollinators. Diversity of pollination systems remained constant despite climate seasonality, indicating that several factors influence the optimum flowering time for pollination in seasonally dry vegetations. Global warming may disrupt phenological patterns and the temporal organization of plant communities, a matter for future studies.

Changes in the structure and composition of the 'Mexical' scrubland bee community along an elevational gradient

'Mexical' scrubland is a sclerophyllous evergreen Mediterranean-like vegetation occurring in the leeward slopes of the main Mexican mountain ranges, under tropical climate. This biome occupies an elevational range approximately from 1900 to 2600 meters above sea level, which frequently is the upper-most part of the mountains range. This puts it at risk of extinction in a scenario of global warming in which an upward retraction of this type of vegetation is expected. The Mexical remains one of the least studied ecosystems in Mexico. For instance, nothing is known about pollinator fauna of this vegetation. Our main objective is to make a first insight into the taxonomic identity of the bee fauna that inhabits this biome, and to study how it is distributed along the elevational gradient that it occupies. Our results highlight that elevation gradient negatively affects bee species richness and that this relationship is strongly mediated by temperature. Bee abundance had no significant pattern along elevational gradient, but shows a significant relationship with flower density. Interestingly, and contrary to previous works, we obtained a different pattern for bee richness and bee abundance. Bee community composition changed strongly along elevation gradient, mainly in relation to temperature and flower density. In a global warming scenario, as temperatures increases, species with cold preferences, occupying the highest part of the elevation gradient, are likely to suffer negative consequences (even extinction risk), if they are not flexible enough to adjust their physiology and/or some life-story traits to warmer conditions. Species occupying mid and lower elevations are likely to extend their range of elevational distribution towards higher ranges. This will foreseeably cause a new composition of species and a new scenario of interactions, the adjustment of which still leaves many unknowns to solve.

Plants and pollinators: Will natural selection cause an imbalance between nectar supply and demand?

Pollination is an important ecological process. However, plant and pollinator needs are not always met. Commonly, pollen limitation reduces seed set or bees experience nectar dearth. Using a cost-benefit approach, we show that natural selection will lead to lower nectar production when pollinators are abundant, and vice-versa. At the community level, competition among plants for pollinators causes positive feedback that exacerbates pre-existing seasonal imbalances between nectar supply and demand. When pollinators are scarce, plants will be selected to produce more nectar to outcompete other plants in attracting pollinators, and when pollinators are abundant, plants will be selected to produce less nectar. We suggest ways to test this positive feedback hypothesis and note that evidence for seasonal variation in nectar availability provides preliminary empirical support. If correct, our hypothesis indicates that pollination faces a particular challenge in balancing nectar supply with pollinator demand and is a further example of the underappreciated role of positive feedback in ecology and evolution.

Genetic diversity and structure of Musa balbisiana populations in Vietnam and its implications for the conservation of banana crop wild relatives

Crop wild relatives (CWR) are an indispensable source of alleles to improve desired traits in related crops. While knowledge on the genetic diversity of CWR can facilitate breeding and conservation strategies, it has poorly been assessed. Cultivated bananas are a major part of the diet and income of hundreds of millions of people and can be considered as one of the most important fruits worldwide. Here, we assessed the genetic diversity and structure of Musa balbisiana, an important CWR of plantains, dessert and cooking bananas. Musa balbisiana has its origin in subtropical and tropical broadleaf forests of northern Indo-Burma. This includes a large part of northern Vietnam where until now, no populations have been sampled. We screened the genetic variation and structure present within and between 17 Vietnamese populations and six from China using 18 polymorphic SSR markers. Relatively high variation was found in populations from China and central Vietnam. Populations from northern Vietnam showed varying levels of genetic variation, with low variation in populations near the Red River. Low genetic variation was found in populations of southern Vietnam. Analyses of population structure revealed that populations of northern Vietnam formed a distinct genetic cluster from populations sampled in China. Together with populations of central Vietnam, populations from northern Vietnam could be subdivided into five clusters, likely caused by mountain ranges and connected river systems. We propose that populations sampled in central Vietnam and on the western side of the Hoang Lien Son mountain range in northern Vietnam belong to the native distribution area and should be prioritised for conservation. Southern range edge populations in central Vietnam had especially high genetic diversity, with a high number of unique alleles and might be connected with core populations in northern Laos and southwest China. Southern Vietnamese populations are considered imported and not native.

Pollination in the campo rupestre: a test of hypothesis for an ancient tropical mountain vegetation

The campo rupestre is a Neotropical OCBIL (old, climatically buffered infertile landscape), a grassy-shrub vegetation with high species richness and endemism, characterized by rocky outcrops surrounded by grasslands distributed in South American ancient mountaintops. We tested one OCBIL prediction: the prevalence of long-distance pollinators ensuring cross-pollination across the archipelago-like landscapes of the campo rupestre. We described the pollination systems and tested whether their frequency differed across vegetation types and elevation, focusing on long-distance systems. We performed non-systematic and systematic surveys of plants and plant-pollinator interactions across the elevation gradient and vegetation types. We also reviewed the literature on campo rupestre pollination and applied an accuracy criterion to infer 11 pollination systems. The bee system was split into large bee (long-distance) and small bee (shorter distances) to test the prevalence of long-distance pollination systems. We surveyed 413 pollinator species, mostly bees (220) and flies (69). Among the 636 plant species studied, the bee pollination system was dominant (56%), followed by wind and hummingbird. Wind, small-bee and fly pollination systems increased with elevation, and small-bee and wind pollination systems prevailed in grasslands. Large-bee and hummingbird long-distance pollination systems remained unchanged with elevation and were more frequent in the highly isolated rocky outcrops corroborating the OCBIL theory.

From Bees to Flies: Global Shift in Pollinator Communities Along Elevation Gradients

Bees decrease in abundance and richness along elevation gradients, while flies replace bees as the dominant flower visitors in higher elevation systems. We reviewed the existing literature to determine if this global phenomenon of pollinator communities switching from bees to flies occurs at the same place along a temperature gradient. Here we examined five studies that have documented this bee-to-fly transition in the North America, South America, Europe &amp; Australia. We determined where the bee-to-fly transition occurred along a temperature/elevation gradient for each study that ranged from 1.1 to 8.3°C. We found that pollinator communities shifted from bee dominated to fly dominated communities between 4.9 and 5.7°C on all elevation gradients worldwide. This shift in pollinators could substantially impact ecological systems reliant on fly pollination as temperatures continue to warm.

Biodiversity and Spatiotemporal Variation of Longhorn Beetles (Coleoptera: Cerambycidae) in Tropical Forest of Thailand

Simple Summary

Longhorn beetles are a large family of beetles and have a wide-geographic distribution. Some of them are pests of many economic plants and invasive species. They also play roles in decomposition and nutrient cycling in forest ecosystems. They feed on living, dying, or dead woody plants in the larval stage. So far, 308 species of longhorn beetles have been reported from northern Thailand. However, the biodiversity and distribution of longhorn beetles in different elevation gradients and seasons, associated with environmental factors across six regions in the country, has not yet been investigated. In this study, longhorn beetle specimens were collected by malaise trap from 41 localities in 24 national parks across six regions in Thailand. A total of 199 morphospecies were identified from 1376 specimens. Seasonal species richness and abundance of longhorn beetles peaked during the hot and early rainy season in five regions, except for the southern region, which peaked in the rainy season. Our finding revealed that most species’ distribution was correlated with the region and forest type (at middle and low elevations). Quantitative data from this study can be useful to manage agricultural and forest plantations.

Abstract

Longhorn beetles are highly diversified and important for agriculture and health of the environment. However, the fauna and ecology of these beetles are not well known in Thailand. This study is the first to report the biodiversity, elevation, and seasonal distribution of longhorn beetles. Specimens were collected by malaise traps from 41 localities in 24 national parks throughout the country during 2006–2009. The traps were operated at each site for 12 consecutive months with a monthly service. A total of 199 morphotaxa in 36 tribes of 6 subfamilies were identified from 1376 specimens. Of these, 40.7% and 14.5% of total taxa were singletons and doubletons, respectively. The Shannon diversity index and observed species richness at Panernthung, Loei Forest Unit and Mae Fang Hotspring were high at 0.96 (30), 0.88 (50), and 0.86 (34), respectively. Local richness ranged between 3 and 50 species, while the species richness estimator showed between 6 and 1275 species. The most relatively abundant species, Nupserha lenita, Pterolophia sp.1, Oberea sp.3, Acalolepta pseudospeciosa, and Ac. rustricatrix represented 4.80%, 4.80%, 4.80%, 4.5%, and 4.43% of the species, respectively. The species with the widest distribution range of percentage of species occurrence (% SO) was Pt. sp.1 (63.4%), followed by Ac. rustricatrix (39%) and Moechotypa suffusa (39%). In a significantly negative relationship between species richness and elevation (p > 0.05, R² = 0.04), the species richness pattern showed a hump-shaped curve that peaked at the middle elevation (501–1000 m asl). Regarding seasonal variation, most of the species occurred during the hot season (March–April) and peaked in early rainy season (May), while a low number of species were found during the mid-rainy (June–October) and cold season (November–February). Ordination analysis indicated that the distribution of most species was associated with regions and forest type, and most of the species correlated with forest located at middle and low elevation. The results of this study indicated the very high biodiversity of longhorn beetles in Thailand, which suggests that an understanding of their seasonal and elevational distribution will be of value to agriculture management and conservation. They also indicated that malaise traps are appropriate for the evaluation of biodiversity.

Manual Sampling and Video Observations: An Integrated Approach to Studying Flower-Visiting Arthropods in High-Mountain Environments

Despite the rising interest in biotic interactions in mountain ecosystems, little is known about high-altitude flower-visiting arthropods. In particular, since the research in these environment can be limited or undermined by harsh conditions and logistical difficulties, it is mandatory to develop effective approaches that maximize possibilities to gather high-quality data. Here we compared two different methods, manual sampling and video observations, to investigate the interactions between the high-mountain arthropod community and flowers of Androsace brevis (Primulaceae), a vulnerable endemic alpine species with a short flowering period occurring in early season. We manually sampled flower-visiting arthropods according to the timed-observations method and recorded their activity on video. We assessed differences and effectiveness of the two approaches to estimate flower-visiting arthropod diversity and to identify potential taxa involved in A. brevis pollination. Both methods proved to be effective and comparable in describing the diversity of flower visitors at a high taxonomic level. However, with manual sampling we were able to obtain a fine taxonomic resolution for sampled arthropods and to evaluate which taxa actually carry A. brevis pollen, while video observations were less invasive and allowed us to assess arthropod behavior and to spot rare taxa. By combining the data obtained with these two approaches we could accurately identify flower-visiting arthropods, characterize their behavior, and hypothesize a role of Hymenoptera Apoidea and Diptera Brachycera in A. brevis pollination. Therefore, we propose integrating the two approaches as a powerful instrument to unravel interactions between flowering plants and associated fauna that can provide crucial information for the conservation of vulnerable environments such as high-mountain ecosystems.

High elevation insect communities face shifting ecological and evolutionary landscapes

Climate change is proceeding rapidly in high mountain regions worldwide. Rising temperatures will impact insect physiology and associated fitness and will shift populations in space and time, thereby altering community interactions and composition. Shifts in space are expected as insects move upslope to escape warming temperatures and shifts in time will occur with changes in phenology of resident high-elevation insects. Clearly, spatiotemporal shifts will not affect all species equally. Terrestrial insects may have more opportunities than aquatic insects to exploit microhabitats, potentially buffering them from warming. Such responses of insects to warming may also fuel evolutionary change, including hitchhiking of maladaptive alleles and genetic rescue. Together, these considerations suggest a striking restructuring of high-elevation insect communities that remains largely unstudied.

High levels of phenological asynchrony between specialized pollinators and plants with short flowering phases

Species phenology plays a key role in determining mutualistic interactions, such as those between plants and pollinators. Notably, temporal synchrony shapes the patterns of interactions by influencing the probability of encounters between interacting partners; thus, species phenology greatly contributes to structuring ecological communities. In these communities, specialized species are expected to show a high level of synchrony with their partners; however, the relationship between species phenology and specialization remains largely unexplored. In three localities in the tropical mountains of Costa Rica, we quantified the level of phenological synchrony in plant-pollinator networks and tested whether phenological synchrony is associated with the degree of pollinator specialization on plant partners. We also tested the relationship between pollinator specialization and the length of the flowering phase of the visited plants. Across all three studied networks, our results show a strong asynchrony between interacting plant and pollinator species. We also found that more specialized pollinators were more asynchronous with their plant partners and, moreover, that specialized pollinators preferably visited plant species with shorter flowering phases compared to generalized pollinators. These patterns suggest that specialized pollinators may be more vulnerable to mutualistic disruptions because they depend primarily on short-lived resources and have a high risk of phenological mismatch. This discovery has important consequences for specialized species' potential to survive and adapt to changes in the phenology of their interacting partners, which is highly relevant in a time characterized by changing climates and associated shifts in species phenology.

Patterns of floral morphology in relation to climate and floral visitors

BACKGROUND AND AIMS

The diversity of floral morphology among plant species has long captured the interest of biologists and led to the development of a number of explanatory theories. Floral morphology varies substantially within species, and the mechanisms maintaining this diversity are diverse. One possibility is that spatial variation in the pollinator fauna drives the evolution of spatially divergent floral ecotypes adapted to the local suite of pollinators. Another possibility is that geographic variation in the abiotic environment and local climatic conditions favours different floral morphologies in different regions. Although both possibilities have been shown to explain floral variation in some cases, they have rarely been competed against one another using data collected from large spatial scales. In this study, we assess floral variation in relation to climate and floral visitors in four oil-reward-specialized pollination interactions.

METHODS

We used a combination of large-scale plant and pollinator samplings, morphological measures and climatic data. We analysed the data using spatial approaches, as well as traditional multivariate and structural equation modelling approaches.

KEY RESULTS

Our results indicate that the four species have different levels of specialization, and that this can be explained by their climatic niche breadth. In addition, our results show that, at least for some species, floral morphology can be explained by the identity of floral visitors, with climate having only an indirect effect.

CONCLUSIONS

Our results demonstrate that, even in very specialized interactions, both biotic and abiotic variables can explain a substantial amount of intraspecific variation in floral morphology.

Environmental filtering of body size and darker coloration in pollinator communities indicate thermal restrictions on bees, but not flies, at high elevations

BACKGROUND

Bees and flies are the two most dominant pollinator taxa in mountain environments of the Southwest USA. Communities of both taxa change dramatically along elevation gradients. We examined whether bee and fly traits would also change along elevation gradients and if so, do they change in a predictable way related to a decrease in temperature as elevation increases.

METHODS

We used insect body size and darkness traits as proxies for energetic requirements and indicators of cold tolerance in order to assess patterns of bee and fly community trait differences along an elevation gradient. We examined 1,922 individuals of bees and flies sampled along an elevation gradient ranging from 2,400 meters to 3,200 meters and from 9.6 °C to 5.2 °C mean annual temperature. We examined bees and flies separately using community weighted means (site-level trait values weighted by species abundance) and estimates of environmental filtering (quantified as the inverse of the standardized range of trait values).

RESULTS

Bees and flies exhibited two somewhat distinct patterns; (1) Community weighted mean body volume and darkness of bees increased sharply at the highest elevation, and the intensity of environmental filtering also increased with elevation. This was due to both a change among bee populations within a species as well as species replacement at the highest elevation. (2) Community weighted mean body volume and darkness of flies also increased moderately with increasing elevation, but did not exhibit patterns of significant environmental filtering. In fact, the intensity of environmental filtering as indicated by the range of fly body volume weakened with elevation.

CONCLUSION

The increase in filter intensity at high elevations exhibited by bees suggests a significant limitation on the breadth of viable functional strategies for coping with extreme cold, at least within this regional species pool. Flies, on the other hand, do not appear to be limited by high elevations, indicating that the shift from bee to fly dominance at high elevations may be due, at least in part, to greater environmental constraints on bee adaptation to colder environments.

Empidine dance flies pollinate the woodland geranium as effectively as bees

Most flowering plants species rely on insects for pollination, a successful mutualism allowing them to reproduce over wide areas while flower-visitors are rewarded with food. This association is so conspicuous in the case of bees that other groups of potential pollinators, especially flies, have long been underestimated. However, visitors are not always pollinators. While the importance of flies in plant-visitor networks is now acknowledged, their pollination effectiveness has hardly been investigated. In this study, we assessed the pollination effectiveness of Geranium sylvaticum flower-visitors using single-visit seed set experiments, in a subalpine meadow where flies are predominant. We found that: (i) empidine dance flies were the most frequent visitors of G. sylvaticum; (ii) a single-visit by an empidine dance fly produced the same average number of seeds as a visit by a bee; (iii) large pollinators were more efficient than small pollinators irrespective of their identity. As a conclusion, large empidines were the main pollinators of G. sylvaticum. Considering the high diversity and abundance of flower-visiting fly species, such results showing their ability to be as effective pollinators as bees should encourage further studies to develop a better understanding on their role in plant-pollinator networks.

The transition from bee-to-fly dominated communities with increasing elevation and greater forest canopy cover

Insect pollinator communities are thought to transition from bee-dominated communities at low elevations to fly-dominated communities at high elevations. We predicted that increased tree canopy cover and a subsequent decrease in meadows and flowering plants would limit bees but not flies at higher elevations. We tested and supported this prediction by examining changes in both abundance and species richness for 128 bee species and 96 fly species at key points along an elevational gradient in Northern Arizona represented by distinct vegetation life zones. In addition to an increase in fly species and abundance relative to bees with increasing elevation, there were changes in community structure). To better understand factors that might influence this transition we examined how tree canopy cover changed along the elevational gradient and how this influenced the change in insect pollinator communities. While bee communities were progressively divergent between forest and meadow habitats with increasing elevation and tree canopy cover, there was no significant pattern with flies between meadow and forest habitats. However, fly abundance did increase with increasing elevation relative to bees. Along a comparable elevational gradient on an adjacent mountain with no tree canopy cover (i.e., a fire burned mountain), the bee-to-fly transition did not occur; bees persisted as the dominant pollinator into the highest life zone. This suggests that tree canopy cover can in part explain the transition from bee-to fly-dominated communities. In conclusion, this is the first study in North America to document a bee-fly transition for both abundance and species richness and show that tree canopy cover may play a role in determining pollinator community composition, by restricting bees to open meadow habitats.

Domestic gardens as favorable pollinator habitats in impervious landscapes

Urban expansion is correlated to negative biodiversity trends. The amount of impervious surfaces in urban areas is a determinant of pollinator species assemblages. While the increase in urbanization and impervious surfaces negatively impacts pollinators, cities also encompass urban green spaces, which have a significant capacity to support biodiversity. Among them, domestic gardens that represent a non-negligible fraction of green spaces have been shown to benefit pollinators. Domestic gardens may form habitat clusters in residential areas, although their value at a landscape scale is still unknown. Here, we investigate the combined effects of impervious surfaces and domestic garden areas on pollinator richness. Due to the difficulty of accessing privately owned domestic gardens, we chose to use citizen science data from a well-established French citizen science program known as SPIPOLL. Using regression tree analysis on buffers located from 50 m to 1000 m around the data points, we show the importance of pollinators being in close proximity to domestic gardens as locally favorable habitats that are embedded within a landscape, in which impervious surfaces represent unfavorable areas. We highlight the inter-connection between local and landscape scales, the potential for patches of domestic gardens in residential areas, and the need to consider the potential of gardeners' coordinated management decisions within a landscape context.

The yellow specialist: dronefly Eristalis tenax prefers different yellow colours for landing and proboscis extension

Droneflies, imagoes of the hoverfly Eristalis tenax, are known to possess a preference for yellow flowers, i.e. they prefer to visit yellow flowers and prefer to extend the proboscis to yellow colours. In this study we disentangle these colour preferences by investigating the landing reaction and proboscis reflex with particular reference to intensity, spectral purity and dominant wavelength of colour stimuli and their UV reflection properties. In multiple-choice tests, naïve and non-trained flies prefer to land on yellow colours independent of their UV reflection characteristics, but also accept blue, white and pink colours if they absorb UV and are of sufficient brightness. Flies trained to land on colours other than yellow still prefer yellow colours to some extent. Moreover, the flies prefer bright over dark yellow colours even if trained to dark yellow ones. The flies refuse to land on dark colours of all hues. Naïve flies exhibit the proboscis reflex only to pure yellow pollen. These experiments show for the first time that landing in droneflies is triggered by a yellow colour independent of its UV reflection properties, but proboscis extension is triggered by yellow colours strongly absorbing blue and UV. The ability to discriminate colours is better than predicted by the categorical colour vision model. The colour preferences in E. tenax represent a fine-tuned ability to visit yellow flowers displaying a UV bull's-eye pattern.

Along urbanization sprawl, exotic plants distort native bee (Hymenoptera: Apoidea) assemblages in high elevation Andes ecosystem

Native bees contribute a considerable portion of pollination services for endemic as well as introduced plant species. Their decline has been attributed to several human-derived influences including global warming as well as the reduction, alteration, and loss of bees' habitat. With human expansion comes along the introduction of exotic plant species with negative impacts over native ecosystems. Anthropic effects may even have a deeper impact on communities adapted to extreme environments, such as high elevation habitats, where abiotic stressors alone are a natural limitation to biodiversity. Among these effects, the introduction of exotic plants and urbanization may have a greater influence on native communities. In this work, we explored such problems, studying the relationship between the landscape and its effect over richness and abundance of native bees from the subandean belt in the Andes mountain chain. Furthermore, we investigated the effects of exotic plant abundance on this high-altitude bee assemblage. Despite the landscape not showing an effect over bee richness and abundance, exotic plants did have a significant influence over the native bee assemblage. The abundance of exotic plants was associated with a relative increase in the proportion of small and medium bee species. Moreover, Halictidae was the only family that appeared to be favored by an increase in the abundance of exotic plant species. We discuss these results and the urgent need for further research of high-altitude environments due to their vulnerability and high endemicity.