Research

Jump to: Review

17 pages, 2192 KiB

Open AccessArticle

The Native Bees of Lolland (Denmark) Revisited after 100 Years: The Demise of the Specialists

by Claus Rasmussen, Markus Arne Kjær Sydenham, Hans Thomsen Schmidt and Henning Bang Madsen

Insects 2022, 13(2), 153; https://doi.org/10.3390/insects13020153 - 31 Jan 2022

Cited by 4 | Viewed by 2811

There is a global concern over insect declines, including both species loss and population declines. In particular, declines of species, such as bees that anchor trophic interactions and shoulder many of the essential ecosystem services, have been the focus of broad public concern. [...] Read more.

There is a global concern over insect declines, including both species loss and population declines. In particular, declines of species, such as bees that anchor trophic interactions and shoulder many of the essential ecosystem services, have been the focus of broad public concern. However, our understanding of what characterizes those species that are lost because of declines over long periods is limited by a scarcity of comparative studies. We here compare the species composition from a collection of bees sampled over two decades (2000–2019) from the island of Lolland in Denmark, with a collection also sampled over two decades (1900–1919), but a century ago by Jørgensen and his contemporaries. We further test if (1) the probability that bee species that were sampled a century ago are also found today depends on their degree of floral specialization; (2) and use information from pollen samples from bees from the historical records to assess if certain floral resources have been lost. In total, 203 species were recorded in the two periods, but less than half, 92 species, occurred in both sampling periods. A total of 174 species of bees were recorded from 1900–1919, and 121 species were recorded from 2000–2019, including 29 species not reported in 1900–1919. Notably, we report a reduction in the species composition among forage specialist bees from 26.4% to 15.7% of the bee fauna, a consistent and highly significant decline both when correcting for parasitic and social species. Pollen swabs from bees collected in the first period, 1900–1919, did not identify any plants that are not available today but documented a series of plants that were important to bees back then. These plants are still common today, such as Taraxacum and Salix. Our findings highlight the importance of local and historical faunistic studies, such as that of Jørgensen, who was a resident schoolteacher on the island of Lolland in southern Denmark, for documenting how changes over time affect the species composition in bee communities. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

19 pages, 2707 KiB

Open AccessArticle

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

by Paige R. Chesshire, Lindsie M. McCabe and Neil S. Cobb

Insects 2021, 12(12), 1060; https://doi.org/10.3390/insects12121060 - 26 Nov 2021

Cited by 6 | Viewed by 2501

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

18 pages, 1359 KiB

Open AccessArticle

The Native Bees of Texas: Evaluating the Benefits of a Public Engagement Course

by Laurel Treviño Murphy, Shelly Engelman, John L. Neff and Shalene Jha

Insects 2021, 12(8), 702; https://doi.org/10.3390/insects12080702 - 05 Aug 2021

Cited by 2 | Viewed by 2220

Abstract

Declines in native bee communities due to forces of global change have become an increasing public concern. Despite this heightened interest, there are few publicly available courses on native bees, and little understanding of how participants might benefit from such courses. In October [...] Read more.

Declines in native bee communities due to forces of global change have become an increasing public concern. Despite this heightened interest, there are few publicly available courses on native bees, and little understanding of how participants might benefit from such courses. In October of 2018 and 2019, we taught the ‘Native Bees of Texas’ course to the public at The University of Texas at Austin Lady Bird Johnson Wildflower Center botanical gardens in an active learning environment with slide-based presentations, printed photo-illustrated resources, and direct insect observations. In this study, we evaluated course efficacy and learning outcomes with a pre/post-course test, a survey, and open-ended feedback, focused on quality improvement findings. Overall, participants’ test scores increased significantly, from 60% to 87% correct answers in 2018 and from 64% to 87% in 2019, with greater post-course differences in ecological knowledge than in identification skills. Post-course, the mean of participants’ bee knowledge self-ratings was 4.56 on a five-point scale. The mean of participants’ ratings of the degree to which they attained the course learning objectives was 4.43 on a five-point scale. Assessment results provided evidence that the course enriched participants’ knowledge of native bee ecology and conservation and gave participants a basic foundation in bee identification. This highlights the utility of systematic course evaluations in public engagement efforts related to biodiversity conservation. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

14 pages, 1345 KiB

Open AccessArticle

Elevated CO₂ Impacts on Plant–Pollinator Interactions: A Systematic Review and Free Air Carbon Enrichment Field Study

by Liam M. Crowley, Jonathan P. Sadler, Jeremy Pritchard and Scott A. L. Hayward

Insects 2021, 12(6), 512; https://doi.org/10.3390/insects12060512 - 01 Jun 2021

Cited by 4 | Viewed by 3946

Abstract

The impact of elevated CO₂ (eCO₂) on plant–pollinator interactions is poorly understood. This study provides the first systematic review of this topic and identifies important knowledge gaps. In addition, we present field data assessing the impact of eCO₂ (150 [...] Read more.

The impact of elevated CO₂ (eCO₂) on plant–pollinator interactions is poorly understood. This study provides the first systematic review of this topic and identifies important knowledge gaps. In addition, we present field data assessing the impact of eCO₂ (150 ppm above ambient) on bluebell (Hyacinthoides non-scripta)–pollinator interactions within a mature, deciduous woodland system. Since 1956, only 71 primary papers have investigated eCO₂ effects on flowering time, floral traits and pollination, with a mere 3 studies measuring the impact on pollination interactions. Our field experiment documented flowering phenology, flower visitation and seed production, as well as the abundance and phenology of dominant insect pollinators. We show that first and mid-point flowering occurred 6 days earlier under eCO₂, but with no change in flowering duration. Syrphid flies and bumble bees were the dominant flower visitors, with peak activity recorded during mid- and late-flowering periods. Whilst no significant difference was recorded in total visitation or seed set between eCO₂ and ambient treatments, there were clear patterns of earlier flowering under eCO₂ accompanied by lower pollinator activity during this period. This has implications for potential loss of synchrony in pollination systems under future climate scenarios, with associated long-term impacts on abundance and diversity. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

11 pages, 3987 KiB

Open AccessArticle

Global Warming, Advancing Bloom and Evidence for Pollinator Plasticity from Long-Term Bee Emergence Monitoring

by James Cane

Insects 2021, 12(5), 457; https://doi.org/10.3390/insects12050457 - 16 May 2021

Cited by 12 | Viewed by 4181

Abstract

Global warming is extending growing seasons in temperate zones, yielding earlier wildflower blooms. Short-term field experiments with non-social bees showed that adult emergence is responsive to nest substrate temperatures. Nonetheless, some posit that global warming will decouple bee flight and host bloom periods, [...] Read more.

Global warming is extending growing seasons in temperate zones, yielding earlier wildflower blooms. Short-term field experiments with non-social bees showed that adult emergence is responsive to nest substrate temperatures. Nonetheless, some posit that global warming will decouple bee flight and host bloom periods, leading to pollination shortfalls and bee declines. Resolving these competing scenarios requires evidence for bees’ natural plasticity in their annual emergence schedules. This study reports direct observations spanning 12–24 years for annual variation in the earliest nesting or foraging activities by 1–4 populations of four native ground-nesting bees: Andrena fulva (Andrenidae), Halictus rubicundus (Halictidae), Habropoda laboriosa and Eucera (Peponapis) pruinosa (Apidae). Calendar dates of earliest annual bee activity ranged across 25 to 45 days, approximating reported multi-decadal ranges for published wildflower bloom dates. Within a given year, the bee H. rubicundus emerged in close synchrony at multiple local aggregations, explicable if meteorological factors cue emergence. Emergence dates were relatable to thermal cues, such as degree day accumulation, soil temperature at nesting depth, and the first pulse of warm spring air temperatures. Similar seasonal flexibilities in bee emergence and wildflower bloom schedules bodes well for bees and bloom to generally retain synchrony despite a warming climate. Future monitoring studies can benefit from several simple methodological improvements. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

18 pages, 1859 KiB

Open AccessArticle

Ensemble Models Predict Invasive Bee Habitat Suitability Will Expand under Future Climate Scenarios in Hawai’i

by Jesse A. Tabor and Jonathan B. Koch

Insects 2021, 12(5), 443; https://doi.org/10.3390/insects12050443 - 13 May 2021

Cited by 22 | Viewed by 3686

Abstract

Climate change is predicted to increase the risk of biological invasions by increasing the availability of climatically suitable regions for invasive species. Endemic species on oceanic islands are particularly sensitive to the impact of invasive species due to increased competition for shared resources [...] Read more.

Climate change is predicted to increase the risk of biological invasions by increasing the availability of climatically suitable regions for invasive species. Endemic species on oceanic islands are particularly sensitive to the impact of invasive species due to increased competition for shared resources and disease spread. In our study, we used an ensemble of species distribution models (SDM) to predict habitat suitability for invasive bees under current and future climate scenarios in Hawai’i. SDMs projected on the invasive range were better predicted by georeferenced records from the invasive range in comparison to invasive SDMs predicted by records from the native range. SDMs estimated that climatically suitable regions for the eight invasive bees explored in this study will expand by ~934.8% (±3.4% SE). Hotspots for the invasive bees are predicted to expand toward higher elevation regions, although suitable habitat is expected to only progress up to 500 m in elevation in 2070. Given our results, it is unlikely that invasive bees will interact directly with endemic bees found at >500 m in elevation in the future. Management and conservation plans for endemic bees may be improved by understanding how climate change may exacerbate negative interactions between invasive and endemic bee species. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

17 pages, 1932 KiB

Open AccessArticle

Joint Impacts of Drought and Habitat Fragmentation on Native Bee Assemblages in a California Biodiversity Hotspot

by Keng-Lou James Hung, Sara S. Sandoval, John S. Ascher and David A. Holway

Insects 2021, 12(2), 135; https://doi.org/10.3390/insects12020135 - 05 Feb 2021

Cited by 8 | Viewed by 5521

Abstract

Global climate change is causing more frequent and severe droughts, which could have serious repercussions for the maintenance of biodiversity. Here, we compare native bee assemblages collected via bowl traps before and after a severe drought event in 2014 in San Diego, California, [...] Read more.

Global climate change is causing more frequent and severe droughts, which could have serious repercussions for the maintenance of biodiversity. Here, we compare native bee assemblages collected via bowl traps before and after a severe drought event in 2014 in San Diego, California, and examine the relative magnitude of impacts from drought in fragmented habitat patches versus unfragmented natural reserves. Bee richness and diversity were higher in assemblages surveyed before the drought compared to those surveyed after the drought. However, bees belonging to the Lasioglossum subgenus Dialictus increased in abundance after the drought, driving increased representation by small-bodied, primitively eusocial, and generalist bees in post-drought assemblages. Conversely, among non-Dialictus bees, post-drought years were associated with decreased abundance and reduced representation by eusocial species. Drought effects were consistently greater in reserves, which supported more bee species, than in fragments, suggesting that fragmentation either had redundant impacts with drought, or ameliorated effects of drought by enhancing bees’ access to floral resources in irrigated urban environments. Shifts in assemblage composition associated with drought were three times greater compared to those associated with habitat fragmentation, highlighting the importance of understanding the impacts of large-scale climatic events relative to those associated with land use change. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

11 pages, 1512 KiB

Open AccessArticle

Use of a Managed Solitary Bee to Pollinate Almonds: Population Sustainability and Increased Fruit Set

by Jordi Bosch, Sergio Osorio-Canadas, Fabio Sgolastra and Narcís Vicens

Insects 2021, 12(1), 56; https://doi.org/10.3390/insects12010056 - 11 Jan 2021

Cited by 15 | Viewed by 2717

Abstract

Osmia spp. are excellent orchard pollinators but evidence that their populations can be sustained in orchard environments and their use results in increased fruit production is scarce. We released an Osmia cornuta population in an almond orchard and measured its population dynamics, as [...] Read more.

Osmia spp. are excellent orchard pollinators but evidence that their populations can be sustained in orchard environments and their use results in increased fruit production is scarce. We released an Osmia cornuta population in an almond orchard and measured its population dynamics, as well as visitation rates and fruit set at increasing distances from the nesting stations. Honeybees were 10 times more abundant than O. cornuta. However, the best models relating fruit set and bee visitation included only O. cornuta visitation, which explained 41% and 40% of the initial and final fruit set. Distance from the nesting stations explained 27.7% and 22.1% of the variability in initial and final fruit set. Of the 198 females released, 99 (54.4%) established and produced an average of 9.15 cells. Female population growth was 1.28. By comparing our results with those of previous O. cornuta studies we identify two important populational bottlenecks (female establishment and male-biased progeny sex ratios). Our study demonstrates that even a small population of a highly effective pollinator may have a significant impact on fruit set. Our results are encouraging for the use of Osmia managed populations and for the implementation of measures to promote wild pollinators in agricultural environments. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

Review

Jump to: Research

18 pages, 1174 KiB

Open AccessReview

Supporting Bees in Cities: How Bees Are Influenced by Local and Landscape Features

by Anthony C. Ayers and Sandra M. Rehan

Insects 2021, 12(2), 128; https://doi.org/10.3390/insects12020128 - 02 Feb 2021

Cited by 60 | Viewed by 14717

Abstract

Urbanization is a major anthropogenic driver of decline for ecologically and economically important taxa including bees. Despite their generally negative impact on pollinators, cities can display a surprising degree of biodiversity compared to other landscapes. The pollinating communities found within these environments, however, [...] Read more.

Urbanization is a major anthropogenic driver of decline for ecologically and economically important taxa including bees. Despite their generally negative impact on pollinators, cities can display a surprising degree of biodiversity compared to other landscapes. The pollinating communities found within these environments, however, tend to be filtered by interacting local and landscape features that comprise the urban matrix. Landscape and local features exert variable influence on pollinators within and across taxa, which ultimately affects community composition in such a way that contributes to functional trait homogenization and reduced phylogenetic diversity. Although previous results are not easily generalizable, bees and pollinators displaying functional trait characteristics such as polylectic diet, cavity-nesting behavior, and later emergence appear most abundant across different examined cities. To preserve particularly vulnerable species, most notably specialists that have become underrepresented within city communities, green spaces like parks and urban gardens have been examined as potential refuges. Such spaces are scattered across the urban matrix and vary in pollinator resource availability. Therefore, ensuring such spaces are optimized for pollinators is imperative. This review examines how urban features affect pollinators in addition to ways these green spaces can be manipulated to promote greater pollinator abundance and diversity. Full article

(This article belongs to the Special Issue Non-Apis Pollinators and Global Change)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Non-Apis Pollinators and Global Change

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (9 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI