Introduction

Native Bee Biology & Ecosystem Services

Figure 1. Example of what solitary bee or wasp nests look like on the outside (A) and (B), and what the cells look like inside (C). These cells were made in artificial nests. It is difficult to tell if a nest belongs to a bee or wasp until they emerge because their life histories and nests can be very similar.

Bumblebee on a dandelion flower.

Bees have diverse life histories. You are probably most familiar with Honey bees which live in large colonies where they produce excess honey. This is not the case for all bees, however. In Alberta most of our native bees are solitary bees, meaning that they do not have colonies or queens [1]. Instead every female is capable of laying her own eggs, building her own nest, and foraging for herself. An exception to this are our Bumble bees, although their colonies are much smaller and produce far less honey than Honey bees!

So where do our little friends live then? Well, most nest underground like in abandoned rodent tunnels [1]. However, many species are cavity nesters, meaning they nest above ground in hollow plant stems or in beetle galleries in wood (Figure 1) [1].

Bees of course feed on nectar and pollen, often pollinating the flower in the process. Many native bees are generalists, meaning that they are not picky eaters. Some native bees are specialists, however, meaning that they only consume the nectar and pollen from specific flower species. These bee species are often sensitive to changes in their environment because if their already limited food supply is reduced or eliminated, their population follows suit [1].

As already mentioned, native bees are important pollinators, especially for native flowers which they co-evolved alongside. Additionally, native bees contribute to crop pollination. In fact, they are often times more efficient at pollinating than honeybees, with some crops almost solely relying on bumblebee pollination, such as blueberries [2]. In Canada native pollinators contribute $2.8 billion to farmers annually [3].

Threats to Native Bees

Agricultural landscapes are associated with low native bee diversity [4]. This decline is largely driven by reduced floral and nesting resources caused by monoculture, land-use-change, and frequent disturbances [4]. Agrochemicals, such as pesticides, also harm native bee populations in these landscapes [4].

Although not the focus of project, other threats to native bees include urbanization, pollution, climate change, disease, and non-native bees which out-compete native species [4].

Expansive wheat field which is an example of a monoculture that displaces floral and nesting habitat.

How Can We Help?

Clover flowers in a highway ditch.

Recent studies have suggested that crop margins, the strips of un-farmed land between crops, increase floral and nesting habitat in agricultural landscapes for pollinators if maintained correctly [5]. Road margins may potentially serve the same purpose. Flowers in ditches may provide native bees with precious floral resources, while treed crop borders between crops and highways may provide native bees with an array of nesting options [1].

Objectives

Objective 1A) Assess if treed crop borders, high roadside floral abundance, and high roadside floral richness individually increase bee abundance (interpreted from bee counts) and richness (Figure 2B, 2C).

Objective 1B) Assess if the highest bee abundance and richness is observed at sites with high floral abundance and when the crop is bordered by trees (Figure 2A). This effect should be more than additive.

Reasoning: Most bee species nest below ground, however, there are some that nest above ground in pithy plant stems or deadwood [1]. Treed crop borders provide bees with a variety of undisturbed nesting options that caters to a various bee species that have different nesting preferences to one another. In contrast, herbaceous crop borders (defined as the absence of trees) only offer nesting habitat to ground nesting bees. Regarding floral abundance, it is well established in literature that bee abundance is strongly correlated to floral abundance. When both floral abundance is high and the crops are bordered by trees, the high floral abundance will attract foraging bees which then build nests in the treed crop borders. Without being drawn into the site by the high floral abundance, some of the nesting bees may not otherwise lay eggs in the treed crop border.

Objective 2) Assess if roadside floral community composition influences bee community composition.

Reasoning: Specialist bee species are strongly tied to their preferred flower species [1]. Therefore, these specialist bees should be observed only in specific floral communities.

Figure 2. Two possible treatments (treed and herbaceous) with a range of floral abundance (simplified here as high and low). Sites that have high floral abundance and treed crop borders should have the highest bee abundance (A). Sites with high floral abundance and herbaceous borders (B), or sites with low floral abundance but treed crop borders (C), should have an intermediate bee abundance. Sites with low floral abundance and herbaceous borders should have the lowest bee abundance (D). Simply put, A > B ≈ C > D.

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