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Pollinators Have Picky Palates

Updated: Mar 3, 2022

Pollinators are currently receiving more attention than at any other time in history. Conservationists, scientists, farmers, and gardeners are recognizing that pollination services provided by insect pollinators are a key ecosystem service in most terrestrial ecosystems. We are in an era of increasing landscape fragmentation and climate change. As more land is converted for human use, it is important to understand how these decisions affect the species that provide a vital ecosystem services and how we can develop conservation strategies to mitigate for habitat loss. In this article, we are going to talk about how creating floral rich landscapes with native species can best support healthy populations of pollinators.

Pollinators are insects that feed on the nectar and pollen of flowering plants, and effectively transfer pollen from plant to plant to ensure the reproductive cycle and production of seed, the plants offspring. Pollinating insects include bees, butterflies, wasps, moths, flies, and beetles - with bees being the most effective and important pollinator. Bees, both wild (bumblebees, etc) and managed (honeybees), have been declining at an alarming rate, and habitat loss is a factor in their decline. The most significant drivers of pollinator declines include: habitat loss and fragmentation due to land-use change; increased prevalence of non-native plants; climate change; the spread of pathogens; increasing pesticide application and environmental pollution; and decreased resource diversity. The loss of bee diversity has threatened the agriculture productivity, which has brought the attention to scientists, policy makers and the general public. Initiatives to address the decline in pollinators have resulted in restoring pollinator habitat in natural areas, agriculture lands and landscape gardens.

With the increase in demand for native plant species, the horticulture industry has sought to make these species commercially available. Plant breeder have taken these native species and selectively bred or altered their genetics to fit into the image of “a pretty plant”, all the while marketing them as ecologically beneficial. Cultivars of native plants, also sometimes called Nativars are propagated and sold in the nursery and landscape industry, but they aren't the best choice for ecological health, as we described in our previous article, “The Importance of Ecological Diversity in Plants”. New research has now provided information that these cultivars are also a less superior choice when it comes to pollinator habitat. If we are to maximize our conservation efforts, it should be noted that native plants are always the best choice, especially for a natural restoration project and even a residential landscape planting.

As land continues to service the growing human population, we need to work with the natural landscapes in a way that fosters reciprocity - a mutual benefit. Land use is intensifying the effects on the worlds wild flora and agriculture crops. Pollinator history is very complex, but the persistent interrelationship among these species is their reliance on flowers and plants as food sources. There is a direct relation among a decrease in native plant species with a decrease in native pollinator species. If we want to conserve pollinator diversity and abundance, we must increase the abundance of native plant species. Pollinator-friendly land management practices, which value natural or restored habitat, can improve bee abundance, richness, and productivity, even in landscapes with little natural habitat.

Bees have the ability to persist in degraded landscapes, including agricultural borders and domestic gardens. This finding allows unique opportunities for the conservation of pollinators through expanding habitat into agro-ecosystems and residential landscapes. Traditional conservation strategies often focus on establishing large nature reserves, but pollinators benefit from connected landscapes, and small habitat patches created in otherwise degraded land fills that gap. Local pollinator habitat efforts can conserve these valuable insects and are economically more feasible and quicker then large scale regional preserves.

Annie White with the University of Vermont has produced research to quantitatively justify plant selection decisions. The objective of her field research was to evaluate the ecological differences between open-pollinated native wildflower species and cultivars of the same species in terms of their ability to attract and support beneficial pollinator populations. The data suggest that using native species is the best planting strategy for pollinator habitat restorations given that some native cultivars are either equally attractive or less attractive to pollinators.

The research selected 11 species of native herbaceous flowering plants for the study, and included early, mid, and late blooming species. Each native species was paired with a native cultivar of the same species, and cultivars were chosen based on being commonly available and used in the nursery and landscape industries. Across the 11 plant pairs, they found 6 native species to be more preferable than their cultivars to all insect pollinators, 4 were equally preferred, and one native cultivar was preferred over the native species.

The data shows that insect pollinators prefer to forage on native species over cultivated varieties of the native species, but not in all cases, and not exclusively. Pollinators rarely prefer to forage on a native cultivar over a native species but some native cultivars may be comparable substitutions for native species for pollinator habitat restoration projects. These mixed results among native cultivars highlights the need for cultivars to be evaluated on an individual basis and for more research to assess the floral rewards available and accessible to pollinators.

Another of Annie White’s floral-pollinator interaction study shows that cultivar and hybrid Echinacea varieties may not be equivalent substitutions for the native species in terms of maximizing attractiveness to pollinators. In pollinator gardens, where the goal is to maximize floral resources for foraging pollinators, cultivar and hybrid varieties should weigh the effects of the potential reduction in floral resources available and accessible to pollinators. This research also highlights that pollinators preferred the native species over the native cultivar in all cases where the cultivar had undergone repeated selections in a breeding program or was a known hybrid of two or more species. This suggests that cultivars that are selections from wild or nursery plant populations and are most similar to the native species in colour, morphology, and phenology are more likely to be equivalent substitutions for the species in pollinator habitat restorations.

Click on the images to enlarge

Figure 2.3, 2.7 and 3.2, and Table 3.1: White, Annie, "From Nursery to Nature: Evaluating Native Herbaceous Flowering Plants Versus Native Cultivars for Pollinator Habitat Restoration" (2016). Graduate College Dissertations and Theses. 626.

Numerous studies also provide evidence that the preservation and restoration of plant biodiversity within and around agricultural landscapes can improve habitat for both domestic and wild bees, as well as for other beneficial insects, which enhance pollination services for crops. Additionally, pollinator habitat provides multifunctional benefits to the landscape, including biodiversity conservation, soil and water quality protection, weed suppression, aesthetics and conservation biological control. Conservation biological control (CBC) is the process of integrating beneficial insects back into crop systems for natural pest control. This strategy is based on research that now demonstrates a link between the conservation of natural habitat and reduced pest problems on farms.

In addition to conserving the ecological diversity of native plants, and providing the best pollinator habitat, native plants also serve as some of the only food sources that some bee species will forage on. Around 25% of the 770 species of bees native to Eastern North America are pollen specialists. Pollen specialist bees coevolved with certain flowering native plants and have specific relationships with their evolution. Oligolectic bees or oligoleges collect pollen from one plant family or a few related plants species and monolectic bees or monoleges only gather pollen from a single plant genus or species. Polylectic bees or polyleges forage pollen from any plant, and make up the other 75% of bee species. Both bees and flowers benefit from this mutual relationship due to better foraging efficiency, pollinating effectiveness and pollen digestibility. The threats to the health of these species due to habitat degradation or loss, pesticides, invasive species, and climate change will cause population declines in both plant and bee species and extinctions through loss of species diversity.

1.Andrena erigeniae 2.Lasioglossum oenotherae 3.Melissodes denticulatus

A specialist of:

1.Spring Beauty (Claytonia sp) 2.Primrose (Oenothera sp) 3.Ironweed (Vernonia sp)

Visit this link for more information on Bee Specialists:

The resiliency of our ecosystems and the health of our pollinators rely on intact and abundant natural habitat - plant native species!

Penstemon and Echinacea photos by: Carrington Lauzon

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