Bumblebee and butterfly community responses to plant diversity and habitat type

Abstract

One of the leading causes of biodiversity loss and species communities’ alteration is land-use change for agricultural purposes. Land-use may affect pollinators directly or indirectly via the plant communities. A better understanding of plant community and pollinators interactions can be important to comprehend the potential for management to support pollinating insects in different habitats. This study aimed to investigate the effects of plant species richness and habitat types on bumblebee and butterfly species richness and abundance, considering plant-pollinator interaction networks for visual evaluation of key species. The study survey was conducted in Jönköpings county, Southern Sweden, in five different habitat types: Cereal, Clear-cut, Forest, Ley, and Pasture. Results showed that both plant species richness and habitat type are good predictors of pollinators abundance and diversity. Plant richness showed a significant positive effect on bumblebee, as well as on butterfly, richness and abundance. In the same way, habitat had a significant effect on both bumblebee and butterfly richness and abundance. In particular, bumblebee species richness appeared significantly higher in open habitats, such as clearcut, pasture, and ley, while it was a bit lower in cereal, and the lowest in the forest. Bumblebee abundance showed significantly higher levels in clearcut and pasture, somewhat intermediate levels in ley and cereal, and low level in forest habitat. Similarly, butterfly species richness was significantly higher in the open habitats (cereal, clearcut, ley, and pasture) than in the forest. Butterfly abundance was significantly higher in clearcut and pasture, with the abundance in the cereal being somewhat intermediate between these two open habitats and ley, while the forest showed once more the lowest abundance value. Moreover, the relationship between plant species richness and pollinators did not differ among habitats, so the relationship between pollinators and plant richness did not depend on the habitat type. Finally, different habitats had specific plant-pollinator interactions, with a higher number of interactions in open habitats (pasture, ley, clearcut, cereal) compared to the forest, where no butterfly-plant interactions were recorded.

Popular Abstract

Pollinators response to plant richness and habitat type

Land-use is changing due to agricultural intensification and abandonment, and it is a major cause for biodiversity and habitat loss. In areas where intensive agriculture is not possible, farmland, including open semi-natural habitats such as pastures and meadows, are decreasing, creating a landscape that is mainly dominated by forest. This land-use change has direct and indirect effects on the pollinator community, creating the need for understanding plant-pollinators interactions at a local level in different kinds of habitat.

Increasing number of studies point out negative consequences for pollinators biodiversity and ecosystem functions due to land-use change. For instance, pollination is a critical function for the reproduction of wild plants and the yield formation of many crops. Two important pollinator groups for studying the effect of land-use change are bumblebees and butterflies. These pollinators are easy to recognize in the field, sensitive to environmental change, and occur in different habitats. We wanted to investigate whether and how the diversity of the plant community and of habitat type can affect these pollinators. Moreover, we want to assess what are the most active species of bumblebees and butterflies in the different habitats and what are the plant species they prefer for feeding purposes.

For this purpose, during the summer of 2019, we collected data in five of the most common habitat types in Jönköping County in Småland, Sweden. The habitat types were classified as: cereal, clear-cut, forest, ley, and pasture (Fig.1). Butterflies, including burnet moths, and bumblebees were directly identified in each field along 5 different linear transects and a free survey, walked where we would expect higher pollinator diversity. We also noted whenever they were visiting a flowering plant. Each transect was long 50 m and we would walk it for about 10 minutes, catching and recognizing any bumblebee and butterfly that was flying by. Plant communities were described collecting data from randomly placed 1 m² quadrats (from 10 up to 60 depending on the habitat’s plant richness) in each field. In addition, we assessed whether plant-pollinator interaction networks differed between the habitats, using flower visitation data from the same sites.

Plant diversity and habitat type directly affect pollinators.
In this study, the results show that with the increase of plant diversity, also the diversity of pollinators and their abundance increased. Moreover, the habitat type had a strong effect on pollinators, with the highest diversity and abundance in open habitats, such as pastures and clear-cuts, followed by ley and cereal sites. The lowest pollinator diversity and abundance was found in the forest, for both bumblebees and butterflies. Nevertheless, the impact of the habitat type on the pollinators could be also explained by the plant diversity, since in every habitat we have different plant species. Thus, even though we did not find that the habitat would influence the plant-pollinator relation, plant diversity can constraint pollinators in habitats where it is low. Thus, considering plant richness and habitat identity together is somewhat more helpful in explaining pollinator communities’ responses. Moreover, we assessed higher number of interactions and frequency, in pasture, and clear-cut followed by ley and cereal for both groups of pollinators. We also found no plant-butterfly interactions in the forest, while some bumblebee species were active in the forest mainly on the plant patches of Melampyrum pratense. Other important plant species were Trifolium sp. in ley for both bumblebees and butterflies, and Leontodon autumnalis for butterflies in all the habitats, except forest.


Bumblebee and butterfly diversity was the highest in open habitats, especially pastures and clear-cuts, followed by ley and cereal fields. This is why conservation plans should focus on increasing these types of habitats, especially in landscapes that are mainly dominated by forest. Another important management approach would be to sustain and increase plant diversity in those open habitats. Of course, we should also consider other habitat characteristics, such as climate variables, and management strategies, such as pesticide exposition, to actually assess what can cause pollinators decline. Another important factor is to keep these habitats well connected to each other so that the pollinators could easily find their way to richer floral and nesting resources. Moreover, monitoring pollinators for longer time frame could guide us into answering questions related to the effect of land-use change in the long run, together with pollinators interactions with wild plant in a changing environment.


Master’s Degree Project in Conservation Biology 45 credits 2019/2020
Department of Biology, Lund University


Advisor: Yann Clough
Centre for Environmental and Climate Science (CEC)

• author: Spatola, Noemi
• supervisor: Yann Clough
• organization: Degree Projects in Biology
• course: BION02 20222
• year: 2023
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9139994
• date added to LUP: 2023-10-13 14:10:15
• date last changed: 2023-10-13 14:10:15