Trends of wing wear for bumblebees, Bombus terrestris L., evaluated from queens in museum collections

Abstract

Insects are the most diverse group of animals, and among the largest contributors to species richness, accounting for around 66% of known species on Earth. Insects are extremely important pollinators, and to understand the timing of pollination, age distribution within time could give important information. Pollinator phenologies advance more rapidly than plant phenologies that can lead to pollination mismatch which is a concern regarding global warming. This study focuses on the bumblebee species Bombus terrestris, using specimens from the Entomological collection at the Ecology Building at Lund University where 1808 specimens were labeled and added to a previously existing database, 712 specimens were imaged and 265 specimens were digitized to study wing wear. Wing wear is irreversible damage to the margin of the wings that has been linked to mortality in bumblebees. The direct mechanism of wing wear correlating with mortality is still unknown. A method to estimate the age of bees is wing wear scoring based on a scale from 0-6 but the findings in this study indicate that more quantitative measurements would be more suitable due to the inaccuracy this method provides. This study revealed a significant correlation between wing wear and various morphological, environmental, spatial, and temporal factors, such as body size, temperature, land use, and collection year. These findings could be useful for future conservation efforts and for a better understanding of how wing wear can be applied to study the age of B. terrestris.

Popular Abstract

Wing wear in bumblebee queens from museum collections.


Insects account for around 66% of known animal species on Earth (Zhang, 2011). Insects are extremely important when it comes to ecological context because they help with pollination, seed dispersal and regulate plant diversity as well as affecting human economies (Scudder, 2017; Crespo-Pérez et al, 2020). Due to climate change the pollination process could be at risk because insects tend to adapt faster to changing environments than plants (Hegland et al, 2009).

Although insects are considered so important not much is known about the longevity and the population age structure of pollinators (Carey, 2001). Being able to use accurate methods to estimate insect age would be valuable to understand the ecology and behavior (Hayes & Wall, 1999). One way that has been used as an indicator of age is estimating wing wear which is irreversible damage to the wings that insects can not repair (Mueller & Wolf-Mueller, 1993; Foster & Cartar, 2011).

Bumblebees are not well adapted to high temperatures and their ability to fly seem do decrease with increasing temperature (Kuo et al, 2023). Bombus terrestris L. is a bumblebee species found in urban areas and agricultural land (Rasmont et al, 2008). There are two periods over the year where the queens can be collected, early in Spring when they emerge from hibernation to found a nest, and late in summer when new queens that are going to hibernate. Bumblebees travel long distances while foraging and can experience wing collision on avagare once per second which can lead to wing wear (Foster & Carter, 2011; Cartar, 1992; Mountcastle et al, 2016). Flight endurance in bumblebees increases until the temperature reaches 25°C and decreases after that (Kenna, Pawa & Gill, 2021). Older bumblebees lose more of the wing area faster than younger bumblebees (Cartar, 1992). Entomological collections can be important for research, conservation because of the accessibility of specimens over time (Reddy & Ronaki, 2023).

Three research questions are posed in this study:
• Is there a relationship between wing wear and other morphological factors, such as size, or external factors, such as environmental complexity?
• Is wing wear affected by landscape or climate patterns (i.e., the result of experiencing the environment).
• Is there a trend in wing wear and time either as a result of age (gerontological) or an artefact of collection and curation factors (between years)?
•
For this study specimens from the Entomological collection at the Ecology Building at Lund University were used. They were labeled where all information was gathered in a large database, wings were imaged and digitized to determine wing wear. When digitizing, the wings were measured and a wing wear score scale from 0-6 was used.



Additional data on temperature form the Climate Research Unit Time-series (CRU TS) and historic land use from the Land-Use Harmonization (LUH2) was acquired to compare to the data from this study (Harris & Jones, 2020; Hurtt et al, 2020). The computer software R was used for data analysis (RStudio Team, 2019).

The results show a relationship between wing wear and body size where wing area increases with increased body size. Wing area decreases with increasing temperature, that matches with the literature because before temperature reaches a certain point the bumblebees are more active and spend more time flying. Wing wear decreases with historic land use of C3 annual crops and increases with increasing natural area. There is a trend between wing wear and year (i.e., curation factors as an artefact of collection) where wing area increases over time, but there is no trend found in wing wear and Julian day (i.e., age) in B. terrestris.

The scoring of wing wear did not correspond well to the measured wing wear from digitizing and highlights the inaccuracy of that method since it depends on visual judgment from the observer each time. The lack of relationship between wing wear and Julian day could be because the analysis does not take the timing of each life stage into account so the collection probably includes both Spring queens and Summer queens. The increase in wing weare with year indicated that older specimens have more wing damage which can point toward a potential museum degradation.

In conclusion this study reveals important relationships when it comes to wing wear and several environmental, spatial and temporal factors. Much is yet to be discovered and understood when in comes to wing wear and what causes it and where the limits are. This study provides insight into how various factors can affect wing wear and how morphology, environment and climate can have combined effects. The effects of temperature and land use could give a valuable insight into the conservation efforts mighty be needed when it comes to wing wear and climate change.

• author: Gylfadóttir, Helena
• supervisor: Charlie Nicholson
• organization: Degree Projects in Biology
• course: BIOM02 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9175870
• date added to LUP: 2024-10-02 14:34:06
• date last changed: 2024-10-02 14:34:06