How are insects doing these days? Bumblebee genes provide the answer.

The period that frames the global impact of human activity on the landscape is referred to as the Anthropocene. This epoch is characterised, for example, by the increasing concentration of greenhouse gases in the atmosphere, the growth of industrial areas, and the massive loss of the earth’s biosphere. The impact of humans on the wildlife environment is widespread and results in major losses of biodiversity. One of the main threats to the well-being of more than just insects is the current intensification of agriculture which is characterised by large areas of monocultures and/or the use of agrochemicals such as fertilisers and pesticides. This activity leads to fragmentation and loss of natural habitats, native vegetation, and thus nesting and breeding sites.

Research on the loss of insect biodiversity is now coming to the fore due to these negative factors. Insects are a key element in the cycle of life on earth – they serve as food and perform important roles as pollinators and decomposers. Investigating and understanding the adaptability of insects to these changing environmental conditions is crucial to predicting their survival. Key pollinators such as bumblebees are not exempt from monitoring. In bumblebees, stress caused by change can manifest itself in insufficient nutrient supplies or in reduced and fragmented populations. In more agriculturally impacted areas, populations may tend to become more isolated, leading to lower genetic variation and a higher tendency for inbreeding or mutations. This can lead to reduced longevity or increased susceptibility to environmental stressors.

Bombus lapidarius – queen.
Source: Wikipedia
Author: Ivar Leidus

Bumblebees are commonly used as effective model species for assessing insect adaptation to anthropogenic stressors. In the current study, the researchers investigated the effects of agricultural pressure on two common European species – the common carder bee (Bombus pascuorum) and the red-tailed bumblebee (Bombus lapidarius). Genome sequencing is a useful method for studying changes in insect populations. Restriction site-associated DNA sequencing (sometimes referred to as restriction genome mapping) has been used to identify loci under selection pressure across agricultural and natural gradients at 97 locations in Europe. A total of 191 unique loci were identified in B. pascuorum and 260 loci in B. lapidarius which are under selection pressure and linked to agricultural stressors. The study aimed to identify genomic regions and corresponding genes displaying differential selection pressures in bumblebees from both natural and agricultural areas. In total, over 200 samples from both species of the genus Bombus, collected from 16 European countries, were sequenced. The loci were subsequently divided into three categories according to sampling location and were differentiated from natural to completely transformed.

Bombus pascuorum – worker.
Source: Wikipedia
Author: André Karwath

By performing RADSeq (a sequencing method) from localities across the European gradient from agricultural to natural landscapes, the researchers were able to detect signs of local adaptation and selection pressure induced by associated stressors. Using the BLAST (gene localisation) method, the researchers matched several candidate genes involved in neurological development or muscle structure. The results revealed that European bumblebees have thus far been able to adapt, but agricultural activity is adversely affecting them and populations may not remain stable. Further studies, using methods such as whole genome sequencing, may provide better clues in the future as to how to use this information for conservation purposes. The results of this study supply insights into agriculture as a stressor for bumblebees and provide a signal for conservation action in the light of ongoing anthropogenic changes. When you see a bumblebee this summer, you may, after reading this article, remember how well they have actually been doing in recent years and that they too have had to adapt to the obstacles humans have put in their way.

Hart AF, Verbeeck J, Ariza D, Cejas D, Ghisbain G, Honchar H, Radchenko VG, Straka J, Ljubomirov T, Lecocq T, Dániel-Ferreira J, Flaminio S, Bortolotti L, Karise R, Meeus I, Smagghe G, Vereecken N, Vandamme P, Michez D and Maebe K (2022) Signals of adaptation to agricultural stress in the genomes of two European bumblebees. Front. Genet.

Tereza Žirovnická