Deciphering the variation in cuticular hydrocarbon profiles of six European honey bee subspecies

Abstract

The Western honey bee (Apis mellifera) subspecies exhibit local adaptive traits that evolved in response to the different environments that characterize their native distribution ranges. An important trait is the cuticular hydrocarbon (CHC) profile, which helps preventing desiccation and mediating communication. We compared the CHC profiles of six European subspecies (A. m. mellifera,A. m. carnica,A. m. ligustica,A. m. macedonica,A. m. iberiensis, andA. m. ruttneri) and investigated potential factors shaping their composition. We found that forager CHC profiles were more subspecies- specific than those of nurse bees. These differences could be partially explained by their molecular phylogeny, indicating genetic drift as an important factor. We did not find adaptation of the CHC profiles of the subspecies to the climatic conditions in their distribution range. Nurse bees showed a larger variation in subspecies-specific CHC profiles, likely due to a controlled environment with less desiccation stress inside the hive. The strongest profile differences appeared between nurse bees and foragers in all subspecies, suggesting an adaptation to social task and a role in communication. Foragers also showed an increase in the relative amount of alkanes in their profiles compared to nurses, indicating adaptation to climatic conditions.

Expression of elongase- and desaturase-encoding genes shapes the cuticular hydrocarbon profiles of honey bees

“…A similar difference has been described for the workers inside and outside the nest of other social insects (Martin and Drijfhout, 2009;Wagner et al, 2001Wagner et al, , 1998. This is thought to respond to the higher desiccation pressure faced by the outside workers (e.g., forager bees) compared to those inside the nest (e.g., nurse bees), due to their higher exposure to weather extremes (e.g., temperature and humidity) (Kather et al, 2011;Martin and Drijfhout, 2009;Rodríguez-León et al, 2024;Wagner et al, 2001Wagner et al, , 1998.…”

“…Menzel et al, 2017). However, differences in CHC composition between A. mellifera subspecies have been suggested to respond to their divergent evolutionary histories and genetic drift, as they do not seem to consistently correlate with the climatic differences (i.e., temperature and precipitation) between their native distributions (Rodríguez-León et al, 2024). Therefore, the adaptive difference in CHC composition we observed between A. m. carnica and A. m. iberiensis, is likely specific to this particular comparison.…”

“…Therefore, as the expression of specific elongase-and desaturase-encoding genes varies with age (Vernier et al, 2019), the differences in the CHC composition between honey bee nurses and foragers are assumed to respond to a developmental regulatory process. Moreover, the difference in the CHC profiles of nurse bees and foragers has been shown to be present among A. mellifera subspecies (Rodríguez-León et al, 2024).…”

“…In honey bees (Apis mellifera), the CHC profiles of the workers differ according to their age, taskperformance, and subspecies (Kather et al, 2011;Rodríguez-León et al, 2024;Vernier et al, 2019). The CHC profiles of nurse bees are characterized by a higher abundance of unsaturated hydrocarbons and longer chain lengths compared to forager bees (Kather et al, 2011;Rodríguez-León et al, 2024). These two groups of honey bee workers are on opposite ends of the age-dependent division of labor in A. mellifera.…”

“…mellifera subspecies have divergent evolutionary histories, leading to both genetic and phenotypic differences (Dogantzis et al, 2021;Garnery et al, 1992;Ruttner, 1988;Ruttner et al, 1978). In consequence, different subspecies have evolved distinct CHC profiles, exhibiting both quantitative and qualitative differences in their composition (Rodríguez-León et al, 2024). This remarkable variability of CHC profiles makes A. mellifera an excellent model organism for studying the molecular mechanisms underlying CHC biosynthesis.…”