When European meets African honeybees (Apis mellifera L.) in the tropics: Morphological changes related to genetics in Mauritius Island (South-West Indian Ocean)

Abstract

The previous genetic characterization of the honeybee population of Mauritius Island (Indian Ocean) revealed an ongoing process of hybridization between the first established African subspecies Apis mellifera unicolor and recently imported European subspecies (A. m. ligustica, A. m. carnica and A. m. mellifera). This context offers the rare opportunity to explore the influence of hybridization between African and European honeybees on phenotypic traits out of the case largely studied of the Africanized honeybee (hybrid between A. m. scutellata from South Africa and European subspecies). We thus conducted geometric morphometric analyses on forewings of 283 workers genetically characterized at 14 microsatellite loci to evaluate (1) if the morphological variability coincides well with the neutral genetic variability, (2) if hybrids exhibited rather parental, intermediate or transgressive traits, and (3) to test if fluctuating asymmetry (FA) of size and shape, as a measure of developmental stability, was elevated in hybrids (due to genetic stress) and/or European bees (due to unsuitable environment) compared to African bees. A strong concordance was found between morphological variability and neutral genetic variability, especially for wing shape, based on partial least-square analyses (PLS). However, on average, the morphology of hybrids was more similar to the African bees, potentially reflecting the dynamics and direction of introgression. Significant FA for wing size as well as wing shape was detected, suggesting the overall presence of stress during the development of the studied individuals. In contrast, the asymmetry levels do not differ according to the ancestry (African, European or hybrid) of the individuals. Therefore, if ongoing hybridization contributed to increasing the genetic and phenotypic diversity of the populations and influences its adaptive potential, developmental stressors could not be identified and their evolutionary consequences remain uncertain.

Africanized honeybee population (Apis mellifera L.) in Nicaragua: Forewing length and mitotype lineages

“…One characteristic for A1 mitotype belonging to A . mellifera iberiensis from south-western Europe could be the size of the forewing, commonly European subspecies have longer wings [ 48 ]. Conversely, in Nicaragua, colonies with mitotypes A4, generally characterized by smaller wings, here had even longer forewings than A1.…”

Selection despite low genetic diversity and high gene flow in a rapid island invasion of the bumblebee, Bombus terrestris

“…It is therefore likely that bees may show phenotypic plasticity or adaptive responses to new environmental conditions. Accordingly, invasive bees might be expected to display such adaptive and physiological responses to changing environments (Christmas et al, 2022;Eggenberger et al, 2019;Miller-Struttmann et al, 2015;Oliveira et al, 2016;Theodorou et al, 2018Theodorou et al, , 2020Tommasi et al, 2022), but few studies have investigated morphological or genetic changes in relation to novel environments in invasive bees (although see Galataud et al, 2020;Kardum Hjort et al, 2023).…”