Fine scale population structure of hoverfly pollinator, Eristalis arbustorum: An integrative study

Determination of the factors influencing the population structure and adaptive tolerance to environmental pressures of the synanthropic hoverfly Eristalis arbustorum is of essential importance in understanding how pollinator populations could respond to climate change or ecosystem management. We addressed the issue of connectivity among conspecific populations sampled in Bosnia and Herzegovina. Twenty environmental factors, mitochondrial DNA sequences of the cytochrome c oxidase subunit I gene (COI mtDNA), allele frequencies at allozyme loci and wing traits (size and shape) were compared for characterization of population structure and environmental niches. Additionally, patterns of within-individual asymmetry (fluctuating asymmetry; FA) in wing size and shape within and among conspecific populations were studied. In line with the overall similarity of the environmental factors extracted for our study sites, the results of COI mtDNA diversity and STRUCTURE allozyme data provide evidence for shallow differentiation among conspecific populations. In contrast, geo-referenced Bayesian clustering methods (BAPS and GENELAND) and population-based approaches (pairwise F-ST values and AMOVA) indicate that the dispersal potential of E. arbustorum may be limited across the study area. Along with a significant FA in wing size and shape, a consistent level of FA regardless of urban/rural sampling origin is an indication of the great potential of E. arbustorum for local adaptation, because increased FA levels can be considered to be a way of expression of phenotypic variation and, hence, may contribute to adaptive responses in populations facing changing environments. Thus, by using a combined genetic-morphological approach, we significantly contributed to the understanding of the fine-scale genetic structure of the synanthropic generalist pollinator E. arbustorum.