The first insight of environmental change impact on Syrphidae (Diptera) morphology: wing fluctuating asymmetry analysis of Merodon aberrans Egger, 1860

Throughout Earth’s history, climate has changed continuously, but at a much slower
pace than currently observed. In Serbia average temperature increase over the territory
is 1.2 °C for the period 1996-2015 with respect to the period 1961-1980, with the
highest increase of maximum daily temperature during the summer season, 2.2 °C. Climate
change is a complicated phenomenon, with various changes including shifts in limits
(maxima and minima), average conditions, and variance, which can all be measured at
different temporal and spatial scales. Insects are ectothermic and critically depend on environmental
temperature throughout all aspects of their life history, but also other niche
aspects are changing—precipitation, humidity, cloud cover, weather extremes, biotic interactions—
with potentially dramatic impacts.
Our research delves into a relatively unexplored area, as there is currently no insight
into the impact of environmental change on the Syrphidae morphology. To investigate
this, we selected populations from a single natural habitat with insignificant anthropogenic
influence. The impact of environmental change on Syrphidae morphology was measured
through fluctuating asymmetry (FA) of wing shape. FA represents slight and random
deviations from bilateral symmetry normally distributed around a 0 mean. Increased FA
reflects the stress an organism undergoes during development, which may be caused by
environmental and genetic stress.
We studied populations of Merodon aberrans Egger, 1860 from the Vrˇsac Mountains,
Serbia, from the 1980s and 2020s, and compared the wing asymmetry between these two
temporal populations. Results showed that the 2020s population exhibited greater wing
FA compared to the 1980s population, with a statistically significant difference. These
indicate that environmental change affects the asymmetry of hoverflies, which, according
to numerous studies, is negatively correlated with organism fitness. Further studies are
crucial to expand this analysis to other species within this family, encompassing all forms
of larval development if feasible, and to compare their response to environmental change.