Annual climatic effects on the autumnal Drosophilids fauna composition at the Font Groga site (Tibidabo, Barcelona)

Abstract

The abundance of different drosophilid species was studied in a series of six consecutive years during autumn at the Font Groga site (Tibidabo, Barcelona). Furthermore, the relation between these abundances and the following climatological variables (Tmean: mean temperature, Tmax: maximum temperature, Tmin: minimum temperature, Hm: mean humidity and Rf: rainfall) were studied. The most common species observed at this location were D. subobscura, D. melanogaster/D.simulans and the invasive species D. suzukii. Other species were trapped depending on the year (D. immigrans, D. buzzatti, D. cameraria, D. phalerata and D. hydei), and the values of several diversity indexes were computed for each annual collections. In general, in those years where D. melanogaster/D. simulans flies were abundant, D. subobscura and D. suzukii were in low frequencies. From the analyses of the climatic variables and the three most abundant species, it seemed that D. subobscura would need environmental conditions characterized by a low Tmin, not a very high Tmax (but with a large difference between both), a certain degree of humidity and scarce rainfall. D. suzukii presented a similar pattern, but not so accused, whereas D. melanogaster / D.simulans group would need high Tmin, low Tmax (with a small difference between Tmin and Tmax values) and low levels of humidity and rainfall. Finally, in these autumnal samples our results would indicate a certain association between the abundances of D. subobscura and D. suzukii, although their breeding sites are clearly different.