Empidine dance flies pollinate the woodland geranium as effectively as bees.

Most flowering plants species rely on insects for pollination, a successful mutualism allowing them to reproduce over wide areas while flower-visitors are rewarded with food. This association is so conspicuous in the case of bees that other groups of potential pollinators, especially flies, have long been underestimated. However, visitors are not always pollinators. While the importance of flies in plant-visitor networks is now acknowledged, their pollination effectiveness has hardly been investigated. In this study, we assessed the pollination effectiveness of Geranium sylvaticum flower-visitors using single-visit seed set experiments, in a subalpine meadow where flies are predominant. We found that: (i) empidine dance flies were the most frequent visitors of G. sylvaticum; (ii) a single-visit by an empidine dance fly produced the same average number of seeds as a visit by a bee; (iii) large pollinators were more efficient than small pollinators irrespective of their identity. As a conclusion, large empidines were the main pollinators of G. sylvaticum. Considering the high diversity and abundance of flower-visiting fly species, such results showing their ability to be as effective pollinators as bees should encourage further studies to develop a better understanding on their role in plant-pollinator networks.

Are empidine dance flies major flower visitors in alpine environments? A case study in the Alps, France.

Pollination is one of the most important ecosystem services and bees the most important pollinators. As a population decline of bees has been documented in numerous regions of the world, it is crucial to develop understanding on other possible pollinators. Here, we study the potential pollination impact of Diptera, and among them Empidinae, in an alpine environment, where the abundance of bees is naturally lower. Interactions between 19 entomophilous plants and their flower visitors were recorded in a subalpine meadow in the French Alps during six weeks. Visitation frequencies were used to build the flower-visitor network. Our results show that interactions between flies and plants are dominant; flies represent more than 60% of all visitors, with 54% of them being Empidinae. We especially found that flies, Empidinae and bees are the main visitors of 11, three and one plants, respectively. When considering both bees and Syrphidae together, six plants were more visited by Empidinae; when considering bees and Syrphidae separately, 10 plants were more visited by Empidinae than by bees or Syrphidae. The results support the idea that flies widely replace bees as main flower visitors at altitude, and among them the Empidinae might play a key role in pollination.

Sexually antagonistic co-evolution can explain female display signals and male sensory adaptations.

The prevalence and diversity of female ornaments poses a challenge to evolutionary theory because males should prefer mates that spend resources on offspring rather than ornaments. Among dance flies, there is extraordinary variation in sexual dimorphism. Females of many species have conspicuous ornaments (leg scales and inflatable abdominal sacs). Meanwhile males of some species have exaggerated regions of their eyes with larger ommatidial facets that allow for regionally elevated photosensitivity and/or acuity. Here, we conduct a comparative study of these traits using both species descriptions available from the literature, as well as quantitative measures of eyes and ornaments from wild-caught flies. We show a conspicuous covariance across species between exaggerated male dorsal eye regions and the extent of female ornaments: species with highly ornamented females have males with more exaggerated eyes. We discuss this pattern in the context of competing hypotheses for the evolution of these traits and propose a plausible role for sexually antagonistic coevolution.

Competition for access to mates predicts female-specific ornamentation and male investment in relative testis size.

Sexually selected ornaments are highly variable and the factors that drive variation in ornament expression are not always clear. Rare instances of female-specific ornament evolution (such as in some dance fly species) are particularly puzzling. While some evidence suggests that such rare instances represent straightforward reversals of sexual selection intensity, the distinct nature of trade-offs between ornaments and offspring pose special constraints in females. To examine whether competition for access to mates generally favors heightened ornament expression, we built a phylogeny and conducted a comparative analysis of Empidinae dance fly taxa that display female-specific ornaments. We show that species with more female-biased operational sex ratios in lek-like mating swarms have greater female ornamentation, and in taxa with more ornate females, male relative testis investment is increased. These findings support the hypothesis that ornament diversity in dance flies depends on female receptivity to mates, which is associated with contests for nutritious nuptial gifts provided by males. Moreover, our results suggest that increases in female receptivity lead to higher levels of sperm competition among males. The incidence of both heightened premating sexual selection on females and postmating selection on males contradicts assertions that sex roles are straightforwardly reversed in dance flies.

The mitochondrial genome of Empis separata (Diptera: Empididae).

The dance fly Empis separata belongs to the subfamily Empidinae of Empididae. The mitogenome (GenBank accession number: MK993569) of E. separata was sequenced, the new representative of the mitogenome of the subfamily. The complete mitogenome is 14,961 bp totally, consisting of 13 protein-coding genes, two rRNAs, and 22 transfer RNAs. All genes have the similar locations and strands with that of other published species of Empididae. The nucleotide composition biases toward A and T, which together made up 76.3% of the entirety. Bayesian inference analysis strongly supported the monophyly of Empidoidea, Empididae, and Dolichopodidae. This result also suggested that Empidinae is the sister group to the clade of Trichopezinae.

The mitochondrial genome of Hilara sp. (Diptera: Empididae).

The dance fly Hilara sp. belongs to the subfamily Empidinae of Empididae. The mitogenome (GenBank accession number: MN064659) of Hilara sp. was sequenced, the new representative of the mitogenome of the subfamily. The nearly complete mitogenome is 14,927 bp totally, consisting of 13 protein-coding genes, 2 rRNAs, and 22 transfer RNAs. All genes have the similar locations and strands with that of other published species of Empididae. The nucleotide composition biases towards A and T, which together made up 75.7％of the entirety. Bayesian inference analysis strongly supported the monophyly of Empidoidea, Empididae, and Dolichopodidae. It is clear that the phylogenetic relationship within Empidoidea: Dolichopodinae was the sister group to Neurigoninae, and Empidinae was the sister group to Trichopezinae, and the clade that contains Dolichopodinae and Neurigoninae was assigned to the sister group to the clade that contains Empidinae and Trichopezinae.

Descrição de três espécies novas de Porphyrochroa Melander (Diptera, Empididae) da Bacia Amazônica, Brasil / Description of three new species of Porphyrochroa Melander (Diptera, Empididae) from the Amazon Basin, Brazil

Descrição de três espécies novas de Porphyrochroa Melander (Diptera, Empididae) da Bacia Amazônica, Brasil Porphyrochroa Melander, 1928 é registrado pela primeira vez na Bacia Amazônica brasileira e três espécies novas são descritas e ilustradas, P. elongata sp. n. (Amazonas e Acre), P. hipandriociliaris sp. n. (Amazonas) e P. vidali sp. n. (Roraima e Amazonas).

Porphyrochroa Melander, 1928 is recorded for the first time in the Brazilian Amazon Basin and three new species are described and illustrated, namely: P. elongata sp. n. (Amazonas and Acre), P. hipandriociliaris sp. n. (Amazonas) and P. vidali sp. n. (Roraima and Amazonas).