Diversity increases with elevation: empidine dance flies (Diptera,Empididae) challenge a predominant pattern

Tropical mountain forests are important reservoirs of biodiversity. They are usually species‐rich and often support endemic species making them prime targets for conservation effort. The aim of this study was to investigate elevational patterns of species diversity and phenology to provide a meaningful understanding of insects’ spatio‐temporal distributions along a tropical gradient of elevation. Our study focuses on the Empidinae communities (Diptera, Empididae) from Doi Inthanon (north Thailand, gradient 400–2556 m asl), sampled during two entire years (2006–2007, 2014). This group of insects is more diverse in temperate localities than in the tropics and we found that: (1) increase in altitude and latitude has a similar effect, so that the diversity of our model increases with elevation; (2) the phenology is strongly influenced by seasonality with a peak of diversity occurring during the transition between the dry and rainy seasons; (3) there is no phenological shift in the diversity peak with elevations; and (4) the species composition changes along the altitudinal gradient and through the year (high beta diversity). The increase in diversity with increasing elevation and the peak of diversity occurring at the transitional period both strongly coincide with abiotic factors, the decreasing temperature and the arrival of the monsoon, respectively.     

Phylogenetic systematics of the Empis (Coptophlebia) hyalea-group (Insecta: Diptera: Empididae)

Six clades are inferred from a phylogenetic analysis including 42 species belonging to the Empis (Coptophlebia) hyalea‐group. These clades are named as follows: E. (C.) acris, E. (C.) aspina, E. (C.) atratata, E. (C.) hyalea, E. (C.) jacobsoni and E. (C.) nahaeoensis. The presence of two dorsal more or less developed epandrial projections is considered autapomorphic for the E. (C.) hyalea‐group in addition to two characters previously found to support the monophyly of this group (presence of an unsclerotized zone in the middle of labella and epandrium unpaired). Amongst the cladistically analysed species, 24 are newly described [ E. ( C. ) acris , E. ( C. ) aspina , E. ( C. ) cameronensis , E. ( C. ) duplex , E. ( C. ) incurva , E. ( C. ) inferiseta , E. ( C. ) kuaensis , E. ( C. ) lachaisei , E. ( C. ) lamellalta , E. ( C. ) lata , E. ( C. ) loici , E. ( C. ) longiseta , E. ( C. ) mengyangensis , E. ( C. ) menglunensis , E. ( C. ) missai , E. ( C. ) nimbaensis , E. ( C. ) padangensis , E. ( C. ) parvula , E. ( C. ) projecta , E. ( C. ) pseudonahaeoensis , E. ( C. ) submetallica , E. ( C. ) urumae , E. ( C. ) vitisalutatoris and E. ( C. ) woitapensis ], five are reviewed [E. (C.) hyalea Melander, E. (C.) jacobsoni De Meijere, E. (C.) ostentator Melander, E. (C.) sinensis Melander and E. (C.) thiasotes Melander] and 13 were recently described in two previous papers. Two additional species, E. (C.) abbrevinervis De Meijere and E. (C.) multipennata Melander, are also reviewed but not included in the cladistic analysis since they are only known from the female. A lectotype is designated for E. (C.) jacobsoni. A key is provided to the six clades of the E. (C.) hyalea‐group as well as to species of each clade. A catalogue of the E. (C.) hyalea‐group, including 72 species, is given. The taxonomic status of 25 additional species mainly described by Bezzi and Brunetti, from the Oriental and Australasian regions, is discussed. The E. (C.) hyalea‐group is firstly recorded from the Palaearctic Region and Australia. Finally, the distribution and the habitats of the species compared with their phylogeny suggest a possible relationship between the diversification of the group and forest fragmentations during the Quaternary. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 145 , 339–391.     

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.     

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.