Themira

Abstract: Elevational gradients influence the distribution and abundance of species drastically and can lead to variation in community composition. Although coprophagous flies are of ecological and economic importance, their biodiversity and distribution are largely neglected. We studied the impact of steep elevational gradients and geography on the distribution of sepsid flies in the Swiss Alps. 2. Sepsidae are a family of acalyptrate flies strongly associated with decaying organic matter and vertebrate dung, and characterised by a high extent of sympatry in their breeding substrates. Historical, haphazardly sampled speci- mens from 116 locations covering an elevational range from 200 to 2000 m were available in ethanol collections of various Swiss museums. 3. Nineteen species encompassing all native genera (Meroplius, Nemopoda, Saltella, Sepsis and Themira) were recorded. Local species richness increased linearly with elevation, while area-corrected regional species richness of eleva- tional belts increased asymptotically. Species occurring at higher altitudes had lower wing loadings and greater elevational ranges than lowland species, sup- porting Rapoport's elevational rule. 4. Despite compositional similarities, the sepsid communities of the northern lowlands differed significantly from the alpine sepsid fauna. The southern low- lands were particularly differentiated in community composition due to a number of presumably thermophilic species that predominantly occur south of the Alps. 5. Relative abundances of several species were thus strongly affected by ele- vation and climatic variables. We illustrate the impact of elevational gradients and geography on a community of closely related, often sympatric species, and discuss potential mechanisms of niche partitioning via temporal succession, thermal adaptation and differential resource use.

Abstract: The result of a phylogenetic analysis of the Sepsidae based on larval characters is presented It is shown that cyclorrhaphan larvae can be as rich a source of characters as Nematocera immatures when investigated using an SEM The cladistic analysis comprised fifty-two species in sixteen genera of the Sepsidae and five outgroup species and used fifty-seven morphological characters It found seven parsimonious trees which only differed with respect to the arrangement of some species within the genus Themira The basal dichotomies of the phylogenetic trees are particularly well supported, indicating the conservative nature of larval characters Orygma is confirmed as the sister group of all the remaining sepsids, the Sepsinae There is good larval evidence that Ortalischema is the sister group of all remaining Sepsinae and that the Toxopodinae constitute an early radiation within the Sepsidae According to larval data, some genera are paraphyletic (Themira, Palaeosepsis), but adult characters appear to contradict these findings Among the traditionally recognized higher taxa within the Sepsidae, Hennig's Themira species-group and Steysbal's Sepsini have to be rejected as polyphyletic However, Hennig's Sepsis species-group is confirmed as monophyletic and will probably constitute one major element of a future phylogenetic system of the Sepsidae States of the strongly modified fore-legs of some adult sepsid males are mapped onto the phylogenetic tree, largely confirming Sulc's ideas about the evolution of these features The origin and evolution of male sternites with brushes and a gland on the tibiae of the males (‘osmeterium’) are discussed Whereas adult characters point to a sister-group relationship between the Sepsidae and the Ropalomeridae, larval characters appear to indicate a sister-group relationship between the Coelopidae and the Sepsidae The evidence for both hypotheses is critically evaluated