Research interest
I am interested in systematics and biogeography of non-biting midges of the family Chironomidae (Diptera). My research focuses on taxonomy, biology, phylogeny, zoogeography and molecular systematics of genera and species in the tribe Tanytarsini. The tribe contains more than 400 species in 25 genera. Several of the genera have a world-wide distribution, but some are endemic to tropical areas in Africa and South America. The larvae and pupae inhabit almost all kinds of aquatic environments, but are most common in streams, rivers and lakes. The adults are flying midges or, rarely, water skaters adapted to a life on the water surface on rivers, and although copulation on the ground exists, most species reproduce through swarming in the air. The great species and habitat diversity of the tribe not only makes it a valuable source of indicator species for lentic- and lotic aquatic ecosystems, but also a most interesting group for phylogenetic and zoogeographical analyses.

In my Dr. scient. thesis I revised the species of four closely related species groups in the genus Tanytarsus (Diptera:Chironomidae). The results of the phylogenetic analyses indicate that the groups originated in Laurasia after the splitting from Gondwanaland, and that African and Australian group members are results of later dispersal over the Middle East and Indonesia. Ole A. Sæther and Trond Andersen supervised me during the Dr. scient. project.

Current projects
Molecular systematics of the tribe Tanytarsini. The project is conducted in collaboration with Prof. Endre Willassen (Bergen, Norway). By using mitochondrial and nuclear gene sequences, and taking advantage of both parsimony and Bayesian inference, we wish to reconstruct the genealogical relationships between genera in the tribe. We expect to use the results to revise the present classification, as well as to model character and gene evolution in Tanytarsini.

Larval head capsules of European Micropsectra, Paratanytarsus and Tanytarsus Diptera: Chironomidae: Tanytarsini). In collaboration with Oliver Heiri (Utrecht, the Netherlands) and Endre Willassen (Bergen, Norway). Our goal with this project is to figure and describe the larval head capsules of the European species in the above genera, with special emphasis on characters available to palaeolimnologists.

Systematics and Biogeography of Zavrelia and Stempellinella (Diptera: Chironomidae). This project focuses on the taxonomy, systematics and zoogeography of the chironomid genera Zavrelia Kieffer and Stempellinella Brundin (Diptera). Through taxonomic revisions, and description of new species and immature stages, identification keys for all life stages will be erected, and morphological as well as molecular characters will be used to infer the phylogenetic relationship of the species in the two genera. The results will either support or refute the hypothesis that the genera Zavrelia and Stempellinella should be synonymized, and provide a solid background for a revision of the current classification. Based on the resulting phylogeny, zoogeographical analyses will be performed and provide the most probable biogeographical history and area of origin for the two genera.

Phylogeography of circumpolar aquatic insects.The evolution and genetic structure of species with circumpolar distributions were greatly influenced by the Pleistocene glaciations. Freshwater species were especially affected since they lived in highly unstable habitats and had limited possibilities of dispersal. The “young” nature of the circumpolar fauna allows one to closely examine gene flow, vicariance, dispersal and hybridisation, and how these effects shape the population genetics and phylogeography of resident taxa. This project is the first to attempt such a study for circumpolar aquatic insects. The insect fauna of polar freshwater lakes is dominated by non-biting midges (Diptera: Chironomidae), and three chironomid species, Tanytarsus gracilentus, Pseudodiamesa nivosa and Micropsectra radialis, will be used as model organisms in this study. The species have a circumpolar distribution, they usually occur in large populations, and the taxonomy and ecology is comparatively well known for all life stages. By utilizing molecular techniques, such as RFLP analysis and direct sequencing of mitochondrial and nuclear DNA, the historical biogeography of these species will be reconstructed to closely examine the extent and effect of vicariance, dispersal, hybridization and isolation on the population structure.

Bibliography

Ekrem, T. (2006). A redescription of Neozavrelia cuneipennis (Edwards) comb. nov., with a checklist of Neozavrelia species of the world (Diptera: Chironomidae). - Zootaxa 1153: 1-16.

Stur, E. & T. Ekrem (2006). A revision of West Palaearctic species of the Micropsectra atrofasciata species group (Diptera: Chironomidae). - Zoological Journal of the Linnean Society 146: 165-225.

Ekrem, T. (2005). Lateral abdominal spur in Stempellinella as pupal 'can opener'. - Chironomus newsletter on Chironomidae research 18: 27-28.

Stur, E., P. Martin, & T. Ekrem (2005). Non-biting midges as hosts for water mite larvae in spring habitats in Luxembourg. - Annales de Limnologie 41 (4): 225-236.

Ekrem, T. & E. Willassen (2004). Exploring Tanytarsini relationships (Diptera: Chironomidae) using mitochondrial COII gene sequences. - Insect Systematics and Evolution 35: 263-276.

Ekrem, T. (2004). Immature stages of European Tanytarsus species I. The eminulus-, gregarius-, lugens- and mendax species groups (Diptera: Chironomidae). - Deutsche entomologische Zeitschrift 51 (1): 97-146

Ekrem, T. (2003). Towards a phylogeny of Tanytarsus van der Wulp (Diptera: Chironomidae. Is morphology sufficient to reconstruct the genealogical relationships? - Insect Systematics and Evolution 34: 199-219

Ekrem, T., M. F. Sublette & J. E. Sublette (2003). North American Tanytarsus I. Descriptions and keys to species in the eminulus, gregarius, lugens and mendax species groups (Diptera: Chironomidae). - Annals of the Entomological Society of America 96: 265-328

Sæther, O. A. & T. Ekrem (2003). Biogeography of Afrotropical Chironomidae (Diptera), with special reference to Gondwanaland. - Cimbebasia 19: 175-191

Ekrem, T. (2002). A revision of the Tanytarsus eminulus, gregarius, lugens and mendax species groups (Insecta: Diptera: Chironomidae). Dr. scient thesis, University of Bergen, Bergen, Norway, 271pp. ISBN: 8291963126

Ekrem, T. (2002). Review of selected South- and East Asian Tanytarsus v.d. Wulp (Diptera: Chironomidae). - Hydrobiologia 474:1-39.

Ekrem, T. (2001). A review of Afrotropical Tanytarsus (Diptera: Chironomidae). - Tijdschrift voor Entomologie 144: 5-40.

Ekrem, T. (2001). Diagnoses and immature stages of some Australian Tanytarsus van der Wulp (Diptera: Chironomidae). - Australian Journal of Entomology 40: 312-325.

Ekrem, T. & O. A. Sæther (2000). Seppia, a new Afrotropical tanytarsine genus (Diptera: Chironomidae). in. Hoffrichter, O. (ed): Late 20th Century Research on Chironomidae: an Anthology from the 13th International Symposium on Chironomidae, pp. 79-87, Shaker Verlag, Aachen.

Ekrem, T. (2000). Bilder fra en verden. - Naturfotografen 15 (1): 28.

Ekrem, T. (2000). Chironomid types at Muséum National d'Histoire Naturelle, Paris (Meigen collection not included). - Chironomus newsletter on Chironomidae research 13: 15-19.

Ekrem, T. (2000). Fjærmygg - mygg som ikke stikker. - Naturfotografen 15 (1): 12-13.

Ekrem, T. (2000). Hvorfor døde Trilobittene ut? - Naturen 124 (4): 194-202.

Stur, E. & T, Ekrem (2000). Tanytarsus usambarae spec. nov. from West Usambara Mts., Tanzania, East Africa. (Insecta, Diptera, Chironomidae). - Spixiana 23: 219-223.

Ekrem, T. & A. D. Harrison (1999). Tanytarsus minutipalpus spec. nov. from the saline lakes in the Rift Valley, East Africa (Insecta, Diptera, Chironomidae). - Spixiana 22 (3): 199-208.

Ekrem, T. & F. Reiss (1999). Two new Tanytarsus species (Diptera: Chironomidae) from Brazil, with reduced median volsella. - Aquatic Insects 21 (3): 205-213.

Ekrem, T. (1999). Cladotanytarsus bukavus (Lehmann, 1979) comb. n. and Cladotanytarsus congolensis (Lehmann, 1979) comb. n. from Central Africa (Diptera: Chironomidae). - Annales de Limnologie 35 (3): 185-191.

Ekrem, T. (1999). Six new Tanytarsus species from Ghana, West Africa (Insecta, Diptera, Chironomidae). - Spixiana 22: 53-68.

Ekrem, T., F. Reiss & Peter H. Langton (1999). Tanytarsus mancospinosus sp. n. (Diptera: Chironomidae) from eutrophic lakes in Europe. - Norwegian Journal of Entomology 46: 79-87.

Sæther, O. A. & T. Ekrem (1999). Molleriella calcarella a new terrstrial orthoclad genus from the Netherlands (Diptera: Chironomidae). - Acta zool. Acad. sci. Hung. 45 (2): 161-168.

Links

The Chironomid home page

Tanytarsini web key to subfossil head capsules

World revision of Stempellinella & Zavrelia