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I am interested in ecology and evolution of – mostly Eurasian (song-) – birds as an investigation of biodiversity in space and time. My research takes place on the following four levels. Insights gained and tools established on lower levels help to answer questions on the higher ones.
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Local populations
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In 2005 I established a constant-effort site in the nature reserve "Eich-Gimbsheimer Altrhein" and maintain this long-term study together with an active team (www.ismega.de). Annually we collect detailed morphological and physiological data from up to 500 birds from three different habitats. The project offers the opportunity to work on wild animals early in the students' career.
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Speciation
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Speciation in birds is almost exclusively allopatric: Beside traditional morphological methods and bioacoustical characters we employ the genetic distance as a temporal measure to consider a population's taxonomic rank as still subspecies or already allospecies. Examples: Pallas's Leaf-Warbler (see figure) and Eurasian Treecreeper with Jochen Martens and Sun Yue-Hua, Coal Tit with Jochen Martens, Sun Yue-Hua and Martin Päckert.
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To which extent do sister species have to differ morphologically (= ecologically) to be able to live sympatrically? Example: treecreepers.
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Experiments with playbacks of different populations on a given one provide hints to whether the alien populations are still considered conspecific and to which song differences act as isolating mechanism. Examples: Eurasian Treecreeper, Coal Tit (see above), Yellowhammer with Jochen Martens and Christine Waßmann.
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Lineage diversification
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Based on dated molecular phylogenies we attempt to trace quite different characters throughout evolution: song, distributional areas, migratoriness, morphology (body dimensions, coloration patterns). Examples: treecreepers with Jochen Martens, Sun Yue-Hua and Martin Päckert, tits (Paridae, Remizidae), buntings (genus Emberiza) and swifts (genera Apus and Tachymarptis) with Martin Päckert, rosefinches with Jochen Martens and Henriette Lehmann.
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Build-up of regional communities
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The Himalayas together with adjacent southwest Chinese mountains are the Eurasian diversity hotspot and thus ideal to ask questions about how communities of bird species came into existence.
- Comparing the historical biogeographies of selected species groups with Martin Päckert, Jochen Martens and others shows temporal and spatial patterns specifically in forest passerines.
- In a research team around Trevor D. Price and Dhananjai Mohan we test historical against ecological causes for the gradient in species richness along the Himalayas. I specifically correlate the steepness of the diversity gradient with geographic origin and alternative factors for some 58 passerine clades.
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