Responsible curator: Dr. Manuel Schweizer
I use comparative methods to study contrasting patterns of biodiversity between different geographic regions and among different taxa. I am especially interested in the roles and interplay of dispersal, vicariance and adaptive shifts during the evolution of different bird groups with a special focus on continental radiations. My research moreover focuses on the evolution of arid-adapted bird taxa of the Palearctic desert belt. Additionally, I have a strong interest in the systematics and taxonomy of different Palearctic bird groups. Scientific collections form the basis for much of my research.
Here some examples from my work:
Diversification of Neotropical parrots
While the grey parrot lives in Africa, the range of the scarlet macaw lies in South America (neotropics). These two well-known representatives of parrots do not only occur on different continents, they also face different ecological challenges. The grey parrot is one of only 19 parrot species of Africa, whereas more than 160 parrot species can be found in the Neotropics. In a recent publication in the “Journal of Biogeography”, I aimed at investigating the cause of this disparity in species richness and illustrate how diversity evolves.
The Andes, whose uplift started about 15 millions of years ago, seem to be one of the main reasons for the high number of parrot species occurring in South America. New habitats emerging as a result of mountain orogenesis, new areas of open vegetation, and wetland and river dynamics may all have promoted diversification by causing habitat fragmentation and vicariance on the one hand, and by offering ecological opportunities associated with competitive release in new and vacant niche space on the other. In Africa in contrast, habitat alterations do not seem to have been as dynamic after this continent had been colonized by parrots.
Neotropical parrots show signs of an early adaptive radiation, as indicated by an ecological diversification early in their evolution. It is usually assumed that that diversification rates will decline in the course of a radiation as a consequence of the available ecological niche space becoming filled and opportunities for ecological speciation or species coexistence diminishing. However, we found no evidence of such a slowdown in speciation rate in Neotropical parrots. Historical processes and environmental changefrom the Miocene onwards may have kept diversification rates roughly constant ever since the colonization of the Neotropics. Thus, Arini may not yet have reached equilibrium diversity. The lack of diversity-dependent speciation might be a general feature of adaptive radiations on a continental scale, and diversification processes on continents might therefore not be as ecologically limited as in isolated lakes or on oceanic islands.
Publication: Schweizer, M., S.T. Hertwig & O. Seehausen 2014. Diversity versus disparity and the role of ecological opportunity in a continental bird radiation. Journal of Biogeography 41, 1301-1312.
Dynamics of the intergradation zone between the yellow wagtail subspecies M. f. flava and M. f. cinereocapilla in Switzerland
The yellow wagtail is a palearctic songbird species displaying an extraordinary geographical variation. 13 different subspecies are usually recognized which differ chiefly in the head pattern of males in breeding plumage. There is a contact zone between two subspecies in Switzerland: Nominate M. f. flava dominates the north-east, whereas the subspecies M. f. cinereocapilla breeds in the southern parts. In the region of the Seeland, in central western Switzerland, breeding yellow wagtails are phenotypically very variable: phenotypes of both subspecies can found, many birds however, show intermediate features between the two subspecies. This population is apparently a rather recent established secondary contact zone. For several years now, I trap territorial yellow wagtails in Switzerland, especially in the Seeland. First, I am at characterizing this intergradation zone in terms of phenotypes. But we also take blood samples for future molecular genetic investigations.