Dennis Hansen

Professional Education

• Candidate of Science (MSc), University of Aarhus Biology (2001)
• Doctor of Philosophy, Universitat Zurich (2006)

Research Interests

I am broadly interested in the ecology, evolution and conservation of pollination and seed dispersal interactions, especially in tropical regions and on islands. My current main project focuses on seed dispersal in Mauritius - where the extinction of the vast majority of seed-dispersing animals have led to the forests being largely populated by ghosts today. In my work I aim to understand the community-level impact of this loss, and how to ameliorate it by introducing analogue species.

Publications

• The critically endangered enigmatic Mauritian endemic plant Roussea simplex (Rousseaceae): geckos as pollinators and seed dispersers Hansen DM,  Müller CB.  International Journal of Plant Sciences.  2009; 170 42-52
• Gut-passage effect of the introduced Red-whiskered Bulbul (Pycnonotus jocosus) on germination of invasive plant species in Mauritius Linnebjerg JF,  Hansen DM, Olesen JM.  Austral Ecology.  2009; in press
• The forgotten megafauna Hansen DM,  Galetti M.  Science.  2009; 324 42-43
• Invasive ants disrupt gecko pollination and seed dispersal of the endangered plant Roussea simplex in Mauritius Hansen DM,  Müller CB.  Biotropica.  2009; 41 202-208
• Exotic pest insects: another perspective on coffee and conservation Kaiser CN,  Hansen DM, Müller CB.  Oryx.  2008; 42 143-146
• Endangered endemic plants on oceanic islands: seed dispersal, seedling establishment, and the use of ecological analogues Hansen DM,  Kaiser CN, Müller CB.  PLoS ONE.  2008; 3 e2111. doi:10.1371/j
• Habitat structure affects reproductive success of the rare endemic tree Syzygium mamillatum (Myrtaceae) in restored and unrestored sites in Mauritius Kaiser CN,  Hansen DM, Müller CB.  Biotropica.  2008; 40 86-94
• Positive indirect interactions between neighboring plant species via a lizard pollinator Hansen DM,  Kiesbüy HC, Jones CG, Müller CB.  American Naturalist.  2007; 169 534-542
• Coloured nectar: distribution, ecology, and evolution of an enigmatic floral trait Hansen DM,  Olesen JM, Mione T, Johnson SD, Müller CB.  Biological Reviews.  2007; 82 83-111
• The openness of a flower and its number of flower-visitor species Olesen JM,  Dupont YL, Ehlers BK, Hansen DM.  Taxon.  2007; 56 729-736
• Mauritian coloured nectar no longer a mystery: a visual signal for lizard pollinators Hansen DM,  Beer K, Müller CB.  Biology Letters.  2006; 2 165-168
• Phelsuma ornata (Ornate Day-gecko) Tail loss Hansen DM,  Herpetological Review.  2005; 36 453
• The enigmatic Mauritian endemic Roussea simplex (Rousseaceae): Bird or gecko pollination? Hansen DM,  Ecotropica.  2005; 11 69-72
• Heterostyly in the Canarian endemic Jasminum odoratissimum (Oleaceae) Olesen JM,  Dupont YL, Ehlers BK, Valido A, Hansen DM.  Nordic Journal of Botany.  2005; 23 537-539
• Evolutionary changes in nectar sugar composition associated with switches between bird and insect pollination: the Canarian bird-flower element revisited Dupont YL,  Hansen DM, Rasmussen JT, Olesen JM.  Functional Ecology.  2004; 18 670-676
• Impact of introduced honey bees on native pollination interactions of the endemic Echium wildpretii (Boraginaceae) on Tenerife, Canary Islands Dupont YL,  Hansen DM, Valido A, Olesen JM.  Biological Conservation.  2004; (118): 301-311
• Structure of a plant – flower-visitor network in the high-altitude sub-alpine desert of Tenerife, Canary Islands Dupont YL,  Hansen DM, Olesen JM.  Ecography.  2003; 26 301-310
• Trees, birds, and bees in Mauritius: exploitative competition between introduced honey bees and endemic nectarivorous birds? Hansen DM,  Olesen JM, Jones CG.  Journal of Biogeography.  2002; 29 721-734
• Native birds and insects, and introduced honey bees visiting Echium wildpretii (Boraginaceae) in the Canary Islands Valido A,  Dupont YL, Hansen DM.  Acta Oecologia.  2002; 23 314-419