Müller
Fakultäten » Mathematisch-naturwissenschaftliche Fakultät » Evolutionsbiologie und Umweltwissenschaften, Institut für » Ecology & Environment » Prof. Dr. Christine Müller (verstorben) » Müller
Completed research project
| Title / Titel | Ecology, Evolution and Conservation of plant-animal interactions on islands | ||||||||
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| Abstract (PDF, 14 KB) | |||||||||
| Summary / Zusammenfassung | The main study site is the island of Mauritius in the Indian Ocean which is a biodiversity hotspot, with many endemic plant and animal species and high rates of extinction. The global distribution, ecology and evolution of coloured nectar, a rare floral trait that is particularly widespread on islands (including Mauritius) and insular mainland habitats such as mountains is reviewed. Once thought to be restricted to three endemic plants in Mauritius, we showed that this is not the case: coloured nectar is found in more than 60 species from many plant families around the world. We discuss the evolution of coloured nectar, and speculated on its ecological function. We experimentally test the possible ecological function of coloured nectar as a signal for floral reward using endemic flower-visiting geckos in Mauritius as our study organism. We find strong support for the signal-hypothesis, with geckos preferring coloured over clear nectar. The endemic Mauritian plant Trochetia blackburniana (Malvaceae) is pollinated by the endemic Phelsuma cepediana gecko. This interaction is structured by the indirect effects of proximity to patches of Pandanus (Pandanaceae) plants – a favoured microhabitat of the geckos. Proximity to Pandanus patches leads to higher gecko visitation rates and a subsequently higher fruitset in T. blackburniana. Some studies have shown how two or more flowering plant species can positively or negatively affect each other’s reproductive success through indirect effects mediated by shared pollinators. We give a unique example of a non-flowering plant affecting the reproductive success of a neighbouring flowering plant. We studied pollination and the seed dispersal ecology of the critically endangered endemic Mauritian tree Syzygium mamillatum (Myrtaceae). We show how weeding of invasive plant species can influence the reproductive success of S. mamillatum in the weeded habitat, based on differences in pollinator behaviour between weeded and unweeded sites. We provided the first experimental evidence of the importance of the Janzen-Connell model for seedling establishment on oceanic islands, and demonstrated how ecological analogue species can be used to resurrect extinct seed dispersal interactions. A study of the pollination and seed dispersal interactions of another critically endangered Mauritian endemic plant, Roussea simplex (Rousseaceae), shows how an invasive ant affects both interactions detrimentally. The endemic Phelsuma cepediana geckos are currently the sole pollinators and seed dispersers of R. simplex, and the presence of the invasive ant Technomyrmex albipes at R. simplex flowers or fruits scare away the geckos, thus rendering the plant without pollinators and seed dispersers. We document the strong negative effects of a coffee pest species on the reproductive success of the endangered Mauritian endemic plant Bertiera zaluzania (Rubiaceae). Our study highlights another perspective to the ongoing scientific debate about coffee as a cash crop and the maintenance of biodiversity in the tropics. Most current studies focus on the benefits that coffee plants can derive from nearby natural habitats, and neglect to investigate the potential detrimental effects of coffee pest species invading these natural habitats. |
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| Publications / Publikationen | Hansen, D.M. (2001) Trees, birds, and bees in Mauritius. Endemic plant-animal interactions, introduced honey bees and conservation. M. Sc. thesis, University of Aarhus, Denmark, 76 pp.Hansen, D. M., J. M. Olesen & C. G. Jones (2002) Trees, birds, and bees in Mauritius: exploitative competition between introduced honey bees and endemic nectarivorous birds? Journal of Biogeography 29: 721-734Hansen, D.M., Kiesbüy1, H.C., Jones, C.G. and Müller, C.B. (2007) Neighbours indirectly affect reproductive success of rare endemic plant. The American Naturalist 169Hansen, D.M., Olesen, J.M., T. Mione, T., Johnson, S.D. and Müller, C.B. 2007 Coloured nectar: distribution, ecology, and evolution of an enigmatic floral trait. - Biological Reviews of the Cambridge Philosophical Society 82: 83-111.Hansen, D.M., Beer, K. and Müller, C.B.2006. Mauritian coloured nectar no longer a mystery: a visual signal for lizard pollinators. Biology Letters 2: 165-168. | ||||||||
| Keywords / Suchbegriffe | Islands, indirect community effect, Trochetia, pollination, conservation, plant reproductive system, lizard pollination, Roussea simplex, Syzygium mamillatum | ||||||||
| Project leadership and contacts / Projektleitung und Kontakte |
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| Funding source(s) / Unterstützt durch |
SNF (Personen- und Projektförderung), Others |
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| In collaboration with / In Zusammenarbeit mit |
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| Duration of Project / Projektdauer | Jan 2003 to Dec 2006 |