Ecology and Conservation of Island Interactions

Ecology and conservation of island interactions Aarhus University Institute of Bioscience Genetics, Evolution and Ecology Supervisor Jens Mogens Olesen Master of Science Thesis by Caroline Vester Villumsen 201206150 June 2017 0 Abstract The effects of the Anthropocene are, among others, shown in the loss of biodiversity worldwide, and especially on islands. A new conservation philosophy attempting to reduce the effect of human sub- jectivity and choice is taking a holistic approach, where the entire system is in focus and not just a single species. The thermophiles forest of the Canarian island of Tenerife is an example of a human- degraded, but still species-rich ecosystem. Here, the interaction structure at the community level between a set of plants and all associated taxa was analysed. The aims were to accumulate baseline knowledge for an integrated conservation of both plants and their associated diversity of animals and other plants and to evaluate the importance of plants as bottom-up drivers of local animal diversity. Eleven study plant species were associated with 381 different taxa during three months and four study localities. The drivers of the associated taxa turned out to be a diverse array of both abiotic and biotic factors. Plant morphological structure (plant architecture), size, abundance and geographic range were especially important. The dynamics in size and composition of the associated diversity between months and localities was relatively low, although proper comparisons cannot be done, because of a lack of similar studies in the literature. The obtained information can be used to focus future conservation management, where most information needs to be gathered at the lowest costs. Parameters of the island as such, like climate, geographical isolation, human disturbance and number of endemic species were also shown to be important. The search for empty niches on plants, although the concept is regarded as controversial, turned out to be very informative about differences both in space and time, and with respect to trophic roles and microhabitats among plant species. I conclude that a strong focus on the associated animals of plants might be a successful step towards a more integrative conservation management, integrating plants and animals and integrating species with their biotic interactions. The study also showed that plants are important drivers of the biodiversity of their ecosystem and that they with profit might be used as unites in ecosystem conservation. 1 Table of content Abstract ............................................................................................................................................................. 1 1.Introduction .................................................................................................................................................... 3 1.1 The loss of biodiversity ........................................................................................................................... 3 1.2 Conservation of interactions .................................................................................................................... 4 1.3 Invasive species ....................................................................................................................................... 7 1.4 Species richness on plants ....................................................................................................................... 8 1.5 Empty niches ........................................................................................................................................... 9 1.6 Island biology ........................................................................................................................................ 10 1.7 Aims of the study ................................................................................................................................... 11 2. Methods ....................................................................................................................................................... 11 2.1 Study site and sampling methods .......................................................................................................... 11 2.2 Identification and data processing ......................................................................................................... 18 2.3 Analyses ................................................................................................................................................ 20 3. Results ......................................................................................................................................................... 21 3.1 Taxonomy .............................................................................................................................................. 21 3.2 Origin ..................................................................................................................................................... 26 3.3 Composition of the associated diversity compared to composition of regional diversity ..................... 27 3.4 Microhabitats ......................................................................................................................................... 32 3.5 Spatial and temporal variation ............................................................................................................... 38 3.6 Niche map .............................................................................................................................................. 42 4. Discussion.................................................................................................................................................... 44 4.1 The diversity of Tenerife ....................................................................................................................... 44 4.2 Spatial and temporal dynamics .............................................................................................................. 46 4.3 Endemics ............................................................................................................................................... 47 4.4 Microhabitat and trophic roles ............................................................................................................... 48 4.5 Plant abundance ..................................................................................................................................... 50 4.6 Invasive species ..................................................................................................................................... 51 4.7 Human disturbance ................................................................................................................................ 51 5. Conclusion ................................................................................................................................................... 52 6. Acknowledgments ....................................................................................................................................... 53 7. References ................................................................................................................................................... 53 8. Supplementary table 1 ................................................................................................................................. 57 2 1. Introduction 1.1 The loss of biodiversity All living organisms are dependent upon other species and interconnected via complex interaction networks, that form life as we know it. Nature is composed of networks, built of interactions between individuals, species, trophic levels and kingdoms. All of these many interactions, some more distinct than others, make nature into a coherent unite (Memmott et al. 2007). In these natural networks plants play an important role as they often structure the entire system physically and provide ecosystem functions, which life on earth could not exist without, like oxygen and biomass production. Biodiver- sity is the complexity and variety of life, on scales from genetic diversity, to species and even to ecosystem diversity, and it is not an ecosystem function or service, in the word’s narrow sense, but biodiversity is closely linked to ecosystem services as both affect each other’s’ expression (Cotter et al. 2017). Plants support directly a huge variety of animals and microorganisms, not only the her- bivores, pollinators and seed dispersers, but also indirectly the predators. In addition, microorganisms, pathogens, and parasites, above as well as below ground, interact with the plants as well as the animals connected to the plant. Finally, the plants also alter the physical and chemical conditions of the habitat, both on the micro – and macroscale. This creates networks of interactions built up around the plants (Memmott et al. 2000). Plants are therefore a very important element of the biodiversity on this planet and important when we talk about biodiversity conservation – the attempt to conserve the natural diversity. First and foremost, plants are important because there are around 400.000 known plant species, but also because of the important roles plants play in sustaining directly or indirectly all other organisms on earth (BGCI). The view of nature described above is assuming a bottom-up control of nature, i.e. that plants structure the animal

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