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Biodiversity conservation in Island protected areas : the case of plant-insect pollinating networks
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Abstract(s)
As preocupações relativamente ao funcionamento dos ecossistemas surgiram com o declínio mundial da biodiversidade. Esta relação é particularmente evidente para os insectos polinizadores responsáveis por um importante serviço de ecossistema: a polinização das plantas, essencial para a manutenção da diversidade biológica das plantas e produção de alimentos. Porém, actualmente as comunidades de polinizadores encontram-se ameaçadas por todo o planeta, principalmente devido às alterações do uso do solo, considerado um dos factores contemporâneos mais importantes pela perda da biodiversidade. As alterações do uso do solo revelam ser mais proeminentes em ilhas oceânicas isoladas que foram desproporcionalmente afectadas pelas perturbações antropogénicas nos últimos séculos. Como tal, é urgente identificar devidamente as vias responsáveis pela mudança das comunidades de insectos polinizadores e subsequente estrutura das redes plantas – insectos polinizadores de modo a planear adequadamente a sua conservação, restauro e para a preservação dos serviços de ecossistemas que podem suprir os humanos. Nesta tese foi investigado o impacto das alterações dos usos do solo: (i) na estrutura da comunidade dos insectos polinizadores (capítulo 2), (ii) nas redes da interacção planta-insecto (capítulo 3), (iii) nos serviços de polinização tendo em conta o seu valor económico (capítulo 4), (iv) e foram propostas áreas prioritárias para a conservação dos insectos polinizadores (capítulo 5). Os insectos polinizadores foram amostrados durante dois anos através de um protocolo de amostragem padronizado em 50 transectos, em cinco tipos de habitat diferentes correspondendo a um gradiente do uso do solo na ilha Terceira (Açores). Os resultados revelam que as comunidades de insectos polinizadores estudadas são constituídas maioritariamente por espécies indígenas (sendo a maioria espécies nativas não endémicas) com prevalência por espécies de abundância intermédia. As comunidades de insectos polinizadores são também muito simplificadas ao longo de todo o gradiente com poucas diferenças entre os habitats, excepto entre a floresta nativa e as pastagens intensivas. Na ausência de fortes competidores exóticos, os insectos polinizadores indígenos expandem e ocupam novos habitats antropogénicos, facilitando assim a expansão de um vasto número de espécies de plantas exóticas. Notavelmente, não só as áreas de vegetação pristina, mas também as áreas agrícolas e de pomares possuem valores elevados de serviços de polinização, apesar de ambos os usos do solo possuírem níveis de perturbação opostos. Quanto às estruturas de rede planta-insecto, estas são basicamente redes pequenas e muito simplificadas, aninhadas e de modularidade não significativa. A natureza generalista e abundância relativa individual dos insectos polinizadores foi considerada como uma das principais causas para a estrutura da rede, o que seria de esperar de uma ilha oceânica recente e pequena. Inclusivé, ao agregar as redes dos habitats numa só matriz, foi verificado que não existe modularidade, sugerindo que as diferenças entre habitats não são suficientes para formar subgrupos interligados, evidenciando assim que a moderna paisagem da ilha Açoreana é uniforme ou homogénea em relação às espécies polinizadoras. Relativamente à valoração económica das comunidades de insectos polinizadores, os insectos contribuem com um total de 36,2% da média anual total do rendimento agrícola das colheitas dependentes dos polinizadores, o que enfatiza a importância dos insectos polinizadores para a produção agrícola. Por fim, a complementar estes resultados, a avaliação dos diferentes usos do solo para a conservação, permitiu verificar que para além das áreas protegidas e bem preservadas de floresta nativa da Terceira, outros usos do solo, como as áreas de vegetação naturalizada, florestas exóticas e pastagens semi-naturais poderão servir como um continuum para a rede de áreas protegidas. Este resultado tem implicações consideráveis para a conservação dos insectos polinizadores da ilha Terceira, implicando a necessidade de uma gestão mais sustentável das práticas humanas nos ecossistemas agrícolas.
ABSTRACT: Worldwide declines in biodiversity have prompted concerns about the functioning of ecosystems that may rely on it. This is particularly true for insect pollinators that provide a key ecosystem service (ES): the pollination of plants, which is essential in the maintenance of plant biological diversity and food production. However, pollinator communities are currently under threat throughout the planet mainly because of land use changes that is considered to be one the most important contemporary drivers of biodiversity loss. Land-use changes are nowhere more apparent than on remote oceanic islands that have been disproportionately affected by anthropogenic disturbances since the last centuries. Therefore, there is an urgent need to better identify the pathways responsible for the alteration of insect pollinator communities and its respective plant-pollinator insects network structure in order to better plan their conservation, restoration and to preserve the ES that they may supply for humans. Here, I investigated the impact of land-use changes: (i) on flower-visiting insect species community structure (chapter 2), (ii) on plant-insect interaction networks (chapter 3), (iii) on pollination ecosystem services provision taking also into account its economic value (chapter 4), and (iv) I propose priority areas for the insect pollinator conservation (chapter 5). Flower-visiting insects were sampled over two years using a standardized protocol along 50 transects across five different habitats corresponding to a land-use gradient in Terceira Island (Azores). The results revealed that the studied flower-visiting insect communities were dominated by indigenous species (mostly native non- endemic species) with a prevalence of species of intermediate abundance. Communities of flower-visiting insects were also highly simplified across the entire gradient with little differences between habitats, except between native forest and intensive pastures. In the absence of strong exotic competitors, indigenous pollinating insects have expanded their range and occupied new anthropogenic habitats, also possibly facilitating the expansion of a large number of exotic plant species. Remarkably, pristine vegetation areas, but also the orchards and agricultural areas have relatively high values of pollination services, even though both land uses have opposite disturbance levels. Concerning the plant-insect network structures, they were small and highly simplified, nested and non- significantly modular. The generalist nature and relative abundance of individual insect pollinators was found to be one of the main drivers of the network structure, which was expected for a young and small oceanic island. Moreover, when I pooled all habitats in one global network, there was no evidence for modularity which suggest that habitats differences did not generate any specific structures highlighting the fact that the modern Azorean island landscape is relatively uniform or homogeneous with respect to pollinator species. Concerning the economic valuation of pollinator insect communities, insect species contribution totals 36.2% of the total mean annual agricultural income of the pollinator-dependent crops, emphasizing the importance of insect pollinators in agricultural production. In addition, and to complement this latter result, I assessed the overall different land uses as possible conservation areas and realized that apart from the well preserved and protected native forest of Terceira, other land uses, such as naturalized vegetation areas, exotic forests, and semi -natural pastures, could serve as a continuum to protected areas network. This result has profound implications for the conservation of Terceira Island insect pollinators, implying the need of sustainable management practices across the landscape.
ABSTRACT: Worldwide declines in biodiversity have prompted concerns about the functioning of ecosystems that may rely on it. This is particularly true for insect pollinators that provide a key ecosystem service (ES): the pollination of plants, which is essential in the maintenance of plant biological diversity and food production. However, pollinator communities are currently under threat throughout the planet mainly because of land use changes that is considered to be one the most important contemporary drivers of biodiversity loss. Land-use changes are nowhere more apparent than on remote oceanic islands that have been disproportionately affected by anthropogenic disturbances since the last centuries. Therefore, there is an urgent need to better identify the pathways responsible for the alteration of insect pollinator communities and its respective plant-pollinator insects network structure in order to better plan their conservation, restoration and to preserve the ES that they may supply for humans. Here, I investigated the impact of land-use changes: (i) on flower-visiting insect species community structure (chapter 2), (ii) on plant-insect interaction networks (chapter 3), (iii) on pollination ecosystem services provision taking also into account its economic value (chapter 4), and (iv) I propose priority areas for the insect pollinator conservation (chapter 5). Flower-visiting insects were sampled over two years using a standardized protocol along 50 transects across five different habitats corresponding to a land-use gradient in Terceira Island (Azores). The results revealed that the studied flower-visiting insect communities were dominated by indigenous species (mostly native non- endemic species) with a prevalence of species of intermediate abundance. Communities of flower-visiting insects were also highly simplified across the entire gradient with little differences between habitats, except between native forest and intensive pastures. In the absence of strong exotic competitors, indigenous pollinating insects have expanded their range and occupied new anthropogenic habitats, also possibly facilitating the expansion of a large number of exotic plant species. Remarkably, pristine vegetation areas, but also the orchards and agricultural areas have relatively high values of pollination services, even though both land uses have opposite disturbance levels. Concerning the plant-insect network structures, they were small and highly simplified, nested and non- significantly modular. The generalist nature and relative abundance of individual insect pollinators was found to be one of the main drivers of the network structure, which was expected for a young and small oceanic island. Moreover, when I pooled all habitats in one global network, there was no evidence for modularity which suggest that habitats differences did not generate any specific structures highlighting the fact that the modern Azorean island landscape is relatively uniform or homogeneous with respect to pollinator species. Concerning the economic valuation of pollinator insect communities, insect species contribution totals 36.2% of the total mean annual agricultural income of the pollinator-dependent crops, emphasizing the importance of insect pollinators in agricultural production. In addition, and to complement this latter result, I assessed the overall different land uses as possible conservation areas and realized that apart from the well preserved and protected native forest of Terceira, other land uses, such as naturalized vegetation areas, exotic forests, and semi -natural pastures, could serve as a continuum to protected areas network. This result has profound implications for the conservation of Terceira Island insect pollinators, implying the need of sustainable management practices across the landscape.
Description
Tese de Doutoramento, Gestão Interdisciplinar da Paisagem, 13 de novembro de 2018, Universidade dos Açores.
Keywords
Biodiversidade Insular Conservação da Natureza Ecossistema Insecto Polinização Solo Ilha Terceira (Açores) Açores Biodiversity Conservation Terceira Island (Azores) Azores
Citation
Picanço, Ana Luísa Coderniz. "Biodiversity conservation in Island protected areas : the case of plant-insect pollinating networks". 2018. 201 p.. (Tese de Doutoramento em Gestão Interdisciplinar da Paisagem). Angra do Heroísmo: Universidade dos Açores, 2018. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/4940>.