The Important Bird Areas (IBAs) network of BirdLife International aims to identify sites that are essential for the long-term conservation of the world’s avifauna. A number of global change events have the potential to negatively affect, either directly or indirectly, most bird species, biodiversity in general and associated ecological processes in these areas identified as IBAs. To assist conservation decisions, I assessed a suite of ten landscape scale anthropogenic pressures to 115 Important Bird Areas (IBAs) in South Africa, both those currently placing pressures on IBAs and those that constitute likely future vulnerability to transformation. These threats are combined with irreplaceability, a frequently used measure of conservation importance, to identify the suite of IBAs which are high priority sites for conservation interventions: those with high irreplaceability and are highly vulnerable to anthropogenic threats. A total of 22 (19%) of the South African IBAs are highly irreplaceable and are highly vulnerable to at least some of the pressures assessed. Afforestation, current and potential future patterns of alien plant invasions affect the largest number of highly irreplaceable IBAs. Only 9% of the area of highly irreplaceable IBAs is formally protected. A total of 81 IBAs (71%) are less than 5% degraded or transformed. This result, together with seven highly irreplaceable IBAs found outside of formally protected areas with lower human densities than expected by chance provides an ideal opportunity for conservation interventions. However, all the pressures assessed vary geographically, with no discernible systematic pattern that might assist conservation managers to design effective regional interventions. Furthermore, I used the newly emerging technique of ensemble forecasting to assess the impact of climate change on endemic birds in relation to the IBAs network. I used 50 endemic species, eight bioclimatic envelope models, four climate change models and two methods of transformation to presence or absence, which essentially creates 2400 projections for the years 2070-2100. The consensual projection shows that climate change impacts are very likely to be severe. The majority of species (62%) lose climatically suitable space and 99% of grid cells show species turnover. Five species lose at least 85% of climatically suitable space. The current locations of the South African Important Bird Areas network is very likely ineffective to conserve endemic birds under climate change along a “business a usual” emissions scenario. Many IBAs show species loss (41%; 47 IBAs) and species turnover (77%; 95 IBAs). However, an irreplaceability analysis identified mountainous regions in South Africa as irreplaceable refugia for endemic species, and some of these regions are existing IBAs. These IBAs should receive renewed conservation attention, as they have the potential to substantially contribute to a flexible conservation network under realistic scenarios of climate change. Considering all the global change threats assessed in this study, the Amersfoort-Bethal-Carolina District and the Grassland Biosphere Reserve (IBA codes: SA018; SA020) are the key IBAs in South Africa for conservation prioritisation. / Dissertation (MSc)--University of Pretoria, 2008. / Zoology and Entomology / unrestricted

Contexte : Gesneria et Rhytidophyllum (Gesneriaceae) sont deux genres de plantes Antillais aillant subi une forte diversification et qui présentent une forte variabilité de modes de pollinisation associés à des traits floraux particuliers. Les spécialistes des colibris ont des fleurs tubulaires rouges, alors que les spécialistes des chauves-souris et les généralistes présentent des fleurs campanulées de couleur pâle. La capacité d’être pollinisé par des chauves-souris (en excluant les colibris ou en devenant généraliste) a évolué plusieurs fois indépendamment au sein du groupe. Ces caractéristiques font de ces plantes un bon modèle pour étudier les relations entre l’évolution des modes de pollinisation et la diversification spécifique et écologique. Pour ceci, nous avons étudié les bases génétiques des changements de mode de pollinisation et les liens entre ces modes de pollinisations et la diversification des niches bioclimatiques. Méthodes : Nous avons réalisé une étude de QTLs pour caractériser les régions génomiques associées à la transition de syndrome de pollinisation entre une espèce à stratégie de pollinisation mixte (Rhytidophyllum auriculatum) et une espèce spécialiste des colibris (Rhytidophyllum rupincola). Nous avons parallèlement analysé les relations entre les changements de modes de pollinisation (dimension biotique de la niche écologique) et l’évolution des niches bioclimatiques chez ces plantes. Enfin, d’un point de vue théorique, nous avons testé l’effet de la fréquence et de l’amplitude des changements environnementaux sur les patrons d’évolution des niches écologiques. Résultats : L’étude des QTLs a montré que la couleur et le volume de nectar sont basés chacun sur un QTL majeur, alors que la forme de la corolle a une base génétique plus complexe. Par ailleurs ces différents QTLs ne sont pas liés physiquement dans le génome. L’analyse des niches bioclimatiques a montré que ces Gesneriaceae antillaises sont caractérisées par un conservatisme phylogénétique de niche bioclimatique (PNC) et que l’évolution de ces niches est indépendante des stratégies de pollinisation. Les plantes semblent aussi être relativement généralistes du point de vue de leur niche abiotique. Finalement, nous avons testé l’hypothèse selon laquelle l’adaptation à un environnement temporellement hétérogène pourrait expliquer à la fois le caractère généraliste des plantes et leur patron de PNC. Cette hypothèse s’est trouvée partiellement vérifiée. Conclusion : Si l’indépendance génétique des traits floraux a pu faciliter l’émergence des syndromes de pollinisation en réduisant les contraintes génétiques, il semble que la répartition largement chevauchante des colibris et des chauves-souris ne représente pas une opportunité écologique suffisante pour expliquer les évolutions répétées vers la pollinisation par les chauves-souris. En revanche, les perturbations environnementales causant régulièrement des déclins dans les populations de pollinisateurs pourraient expliquer l’avantage des plantes qui ont une stratégie de pollinisation mixte. / Background: Gesneria and Rhytidophyllum (Gesneriaceae) are two genera endemic to the Antilles that underwent an important diversification and that present a great vari- ability in pollination modes with regard to specific floral traits. Hummingbird specialists harbour red tubular flowers while bat specialists and generalists have campanulate (i.e., bell shaped) flowers with pale colours. Bat pollination (excluding or not hummingbirds) evolved multiple times independently in this group. These plants are thus a good model to study the relationship between the evolution of pollination mode and ecological and species diversification. To understand these relationships, we studied the genetic basis of pollination mode transition and the link between pollination mode and bioclimatic niches diversification. Methods: We performed a QTL analysis to detect genomic regions underlying the floral traits involved in the pollination syndrome transition between Rhytidophyllum auriculatum (a generalist species) and Rhytidophyllum rupincola (a hummingbird specialist). Also, we analysed the consequence of pollination mode transitions (which represent the biotic part of ecological niches) on bioclimatic niches evolution in Gesneria and Rhytidophyllum. Then, we tested whether environmental changes can result in patterns of phylogenetic bioclimatic niche conservatism through time. Results: The QTLs analysis showed that corolla colour and nectar volume are both based on one major QTL, while corolla shape is determined by a more complex genetic architecture involving several unlinked QTLs. These Antillean Gesneriaceae were found to have a pattern of phylogenetic (bioclimatic) niche conservatism (PNC) and their niche evolution was found to be independent from pollination strategies. Overall, the plants were found to have relatively widespread bioclimatic niches. Finally, we partially confirmed the hypothesis that adapting to temporally variable environment might cause both species generalization and PNC pattern. Conclusion: Genetic independence of floral traits might have facilitated pollination syn- dromes evolution by reducing genetic constraints. However, the overlapping distribution of hummingbirds and bats do not represent an ecological opportunity that could explain re- peated evolutions toward bat pollination. However, environmental perturbations causing regular pollinator populations collapses could explain the advantage for plants to favour generalist strategies.