Invasive exotic species threaten biodiversity and ecosystem functions globally, creating need for and encumbering ecological restoration. When restoring exotic plant-dominated ecosystems, reinvasion pressure is the rate of new exotic recruitment following mature exotic removal. It can vary broadly among similarly invaded habitats and is crucial to restoration outcomes and costs, but is difficult to predict and poorly understood. Initial results from the experimental restoration of a wetland dominated by Triadica sebifera led us to develop the ‘outgrow the stress’ hypothesis. It holds: (1) Variation in reinvasion pressure is driven by differences in propagule abundance and spatiotemporal availability of realized recruitment windows, which are defined by abiotic conditions and biotic interactions. (2) Differences in reinvasion pressure become masked by exotic dominance when increases in niche breadth during development enable exotic persistence across sites where recruitment windows range from frequent to episodic. We validated this hypothesis. First, we used greenhouse and field experiments to quantify Triadica’s moisture niche early in development. By two months post-germination, seedling tolerances broadened to include conditions unsuitable for germination. This clearly demonstrated a rapid ontogenetic niche expansion, which could decouple mature Triadica density and average reinvasion pressure. Second, we used a greenhouse mesocosm experiment to quantify how recruitment window duration, competition and fertility impacted population-level Triadica establishment in stressful environments. As ‘outgrow the stress’ predicts, longer windows increased Triadica success and multi-factor interactions were common, with competition and fertility effects varying among environmental contexts. Third, we substantiated predictions of ‘outgrow the stress’ regarding propagule availability and soil moisture by manipulating these in a multi-site field experiment spanning eleven experimental restorations of Triadica-dominated habitats along a moisture gradient. Triadica reinvasion pressure varied broadly among sites but correlated with moisture and fertility. Propagule availability drove reinvasion in favorable environments, but availability of suitable conditions trumped propagules in extreme environments. Competition reduced Triadica performance and sometimes survival. Triadica prevalence reduced native plant prevalence. Six restorations require minimal Triadica management for success. This work advances our understanding and enables better predictions of reinvasion pressure and invasions in general. Accurate predictions enhance restoration efficiency by informing site selection and optimal management strategies.

Many regional and local factors can influence the distribution of native and exotic species in ecological communities. I examined the regional- and local-scale determinants of native and exotic vascular plant species richness and composition in a highly fragmented oak savanna ecosystem on southeastern Vancouver Island. In sharp contrast to most reported results, I found a negative relationship between native and exotic richness at the regional scale, and no relationship at the local scale. Two extrinsic factors, surrounding road density and climate, best explained the regional-scale relationship by each affecting natives and exotics in opposite ways. Road density and climate were also the dominant predictors of native and exotic composition at the regional scale. Patterns in the patch occupancy of individual species confirmed the importance of these factors but I found that low surrounding road densities and cool, wet conditions predicted the presence of many natives and the absence of many exotics. Environmental factors explained variation in richness and composition at the local scale, but these factors were different for natives and exotics. My results suggest that natives and exotics respond to roads and climate in fundamentally different ways. Roads increase both exotic propagule pressure and disturbance, which may facilitate exotic invasion. In contrast, disturbance from roads may increase the likelihood of local extinction for particular natives. Differing climatic preferences within the native and exotic species pools may also partially explain the observed patterns. There was no evidence that native diversity directly affects exotic diversity (or vice versa). Surprisingly, I found that connectivity was not an important predictor of richness or composition despite the high degree of habitat fragmentation in this ecosystem.

Global environmental changes, especially land-use changes, have profound effects on both ecosystem functioning and biodiversity, having already altered many ecosystem services. These losses emphasize the need to preserve what remains; however when conservation programs are not sufficient, restoring areas that have been destroyed or disturbed can improve conservation efforts and mitigate damages. This work focuses on campos rupestres, Neotropical grasslands found at altitudes, which are part of the Cerrado (Brazilian savannas). They host a great biodiversity with a high level of endemism and, like other mountain ecosystems, provide valuable ecosystem services, such as water purification and recreational services. They have been and still are being impacted by human activities, such as civil engineering construction, quarrying or mining. The first objective of this thesis was to describe the reference ecosystem in order to aim for a clear restoration target and to monitor progress and success. We show that campos rupestres are composed of at least two distinct plant communities (i.e. sandy and stony grasslands), each having a specific composition and structure, hosting a great biodiversity. Several phenological patterns occur among the herbaceous communities: the majority of species flowers and fruits appear during the rainy season but other patterns can be observed. During our 2-year survey, some dominant species belonging to Poaceae, among others, were not observed reproducing, which implies limited chances to disperse on degraded areas. Campo rupestre vegetation is not resilient following a strong disturbance: several years after the disturbance, almost no native species are encountered on the degraded areas, soils are completely altered and seed bank recomposes only with non-target ruderal species. According to the filter model, a local community is a subset of the regional species pool determined by a set of dispersal, abiotic and biotic filters. Acting on the different filters to influence the plant community was the core of our restoration interventions. We then applied three in-situ restoration protocols (hay transfer, species translocation and turf translocation) to restore both kinds of grassland. Hay transfer does not allow the restoration of campo rupestre vegetation because of soil alteration and mainly because of poor seed quality. Indeed, germination studies show that, while some Xyridaceae and Velloziaceae have a high germinability, some dominant Poaceae, Cyperaceae or Asteraceae species have embryoless, unviable or dormant seeds, which makes seeding less efficient. There is no evidence that fire-related cues enhance germination in campos rupestres. Species translocation is successful for only one species, Paspalum erianthum; for the others, root damages probably impede survival. Finally, turf translocation is the most successful method, since numerous species are re-introduced on degraded areas. However due to the low resilience of pristine campos rupestres where turfs are taken from, turf translocation can only be considered in the case of habitat rescue, in circumstances when complete habitat destruction is otherwise unavoidable. Face to the difficulty to restore these peculiar grasslands, the protection and the conservation of campos rupestres must be made a high priority

No description available.

Os padrões de associação entre epífitos e forófitos não podem ser considerados espécie-específicos, mas as árvores que os epífitos colonizam também não são um conjunto aleatório das espécies forofíticas de um determinado local. Ao invés disso, parece haver uma preferência de certos epífitos por diferentes forófitos. No entanto, se conhece pouco sobre os fatores que determinam essa preferência. Nosso objetivo nesse trabalho é avaliar como os atributos funcionais e a filogenia dos epífitos vasculares influenciam na associação dos epífitos com os forófitos em uma Floresta Ombrófila Mista no sul do Brasil. Para isso nós (1) investigamos padrões de associação positiva e negativa entre grupos funcionais de epífitos e grupos de forófitos e como a diversidade e os atributos funcionais dos epífitos variavam em função do tamanho do forófito e (2) inferimos sobre a existência de sinal filogenético no uso de árvores hospedeiras pelos epífitos, procuramos por estrutura filogenética nas comunidades epifíticas e investigamos diferenças de composição filogenética de epífitos vasculares em diferentes clados de forófitos. Foram amostrados 70 forófitos compreendendo 15 espécies pertencentes a diversos clados e com arquiteturas e características variadas. A amostragem compreendeu 31 espécies epifíticas com os principais clados sendo Polypodiaceae, Bromeliaceae e Orchidaceae. A associação de grupos de epífitos vasculares com diferentes grupos de forófitos sugere que as características dos forófitos proporcionam ambientes contrastantes e que diferentes valores de atributos são necessários para colonizar esses ambientes. Mais especificamente espécies epifíticas com menor área específica foliar (SLA) parecem predominar em árvores maiores e maior SLA em árvores menores. Encontramos sinal filogenético na utilização dos forófitos, sugerindo que a conservação das interações com os forófitos deve ter sido importante ao longo da evolução dos epífitos. A tendência a agrupamento filogenético nas comunidades epifíticas sugere a influência de filtros ambientais representados pelas diferentes características dos forófitos estruturando as assembleias de epífitos. Clados mais basais de forófitos apresentaram composição filogenética distinta devido, sobretudo, a presença de diferentes clados de monilófitos epifíticos nessas árvores. Angiospermas epifíticas ocorreram principalmente em forófitos pertencente as eurosídeas. A preferência de epífitos por forófitos parece ser influenciada pelo surgimento de novidades morfológicas e ecofisiológicas em alguns clados, enquanto outros mantiveram o seu nicho ancestral. A composição florística das florestas quando da origem dos clados epifíticos também parece influenciar a associação entre epífitos e forófitos. Ao utilizar informações sobre os atributos e filogenia das espécies de epífitos vasculares nós podemos melhor compreender os mecanismos ecológicos e históricos que influenciam os padrões de associação entre epífitos e forófitos. / It has been shown that patterns of association between epiphytes and phorophytes can not be considered species-specific, although the trees that epiphytes colonize are not a random subset of phorophyte species in a particular location. Instead, there seems to be a preference of some epiphytes for different phorophytic species. However, little is known about the factors determining this choice. Our objective in this study is to assess how functional attributes and phylogeny of vascular epiphytes influence the association of epiphytes with the phorophytes in an Araucaria Forest in Southern Brazil. For that we (1) investigated the positive and negative association patterns between functional groups of epiphytes and groups of phorophytes and how functional diversity and functional traits of epiphytes varied with host tree size and (2) inferred about the existence of phylogenetic signal on the host trees use by epiphytes, looked for phylogenetic structure in the epiphytic communities and investigated differences in the phylogenetic composition of vascular epiphytes in different phorophyte clades. We used a sample of 70 phorophytes comprising 15 species and belonging to different clades and with different architectures and traits. The sample comprised 31 epiphytic species, the major clades being Polypodiaceae, Bromeliaceae and Orchidaceae. The combination of vascular epiphyte groups with different groups of 15 phorophytes suggests that phorophyte traits provide contrasting environments and that different trait values are needed to colonize these environments. More specifically, epiphytic species with lower specific leaf area (SLA) seem to predominate on larger trees and with higher SLA values on smaller trees. We found phylogenetic signal on the host tree use, suggesting that conservatism of the interactions with phorophytes must have been important throughout the evolution of epiphytes. The tendency to phylogenetic clustering in the epiphytic communities suggests the influence of environmental filters represented by phorophyte traits structuring epiphyte assemblages. More basal clades of phorophytes showed different phylogenetic composition mainly due to the presence of different epiphytic monilophyte clades on these trees. Epiphytic angiosperms occurred mainly on those trees belonging to eurosids. The preference of epiphytes for phorophytes seems to be influenced by morphological and ecophysiological novelties in some lineages, while other clades kept their ancestral niche. The floristic composition of forests at the origins of epiphytic lineages also appears to influence the association between epiphytes and phorophytes. By using information about the traits and phylogeny of species of vascular epiphytes we can better understand the ecological and historical mechanisms that influence the patterns of association between epiphytes and phorophytes.

La compréhension des processus écologiques qui sous-tendent l’assemblage des communautés végétales et la coexistence des espèces est un objectif central en écologie. Ces processus sont potentiellement nombreux et de natures contrastées. Ainsi, la composition d’une communauté de plantes dépend de processus déterministes liés aux conditions environnementales abiotiques (climat, conditions physiques et chimiques du sol, lumière) et d’interactions biotiques complexes, positives (facilitation, symbioses) comme négatives (compétition, prédation, pathogènes). En outre, les communautés sont influencées par des processus stochastiques (capacité de dispersion limitée, dérive écologique). Si les mécanismes à l’origine de ces processus sont très différents, ils ont néanmoins en commun la génération de motifs (patterns) spatiaux de distribution d’espèces dans les communautés. L’analyse de la structure spatiale des communautés permet ainsi une étude indirecte des processus régissant les communautés. La nature complexe de ces patterns spatiaux a mené au développement de nombreuses méthodes statistiques de détection et de description de patterns. Les méthodes basées sur des vecteurs propres spatiaux sont parmi les plus puissantes et précises pour détecter des patterns complexes et multi-échelles. Ces vecteurs propres, utilisés comme prédicteurs spatiaux, peuvent être combinés à un ensemble de variables environnementales dans un cadre de partition de variation. Celui-ci permet, en théorie, de démêler les effets uniques et l’effet conjoint des variables environnementales et spatiales sur la variation de composition d’une communauté. Il mène ainsi à une quantification de l’action des processus déterministes et des processus stochastiques sur l’assemblage de la communauté. Néanmoins, je montre dans cette thèse qu’un certain flou méthodologique concernant deux étapes déterminantes des analyses basées sur les vecteurs propres spatiaux a mené une proportion élevée d’études à utiliser ces méthodes de manière sous-optimale, voire fortement biaisée. Ceci compromet la fiabilité des patterns spatiaux détectés et des processus écologiques inférés. Une autre limitation de ce cadre d’analyse concerne la fraction de la partition de variation décrivant l’effet environnemental spatialement structurés qu’aucune méthode ne permet de tester.Cette thèse présente des solutions non biaisées, puissantes et précises à ces différentes limitations méthodologiques et permet d’élargir le cadre de l’inférence de processus écologique à partir de patterns spatiaux de communautés. Les différentes étapes d’amélioration de ces méthodes ont également été illustrées dans la thèse au travers de trois cas d’études fournis par deux communautés d’arbres tropicale et tempérée et une communauté de champignons symbiotiques des arbres. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Os padrões de associação entre epífitos e forófitos não podem ser considerados espécie-específicos, mas as árvores que os epífitos colonizam também não são um conjunto aleatório das espécies forofíticas de um determinado local. Ao invés disso, parece haver uma preferência de certos epífitos por diferentes forófitos. No entanto, se conhece pouco sobre os fatores que determinam essa preferência. Nosso objetivo nesse trabalho é avaliar como os atributos funcionais e a filogenia dos epífitos vasculares influenciam na associação dos epífitos com os forófitos em uma Floresta Ombrófila Mista no sul do Brasil. Para isso nós (1) investigamos padrões de associação positiva e negativa entre grupos funcionais de epífitos e grupos de forófitos e como a diversidade e os atributos funcionais dos epífitos variavam em função do tamanho do forófito e (2) inferimos sobre a existência de sinal filogenético no uso de árvores hospedeiras pelos epífitos, procuramos por estrutura filogenética nas comunidades epifíticas e investigamos diferenças de composição filogenética de epífitos vasculares em diferentes clados de forófitos. Foram amostrados 70 forófitos compreendendo 15 espécies pertencentes a diversos clados e com arquiteturas e características variadas. A amostragem compreendeu 31 espécies epifíticas com os principais clados sendo Polypodiaceae, Bromeliaceae e Orchidaceae. A associação de grupos de epífitos vasculares com diferentes grupos de forófitos sugere que as características dos forófitos proporcionam ambientes contrastantes e que diferentes valores de atributos são necessários para colonizar esses ambientes. Mais especificamente espécies epifíticas com menor área específica foliar (SLA) parecem predominar em árvores maiores e maior SLA em árvores menores. Encontramos sinal filogenético na utilização dos forófitos, sugerindo que a conservação das interações com os forófitos deve ter sido importante ao longo da evolução dos epífitos. A tendência a agrupamento filogenético nas comunidades epifíticas sugere a influência de filtros ambientais representados pelas diferentes características dos forófitos estruturando as assembleias de epífitos. Clados mais basais de forófitos apresentaram composição filogenética distinta devido, sobretudo, a presença de diferentes clados de monilófitos epifíticos nessas árvores. Angiospermas epifíticas ocorreram principalmente em forófitos pertencente as eurosídeas. A preferência de epífitos por forófitos parece ser influenciada pelo surgimento de novidades morfológicas e ecofisiológicas em alguns clados, enquanto outros mantiveram o seu nicho ancestral. A composição florística das florestas quando da origem dos clados epifíticos também parece influenciar a associação entre epífitos e forófitos. Ao utilizar informações sobre os atributos e filogenia das espécies de epífitos vasculares nós podemos melhor compreender os mecanismos ecológicos e históricos que influenciam os padrões de associação entre epífitos e forófitos. / It has been shown that patterns of association between epiphytes and phorophytes can not be considered species-specific, although the trees that epiphytes colonize are not a random subset of phorophyte species in a particular location. Instead, there seems to be a preference of some epiphytes for different phorophytic species. However, little is known about the factors determining this choice. Our objective in this study is to assess how functional attributes and phylogeny of vascular epiphytes influence the association of epiphytes with the phorophytes in an Araucaria Forest in Southern Brazil. For that we (1) investigated the positive and negative association patterns between functional groups of epiphytes and groups of phorophytes and how functional diversity and functional traits of epiphytes varied with host tree size and (2) inferred about the existence of phylogenetic signal on the host trees use by epiphytes, looked for phylogenetic structure in the epiphytic communities and investigated differences in the phylogenetic composition of vascular epiphytes in different phorophyte clades. We used a sample of 70 phorophytes comprising 15 species and belonging to different clades and with different architectures and traits. The sample comprised 31 epiphytic species, the major clades being Polypodiaceae, Bromeliaceae and Orchidaceae. The combination of vascular epiphyte groups with different groups of 15 phorophytes suggests that phorophyte traits provide contrasting environments and that different trait values are needed to colonize these environments. More specifically, epiphytic species with lower specific leaf area (SLA) seem to predominate on larger trees and with higher SLA values on smaller trees. We found phylogenetic signal on the host tree use, suggesting that conservatism of the interactions with phorophytes must have been important throughout the evolution of epiphytes. The tendency to phylogenetic clustering in the epiphytic communities suggests the influence of environmental filters represented by phorophyte traits structuring epiphyte assemblages. More basal clades of phorophytes showed different phylogenetic composition mainly due to the presence of different epiphytic monilophyte clades on these trees. Epiphytic angiosperms occurred mainly on those trees belonging to eurosids. The preference of epiphytes for phorophytes seems to be influenced by morphological and ecophysiological novelties in some lineages, while other clades kept their ancestral niche. The floristic composition of forests at the origins of epiphytic lineages also appears to influence the association between epiphytes and phorophytes. By using information about the traits and phylogeny of species of vascular epiphytes we can better understand the ecological and historical mechanisms that influence the patterns of association between epiphytes and phorophytes.

Indivíduos, populações e espécies tendem a usar e selecionar habitats de modo não-aleatório. Consequentemente, a perda e a degradação de habitats geram impactos distintos sobre os organismos dependendo de seus atributos. Os efeitos da perda de habitat são claros – os organismos são eliminados ou desalojados por falta de habitat ou baixo sucesso reprodutivo. As consequências da degradação de habitat são mais sutis, e resultam na incapacidade de um ecossistema sustentar determinadas espécies. Como a perda e a degradação de habitat reduzem a disponibilidade de nichos, espera-se que táxons ecologicamente especializados e com requerimentos estreitos de nicho sejam mais propensos à extinção que generalistas. Organismos que são negativamente afetados por perda e degradação de habitat em geral exibem porte muito grande ou muito pequeno, baixa mobilidade, baixa fecundidade, reduzido recrutamento e estreitos requerimentos de nicho. Campos temperados constituem ambientes particularmente afetados por perda e degradação de habitat. No sudeste da América do Sul, como em muitas outras regiões do planeta, a expansão da agricultura e silvicultura são os principais responsáveis pela perda de habitat campestre. Os remanescentes de vegetação natural são usados para criação de gado, estando sujeitos à degradação pelo sobrepastejo, pisoteio e técnicas de manejo. Avaliar como a perda e degradação de habitat afetam a diversidade de organismos campestres é vital para o desenvolvimento de estratégias de conservação e manejo. A presente tese tem por objetivo investigar como a degradação e perda de habitat induzidas pela pecuária e silvicultura afetam a diversidade e a composição das comunidades de aves. Inicialmente, exploramos as relações entre variáveis de habitat e a composição da comunidade de aves num gradiente de altura da vegetação determinado por pastejo em campos litorâneos do Rio Grande do Sul. Posteriormente, avaliamos como variações no relevo interagem com variáveis de habitat e afetam a diversidade de aves em áreas de pecuária na Campanha gaúcha. Finalmente, avaliamos de que forma a perda de habitat resultante do estabelecimento de plantações industriais de celulose em áreas de campo afeta a composição de comunidades de aves campestres. Nossos resultados demonstram que a degradação de habitat decorrente do manejo de gado em campo nativo afeta a comunidade de aves de forma diferencial. Aves adaptadas a campos ralos ou generalistas tendem a ser beneficiadas pelo pastejo, ao passo que as espécies associadas à vegetação alta e densa são desfavorecidas. As variações na topografia reduzem os impactos da degradação de habitat nos campos. Essas variações interagem com o habitat e afetam de forma diferencial os distintos componentes da diversidade. Por outro lado, a perda de habitat decorrente da silvicultura gera um impacto de maior magnitude, alterando a composição das comunidades de aves e favorecendo aves não-campestres. Nesse contexto, impedir que novas áreas de campo nativo sejam convertidas em plantações de árvores passa a ser imperativo. Embora o manejo do gado aumente a diversidade em nível de paisagem ao criar um mosaico de manchas de vegetação de alturas distintas, maior atenção deve ser dada à manutenção e recuperação de formações densas de herbáceas de grande porte. Isso somente pode ser assegurado através de mudanças no regime do pastejo ou do desenvolvimento de técnicas de manejo alternativas. / Individuals, populations and species tend to select habitats in a non-random way. Consequently, habitat loss and degradation will have different impacts on organisms according to their traits. The effects of habitat loss are straightforward – organisms are eliminated or displaced because of the inexistence of adequate habitat or of low breeding success. Effects of habitat degradation are more subtle and result in the reduction of the capacity of an ecosystem to support some subsets of species. Since habitat loss and degradation reduce niche availability, ecologically specialized taxa with narrow niche requirements are expected to be more extinction prone than habitat generalists. Temperate grasslands have been strongly impacted by habitat loss and degradation. In southeastern South America, the expansion of agriculture and industrial pulpwood plantations are the main sources of habitat loss. Remnants of natural grassland vegetation are used for livestock ranching, being subject to habitat degradation from overgrazing, trampling and inadequate management techniques. The evaluation of how habitat loss and degradation affect the diversity of grassland organisms is vital for the development of management and conservation techniques. The main goal of this thesis is to evaluate how habitat degradation and loss related to cattle ranching and pulpwood plantations affect the diversity and composition of bird communities. We began by exploring the relationship between habitat variables and the composition of the bird community along a gradient of vegetation height determined by grazing in coastal grasslands of the state of Rio Grande do Sul. We then assessed how variations in the relief interact with habitat variables e affect the diversity of birds in rangelands of the Campanha gaúcha. Finally, we evaluated how habitat loss related with grassland afforestation for pulpwood plantations affects the composition of grassland bird communities. Our results demonstrate that habitat degradation resulting from livestock ranching in natural grasslands affects bird communities in a differential way. Birds adapted to stunted grasslands or habitat generalists tend to benefit from grazing, whereas tall-grass specialists are negatively affected. Variations in topography are responsible for reducing the impacts of habitat degradation in grasslands. These variations interact with habitat and have a differential effect on distinct components of diversity. On the other hand, the magnitude of the impact of habitat loss from afforestation is larger, altering the composition of bird communities and favoring a series of non-grassland species. In this sense, protecting remaining grasslands from afforestation is imperative. Although cattle ranching increases diversity at the landscape level by creating a mosaic of vegetation patches of different height, more attention should be given in maintaining and recovering dense formations of tall grassland plants. This can only be achieved by changing grazing regimes or developing alternative management techniques.

Macroecology is the study of relationships between organisms and the environment at large spatial and temporal scales. This field of research examines patterns in species abundance, distribution and diversity. Understanding patterns in species distribution and richness can contribute significantly to our knowledge of community assembly and macroecological patterns, as well as to the effective conservation of threatened species and habitats. Although there have been a plethora of studies on birds in India over the years, there is a critical need to accurately delineate species distributions and understand patterns of richness. The focus of this study was to understand the factors (abiotic and biotic) that influence the distribution and composition of bird species in the Western Ghats, as well as to explore patterns in their geographic range sizes. The objectives of this study were addressed at the scale of the entire Western Ghats using a combination of field surveys, secondary data collection and species distribution modeling. The specific approaches to address these questions and the findings are outlined below. Chapter 2: Bird species in the Western Ghats – Patterns in composition and richness Fine-scale data on species presence and abundance are essential for exploring patterns in species distribution and richness. Despite the fact that birds have been extensively studied in the Western Ghats, systematic data collection and compilation of information over the entire mountain range has not been carried out, especially for the purpose of testing macroecological questions. This chapter describes patterns in bird species presence, abundance, composition and richness within the Western Ghats. The study area, site selection protocol and the sampling technique have also been described in detail. This dataset establishes a baseline of information about birds in the Western Ghats and subsets of this larger dataset will be used to address various questions in the following chapters. Chapter 3: Predicting bird species distribution in the Western Ghats Detailed knowledge of species’ ecological and geographical distributions is fundamental for conservation, as well as for understanding ecological and evolutionary determinants of spatial patterns of biodiversity. However, occurrence data for a vast majority of species are sparse, resulting in information about species distributions that is inadequate for many purposes. Species distribution models attempt to provide detailed predictions of distributions by relating presence or abundance of species to environmental predictors. In this chapter, we describe the usage of Maxent, a species distribution modelling technique based on presence-only data, to predict the distributions of bird species within the Western Ghats. For this purpose, we put together primary locations of bird species presence along with a published dataset. Using a number of important environmental layers, predicted species distribution maps were derived for 98 bird species, including 13 endemics, in the Western Ghats. Additionally, we calculated predicted range sizes for each of these species and obtained percentage contributions of important environmental predictors to each species’ distribution. This is the first study to develop species distribution models for bird species within the Western Ghats. Chapter 4: Patterns of range size among bird species Understanding large-scale patterns of variation in species geographic range size is fundamental to questions in macroecology and conservation biology. In general, range is believed to be influenced by a combination of environmental factors, evolutionary history and biotic interactions, mediated by species specific traits. These patterns need to be examined even for well-studied taxa like birds, especially within biodiversity hotspots faced by persistent degradation due to anthropogenic activities such as the Western Ghats. In this chapter, we use a dataset of 98 bird species within the Western Ghats to examine trends in range sizes, measured as latitudinal extent of occurrence and predicted range size from species distribution models. We show a significant relationship between latitude and range size for these bird species, supporting Rapoport’s rule. As far as we know, this relationship has never been tested at such low latitudes for birds. We also find that species traits such as body size, mean abundance and diet do not seem to show any discernable effect on patterns of range size. Additionally, we found that widely-used bird species range maps (in this case, from BirdLife International) are inaccurate representations of species ranges in comparison to the predicted species distribution maps that were derived in the previous chapter. We quantitatively demonstrated that these expert-drawn maps need to re-evaluated, especially since they are used to make conservation decisions. This is the first study to quantify species range sizes of birds within the Western Ghats and assess such range maps that are used to determine conservation status of species. Chapter 5: Environmental predictors of bird species distribution One of the major goals in ecology is to understand patterns and processes that determine species diversity. The drivers of global species richness gradients have been studied, especially in the case of birds, in terms of contemporary and historical factors. Such broad scale processes may not always reflect the processes affecting richness and distribution at smaller scales. Therefore, understanding the factors that influence individual species distributions is the first step towards this larger goal. In this chapter, we examined the environmental predictors that contributed to the predicted distribution of bird species observed in the Western Ghats, using the variable importance contribution values derived in Chapter 3. We found that a large proportion of the 98 bird species studied were influenced by normalized differential vegetation index, annual precipitation and elevation. The predictors did not differ among birds of different diet guilds and body size classes. Using Prinicipal components analysis, we observed that all 98 bird species are spread out across the environmental ordination space depicted by the PC axes 1 and 2. These axes are governed by measures of habitat heterogeneity and water-energy related variables, consistent with other tropical studies. The insectivorous guild seemed to occupy a variety of environmental niches across this space and other guilds seemed to be nested within the insectivorous guild. Similarly, larger sized birds were spread across the entire environmental ordination space, with species of smaller sizes nested within. This is the first step in trying to understand environmental predictors acting on birds in the Western Ghats. Further detailed studies need to be carried out to come to definite conclusions. Chapter 6: Relative roles of floristics and vegetation structure on bird species composition On the basis of the hierarchical model of habitat selection, it is known that birds select suitable habitats based on vegetation structure (physiognomy) at coarse biogeographic scales, and plant species composition (floristics) at more local scales. This chapter examines the relative influence of tree species composition and vegetation structure on bird species composition in the Western Ghats. These relationships were specifically assessed across the entire Western Ghats, within regions of the Western Ghats as well as within specific forest types. We found that floristics had a strong association with bird species composition across the Western Ghats and within evergreen and mixed deciduous habitat types. This association seems to be independent of the structural variation in the region. There was a decrease in association strength from the southern to the northern Western Ghats, in terms of both floristics and structure. We did not find an association between vegetation structure and insectivore composition, whereas phytophage composition did show a stronger association with floristics than structure. This is the first study at the scale of the entire Western Ghats to test the relative roles of floristics and vegetation structure. Taken as a whole, this dissertation examines large-scale macroecological questions regarding species distribution, range size and patterns of composition using primary data at the scale of the Western Ghats. The findings of this study have established a foundation that will help further our understanding of species distribution and richness in the Western Ghats, and aid in the decision making for conservation strategies in the future.

Indivíduos, populações e espécies tendem a usar e selecionar habitats de modo não-aleatório. Consequentemente, a perda e a degradação de habitats geram impactos distintos sobre os organismos dependendo de seus atributos. Os efeitos da perda de habitat são claros – os organismos são eliminados ou desalojados por falta de habitat ou baixo sucesso reprodutivo. As consequências da degradação de habitat são mais sutis, e resultam na incapacidade de um ecossistema sustentar determinadas espécies. Como a perda e a degradação de habitat reduzem a disponibilidade de nichos, espera-se que táxons ecologicamente especializados e com requerimentos estreitos de nicho sejam mais propensos à extinção que generalistas. Organismos que são negativamente afetados por perda e degradação de habitat em geral exibem porte muito grande ou muito pequeno, baixa mobilidade, baixa fecundidade, reduzido recrutamento e estreitos requerimentos de nicho. Campos temperados constituem ambientes particularmente afetados por perda e degradação de habitat. No sudeste da América do Sul, como em muitas outras regiões do planeta, a expansão da agricultura e silvicultura são os principais responsáveis pela perda de habitat campestre. Os remanescentes de vegetação natural são usados para criação de gado, estando sujeitos à degradação pelo sobrepastejo, pisoteio e técnicas de manejo. Avaliar como a perda e degradação de habitat afetam a diversidade de organismos campestres é vital para o desenvolvimento de estratégias de conservação e manejo. A presente tese tem por objetivo investigar como a degradação e perda de habitat induzidas pela pecuária e silvicultura afetam a diversidade e a composição das comunidades de aves. Inicialmente, exploramos as relações entre variáveis de habitat e a composição da comunidade de aves num gradiente de altura da vegetação determinado por pastejo em campos litorâneos do Rio Grande do Sul. Posteriormente, avaliamos como variações no relevo interagem com variáveis de habitat e afetam a diversidade de aves em áreas de pecuária na Campanha gaúcha. Finalmente, avaliamos de que forma a perda de habitat resultante do estabelecimento de plantações industriais de celulose em áreas de campo afeta a composição de comunidades de aves campestres. Nossos resultados demonstram que a degradação de habitat decorrente do manejo de gado em campo nativo afeta a comunidade de aves de forma diferencial. Aves adaptadas a campos ralos ou generalistas tendem a ser beneficiadas pelo pastejo, ao passo que as espécies associadas à vegetação alta e densa são desfavorecidas. As variações na topografia reduzem os impactos da degradação de habitat nos campos. Essas variações interagem com o habitat e afetam de forma diferencial os distintos componentes da diversidade. Por outro lado, a perda de habitat decorrente da silvicultura gera um impacto de maior magnitude, alterando a composição das comunidades de aves e favorecendo aves não-campestres. Nesse contexto, impedir que novas áreas de campo nativo sejam convertidas em plantações de árvores passa a ser imperativo. Embora o manejo do gado aumente a diversidade em nível de paisagem ao criar um mosaico de manchas de vegetação de alturas distintas, maior atenção deve ser dada à manutenção e recuperação de formações densas de herbáceas de grande porte. Isso somente pode ser assegurado através de mudanças no regime do pastejo ou do desenvolvimento de técnicas de manejo alternativas. / Individuals, populations and species tend to select habitats in a non-random way. Consequently, habitat loss and degradation will have different impacts on organisms according to their traits. The effects of habitat loss are straightforward – organisms are eliminated or displaced because of the inexistence of adequate habitat or of low breeding success. Effects of habitat degradation are more subtle and result in the reduction of the capacity of an ecosystem to support some subsets of species. Since habitat loss and degradation reduce niche availability, ecologically specialized taxa with narrow niche requirements are expected to be more extinction prone than habitat generalists. Temperate grasslands have been strongly impacted by habitat loss and degradation. In southeastern South America, the expansion of agriculture and industrial pulpwood plantations are the main sources of habitat loss. Remnants of natural grassland vegetation are used for livestock ranching, being subject to habitat degradation from overgrazing, trampling and inadequate management techniques. The evaluation of how habitat loss and degradation affect the diversity of grassland organisms is vital for the development of management and conservation techniques. The main goal of this thesis is to evaluate how habitat degradation and loss related to cattle ranching and pulpwood plantations affect the diversity and composition of bird communities. We began by exploring the relationship between habitat variables and the composition of the bird community along a gradient of vegetation height determined by grazing in coastal grasslands of the state of Rio Grande do Sul. We then assessed how variations in the relief interact with habitat variables e affect the diversity of birds in rangelands of the Campanha gaúcha. Finally, we evaluated how habitat loss related with grassland afforestation for pulpwood plantations affects the composition of grassland bird communities. Our results demonstrate that habitat degradation resulting from livestock ranching in natural grasslands affects bird communities in a differential way. Birds adapted to stunted grasslands or habitat generalists tend to benefit from grazing, whereas tall-grass specialists are negatively affected. Variations in topography are responsible for reducing the impacts of habitat degradation in grasslands. These variations interact with habitat and have a differential effect on distinct components of diversity. On the other hand, the magnitude of the impact of habitat loss from afforestation is larger, altering the composition of bird communities and favoring a series of non-grassland species. In this sense, protecting remaining grasslands from afforestation is imperative. Although cattle ranching increases diversity at the landscape level by creating a mosaic of vegetation patches of different height, more attention should be given in maintaining and recovering dense formations of tall grassland plants. This can only be achieved by changing grazing regimes or developing alternative management techniques.