Aquesta tesi examina els mecanismes ecològics i evolutius que mantenen els gradients de riquesa específica en ocells. S'examinen en primer lloc el patrons de diversitat de l'avifauna de Nord Amèrica. (capitol 1). Tot seguit es testen mecanismes a escala regional, tot estudiant el cas de l'avifauna de Catalunya (capitols 2 i 3). Finalment, es testen diferents mecanismes que regulen la diversitat a escala local en una comunitat d'ocells frugívors al Parc nacional de Doñana. El capitol 6 integra tots els anteriors i els relaciona tot fent una revisió bibliogràfica en profunditat.Paraules clau: biodiversitat, ocells, adaptació, filogènia, switching behaviour, xarxes d'interacció, Nord Amèrica, Catalunya, Doñana, gradients altitudinals, productivitat. / Species richness gradients have been analyzed during many decades and they have progressively emerged as a central topic in community ecology (Darwin 1859, Wallace 1878, Willis 1922, Dobzhansky 1950, Fisher 1960, Hillebrand 2004, Riclkefs 2004, Mittelbach et al. 2007, among others). Historically, species richness gradients have been analyzed from two main points of view: the ecological and the evolutionary perspective (Ricklefs 2004, 2006b). The ecological perspective assumes that populations are evolutionarily fixed and studies species richness gradients as the result of regional colonization and extinction processes, and ecological interactions (MacArthur and Wilson 1967b, Scheiner and Willig 2005). Contrarily, the evolutionary approach states that species richness gradients are the result of geographic differences in the long-term evolutionary processes of speciation and lineage extinction (Rohde 1978, 1992, Mittelbach et al. 2007). For instance, according to the evolutionary view, tropical regions achieve higher species numbers due to increased diversification rates in low latitude areas (i.e. increased speciation and/or reduced extinction rates). Interestingly enough, recent empirical evidence derived from phylogenetic studies suggests that bird diversification rates are effectively higher in the tropics thus providing empirical support for the evolutionary view (Cardillo 1999, Cardillo et al. 2005, Golberg et al. 2005, Ricklefs 2006a, Jablonski et al. 2006, Weir and Schluter 2007). In contrast with the evolutionary approach, the ecological approach assumes that populations are evolutionary stable units and focus on the effect of regional colonization-extinction dynamics, local conditions and local interactions in determining species richness gradients (Hutchinson 1959, MacArthur and Wilson 1963, 1967ab, MacArthur and Levins 1967, May 1975, Riclkefs 2006b). The ecological approach highlights that species richness gradients can be generated by ecological mechanisms independently of the evolutionary processes of speciation and lineage extinction that conform the regional pool of available species. For instance, an environmental gradient can cause a species richness gradient by limiting the number of successful colonizations in environmentally severe localities without the participation of any speciation process in the regional pool (Wright 1983, Hanski 1997, Boulinier et al. 1998).These two contrasting and complementary views, the evolutionary and ecological approaches, are progressively being merged in a unified framework (Ricklefs 2006b, Johnson and Stinchcombe 2007). For instance, Johnson and Stinchcombe have recently proposed that two general hypotheses (H1, H2) are underlying a new synthesis between community ecology and evolutionary biology. On one hand (H1), evolutionary processes explain present-day community patterns and the ecological dynamics of species interactions. For instance, extinction and colonization processes that generate species richness gradients might be shaped by species' adaptations, history and phylogenetic relationships (Wiens and Donoghue 2004, Wiens and Graham 2005, Kraft et al. 2007). On the other hand (H2), Johnson and Stinchcombe highlighted that both species interactions and community context strongly influence the direction, rate and outcome of present-day evolutionary processes (Benkman 1999, Thompson 2005). Overall, the emerging synthesis of community ecology and evolutionary ecology highlights that ecological and evolutionary views are profoundly interlinked. Here we applied an evolutionary and ecological synthetic perspective to the study of the generation and maintenance of species richness in bird communities (Johnson and Stinchcombe 2007). As a first preliminary step, we examined geographical patterns of bird species richness in North America in several functional groups and the associated environmental correlates at the continental scale (Chapter 1). Our results showed that global large-scale patterns of avian diversity in temperate regions were best viewed as the overlayed response of distinct species groups to diverse ecological factors. These results strongly suggested the convenience of choosing specific functional groups in order to examine specific macroecological evolutionary and ecological hypotheses. Consequently, in Chapter 2, we next chose forest birds as a study group for the analysis of macroecological patterns, because they are the largest group in Nearctic and Palaeoarctic regions among terrestrial birds, and hold strong species-energy relationships (Mönkkönnen et al. 2006). Regional data with colonization and extinction estimates for forest birds were available in Catalonia along an altitudinal gradient (Estrada et al. 2004) providing an exceptional dataset to study the ecological and evolutionary processes behind species richness gradients (Chapters 2 and 3). We examined the altitudinal species richness gradient in Catalonia from an evolutionary and ecological synthetic perspective. First, the role of evolutionary processes in the gradient was assessed studying changes in community phylogenetic structure along the altitudinal gradient. Secondly, the role of ecological processes was examined by studying colonization and extinction dynamics at an ecological time-scale (20 years). These analyses allowed us to examine the role of phylogeny, colonizations, extinctions, community size, productivity, habitat availability, and dispersal limitation in generating bird species richness gradients in Catalonia. However, due to the coarse structure of macroecological data used, the role of local species interactions in such processes remained yet obscure and elusive.Understanding the role of species interactions in the processes of coexistence and diversification of bird communities thus remained as a big challenge. Since long ago, ecological interactions have been hypothesized to play a role in the maintenance of diversity (Hutchinson 1959, MacArthur and Levins 1967, McPeek 1997, Mittelbach et al. 2007). Therefore, the quantitative study of species interactions was expected to provide insights on the processes that ultimately generate species richness in bird communities (Cattin et al. 2006, Rezende et al. 2007). However, data on species interactions is usually available only for specific local communities. Therefore, a macroecological approach is precluded because the bulk of the studies of community interaction networks are carried out at local scales. Accordingly, we examined the role of species interactions in the generation of species richness in a local Mediterranian bird community for which interaction good-quality data was available (Chapters 4 and 5) (Jordano 1984, 1987). We addressed the two general hypotheses delineated by Johnson and Stinchcombe (2007). First, in chapter 4, we analyzed if evolutionary processes causally affect present-day community interaction patterns and the dynamics of species interactions (H1). Secondly, in chapter five, we assessed if species interactions and community context might influence the direction, rate and outcome of present-day diversification processes that ultimately generate species richness (H2). Overall, our results provide strong support for the two hypotheses examined, thus highlighting the idea that evolutionary and ecological processes are effectively profoundly interlinked. On one hand, we show that long-term evolutionary processes effectively modulate present-day community interaction patterns and dynamics (Webb et al. 2002, Cavender-Bares and Wilczek 2003, Johnson and Stinchcombe 2007, Chapter 4). Likewise, we demonstrate that community context can potentially shape bird morphological diversification processes and drive speciation (Thompson 2005, Abrams 2006, Johnson and Stinchcombe 2007, Chapter 5). Overall, Chapters 4 and 5 provide some new empirical and theoretical insights dealing with the processes that generate and maintain local bird diversity from an integrated evolutionary and ecological perspective.

Title: Mountain birds – a comparative study from valley to mountaintop in a northern and southern Swedish fjeld   Author: Kristian Zackrisson   Abstract Main aim in this study was to increase the knowledge about birds in the Swedish mountain area. Three questions were asked: 1) Which bird species can be found during the breeding season along a low mountain slope from a forested valley to a mountaintop with bare mountain environment? 2) Do the number of species and individuals differ in different elevation zones? 3) Is the composition of bird species along a low mountain slope the same in the Kebnekaise mountains inLaplandand the Grövelsjön mountains in Dalarna? Bird census in two study sites located in the Kebnekaise mountains and the Grövelsjön mountains and subsequent analysis of the results from the bird census was the main parts in this study. Totally 20 bird species were found along a low mountain slope in the Kebnekaise mountains. In a lower elevation zone below the forest boundary there was 16 bird species and 509 individuals observed. 6 bird species and 65 individuals were registered in an upper elevation zone above the forest boundary. The lower elevation zone indicated a higher biodiversity for birds compared to the upper elevation zone. Bird species composition varied between the two study sites. Five species that had been observed in the Kebnekaise mountains where not found in the Grövelsjön mountains which instead had six species that were not found in the Kebnekaise mountains. Compared to other studies the 20 observed bird species are some of several species in the specific area. The higher biodiversity in the lower elevation zone can be related to declining temperature by elevation gradients. Previous bird censuses indicate that the bird species observed in the Kebnekaise mountains also can be found in the Grövelsjön mountains.

Invasive organisms are one of the major threats to the ecological integrity of aquatic systems in the 21st century. Among the most notorious and important aquatic invasive organisms are the dreissenid mussels, Dreissena polymorpha and D. rostriformis bugensis, which having originated in the Ponto-Caspian region are now common in many parts of Europe and North America. Dreissenids have large impacts on many aspects of lentic ecosystem functioning, the sum of which is thought to lead to the translocation of biological production from the pelagic to the littoral zones of lakes. In this thesis I explore the effects of dreissenids on the nearshore zones of large lakes, investigate the mechanisms by which dreissenids couple the pelagic and nearshore zones of lakes and attempt to elucidate the factors affecting the strength of the dreissenid-mediated connection between the pelagic and littoral zones. The effects of invasive organisms on an aquatic ecosystem will depend, in part, on the distribution and biomass of the invasive organisms in the system. In chapter 2 I present the results of a lake-wide survey of the distribution of invasive dreissenid mussels in Lake Simcoe, Ontario and discuss some of the factors that shape their distribution pattern in the lake. Dreissenid biomass averaged 27.2 (±24.3 SD) g shell-free dry mass (SFDM)/m2 in the main basin of Lake Simcoe and 12.4 (±16.9 SD) g SFDM/m2 in macrophyte-dominated Cook’s Bay. I argue that water movement is an important determinant of dreissenid distribution, both through catastrophic disturbance in shallow water and through non-catastrophic effects on substrate distribution and possibly food supply rates. In areas of dense macrophyte growth, mussel abundance was shown to be associated with that of preferred macrophyte taxa, in particular with that of Ceratophyllum demersum. I used the results of my survey and the relationships between environmental variables and dreissenid biomass to estimate the total biomass of dreissenids in Lake Simcoe: 12,000 tonnes SFDM. Most of the dreissenid biomass in Lake Simcoe was concentrated in the nearshore zone, where dreissenids would have maximal impacts on littoral biological production. One of the effects of the dreissenid invasion into the Laurentian Great Lakes appears to be a resurgence in the abundance of the nuisance alga Cladophora glomerata which experienced a marked decline following phosphorus abatement in the late 1970s and early 1980s. A subsidy of bioavailable phosphorus excreted by dreissenid mussels could be an important mechanism facilitating the growth of C. glomerata. In chapter 3, I describe a survey of dreissenid distribution and abundance followed by in situ experiments designed to measure dreissenid phosphorus excretion rates. Average dreissenid mussel abundance in our study area was 3674 (±2233 SD) individuals/m2, with an average biomass of 52.2 (±29.0 SD) g of shell free dry mass/m2. The mussels excreted bioavailable soluble reactive phosphorus (SRP) at an average rate of 7.0 μg SRP/g shell free dry mass/hour, contributing about 11 tonnes of SRP to the study area over the C. glomerata growing season. Dreissenids appear to be an important source of recycled bioavailable phosphorus to the littoral zone, potentially supplying more soluble reactive phosphorus to the study area than local watercourses and waste water treatment plants, and more phosphorus than is required to sustain local C. glomerata growth. Dreissenid establishment in many systems coincides with increases in the abundance and diversity of littoral benthic invertebrates and with changes to community composition of the benthos. Currently, there is a lack of long-term studies of the impact of dreissenid mussels on hard-substrate inhabiting littoral benthos. In chapter 4 I compare the littoral benthos of Lake Simcoe, Ontario just prior, and 14 years following the establishment of dreissenids in the lake. Densities of non-dreissenid invertebrates on hard substrata increased by nearly 50 times, from an average of 367.9 (±460.8 SD) individuals/m2 in 1993 to an average of 16,706.4 (±10,204.5 SD) individuals/m2 in 2008. The taxonomic diversity of the benthos increased significantly. The distribution of benthic organisms also changed; the numerical abundance of benthos has become more even across depths and sites, as has community composition. I suggest that in addition to increasing resource availability to benthic organisms dreissenids have also caused a homogenization of the littoral habitat by increasing the evenness of the distribution of food and habitat resources. The changes in the littoral benthic community in Lake Simcoe likely have wide-ranging implications to higher trophic levels and the cycling of energy in the lake. In addition to impacting nutrient cycling and the benthic invertebrate communities of littoral zones, dreissenid mussels can have large effects on food webs and energy cycling. In chapter 5 I used stable isotope analysis of pre- and post-dreissenid components of the nearshore food web of Lake Simcoe, Ontario to determine how dreissenids affected food sources and energy flow in the littoral zone of Lake Simcoe. Results suggest that the post-dreissenid food web relies about equally on two energy sources: dreissenid biodeposits (redirected pelagic primary production) and littoral benthic primary producers. Although the relative importance of pelagic and benthic primary production to benthic organisms has not changed much following dreissenid establishment, the absolute importance of both increased considerably in the post-dreissenid littoral zone: the large increase in invertebrate biomass that followed dreissenid establishment means that the amount of both pelagic and benthic primary production needed to sustain post-dreissenid organisms had to increase considerably. The results of this chapter suggest that dreissenids increase the availability to food to littoral organisms by redirecting pelagic primary production to the benthos and by stimulating littoral benthic primary production. The impacts of dreissenids on littoral benthic organisms probably have large effects on littoral and pelagic fish communities of lakes. Dreissenid mussels translocate biological production to the benthos by stimulating benthic primary production through nutrient excretion and increases in water clarity, by increasing habitat availability for benthic organisms and by biodepositing pelagic material that becomes available to benthic organisms and the fish that feed on them. I argue that hydrodynamic factors are important in controlling the strength of the dreissenid-mediated pelagic-littoral connection in lakes. Because hydrodynamics relate to lake size, a relationship between lake size and the ability of dreissenids to translocate production the littoral zone can be postulated, where dreissenid effects are maximal in intermediate-sized lakes.

Arundo donax, or giant reed, is a large, bamboo-like plant native to Spain that has invaded several thousand acres of the Rio Grande riparian in Texas. The plant grows to 18-24 feet, consuming large quantities of water per acre per year. With concern of increased water demands in the Texas Lower Rio Grande Valley region, the United States Department of Agriculture-Agricultural Research Service (USDA)ARS) is investigating four herbivorous insects as potential biological control agents for Arundo donax to facilitate increased water supply. This study examines select economic implications for agricultural water users in the United States of applying these biological control agents along the Rio Grande. The research includes (a) estimating the value of the water saved due to the reduction of Arundo donax, (b) a benefit-cost analysis, (c) regional economic impact analysis, and (d) an estimate of the per-unit cost of water saved over a 50-year planning horizon (2009 through 2058). The model ArundoEcon is used to perform a deterministic analyses using low- and high-marginal-composite acre values. Regional results indicate present values of farmlevel benefits ranging from $97.80 to $159.87 million. Benefit-cost ratios are calculated with normalized prices and range from 4.38 to 8.81. Sensitivity analyses provide a robust set of results for Arundo water use, replacement species water use, Arundo expansion rate after control, value of water, and the cost of the program. The pre-production processes and farm-gate economic impact analysis is estimated using multipliers from the IMPLAN model. Regional results reveal a range of $8.90 to $17.94 million annually in economic output and 197 to 351 new jobs for the year 2025. Further results show the cost per acre-foot of water saved is $44.08. This amount is comparable to other projects designed to conserve water in the region. The USDA)ARS, Weslaco, Texas Arundo donax biological control project realizes positive results for the benefit-cost ratios, economic impact analyses, and competitive results for the per-unit cost of saving water. These positive results indicate this project will have positive economic implications for the U.S. and the Texas Lower Rio Grande Valley.

Using four AFLP markers and seven polymorphic microsatellite loci, we examined the genetic structure of the rare and endangered Spiranthes parksii Correll (Orchidaceae). Spiranthes parksii is not distinguishable from sympatric S. cernua (L.) Rich based on these data, though low levels of polymorphisms exist within both. These low levels of genetic diversity are likely a result of high levels of agamospermic reproduction through adventitious embryony. These results suggest that both S. parksii, as well as the sympatric, open flower form of S. cernua, are products of the more widely distributed S. cernua complex. Further, another local form of S. cernua, distinguished by its tendency to produce closed flowers is genetically distinct from both S. parksii, as well as the openflower form of S. cernua, as shown by AFLPs and microsatellite loci. This is the first known set of microsatellite primers developed specifically for use in Spiranthes. The application of these markers may be used to address other unresolved relationships among species of Spiranthes, many of which are also endangered or have populations in decline.

Thesis (PhD.)--University of Canberra, 2007. / Includes bibliography (p. 152-176)

Thesis (All-College Honors) - - State University of New York College at Cortland, 2004 - - Department of Biology. / Includes bibliographical references (p.59-60).

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 520-556). Also available on the Internet.

Thesis (Ph. D.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 520-556). Also available on the Internet.