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The golden mouse (Ochrotomys nuttalli), a state-threatened species in Illinois, is sympatric throughout most of its geographic range with the ubiquitous white-footed mouse (Peromyscus leucopus). The degree of interspecific competitive interaction between these species has been investigated by previous researchers, with often conflicting results. I live trapped and marked both species on two grids from 21 May 2008 through 8 May 2009. One grid was the control area; from the second grid I removed white-footed mice. Habitat on the grids was very similar for six measured habitat variables. My objectives were to document the extent of competition between the two species as indicated by a population density or behavioral response of golden mice to removal of white-footed mice on the experimental grid, and to determine if white-footed mouse presence or habitat variables affected the capture of golden mice. During 6,528 trap nights per grid, I captured a total of 22 individual O. nuttalli and 66 P. leucopus on the control grid, and 48 O. nuttalli and 202 P. leucopus on the removal grid. Compared to previous studies (Rose, 2008), the number of individual golden mice captured on my two sites (n = 70) was very large. Whereas I expected an increase in numbers and space use of golden mice upon removal of Peromyscus, the only statistically significant change was an apparent decrease in space use--there was no population density change. These results, which may indicate a lack of interspecific competition, are more likely the result of experimental design flaws, especially considering the following results. The likelihood of trapping a golden mouse at any given station on the control site was unaffected by any of the six habitat variables. White-footed mouse presence significantly decreased the likelihood of capturing golden mice on both sites. These results were the same for both elevated and ground traps. On the experimental site, golden mice changed from predominantly arboreal space use before Peromyscus removal to equal space use between arboreal and ground habitat after Peromyscusremoval. These results illustrate a spatially segregated habitat with competitively superior white-footed mice dominating the ground level microhabitat and golden mice staying predominantly in elevated microhabitat. My study, and others, demonstrate that golden mice in southern Illinois are likely habitat generalists (Morzillo et al., 2003), competitively inferior to Peromyscus(Feldhamer and Maycroft, 1992), and excluded from certain microhabitat; although it may be they actually prefer different microhabitats.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / It is widely reported that snakes can be major predators of avian nests, but the use of a single avian prey type by competing species has rarely been examined. This study aimed to investigate predation of a single food resource by the sympatric snakes Naja nivea and Dispholidus typus. Specifically, I aimed to 1) identify factors influencing snake presence in sociable weaver colonies and 2) quantify snake predation and potential differences in the consumption of prey by the two competing snakes. I used repeated visual surveys of sociable weavers to obtain presence-absence data of cape cobra and boomslang in sociable weaver colonies over an entire breeding season. I related the presence-absence data of the two snake species to spatially- and temporally-variable factors using principal component analyses (PCA) and multiple logistic regression analyses. The presence of snakes in sociable weaver colonies is primarily influenced by temporal factors, but spatial factors also play a role.

Mule deer (Odocoileus hemionus) populations are influenced by multiple factors, including interspecific competition and predation. Interspecific competition can affect resource acquisition and survival through altering space use and access to preferred habitat. Mule deer in some areas alter space use in the presence of competing species, including bison (Bison bison), cattle (Box taurus), elk (Cervus canadensis), and feral horses (Equus caballus), however the influence of competition on survival of mule deer during specific life history stages, such as birthing and rearing of neonates, is largely unknown. In addition to competition, predation can influence mule deer populations and even limit population growth by reducing recruitment of neonates into the adult population. The effects of predation may increase within a complex predator community, as predator species differ in hunting strategies, which may influence timing of predation events. We investigated the effects of interspecific competition on space use by mule deer during birthing and rearing of young (Chapter 1) and analyzed temporal patterns of predator kills of neonate mule deer in a complex predator community (Chapter 2). We hypothesized that mule deer would avoid competing ungulate species during birth and rearing of young, and that survival of neonate mule deer would decrease in areas of with increased likelihood of competition. We also hypothesized that timing of kills and habitat characteristics of kill sites would differ by predator species due to different hunting strategies. We captured 98 neonate mule deer and fit them with mortality-sensing radiocollars to test our hypotheses. We did not observe any evidence of competitive interactions between mule deer and other ungulate species. Further, we observed a positive association between space use by mule deer and elk following parturition. We also observed an increase in probability of survival for neonate mule deer in areas with higher probability of use by elk (Hazard ratio= 0.185, SE=0.497). We observed differences in timing of kills among predator species (p=0.026), however habitat characteristics of kill sites did not differ for those species. It appears that resource availability and climatic conditions influence space use by mule deer more strongly than space use by competing species. Further, timing of kills of neonate mule deer differ by predator species, which may lead to an additive effect of predation within a complex predator community.

Doctor of Philosophy / Department of Plant Pathology / James Stack / The trade of food, plant, and animal products has increased the worldwide movement and establishment of exotic pathogens with dramatic negative impacts on plant systems. Fusarium proliferatum is a broad host-range pathogen and among the most common maize pathogens globally. It is often seed-borne and symptomless in maize, making it a high risk for introduction in maize and other grains. Considering the global distribution of maize and the wide host range and production of mycotoxins by F. proliferatum, a better understanding of its life history is needed. To provide markers for tracking F. proliferatum in laboratory experiments, strains of F. proliferatum were transformed to express a green fluorescent protein (GFP). Active dispersal (at least 1.5cm at 25°C and -50mb soil matric potential) and colonization of organic matter in nonsterile field soil was demonstrated in soil microcosms. Fusarium verticillioides is commonly isolated from maize seed also colonized by F. proliferatum. A red fluorescent (mRFP) F. verticillioides transformant was developed to study competition with F. proliferatum. For quantification in host tissues, a TaqMan multiplex qPCR protocol was developed using primer and probe sets targeting fragments of the green and red fluorescence genes to detect F. proliferatum and F. verticillioides, respectively. Prior colonization of maize tissues by F. verticillioides (p=0.6749) and other seed-borne microorganisms (p=0.1910) did not affect subsequent colonization by F. proliferatum. Genotyping-by-sequencing (GBS) was used to identify genetic markers in F. proliferatum. Primer sets based GBS markers were designed to allow detection of specific isolates in field experiments. F. proliferatum populations were characterized from maize seed prior to planting and again after harvest. End-point PCR identified F. proliferatum isolates containing the GBS marker. AFLP-fingerprinting indicated that 23 of the 817 F. proliferatum isolates contained the molecular marker and were genetically related to the original isolate. Based on the subclade and percentage similarity in UPGMA phylogenetic trees, and the population grouping observed in STRUCTURE and Principal Coordinate Analysis, these isolates could have a single origin and be clonal. Understanding the life cycle of F. proliferatum is critical for learning more about the risk of introducing seed-borne exotic isolates into new environments.

La communication est essentielle à de nombreuses fonctions vitales en permettant le transfert d’information entre les individus via des signaux. Alors que les fonctions de ces signaux ainsi que les contraintes à leur propagation ont été intensivement étudiées, leur évolution a majoritairement été envisagée à travers le prisme de la dyade constituée par l’émetteur du signal et le récepteur du signal. Pourtant les signaux sont toujours émis au sein de communautés sensorielles et de nombreuses interactions interspécifiques conditionnent les pressions de sélections qui les affectent. Dans cette thèse je me suis intéressé aux liens entre différentes composantes de la composition des communautés et l'évolution du chant et de la couleur chez les oiseaux. Tirant partie des conditions particulières retrouvées dans les îles océaniques, j'ai étudié comment les changements de richesse spécifique, densité de conspécifique et présence de prédateur étaient susceptibles de modifier les comportements de communication et les caractéristiques des signaux émis. Cette approche écologique de l'évolution des signaux est nécessaire pour comprendre leur évolution au sein de communautés sensorielles. Elle m’a permis de mettre en évidence le rôle potentiellement majeur des interférences acoustiques sur la niche sensorielle des espèces ainsi que celui de la prédation sur les changements de coloration en milieu insulaire. Dans le dernier chapitre de cette thèse, je me suis intéressé à un phénomène complémentaire en étudiant les liens entre l’extravagance des signaux et la dynamique des populations au sein des communautés aviaires. Cette thèse produit des éléments forts pour affirmer que la composition des communautés détermine une part des pressions évolutives conditionnant la communication mais qu’à l'inverse, les liens entre caractéristiques des signaux et la composition des communautés sont complexes et difficile à déterminer. / Communication efficiency is related with many essential functions determining the fitness of individuals. Mating signals leads to reproductive isolation, and hence to speciation and a huge amount of studies focused on their evolution. However signals are shaped by environmental properties including the composition of signalling community but this have been understudied. Here, I examined the link between different components of communities’ composition and the evolution of two mating signals: song and coloration in birds. Taking advantage of the particular conditions found in oceanic islands, I studied how species richness, conspecific density, and predator presence were likely to alter communication behaviors and the peculiarities of the transmitted signal. In doing so, I adopted an ecological approach of communication study which I believed to be necessary to understand the evolution of signal within sensory spaces. In the last chapter of this thesis, I focused on a complementary phenomenon by studying how such signals can be deleterious for species decreasing the life expectancy of populations. Overall, this thesis produces additional evidence that the composition of communities partly determines evolutionary pressures conditioning the communication and that conversely, signal characteristic can affect the composition of the communities by determining the viability of certain populations.

This thesis investigates the impact of avian malaria (Haemosporidia) parasites on the outcome of interspecific competition between two closely related bird species, pied (Ficedula hypoleuca) and collared (F. albicollis) flycatchers. I further investigated how variation in timing of breeding, life history strategies and immune competence genes (MHC genes) modulate the fitness effects of malaria parasites in one of the two species i.e. collared flycatchers. Collared flycatchers colonized the Baltic island Öland in the late 1950-ties and has since then been expanding their breeding range while competitively excluding pied flycatchers from the favourable habitats (deciduous forests). I investigated the underlying mechanisms behind this exclusion by combining detailed long-term breeding data with modern molecular genetic techniques identifying both the presence/absence and lineage specificity of haemosporidian blood parasites. I found that the rapid decline of pied flycatchers can be explained by the combined effects of competition over nestling sites, hybridization and haemosporidian infections. Haemosporidian infections have a negative impact on survival of pied flycatcher females but no detectable effect on collared flycatchers’ longevity or reproductive success. This may be due to the fact that collared flycatchers carry (and are potentially exposed to) a higher diversity of parasites than pied flycatchers, which in turn may select for a higher diversity of MHC genes and hence a better overall protection from the negative impact of parasites. Indeed, functional MHC diversity correlates negatively with malaria prevalence among collared flycatchers from Gotland. Moreover, I found that both, malaria infection intensity and immunoglobulin level influences how infected collared flycatchers respond to increased nestling food-demands. The latter results mean that there is variation in allocation strategies (i.e. in resource allocation between reproductive effort and immune competence) within the collared flycatcher population. Hence, this population has the ability to respond to novel selection pressures in terms of optimal allocation of resources into immune functions. In summary, my results show that local parasites may facilitate the expansion of a new colonizer. This is important in the context of global climate change that will probably increase the colonization rate of southern species and lead to novel host-parasite interactions.

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