Non-native scale insects can be economically and ecologically important pests of urban forests. Crapemyrtle bark scale (CMBS), Acanthococcus lagerstroemiae Kuwana (Hemiptera: Eriococcidae), is a scale that causes declines in plant vigor for a popular ornamental tree in the southeastern United States, crapemyrtle (Lagerstroemia spp.). CMBS has spread rapidly throughout the Southeast and, more recently, into the Middle Atlantic. Despite problems associated with CMBS, important aspects of its ecology, such as the role of propagule pressure in establishment and the relative importance of mechanisms for between-tree dispersal, are not well-understood. We used field and laboratory studies to investigate these aspects of CMBS population ecology, finding that just one female CMBS ovisac can establish new populations and that nymphs are dislodged at low wind speeds (7 m/s) from crapemyrtle twigs. Our results highlight the importance of thorough phytosanitation practices in crapemyrtle nurseries and provide evidence for wind-mediated and phoretic dispersal by CMBS.

Master of Science / Division of Biology / John M. Blair / Temperate grasslands are among the most threatened biomes in the world, with the largest historical losses due to conversion to agricultural land. While much of this biome has already been converted, there is concern the last remaining remnants in North America will be converted in response to increasing demand for crops used for ethanol production. Thus, restoring grasslands post-anthropogenic disturbance is increasingly important for conserving grassland biodiversity. Two major challenges for prairie restorations are establishing the many subdominant and rarer species found in native prairie, and offsetting the typical decline in richness and diversity over time as restorations age. Repeated seed addition of targeted species is commonly used to override low and declining plant richness and diversity. While this is generally effective early in restoration (i.e., as communities are establishing), its effectiveness in later stages (i.e., when established communities are often losing diversity) remains unknown. I investigated plant community responses to combinations of resource manipulations and disturbances coupled with a seed addition in a 15-yr old restored grassland to test the hypothesis that spatial resource heterogeneity increases the rate of colonization into established prairie restoration communities. Seeds were added to a long-term restoration experiment involving soil depth manipulations (deep, shallow) crossed with nutrient manipulations (reduced N, ambient N, enriched N). Seedling emergence was generally low and only 8 of the 14 forb species added were detected in the first growing season. I found no effect of increased resource heterogeneity on the abundance or richness of seedlings. There was a significant nutrient effect (p<0.1, α=0.1) on seedling abundance, with higher emergence in the enriched N than the ambient N treatment. I also found unexpected nutrient effects on richness, diversity and Mean C (Mean C = Σ CoCi*Ai, where CoC=Coefficient of Conservatism and A=relative abundance of the ith species). All values, except Mean C, were higher in the enriched N treatment than in either the reduced or ambient N treatments. Mean C was lowest in the enriched N treatment, and highest in the whole-plot control, suggesting that the majority of species contributing to higher richness and diversity in the enriched N treatment were “weedier” species. In a separate experiment, I found no effect of small-scale disturbances (aboveground biomass removal or soil disturbance) on seedling abundance or seedling richness. I did find a marginal effect of disturbance type on seedling richness (p=0.11, α=0.1), with higher seedling richness in the soil disturbance than the aboveground biomass removal treatment. I did not find any disturbance effects on community response variables. These results indicate that recruitment from seed additions into well-established restored communities is relatively low in the first year following a seed addition, regardless of resource availability and heterogeneity. Follow-up studies to determine recruitment rates in subsequent years are needed to elucidate whether recruitment responses are driven more by individual species differences or by environmental mechanisms.

No description available.

Les invasions biologiques sont reconnues comme un facteur évolutif important sur une échelle de temps courte. Elles affectent notamment la structure génétique des populations, les patrons d’évolution phénotypique et la richesse des faunes de parasites associées aux populations envahissantes. Cette étude se propose de quantifier les conséquences d’une invasion biologique suivant ces trois niveaux (génétique, phénotypique et parasitologique) en prenant pour exemple le cas du tilapia du Mozambique Oreochromis mossambicus. Ce cichlidé africain présente un statut remarquable en biologie de la conservation puisqu’il est à la fois (i) l’une des espèces les plus envahissantes au monde car dispersée à l’échelle globale au cours du XXème siècle et (ii) une espèce « quasi-menacée » (UICN) sur son aire native (partie du sud-est de l’Afrique) du fait de son hybridation massive avec d’autres Oreochromis sp. introduits. La démarche générale employée ici est de décrire l’histoire récente des populations à l’aide de marqueurs nucléaires (AFLP) et des séquences de l’ADN mitochondrial (ADNmt), puis de mettre en relation ces résultats génétiques avec la diversité morphologique et la parasitologie des populations. Deux systèmes différents ont été étudiés : Au sein de l’aire native, l’étude se focalise sur le Limpopo inférieur et le sous-bassin de la Changane (Mozambique). Des patrons d’introgression incluant trois espèces en présence sont détectés, mais les hybrides sont peu fréquents et leur expansion limitée. Ces résultats sont de plutôt bonne augure pour la conservation d’O. mossambicus et ils permettent d’identifier deux zones de conservation prioritaires. L’étude des parasites indique une plus grande diversité parasitaire mais de faibles prévalences dans les sites de moindre valeur en conservation, ce qui pourrait favoriser le succès des espèces introduites et de leurs hybrides. Parmi les territoires envahis, les AFLP et l’ADNmt soutiennent une homogénéité générale et une diversité génétique faible, qui sont interprétées comme le résultat d’un fort goulot d’étranglement précédant l’expansion à l’échelle mondiale. Une structure des populations en lien avec la géographie à large échelle (Nouvelle-Calédonie, Guadeloupe, Jamaïque) est cependant détectée. La variation de la forme du corps est également structurée à large échelle géographique, ce en dépit des fortes variations environnementales enregistrées à l’échelle locale. Cela suggère un effet des contraintes génétiques sur la diversification morphologique contemporaine. L’absence de parasites monogènes sur les populations introduites en Nouvelle-Calédonie peut être mise en relation avec un évènement fondateur, et est proposé comme l’un des facteurs ayant pu favoriser le succès de l’espèce. En conclusion, une faible diversité génétique ne contraint vraisemblablement pas un potentiel envahissant élevé et une diversification rapide chez les tilapias. / Biological invasions are recognized as a significant evolutionary factor over short time scales. In particular, their effect is well recorded on the genetic structure of populations, the patterns of phenotypic evolution and the richness of parasite fauna associated to invasive populations. This study aims at quantifying the consequences of a biological invasion according to these three levels (genetical, phenotypical and parasitological) taking as example the Mozambique tilapia Oreochromis mossambicus. This African cichlid is characterized by an unusual conservation status since it is both (i) ranked among the world’s worst invasive species due to its global dispersion during the 20th century and (ii) sorted as “near-threatened” (IUCN) over its native range (a part of south-east Africa) because of massive hybridization with alien introduced Oreochromis species. The approach used in this study imply to describe the recent history of populations using nuclear (AFLP) and mitochondrial DNA (mtDNA) markers, and then to compare this genetic background to results describing the morphological and parasitological diversity of populations. Two different biological systems were studied: 1) Within the native range, the study focuses on the Lower Limpopo and the Changane sub-drainage (Mozambique). Introgression patterns involving the three co-occurring species were detected, but the frequency of hybrid is low and their geographic expansion is limited. These results provided rather good auspices for the conservation of O. mossambicus, and they allowed to identify two zones of high conservation priorities. The parasitological survey reveals high parasite richness and low prevalences among sites of low conservation values. This last pattern could favour the success of alien introduced species and their hybrids. 2) Among the invasive range of O. mossambicus, both AFLP and mtDNA support a strong genetic homogeneity and a low genetic diversity, a pattern interpreted as resulting from a strong population bottleneck preceding the events of global dispersion. A pattern of population structure related to large scale geography (New Caledonia, Guadeloupe, Jamaica) is nevertheless detected. Body shape variation is also primarily structured at large geographical scale, suggesting a role for genetic constrains on contemporary morphological diversification. The total absence of monogenean parasites in the populations of New Caledonia could result from a founding event and is suggested as a potential factor that could have favoured the O. mossambicus’ success. In conclusion, a low genetic diversity does not likely constraint a strong invasive potential and a rapid phenotypic diversification in tilapias.

O movimento dos animais desempenha papel importante na aptidão dos indivíduos, no fluxo gênico, na dinâmica de metapopulações e na persistência, a longo prazo, de espécies em um ambiente. Dessa forma, o objetivo deste estudo foi compreender aspectos relacionados à ecologia do movimento da rã-manteiga (Leptodactylus latrans) e da rã-touro (Lithobates catesbeianus). Para isso, indivíduos de ambas as espécies foram marcados com radiotransmissores e rastreados com o objetivo de coletar informações sobre seus movimentos. Ressaltamos os seguintes resultados deste trabalho: (1) a área de vida média de L. latrans é de 2034,2 m2; (2) com o aumento do tamanho corpóreo de anuros há o aumento do tamanho da área de vida; (3) indivíduos de L. latrans se locomovem mais em noites escuras, chuvosas e quentes; e (4) o aumento da pressão de propágulos não reflete uma maior probabilidade no aumento da distribuição geográfica de uma dada população de L. catesbeianus. Entender os padrões de locomoção dos anfíbios e como utilizam o espaço na natureza é fundamental para o entendimento de processos ecológicos e evolutivos relacionados às histórias de vida das espécies desse grupo. Além disso, esse conhecimento serve como uma ferramenta importante no estabelecimento de limites de áreas de conservação com significado biológico para espécies ameaçadas. Ainda, saber como espécies invasoras se locomovem é um dos primeiros passos para que se tomem medidas de controle populacional e para o bloqueio do avanço da distribuição de espécies exóticas / The ability of animals to move plays an important role in individual fitness, gene flow, population regulation, metapopulation dynamics and long-term persistence of species. The aim of this study was to understand aspects related to the movement ecology of the Butter Frog (Leptadactylus latrans) and the Bullfrog (Lithobates catesbeianus). We collected movement data by radio tracking individuals of both species. Some of the most important results obtained were: (1) the mean home range of L. latrans is 2034.2 m2; (2) increasing body size increases home range size in anurans; (3) individuals of L. latrans are more likely to move larger distances in dark, rainy and warm nights; (4) the increase in propagule pressure does not reflect an increase in the probability of geographical spread of a given population of L. catesbeianus. Understanding how amphibians move and use the space in nature is fundamental for the understanding of basic ecological and evolutionary processes related to life history of the species. Moreover, this knowledge is a useful tool to establish biologically meaningful conservation boundary areas to threatened species. Yet, understanding how invasive species move in nature is one of the first steps to population control and to block the spread of geographical distribution of exotic species

The invasibility, or susceptibility of an ecosystem to biological invasion is influenced by changes in biotic and abiotic resistance often due to shifts in disturbance regime. The magnitude of invasive propagule pressure interacts with an ecosystem's invasibility to determine the extent of a biological invasion. I examined how propagule pressure, forest community structure and disturbance interact to influence the invasibility of temperate Pacific Northwest forests by the newly-invasive grass, Brachypodium sylvaticum. My goal was to identify which of these factors is most instrumental in enabling the shift from establishment to population growth in B. sylvaticum at the edge of its expanding range. Both observational and experimental studies were employed to identify the many ecological components of this problem. Ecological sampling methods were used to identify trends in B. sylvaticum habitat preference and signs of habitat disturbance. In addition, an experimental study was performed to test the effects of soil and vegetation disturbance on B. sylvaticum seedling propagation. I found that while soil disturbance did not have a significant effect on seedling propagation, vegetation disturbance was implicated in B. sylvaticum spread. Higher propagule pressure and coniferous forest type were also strong predictors of increased B. sylvaticum seedling propagation and survival within established sites. My study demonstrates how propagule pressure and plant community dynamics interact to shift the invasibility of Pacific Northwest forests and facilitate the transition from establishment to spread in the invasion of B. sylvaticum.

Tallgrass prairie restoration is an important conservation activity in rural areas. However, little is known about prairie restoration in urban environments. The overall objective of this study was to characterize and better understand urban prairie restoration. This was carried out through an examination of 29 restoration sites within Winnipeg, Manitoba. The results indicated that actively restored urban prairies were successful and high in diversity. Multiple attributes of the restorations were examined as indicators of success including vegetation, the propagule bank and insects. However, not all attributes delivered equivocal results. This suggests that multiple measures should be used to assess a restoration site. Anthropogenic and biophysical variables were found to influence vegetation of the restorations equally, highlighting the importance of incorporating a human component in urban ecological research. These urban restorations were seen to surpass larger rural restorations in quality; thus, efforts should be made to increase their prevalence. / February 2008

Tallgrass prairie restoration is an important conservation activity in rural areas. However, little is known about prairie restoration in urban environments. The overall objective of this study was to characterize and better understand urban prairie restoration. This was carried out through an examination of 29 restoration sites within Winnipeg, Manitoba. The results indicated that actively restored urban prairies were successful and high in diversity. Multiple attributes of the restorations were examined as indicators of success including vegetation, the propagule bank and insects. However, not all attributes delivered equivocal results. This suggests that multiple measures should be used to assess a restoration site. Anthropogenic and biophysical variables were found to influence vegetation of the restorations equally, highlighting the importance of incorporating a human component in urban ecological research. These urban restorations were seen to surpass larger rural restorations in quality; thus, efforts should be made to increase their prevalence.

Invasive alien species (IAS) pose a serious threat to ecosystems and societies worldwide. Local ecological knowledge (LEK) is increasingly valued as a means of understanding environmental issues; however, its application in the context of IAS research has been limited. The overall objective of this study was to document the LEK of farmers and Weed Supervisors to gain insight into a recent IAS, Odontites serotina. I conducted semi-structured interviews with farmers and Weed Supervisors with O. serotina management experience. Results indicated that the socio-economic impacts for farmers were severe in affected rural communities. However, participants had developed promising control techniques, including the application of compost mulch. I used this LEK as well as data on species occurrence, environmental variables, and measures of propagule pressure to forecast the potential distribution of O. serotina across Manitoba. The risk map generated will be useful for guiding future monitoring and public outreach efforts.

A fundamental stage in rocky-shore seaweed life history is the recruitment process involving external fertilisation and then settlement of the propagules on a suitable substrate. The ultimate step in this settlement stage is the crossing of the viscous sub-layer and attachment to the substrate. Given the extreme conditions met in the intertidal zone, propagules can be dislodged at any time before they secure a strong enough anchoring. Flow conditions and propagule properties are key to this process. The settlement process under turbulent conditions was recreated within a stirred benthic chamber for five different species. Whereas propagule properties (size, density) vary with species, and propagules are adapted to the different conditions in the intertidal, they exhibit the same settlement behaviour. They nevertheless exhibit different settling velocities and settlement thresholds. Several methods of characterisation of the tank flow from particle tracking velocimetry and acoustic Doppler velocimetry data are reviewed, as well as an analytical model. Turbulent settling was found to be independent of the well-mixed tank bulk flow and to depend only on the boundary-layer mechanics. A model of settlement threshold is presented from which propagule mucilage adhesiveness estimates are derived, leading to good correlations between adult plant exposure and the stickiness of its propagules and to the conclusion that settlement can only occur in calm conditions. To extend the work, computational fluid dynamic techniques are developed by extending the Gerris Flow Solver. A 2-D approach to tank modelling and a pilot study of expansion to 3-D is described. This extends the perspective given by the experiments, notably through output of the hydrodynamical forces experienced by the propagules. Finally, in the view of realizing direct numerical simulations of propagule behaviour in the viscous sub-layer, a new and unique 2-D/3-D fully conservative solid/fluid interaction model is developed and tested with success.