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Approximately two thirds of the world’s land is directly supporting human population contributing to an accumulation of disturbed habitats. This dissertation investigates the impact of human mediated habitat disturbance, in introduced Eucalyptus plantations, on community diversity and population divergence using Brazilian Cerrado lizards as a model. Data was collected along a gradient from undisturbed cerrado to disturbed Eucalyptus plantations. Community diversity differences and indicator species were identified. Furthermore, the role of phenotypic divergences were determined based on populations able to persist in disturbed habitats. Dispersal, food availability (body condition), competition and predation (caudal autotomy) were tested as potential mechanisms driving phenotypic divergences. Additionally, I investigated phylogenetic community structure differences between habitats to test for a phylogenetic signal to disturbance. The evidence showed community diversity indices were significantly lower in Eucalyptus plantations with a decrease along the cerrado– Eucalyptus gradient. Furthermore, 29 % of the Cerrado species suffered local extinctions in the disturbed habitat and of these 80 % are endemic species. One indicator species was identified for the disturbed habitat and seven species were identified for the undisturbed habitat. Species able to persist in both habitats demonstrated morphological trait divergences. These species showed short dispersal distances with only two individuals dispersing between habitats indicating a mechanism driving the observed phenotypic divergences. Another mechanism is body condition, which was higher in the disturbed habitats, reflecting increased food availability possibly due to the decreased abundances. Caudal autotomy showed no difference between the habitats indicating that competition and predation are not driving phenotypic divergences. Phylogenetic community structure demonstrated a phylogenetic signal to disturbance. The undisturbed habitat consists of communities with more closely related species compared to the disturbed habitat: indicating evolutionary forces such as habitat filtering as the stronger process structuring these communities. Whereas, disturbed communities are structured by ecological forces such as competition. This research provides information for the preservation and maintenance of the Cerrado biodiversity and has an even broader impact since habitat change caused by human activities touches a plethora of ecosystems. / text

Invasive plants are widely cited as a major threat to native plant communities, and the correlation between plant invasions and a subsequent decline in native species is well documented at some scales. However, one outstanding question is the degree to which invasive species are a driver of native plant declines versus a correlate of other drivers, such as habitat disturbance. These two hypotheses to explain the dominance of invasive species in communities have been termed the ‘driver’ and ‘passenger’ models, respectively. In order to understand the impacts of plant invasion on native plants we need more studies that consider the role of correlated environmental predictors, which may play unseen roles in the response and recovery of native plant communities frequently attributed to invasion alone. Using a large database of plant community and environmental data from sites across Southern Ontario, I used path analyses to examine the direct and indirect relationships between disturbance, exotic and native plant richness, and relative abundance. Counter to my initial predictions, I found support for both the partial passenger and partial driver models of invasive dominance, while full passenger models were outright rejected. The causal hypotheses consistent with the data indicated significant relationships between native and exotic species richness and native and exotic relative abundance across models. An exploratory analysis, which examined species-specific models, found that the data was consistent with seven out of twelve causal hypotheses. Models that could not be rejected were split almost evenly across full passenger, partial passenger, and partial driver models. Model support varied according to the species included in the dataset suggesting that the best fit underlying model of invasive dominance likely varies by species. While the partial passenger and partial driver models were recurrently consistent with the data, no single model described the underlying patterns of invasive dominance across all systems.

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Soft-sediment ecosystems can be degraded through anthropogenic development, leading to reduced habitat suitability for biological communities. On the North Coast of British Columbia, Canada, intensive industrial activity and coastal development has occurred, specifically around the Skeena and Kitimat River Estuaries. In addition to current development, both regions have the potential for further development, while also undergoing passive restoration from historical disturbances. Therefore, I aimed to broaden our understanding of passive restoration and non-invasive monitoring of intertidal soft-sediment ecosystems, by carrying out experiments at mudflats in both estuaries during the summer of 2017. Specifically, I aimed to expand the use of a non-invasive population assessment technique to novel species in soft-sediment ecosystems. Relationships between burrowing decapod abundance and burrow openings have been successfully used to estimate population sizes, but this technique has yet to be applied to large burrowing polychaetes, bivalves, or in regions of high macrofaunal diversity. As such, I assessed mudflats in regions of low (n = 1 species) and high (n = 8 species) biodiversity to determine if macrofauna abundances could be estimated from burrow openings on the sediment surface. Where only one burrowing bivalve species was present, a relationship between burrow openings and population abundance was not feasible, but burrow openings were useful in estimating total macrofaunal community abundance at a high diversity mudflat. This suggests that monitoring through burrow opening counts has the ability to detect overall changes in population abundance. Next, I examined the infaunal community, sediment conditions, and nutrient availability at one intertidal mudflat in the Skeena River Estuary following the cessation of heavy industrial activities (i.e. a salmon cannery and pulp mill) to determine the capacity for passive restoration. Sediment conditions varied spatiotemporally, and nutrient availability showed temporal variation but trends were difficult to relate to historical or current potential disturbances. The legacy of past development is still apparent on the infaunal community in the form of patchy distributions of disturbance-indicating taxa, but the mudflat appears to be in an overall healthy state with a diverse and functioning food web, indicating community recovery from historical activities. Results from these studies indicate passive restoration can be appropriate for estuarine soft-sediment ecosystems, while monitoring population abundance through burrow openings could be a method of detecting disturbances or tracking recovery of macrofaunal populations. / Graduate / 2020-06-28

Ecological interactions within a community shape the structure of ecosystems and influence ecosystem function. Plant-pollinator interactions exist as mutualistic exchange networks that may collapse as habitat loss occurs, thereby threatening the overall health of an ecosystem. Understanding the impacts of human-mediated habitat disturbance on ecological interactions is therefore crucial for conservation efforts. Archbold Biological Station (ABS) in Venus, Florida contains over 2000 hectares of protected Florida scrub habitat nested within a human-dominated environment that is threatened by anthropogenic habitat disturbance. In past studies, over 113 bee species and 157 associated host plants, many endemic to the Lake Wales Ridge, have been found on ABS property, providing an understanding of this system's plant-bee network. Using those data as a baseline, this study investigated the effects of varying levels of mechanical habitat disturbance intensity on the diversity and network structure of plant-bee interaction networks. Flowering plant abundance, richness, diversity, and composition as well as bee abundance and composition were significantly different across mechanical habitat disturbance levels. Interactions between bees and flowering plants also differed with varying disturbance intensity. From these results, it is clear that plants, bees and interactions between them are impacted by mechanical habitat disturbance in this system. This project informs management efforts not only for natural systems with the threat of alteration, but also for agricultural systems, many of which heavily rely on flower visitation by bee pollinators. This research also contributes to the growing field of interaction ecology by increasing understanding of habitat alteration effects on a valuable ecological interaction and ultimately ecosystem function.

Orientador: Thomas Michael Lewinsohn / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T17:54:45Z (GMT). No. of bitstreams: 1 AlmeidaNeto_Mario_D.pdf: 4855549 bytes, checksum: 4daf7795fa92679c987ea39ce90c2f73 (MD5) Previous issue date: 2006 / Resumo: Examinei os efeitos da degradação antrópica sobre diferentes aspectos da diversidade de espécies e interações entre plantas da família Asteraceae e os insetos herbívoros cujas larvas se alimentam no interior de seus capítulos. Toda a amostragem de campo foi realizada em vinte áreas de cerrado com diferentes níveis de degradação antrópica em três municípios vizinhos do estado de São Paulo. A densidade de gramíneas invasoras foi usada como medida indireta do nível de degradação antrópica das áreas. A riqueza de Asteraceae apresentou uma relação quadrática com a degradação, com um pico em níveis intermediários. A proporção de espécies típicas de cerrado diminuiu em áreas mais degradadas, mas a representatividade dos diferentes grupos taxonômicos não apresentou nenhuma variação consistente. Como esperado, a riqueza de plantas hospedeiras foi o principal preditor do número de herbívoros nas áreas. Conseqüentemente, a riqueza de herbívoros também apresentou uma relação quadrática com a degradação, mas pico marginalmente significativo em níveis intermediários. Quando o efeito da riqueza de hospedeiras é descontado através de uma regressão múltipla, o efeito final da degradação sobre a riqueza de herbívoros passa a ser negativo. Portanto, a relação quadrática entre degradação e riqueza de herbívoros é um efeito indireto via plantas hospedeiras. O número de interações distintas entre herbívoros e plantas também apresentou uma relação quadrática com a degradação. Visto que a conectância das redes de interações tende a diminuir com o aumento da riqueza, as áreas com níveis intermediários de degradação apresentaram valores de conectância menores que as áreas menos e mais degradadas. Quando a influência da riqueza de espécies é controlada através de uma análise alométrica, os valores de conectância mostraram uma queda em áreas onde a degradação é maior. O grau de anillhamento de interações planta-herbívoro também diminuiu significativamente nas áreas mais degradadas, enquanto que a degradação parece não afetar de forma consistente o grau de compartimentação das interações. Por fim, a degradação influenciou a resistência das redes de interações a extinções secundárias, mas seus efeitos não foram uniformes ao longo do gradiente de degradação / Abstract: This study aimed to investigate the effects of anthropogenic disturbance on the diversity and structure of interactions between species of Asteraceae and the endophagous insects whose larvae feed inside their flower heads. Field sampling was performed in 20 remnants of cerrado vegetation in three adjacent counties in the state of São Paulo, Southeastem Brazil. The density of invasive grass cover was used as surrogate of anthropogenic disturbance leveI. Asteraceae richness showed a quadratic ;elationship with disturbance and peaked at intermediate disturbance levels. The proportion of typical Asteraceae from cerrado decreased in more disturbed sites, but the taxonomic distinctness of Asteraceae did not change consistently along the disturbance gradient. As expect, host plant richness was the major predictor ofherbivore richness. Consequently, the richness of endophages also showed a quadratic variation along the disturbance gradient. However, when the effect of host plant richness on endophages is added into a multiple linear regression, the final direct effect of disturbance on insect richness is negative. Thus, the quadratic relationship between disturbance and endophage richness is explained through an indirect effect via host plant richness. The number of interactions between endophages and plants was also quadratical1y related to disturbance. Since connectance as a rule is negatively related to species number, those sites with intermediate disturbance levels presented lower connectance values than sites at the extremes of the gradient. Afier controlling for the influence of species richness on connectance values, this network property decreased at higher disturbance levels. The degree of nestedness of recorded plant-herbivore interactions was ais o lower in more disturbed sites. In contrast, disturbance leveI had no consistent effect on the leveI of compartmentation of the interactions. Finally, anthropogenic disturbance affected the fragility ofthe plant-herbivore intera~tion networks to secondary extinctions, but their effects were not uniform along the disturbance gradient / Doutorado / Ecologia / Doutor em Ecologia