The structuring of ant assemblages in a Southern African savanna was investigated using data from the only long-term, large-scale savanna fire experiment in Africa. A comprehensive survey of three habitats in the Kruger National Park (KNP) revealed a total of 169 ant species from 41 genera. The sampling efficiency and consistency of pitfall traps and Winkler samples for inventory, bioindicator and ecological studies in savanna habitats was compared using ants. Pitfall traps were more efficient and productive than Winkler sampling for epigaiec ants, with a greater total species richness and higher abundance of ants recorded. Suggestions were made to improve Winkler sampling output, and to allow quantitative data to be collected. With the structuring of local assemblages, competition was the most significant local factor tested. The relationship between ant dominance and ant species richness was consistent across three continents. A model developed to test mechanisms that could be responsible for the form of this relationship supported the hypothesis that competitive exclusion by dominant ants at least partially reduces species richness. Stress was only partially responsible for low dominance and low species richness, while scatter in the data points is related to patchiness of ants at baits. These findings contrast strongly with previous claims regarding the relationship between richness and dominance. Habitat complexity was not found to play an important role in determining ant assemblage body size in this savanna system. The size-grain hypothesis (Kaspari&Weiser 1999) which predicts that environmental rugosity results in positive allometric scaling of leg length on body length because of changes in locomotion costs, was tested by comparing the body sizes of ants from areas of contrasting habitat complexity. No support for the hypothesis was found. Phylogenetic independent contrast methods did however support the allometric relationship found by Kaspari and Weiser (1999). Ant assemblages in KNP exhibited a remarkable degree of resistance, and in some cases resilience, to burning. Species richness or abundance did not vary with different burning treatments, although ant assemblage composition was sensitive to burning treatment. This difference, however, was only pronounced between burnt and unburnt plots, not between burning treatments. The degree of response of ant assemblages is likely to be related to two main contributory factors: mean annual rainfall and changes in vegetation structure with burning, and the assemblage's history of association with fire. An overview of published research on the effects of fire on fauna in Southern Africa was undertaken. Few studies have examined the effects of fire on amphibians or reptiles and few experimental studies have been undertaken using an experimental fire regime applied over appropriately long time intervals. Most studies provided no information on the scale of the study. Replication was often not reported, and was generally inadequate. Information on the effects of fire on fauna in Southern Africa is fragmentary, and consequently informed management decisions regarding the consequences of burning policies on the conservation of biodiversity both within and outside protected areas are problematic. Recommendations and suggestions for improving fire research are given. / Thesis (DPhil (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

MSc (Zoology) / Department of Zoology / See the attached abstract below

Thesis (PhD (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / The mutual association between honeydew foraging ants and vine mealybugs in vineyards is detrimental to the biological control of the vine mealybug Planococcus ficus (Signoret). This study investigated the relationship between ants, vine mealybugs and their parasitoids to improve biological control of the vine mealybug. The investigation was carried out during two consecutive growing seasons (2005-2006 and 2006-2007) in two major wine grape growing areas of the Western Cape Province, Simondium (two farms) and Breede River Valley (one farm). A presence – absence cluster sampling system was used on a biweekly basis throughout both growing seasons from October to February on each of the farms. Additionally, yellow delta traps with vine mealybug pheromone, were used to catch parasitoids in vineyards. Prior to harvest, economic damage to grape bunches was assessed using a 0-3 damage rating index. Three ant species, Anoplolepis steingroeveri (Forel), Crematogaster peringueyi Emery and Linepithema humile (Mayr) foraged mainly on vine stems during both seasons, relative to other plant parts. Vine mealybugs of all stages were found on all sampling dates. Three species of primary parasitoids attacked the vine mealybug, including Anagyrus sp. near pseudococci (Girault), Coccidoxenoides perminutus (Timberlake) and Leptomastix dactylopii Howard. Bunch damage was significantly different between seasons in the Breede River Valley but not in Simondium. There was a negative linear relationship between ants and parasitoid activity in all vineyards. Spatial Analysis by Distance IndicEs (SADIE) was used to analyse spatial distribution of ants and parasitoids and ArcView, with its extension, Spatial Analyst, were used to map the gap, patch and local association indices where significant association and disassociation occurred. A significant association was found between C. peringueyi and parasitoids and L. humile and parasitoids. There was a significant disassociation between L. humile and C. peringueyi and between A. steingroeveri and C. peringueyi indicating interspecific hostility.

Temperature is a fundamental environmental force shaping species abundance and distributions through its effects on biochemical reaction rates, metabolism, activity, and reproduction. In light of future climate shifts, mainly driven by temperature increases, how will organisms persist in warmer environments? One molecular mechanism that may play an important role in coping with heat stress is the heat shock response (HSR), which protects against molecular damage. To prevent and repair protein damage specifically, Hsps activate and become up-regulated. However, the functional diversity and relevance of heat shock proteins (Hsps) in extending upper thermal limits in taxonomic groups outside marine and model systems is poorly understood. Ants are a good system to understand the physiological mechanisms for coping with heat stress because they have successfully diversified into thermally stressful environments. To identify and characterize the functional diversity of Hsps in ants, I surveyed Hsp orthologues from published ant genomes to test for signatures of positive selection and to reconstruct their evolutionary history. Within Hymenoptera, ants utilize unique sets of Hsps for the HSR. Stabilizing selection was the prevailing force among Hsp orthologues, suggesting that protein activity is conserved. At the same time, regulatory regions (promoters) governing transcriptional up-regulation diversified: species differ in the number and location of heat shock elements (HSEs). Therefore, Hsp expression patterns may be a target for selection in warm environments. I tested whether Hsp expression corresponded with variation in upper thermal limits in forest ant species within the genus Aphaenogaster. Whole colonies were collected throughout the eastern United States and were lab acclimated. There was a positive relationship between upper thermal limits (Critical Thermal maxima, CTmax) and local temperature extremes. Upper thermal limits were also higher in ant species that lived in open habitats (shrub-oak and long-leaf pine savannah) than species occupying closed habitats (deciduous forest). Ant species with higher CTmax expressed Hsps more slowly, at higher temperatures, and at higher maximum levels than those with low CTmax. Because Hsps sense and repair molecular damage, these results suggest the proteomes of open relative to closed canopy forests are more stable. Although deciduous forest ant species may be buffered from temperature stress, it is likely that temperature interacts with other environmental stressors such as water and nutrient availability that may impact upper thermal limits. I measured the influence of dehydration and nutrition stress on upper thermal limits of forest ants from a single population. Ants that were initially starved were much less thermally tolerant than controls and ants that were initially desiccated. Because ants are likely to experience similar combination of stressors in the wild, upper thermal limits may be severely overestimated in single factor experiments. Therefore, realistic forecasting models need to consider multiple environmental stressors. Overall, adaptive tuning of Hsp expression that reflects better protection and tolerance of protein unfolding may have facilitated ant diversification into warm environments. However, additional stressors and mechanisms may constrain the evolution of upper thermal limits.

A forma como as formigas se dispersam pelo espaço está relacionada tanto à processos coletivos de formação de trilhas preferenciais de forrageamento por meio de marcação feromonal quanto à fatores individuais como orientação por ângulos, distância e direção da colônia, o comportamento em bifurcações e memória individual. Entretanto a compreensão de como esses mecanismos se articulam na produção de uma resposta da colônia frente à uma tarefa espacial poucas vezes foi focado. Além disso, assim como no forrageamento, a forma como se dá a dispersão pelo espaço na exploração também é crítica. Sendo assim, a dispersão das formigas pelo espaço representa um ponto de balanço entre a exploração e o forrageamento, em que os fatores individuais e coletivos compõem conjuntamente uma resposta ao desafio espacial. No entanto, na medida em que o uso do espaço é frequentemente observado pelo ponto de vista da otimização do forrageamento, esse balanço é pouco explorado. O objetivo do trabalho foi avaliar como a dispersão espaço-temporal das formigas de uma colônia, produzida por mecanismos coletivos e individuais, reflete tanto o esforço exploratório quanto o de forrageamento. Para isso, foi criado um labirinto hexagonal duplo concêntrico e foram comparadas as dispersões das formigas em duas condições: com alimento numa posição específica, e em uma condição controle, em que o alimento era oferecido junto à colônia de forma que a dispersão fosse uma exploração desvinculada do forrageamento. Para a observação das formigas no labirinto, foram dispostas câmeras de vídeo sobre os corredores e foi desenvolvido um software de análise de vídeo para a contagem de formigas. Embora a dispersão decorrente do forrageamento e da exploração sejam indissociáveis, através da simulação computacional com modelos de referência em que predominam um dos casos foi possível avaliar o grau de contraste com dispersões observadas experimentalmente. Observamos que, de fato, os controles são mais próximos do modelo nulo de exploração e os experimentos com folhas do modelo de forrageamento. Embora o caminho preferencial observado tenha divergido do modelo, são mais próximos do modelo de forrageamento, mostrando a relação entre a forma da dispersão e os comportamentos subjacentes. Além disso, houve uma baixa convergência nos controles, ao passo que nos experimentos com folhas a formação de trilhas preferenciais apresentou graus variados de convergência. Na condição experimental a formação de trilhas preferenciais decorrente da marcação feromonal coletiva, em conjunto com o comportamento individual nas bifurcações assimétricas e o próprio desenho do labirinto favoreceram a separação entre as trilhas de ida e volta do alimento. Enquanto o caminho de ida permaneceu o mais provável dado o labirinto, o caminho de retorno foi otimizado, estabelencendo um caminho mínimo contralateral ao caminho de ida. Assim, a relação entre os mecanismos coletivos e individuais fornece um cenário apropriado para a análise do balanço entre o forrageamento e a exploração / The means by which ants disperse is given by collective processes of preferential foraging trail formation by means of pheromone marking as well as by individual factors such as orientation by features\' angles, colony distance and direction, choices at bifurcations and individual memory. However, how these mechanisms interact in producing a colony response given a spatial task has rarely been the focus of studies. In addition, as in the case of foraging, the spatial dispersal pattern for exploration is also critical. So, the ants dispersal in space represents a balance point between exploration and foraging, in which the individual and collective factors together compose a response to the spatial challenges. However, as the space occupation is frequently studied regarding foraging optimization, this balance is disregarded. The objective of this study is to understand how the spatio-temporal dispersal of ants in a maze, as produced by such collective and individual mechanisms, reflects both the exploratory and foraging efforts. With that aim, I created a double concentric hexagonal maze and compared the ants dispersal in two conditions: in the offering of food in a specific place, and in a control condition, food was given in the same place as the colony such that its dispersal is unrelated to foraging. In order to observe the ants behaviour, video cameras were set on top of each maze connection and a software was developed to count the passage of the ants. Although the dispersal due to foraging and from exploration are inseparable, using computer simulations of reference theoretical models of each case it was possible to contrast and measure the differences to the experimentally observed dispersals. We observed that indeed, the experimental group was closer to the foraging model while the control was closer to the null model of exploration. Although the observed preferential path was different from that of the foraging model, it was still closer, showing the relationship between the observed dispersal and the underlying behaviours. Moreover, there was a low convergence in the control group, while various degrees of convergence were observed in the experimental group. In the experimental group, the formation of preferential paths by means of collective pheremonal markings, together with individual preferences at asymmetric bifurcations and the design of the maze, favoured the separation between outbound and inbound paths. Whilst the outbound path remained the most probable given the geometry of the maze, the inbound path was optimised, establishing a minimal path on the opposite side of the outbound path. Thus, the relationship between the collective and individual mechanisms provide a more than appropriate scenario for the analysis of the balance between foraging and exploration

O comportamento de insetos sociais, em especial de formigas, tem sido muito estudado nos últimos tempos, devido à capacidade destes insetos realizarem tarefas complexas a partir de interações entre indivíduos simples. Ao se moverem sobre um ambiente na busca de alimento, as formigas depositam no solo uma substância química, denominada feromônio, que atrai as formigas que se encontram no ninho e as guia em direção ao alimento encontrado. O processo de construção e seguimento destas trilhas permite que as formigas descubram os menores caminhos e as melhores fontes de alimento no ambiente. Com o objetivo de estudar as características das formigas que contribuem para a sua adaptação a diferentes condições do meio, diversos experimentos vêm sendo realizados com estes insetos. Dentro deste contexto, esta tese apresenta experimentos inéditos realizados com formigas em laboratório, sobre uma rede artificial de túneis, onde diversos caminhos interconectados conduzem a uma fonte de alimento. As decisões das formigas foram analisadas nos níveis individual e coletivo, sob mudanças no meio, compreendendo o bloqueio/desbloqueio de ramos. A medição de diversas características individuais das formigas permitiu desenvolver dois modelos matemáticos sobre o seu comportamento, que foram aplicados à situação em que não se alterou a condição do ambiente com relação ao acesso aos ramos (estática), como também a mudanças no meio (dinâmica). A análise realizada do comportamento coletivo foi utilizada na comparação dos resultados obtidos pelas simulações dos modelos. De forma geral, o segundo modelo proposto foi mais eficiente que o primeiro na situação estática, porém ele ainda necessita de ajustes nas demais situações. O bom desempenho do segundo modelo proposto levou a aplicação de sua principal característica, a função de escolha que considera a concentração de feromônio sobre os ramos do meio e a capacidade de orientação das formigas, a um problema de otimização combinatorial, o roteamento em redes de telecomunicações. O algoritmo de roteamento proposto foi avaliado sob variações no nível de tráfego e topologia da rede, e seu desempenho foi comparado ao de dois algoritmos usados por concessionárias de telecomunicações, considerando diversas medidas de desempenho. O algoritmo desenvolvido obteve resultados encorajadores, sugerindo a aplicabilidade da estrutura do modelo proposto a outros problemas complexos de otimização. / The behavior of social insects, particularly of ants, has been intensively studied in the last years, due to their capacity to perform complex tasks through interactions among simple individuals. When moving in the environment searching for food, ants deposit on the ground a chemical substance, called pheromone, to attract ants in the nest and guide them towards the source of food that was found. The process of laying/following the pheromone trails allows ants to find the shortest paths and best sources of food of the environment. With the aim to study the characteristics of the ants that contribute to their adaptation to different environment conditions, several experiments with ants have been performed and reported in this research. In this context, this thesis presents novel experiments with ants in the laboratory, in an artificial network of tunnels, where several interconnected paths lead the insects from the nest to the food source. Ants\' decision were analyzed according to the individual and collective levels, under changes in the environment, comprising the blockage/release of branches. The measure of several individual characteristics of ants allowed the development of two mathematical models of their behavior, which were applied to the non-changing (static) environment access to all branches and to changing (dynamic) access. The analysis of the collective behavior of ants in the experiments was used to compare the results derived from the simulations of the models. In general, the second proposed model was more accurate than the first one in simulating ants behavior for the static situation, however, it needs some improvements for the other situations. The satisfactory behavior of the second model led to apply its main feature, the choice taking into consideration the pheromone concentration over the branches and the ants ability to orient themselves, to solve an optimization problem, the routing in telecommunications networks. The proposed routing algorithm was evaluated under variations on the traffic level and topology of the network, and its performance was compared with two routing algorithms used by telecommunications companies, considering several performance measures. The developed algorithm produced encouraging results, suggesting the possibility to apply the framework of the proposed model to other optimization problems.

I examined the impact of the exotic, invasive plant Old World climbing fern, Lygodium microphyllum (Cav.) R. Brown, on tree island plant and ant communities in the northern Everglades. I selected 15 tree islands representing four groups: non-Lygodium islands, islands with low levels of Lygodium, islands with high levels of Lygodium, and disturbed islands impacted by people. I used a variety of diversity indices to compare plant and ant data among habitats. The ant communities studied included native and exotic species typical of south Florida. Tree island plant communities were consistent with descriptions from previous studies. Plant species richness decreased with the level of L. microphyllum in the ground and midstory layers. Abundance of native plants decreased with level of L. microphyllum in the ground, midstory, and overstory layers. Lygodium microphyllum did not affect ant communities suggesting that although it negatively impacts plant communities it can provide habitat for ants. / by Camille Darby Carroll. / Thesis (M.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Gene expression research is a valuable tool for investigating how gene regulation and expression control the underlying behaviors that structure a eusocial insect colony. However, labs that focus on ant research frequently keep ant colonies in the lab for ease of sampling. These laboratories typically do not attempt to completely emulate the ant's natural environment, and thus can expose the colonies to drastically different environmental conditions and food sources than they are used to in the wild. These shifts in diet and environment can cause changes in gene expression of the ants, affecting downstream behavioral and physiological systems. To examine the nature of these changes, colonies of the Argentine ant, <i>Linepithema humile, </i>(Mayr, 1868), were excavated from North Carolina and transferred to the lab, where they are sampled monthly. Illumina and qPCR analyses were conducted on forager samples to detect any changes in gene expression. Approximately six percent of the Argentine ant genome showed changes in gene regulation after six months in the laboratory environment. The subset of these genes examined via qPCR show that the expression of many genes are correlated with each other, indicating that these genes might be a part of a regulatory network. These findings showed that ant colonies kept in the lab experience changes in gene expression, resulting in downstream effects. Therefore, lab ant colonies are not necessarily representative of wild colonies when conducting experiments on the gene expression, behavior, and physiology of these colonies.<br>

Rocky plateaus are globally threatened ecosystems and the lateritic plateaus in northern section of the Indian Western Ghats/Sri Lanka Biodiversity Hotspot (NWG) are notable landscape features. The NWG are geologically distinct from and biologically isolated from the other two sections of the Western Ghats. The NWG is known to possess elevated levels of endemic flora their biotic relationships remain poorly understood. We present here the first quantitative multi-taxa comparative study of plateau fauna in the northern Western Ghats. Ants, water beetles and amphibians were selected for the comparison as they use different ecological resources from each other and at various times of year therefore may provide a wider representation of plateau usage. Distribution and endemism were expected to reflect distribution and isolation by plateau and inter-plateau environment related to elevational, latitudinal, climatic and land-use clines. The study explored patterns of amphibian, water beetle, ant and fungal distribution and sampling seasonal pools and terrestrial surfaces of 13 representative plateaus in western Maharashtra, with sites ranging from 67-1179 m and across 2° of (sub) tropical latitude. Distribution of all taxonomic groups was spatially non-random at all levels of organisation and across all spatial scales. At the macroscale assemblages differed significantly with climate related to elevation, latitude but at a local scale land-use and microhabitat availably had an impact. Ants displayed a large seasonal assemblage variation, responding to seed availability. Water beetles the ants (combined survey data) were the best surrogates for all taxa data with amphibians the weakest representatives. Infection by the fungal pathogen, Batrachochytrium dendrobatidis, was extensive but less intense below the escarpment. We report the first records of infection in 13 endangered and data deficient amphibian species in the Western Ghats. The plateaus of western Maharashtra have recently been recognised as fragile and threatened ecosystems most still lack adequate statutory protection. In the absence of peer reviewed comparative data, the importance of individual sites is difficult to demonstrate hampering evidence-based conservation decisions.

Worldwide, sea turtles are especially vulnerable immediately after emerging from nests. Many monitoring programs measure hatchling production from nest inventories. These inventories rarely account for mortality occurring post-emergence, leaving an incomplete estimate of hatchling production. This study addresses the nest-to-surf data gap for Florida’s east coast nesting assemblages of loggerhead sea turtles (Caretta caretta). Five locations were surveyed during the 2016 nesting season by using infrared time-lapse imagery, night vision optics, and track maps. Over all beaches, 7.6% of the observed hatchlings did not survive to reach the water. Mortality sources varied by location. Observed predators included: foxes, bobcats, yellow-crowned night herons, ghost crabs, and gulls. Hatchling disorientation and misorientation occurred more frequently in urban areas than natural areas. Factors including number of hatchlings emerging, nest-to-surf distance, and urbanization may help managers estimate nest-to-surf mortality. This study will improve life history models that serve as foundations of conservation management. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection