Lepidoptera (butterflies and moths) comprises a fairly well-studied invertebrate taxon. The body of knowledge that has been acquired, especially on butterflies, allows for more convincing assessments of the significance of species distributions, for example assessments of rarity and endemism. In spite of their taxonomically well-known status, little is known about the different ranges and limiting factors controlling habitat specificity amongst species at a local scale. Aiming at ensuring more efficient and inclusive conservation planning for new developments and for rehabilitation of disturbed areas this study focused on the identification of species specific and local scale (biotopic) microhabitat attractants. This was done by identifying and classifying locally occurring butterflies in the context of small scale habitat preferences on a spatial and temporal scale taking into account correlations in distributions of butterflies, plants and bio-physical gradients. Results were compared to previous studies to evaluate the use of recorded species as bio-indicators. The methodology entailed the use of twelve 250m fixed belt transects that were sampled in alternating directions across four sites within the West Coast National Park. Seven sampling sessions were set out during four sampling months mainly during the summer of the 2006/07 season. Sampling was conducted through visual observations while walking transects at a constant pace. Distributional variation between species was observed within a relatively small area with limited apparent variation in vegetation, topography and altitude. Pronounced temporal variation and correlation between butterfly species distribution and microhabitats were observed although this is strongly linked to the scale of the study in relation to the species studied. Factors that will affect the choice of microhabitat across time include amongst others: the prevailing sex ratio, temperature and the presence of invasive ants. The influence of plant distribution in predicting butterfly species distribution seemed to be less important. Myrmecophilous butterflies could probably play some role in bio-indication although much more work needs to be done to confirm this. The identification of stepping stone sites with optimum microhabitats during the environmental assessment phase in areas with endangered butterfly species should determine the face of the development and not the other way around. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2010.

Lepidoptera (butterflies and moths) comprises a fairly well-studied invertebrate taxon. The body of knowledge that has been acquired, especially on butterflies, allows for more convincing assessments of the significance of species distributions, for example assessments of rarity and endemism. In spite of their taxonomically well-known status, little is known about the different ranges and limiting factors controlling habitat specificity amongst species at a local scale. Aiming at ensuring more efficient and inclusive conservation planning for new developments and for rehabilitation of disturbed areas this study focused on the identification of species specific and local scale (biotopic) microhabitat attractants. This was done by identifying and classifying locally occurring butterflies in the context of small scale habitat preferences on a spatial and temporal scale taking into account correlations in distributions of butterflies, plants and bio-physical gradients. Results were compared to previous studies to evaluate the use of recorded species as bio-indicators. The methodology entailed the use of twelve 250m fixed belt transects that were sampled in alternating directions across four sites within the West Coast National Park. Seven sampling sessions were set out during four sampling months mainly during the summer of the 2006/07 season. Sampling was conducted through visual observations while walking transects at a constant pace. Distributional variation between species was observed within a relatively small area with limited apparent variation in vegetation, topography and altitude. Pronounced temporal variation and correlation between butterfly species distribution and microhabitats were observed although this is strongly linked to the scale of the study in relation to the species studied. Factors that will affect the choice of microhabitat across time include amongst others: the prevailing sex ratio, temperature and the presence of invasive ants. The influence of plant distribution in predicting butterfly species distribution seemed to be less important. Myrmecophilous butterflies could probably play some role in bio-indication although much more work needs to be done to confirm this. The identification of stepping stone sites with optimum microhabitats during the environmental assessment phase in areas with endangered butterfly species should determine the face of the development and not the other way around. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2010.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第18359号 / 人博第672号 / 新制||人||162(附属図書館) / 25||人博||672(吉田南総合図書館) / 31217 / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 市岡 孝朗, 教授 加藤 眞, 教授 松井 正文 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

Ce travail porte sur la dispersion des graines par les fourmis et se divise en deux parties :l’une expérimentale (Chapitres 1, 2 & 3) et l’autre synthétique (Chapitres 4 & 5). L’approche expérimentale a consisté en une exploration en conditions de laboratoire des comportements des fourmis à deux étapes du processus de myrmécochorie: à la source de graines et dans le nid. Des graines des plantes myrmécochores Viola odorata et Chelidonium majus ont été présentées aux fourmis Lasius niger et Myrmica rubra. Chaque étape de la séquence myrmécochorique a généré une variabilité des comportements propre à chacun des quatre couples fourmis-graines. <p>L’élaiosome n’attire pas les fourmis à distance. Les fourmis suivent toujours la même séquence de comportements :antennation, manipulation et prise des graines. Le nombre d’antennations et de manipulations avant la prise de graines peut être considéré comme un indicateur de l’« hésitation » des fourmis à prendre les graines. L’espèce à tendance carnivore Myrmica rubra a été plus rapide et efficace dans la prise de graines que l’espèce éleveuse de pucerons Lasius niger. Parallèlement, les fourmis ont moins antenné, moins manipulé et plus pris de graines de Chelidonium majus, ce qui montre un intérêt particulier pour cette espèce. Un jour après l’expérience, toutes les graines des deux espèces se trouvaient dans les déchets à l’extérieur du nid, avec au moins la moitié des élaiosomes consommés (Chapitre 1).<p>Lors du passage des graines à l’intérieur du nid, les fourmis Myrmica rubra ont également montré une capacité à traiter les graines rapidement, en montrant une dynamique d’arrachage de l’élaiosome et de rejet des graines hors du nid plus rapide. Le taux d’arrachage de l’élaiosome a été influencé par l’espèce de graine, plus important pour les graines de Chelidonium majus. Nous avons montré qu’une proportion variable de graines rapportées au nid (moins de la moitié) étaient déposées directement au contact des larves, les autres étant traitées ailleurs par les ouvrières ou laissées temporairement à l’abandon dans le nid. Par ailleurs, les dynamiques de rejet des items hors du nid ont curieusement été peu influencées par l’espèce de graine. Pour une graine, le fait de ne plus avoir d’élaiosome diminue le nombre moyen d’ouvrières qui la contacte simultanément. Parallèlement, même si la réponse n’est pas de type « tout ou rien », l’absence d’élaiosome accroit aussi la probabilité qu’une graine a d’être rejetée. (Chapitre 2).<p>Nous avons isolé expérimentalement le paramètre de dessiccation des graines afin mesurer son influence sur le taux de prises. La dessiccation progressive des graines réduit les taux de prises par les fourmis Myrmica rubra. La réhydratation des mêmes graines leur permet de retrouver une attractivité et donc une valeur fonctionnelle prolongée. Les graines de Viola odorata perdent presque toute attractivité après 4 jours de dessiccation et leur réhydratation ne rétabli que faiblement leur attractivité. A l’inverse, les graines de Chelidonium majus gardent un tiers de leur attractivité après un mois de dessiccation et leur réhydratation restaure presque entièrement leur attractivité (Chapitre 3).<p>La synthèse bibliographique a permis de dresser un aperçu des principales caractéristiques des fourmis dispersatrices de graines myrmécochores. Certains traits « généralistes » rendent les rencontres entre fourmis et graines très probables :leur ubiquité et diversité taxonomique, leur régime alimentaire omnivore, et leur fourragement « diffus » et opportuniste. Les fourmis possèdent des traits qui les rendent uniques par rapport aux autres insectes :le fourragement au sol, la capacité à transporter de la nourriture, ainsi que la nidification. Certains traits des fourmis ont une influence considérable sur la dispersion des graines :leur taille, les préférences de régime alimentaire, la phénologie, la capacité d’apprentissage et la fréquence de déménagement des nids. Nous développons également l’hypothèse que la rapidité et l’efficacité du traitement des graines par les fourmis seraient une conséquence d’un comportement hygiénique des fourmis à tendance carnivore, habituées à gérer des proies périssables (Chapitre 4).<p>Nous avons dressé pour la première fois une liste des espèces de plantes myrmécochores et potentiellement myrmécochores des régions d’Europe tempérée (260 spp.). Nous montrons que ces dernières sont majoritairement herbacées, et ont tendance à fleurir plus précocement que les autres espèces. La proportion de graines myrmécochores comprises entre 1 et 3 mm et entre 0,6 et 10 mg est plus importante que dans le reste de la flore (Chapitre 5).<p>/<p>This study concerns seed dispersal by ants and is divided in two parts: one experimental (chapters 1, 2 & 3), and one synthetic (chapters 4 & 5). <p>Experimental work consisted in a series of laboratory experiments, in which ant behaviour was studied at two stages of the dispersal process: at the seed source and inside the nest. Seeds of the myrmecochorous plants Viola odorata and Chelidonium majus were presented to two ant species: Lasius niger and Myrmica rubra. Each stage of the myrmecochory sequence generated a variability of behaviours for each of the four ant-seed pairs.<p>The elaiosomedo not attract seed at a distance. Ants followed always the same behavioural sequence: antennations, manipulations, and removal. The number of antennations and manipulations before removal can be considered as a measure of ants’ “hesitation” to remove seeds. The carnivorous species Myrmica rubra was faster and more efficient at taking seeds than the aphid-tending Lasius niger. At the same time, ants antennated and manipulated less Chelidonium majus seeds, which shows a particular interest for this seed species. One day after the experiment, all seeds of both species were located outside the nest in the refuse piles. At least half of their elaiosomes had been consumed (chapter 1). <p>Inside the nest, Myrmica rubra also showed a great ability to treat seeds quickly, i.e. quicker dynamics of elaiosome removal and seed rejection outside the nest. Elaiosome removal rates were influenced by seed species (higher for Chelidonium majus). We showed that a variable proportion of seeds (less than half) was directly deposited in contact with larvae. The rest of the seeds were handled elsewhere by workers, or left temporarily unattended in the nest. Dynamics of seed rejection outside the nest were curiously little influenced by the seed species. For a seed, to loose the elaiosome decreased the number of workers manipulating it. At the same time, even if the rejection response is not automatic, the absence of elaiosome increases the probability for a seed to be rejected (Chapter 2).<p>We isolated the desiccation parameter in order to measure its influence on seed removal rates. Progressive seed desiccation reduced Myrmica rubra removal rates. Rehydration of the same seeds restored their attractiveness, thereby prolonging their functional life. Viola odorata seeds lost almost all their attractiveness after 4 days of desiccation, and rehydration only restored a reduced part of their attractiveness. On the contrary, Chelidonium majus seeds kept one third of their attractiveness after one month of desiccation, and recovered almost all their attractiveness after rehydration (Chapter 3). <p>The bibliographic review allowed us to compile an outline of the main features of seed-disperser ants. Some generalist features highly increase the probability that ants encounter seeds: their ubiquity and taxonomic diversity, omnivorous diet and their opportunistic “diffuse” foraging. Among insects, ants have unique traits that make them broad dispsersers: ground foraging, the ability to transport items, and nesting behaviour. Some other traits have a great influence on the seed dispersal system: the ant body size, their diet preferences, the phenology of the colony, the learning, and the frequence of nest relocation. We also develop the hypothesis according to which, handling efficiency of ants is a byproduct of hygienic behaviour of carnivorous oriented species, since they are used to manage perishable preys (Chapter 4). <p>We compiled the first list of myrmecochorous and potentially myrmecochorous plants species of European temperate regions (260 spp.). We show that these plants are mainly herbaceous. They also tend to flower earlier than the whole flora. The proportions of myrmecochorous seeds having a size range between 1 and 3 mm, and a weight range between 0.6 and 10 mg are higher than in the rest of the flora (Chapter 5). <p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished