All potential myrmecochorous plants of the Czech Republic have been detected from different published sources. My study aims to describe common traits of myrmecochorous plants of the Czech flora. One of myrmecochores, lousewort (Pedicularis sylvatica), was chosen for the purpose of finding peaks in seed removal by a Myrmica scabrinodis ant species during a day and year

A seed sowing experiment was conducted in a mixed secondary woodland on acidic soils in NE Germany with <i>Melampyrum pratense</i>, an annual ant-dispersed forest herb which lacks a natural population in the study area, but is abundant in similar habitats. Each set of 300 seeds was sown within one square metre at three sites in 1997, and the development of the populations was recorded from 1998 onward. Additionally, seed fall patterns were studied in a natural population by means of adhesive cardboard. All trials resulted in the recruitment of populations, which survived and increased in both individual number and area, up to the year 2001. Thus, local distribution of <i>Melampyrum pratense</i> is dispersallimited. Total individual number increased from 105 to 3,390, and total population area from 2.07 to 109.04 m². Migration occurred in all directions. Mean migration rate was 0.91 m per year, and the highest migration rate was 6.48 m. No individual was recorded beyond 7.63 m from the centres of the sawn squares after three years, suggesting exclusive short-distance dispersal. As primary dispersal enables only distances of up to 0.25 m, ants are presumed to be the main dispersal vectors. Despite differences in individual number and colonization patterns, migration rates did not differ significantly between the populations, but were significantly higher in 2001 due to an increased population size. Colonization patterns were characterized by a rapid, negative exponential decrease of population density with increasing distance from the sown plot, suggesting a colonization by establishment of more or less isolated outposts of individuals and a subsequent gradual infill of the gaps between. My results resemble myrmecochorous dispersal distances in temperate woodlands, and migration rates and patterns across ecotones from ancient to recent deciduous forests. They may function as a colonization model of <i>Melampyrum pratense</i> after accidental long-distance dispersal.

Prescribed fire in the southern Appalachians is a frequently used and controversial forest management practice. Research is limited on the effects of prescribed fire in the mesic southern Appalachians, where many of Tennessee's rare and regionally endemic plant species occur. This study examined the effects of prescribed fire on the herbaceous layer. Field work was conducted on six previously burned sites within the Cherokee National Forest in northeast Tennessee. Complimentary non-burned sites were selected based on similarity of physical characteristics and forest structure. The numbers of herbaceous species and individuals and the total numbers of species and individuals were determined and used to compare burned and unburned forest. Following prescribed fires there were significant reductions in the number of herbaceous species and individuals. Species with myrmecochorous (ant-dispersed) seeds were markedly reduced on burned sites. Despite considerable variation among sites, the negative impact of fire on forest herbs was clearly evident.

Made available in DSpace on 2015-03-26T13:30:45Z (GMT). No. of bitstreams: 1 texto completo.pdf: 217263 bytes, checksum: b7eaa9b8e9f60a6de279fb7af5b07bce (MD5) Previous issue date: 2013-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Ants are one of the most important groups in seed dispersal. Seed removal by ants seems to be affected by four factors: ant species richness, the existence of keystone ant species, type of habitat and the size of diaspores. Te aim of this work was to test the following hypotheses: 1) the seed removal rate is higher for small seeds than for large ones in both Cerrado vegetation (Brazilian savanna) and Atlantic rain forest; 2) the rate of seed removal by ants is higher in cerrado than in Atlantic rain forest; 3) the frequency of seed removal events is positively related to ant species richness in both habitats; 4) in cerrado vegetation, seed removal is increased by the presence of keystone ant species, contrary to the forest, where these species do not occur. The work was carried out in fragments of cerrado and rain forest, both in private areas, located on the region of São João Del Rei town, Minas Gerais state, Southeastern Brazil, where the ant communities were sampled and experiments of seed removal were performed, using artificial seeds. The following results were found: 1) in cerrado vegetation, removal rate of small seeds was higher than that of large ones, while in forest there was no such difference; 2) seed removal rate varied between the habitats only for the small seeds, being higher in cerrado vegetation; 3) there was no correlation between seed removal and ant species richness in the two habitats; 4) according the expectation, there were keystone species in cerrado, and not in forest. Thirteen ant species were found removing seeds in cerrado and eight in forest. In forest, contrary to cerrado, there were more species that explored the seeds on the spot instead of removing them. These differences between the number of ant species in both environments, the ants behavior in relation to the seeds and the presence of keystone species in cerrado seem to be determinants of differences between patterns of seed removal found. There were two keystone ant species: one of them being specific for small seeds (Pheidole oxyops), and the other, for the large ones (Atta laevigata). Both genera have morphological and behavioral characteristics that enable them to be efficient dispersers of diaspores of different sizes. Thus, for forest and cerrado fragments studied, it is possible to conclude that seed dispersal by ants is not affected by the dispersers species richness, but in Atlantic rain forest it is an evenly diffuse mutualism, while in cerrado vegetation, this mutualistic relationship, although being also diffuse, is marked by the presence of more representative species. The role of the variables type of habitat and diaspore size is, at least in part, corroborated in this work. / As formigas são um dos grupos de animais mais importantes como dispersores de sementes. A remoção de sementes por formigas parece ser influenciada por quatro fatores: tamanho de diásporos, tipo de ambiente, riqueza de espécies de formigas e existência de espécies-chave de formigas. O objetivo do presente trabalho foi testar as seguintes hipóteses: 1) há mais remoção de sementes pequenas do que grandes tanto em Cerrado quanto em Mata Atlântica; 2) a taxa de remoção de sementes por formigas é maior em Cerrado do que em Mata Atlântica; 3) a frequência de eventos de remoção de sementes relaciona-se positivamente à riqueza de espécies de formigas nas duas formações; 4) no Cerrado, a remoção de sementes é aumentada pela presença de espécies-chave, ao contrário da Floresta, onde estas não devem ocorrer. O trabalho foi realizado em um fragmento de Cerrado e um de Floresta Atlântica, ambos em áreas particulares, situados na microrregião de São João Del Rei, MG, onde foram amostradas as comunidades de formigas e feitos experimentos de remoção utilizando-se sementes artificiais. Como resultados foram encontrados: 1) no Cerrado, a remoção de sementes pequenas foi maior do que a de sementes grandes, ao passo que na Floresta não houve diferença com relação ao tamanho da semente; 2) a remoção de sementes diferiu entre os ambientes apenas para as sementes pequenas, sendo maior sua remoção no Cerrado; 3) não houve correlação entre remoção de sementes e riqueza de formigas em nenhum dos dois ambientes, ao contrário do esperado; 4) conforme esperado, houve espécies-chave no Cerrado e não na Floresta. Ocorreram 13 espécies de formigas removedoras no Cerrado e oito na Floresta. Na Floresta, ao contrário do Cerrado, havia mais espécies que exploravam as sementes no local em vez de removê-las. Essas diferenças entre números de espécies removedoras nos dois ambientes, comportamento das formigas junto às sementes e a presença de espécies-chave no Cerrado podem ter sido determinantes das diferenças entre os padrões de remoção encontrados. As espécies-chave foram duas: uma delas, específica para sementes pequenas (Pheidole oxyops) e a outra, para as grandes (Atta laevigata). Ambos os gêneros possuem características morfológicas e comportamentais que lhes possibilitam a eficiência como dispersores-chave de diásporos de diferentes tamanhos. Conclui-se para os fragmentos de Floresta e Cerrado estudados que a dispersão de sementes por formigas é um fenômeno não influenciado pela riqueza de espécies das dispersoras, mas em Floresta Atlântica é um mutualismo totalmente difuso, enquanto no Cerrado a relação mutualística, apesar de também difusa, é marcada pela presença de espécies mais representativas na interação. O papel das variáveis tipo de ambiente e tamanho do diásporo é, pelo menos em parte, corroborado neste trabalho.

This thesis is focused on the dispersal, distribution, and genetic diversity of the taxonomically highly diverse Melampyrum subalpinum group. A complete revision of the localities of M. subalpinum in the Czech Republic and Slovakia is presented. The genetic variation and population structure of the M. subalpinum group across its distribution range is described based on allozymes, nuclear and chloroplast gene sequencing, and genome size. Signs of historical hybridization with M. nemorosum were found in some populations. A comparison of seed dispersal by ants between the co-occurring M. subalpinum and M. pratense and the influence of differences in this process are presented. A new mean of seed dispersal (endozoochory) is introduced for Melampyrum. Myrmecochorous dispersal distances are tested and Holocene migration possibilities are discussed taking into account endozoochory.

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. 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). 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). 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). 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). 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). / 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). 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. 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). 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). 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). 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). 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).

La biosphère traverse une crise de biodiversité pour laquelle les milieux insulaires sont l’épicentre. Les invasions biologiques y constituent l’un des principaux facteurs de forçage, notamment du point de vue de l’altération des mutualismes, pour le fonctionnement et le maintien des écosystèmes. Durant notre travail en Nouvelle-Calédonie, nous nous sommes intéressés à un groupe clé de voute pour le fonctionnement des écosystèmes, les fourmis, et leur implication vis-à-vis de la dispersion de graines (myrmécochorie). Nous avons réalisé la première identification de plantes autochtones myrmécochores, avec une prépondérance des espèces sur substrats ultramafiques. Puis, nous avons testé la dispersion par les fourmis sur ces substrats. Après avoir caractérisé les communautés selon un gradient de perturbation anthropique, nous avons évalué la dispersion et la contribution des fourmis invasives à ce service par rapport aux fourmis natives. Ainsi, Solenopsis geminata semble capable d'une meilleure dispersion que les espèces natives. A contrario, Wasmannia auropunctata exclue les espèces natives sans assurer de dispersion efficace. Dans le contexte d’un régime de perturbations intense, nos travaux illustrent une communauté néo-assemblée de fourmis, dominée par des exotiques dont certaines pourraient assurer un relai de fonction pour la dynamique des maquis. Nos travaux illustrent la « contexte dépendance » des impacts d’espèces invasives en fonction du niveau de perturbation anthropique. Ils permettent de discuter la contribution possible de ces fourmis pour la restauration après perturbation sur substrats ultramafiques, voire de leur valorisation en ingénierie écologique. / The biosphere is experiencing a biodiversity crisis, which for islands are the epicenter. Biological invasions are there, one of the main drivers, especially regarding the alteration of mutualistic relationships for the functioning and the maintenance of ecosystems. Thus, during our work in New Caledonia, we focused on a key group for ecosystem functions: ants, and their involvement in seed dispersal (myrmecochory). We carried out the first assessment of this mutualism in New Caledonia with the identification of indigenous myrmechorous plants, with a preponderance of species on ultramafic soils. Then, we evaluated the magnitude of seed dispersal by ants on these soils. After the characterisation of ant communities across an anthropic disturbance gradient, we evaluated seed dispersal capabilities of exotic ant compared to native ones. Solenopsis geminata appears to offer a more efficient seed dispersal than natives. On the other hand, Wasmannia auropunctata excludes native species without ensuring effective dispersal. In the context of an intense disturbance regime, our work illustrates a neo-assembled community of ants, dominated by exotic ones, some of which could provide a function relay with respect to maintaining the dynamic of maquis. Our work illustrates the “context dependency” of invasive species’ impacts as a function of anthropogenic disturbance’s level. It also discusses the possible contribution of these ants in a context of restoration after disturbance of habitats on ultramafic substrates, or even their use in ecological engineering program.

Various aspects of myrmecochory were investigated. Effect of different storage methods on atractiveness of seeds with elaiosomes for ants was examined. Viable seed bank of refuse piles (places where ants deposit unused objects from ant nests, e.g. seeds after the elaiosome was eaten) and places outside them were compared. Chemical content of five major chemical groups, specifically amino acids, free fatty acids, organic acids, polyols and sugars, of elaiosomes and seeds of selected species was determined, and compared with respect to their taxonomic relatedness.

Various aspects of myrmecochory were investigated. Effect of different storage methods on atractiveness of seeds with elaiosomes for ants was examined. Viable seed bank of refuse piles (places where ants deposit unused objects from ant nests, e.g. seeds after the elaiosome was eaten) and places outside them were compared. Chemical content of five major chemical groups, specifically amino acids, free fatty acids, organic acids, polyols and sugars, of elaiosomes and seeds of selected species was determined, and compared with respect to their taxonomic relatedness.

Forest ants of the genus Formica are legally protected animals. With the environmental services they provide, ensure ecological stability of forest ecosystem and are an important part of ecosystem. This work was focused on the study of ecological linkages (trofobiosis, myrmecochory and myrmecofily) and mapping damage nesting by woodpecker and wild pigs. Their destructive activities in the studied area are very high. The work also oriented on gaining a new approach to protect the ants of the genus Formica, which is based on the Red List of endangered species in the Czech Republic. Existing species protection is extended to protect the environment and the creation of a comprehensive protection.