Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xv, 155 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references.

Nigeria is the most densely populated country in Africa and one of the most advanced economically in terms of both industry and soil and landscape utilization. This country is projected to have one of the largest urban growth rates by 2050. Thus, the demands of the rapidly increasing human population and its material consumption represent a severe threat to biodiversity. Nigeria has the highest deforestation rate of natural forest in the world, its original vegetation has largely been replaced by farming activities, urban development and other products of human activities. The principal causes of the decline and loss of biodiversity in Nigeria include human exploitation of natural resources, fragmentation of habitats and populations, conversion of wild areas to agriculture and other intensive human use and alterations in the structure and function of ecosystems. Amphibians are the vertebrate group with the highest number of species threatened with extinction and habitat loss and fragmentation are considered to be among the leading causes of their declines and extinctions. It has been recognized that one of the most severe problems in conservation biology is the scarcity of baseline data. Such lack prevents evaluation of the effect of the expanding anthropogenic impact and determination of potential population declines. The mountains of eastern Nigeria, within Taraba State, are regionally important in terms of biodiversity and endemism, however, its herpetofaunal diversity has received little attention. Moreover, no studies have investigated how habitat loss and fragmentation may affect dispersal and gene flow among small and isolated amphibian populations, and in the absence of such studies attempts at amphibian conservation are compromised. The aims of this project were threefold. Firstly, a comprehensive inventory of the amphibians and reptiles of Ngel Nyaki and Kurmin Danko Reserve on the Mambilla Plateau was compiled. The outcome, an annotated list of 21 amphibians and 11 reptiles, represent the most thorough inventory to date of the herpetofauna on the Mambilla Plateau. Based on this inventory four key anuran species were selected to conduct a population genetics study. Secondly, molecular tools specifically AFLP markers were developed and used to analyze the genetic population structures of the four frog species Cardioglossa schioetzi, Leptodactylodon bicolor, Astylosternus sp. 1 and Astylosternus sp. 2. differing in geographic distribution and life history traits within the study area. Thirdly, these species were assessed to understand dispersal and connectivity among fragmented and continuous populations on the Ngel Nyaki and Kurmin Danko Reserve. Genetic differentiation among the forest and the riparian fragment populations was observed for three of the target species, however, no significant genetic differentiation was detected among the populations located in continuous forest for any of the four frog species. In addition, geographic and genetic distances were not correlated significantly for any of the four target species, suggesting no isolation by distance at this fine geographic scale. Results from both the inventory and the genetic population structure study revealed that the riparian forest fragments are of utmost importance for the persistence and migration of Cardioglossa schioetzi, and potentially for many other amphibian species. The new scientific findings are now part of the valuable baseline data on the diversity and genetic population structure of amphibian species in Ngel Nyaki and Kurmin Danko Forest Reserve. These results will better inform conservation managers who need to make decisions around management of montane habitat for amphibian species.

No description available.

Magistro darbe tiriamas varliagyvių vystymasis ir jų pasiskirstymas Krekenavos regioniniame parke. Darbo objektas – varliagyviai Krekenavos regioniniame parke Darbo tikslas – nustatyti Krekenavos regioninio parko varliagyvių rūšinę įvairovę ir jos pasiskirstymą. Darbo metodai – eksperimentas, natūralus stebėjimas, matavimas, maršrutinis metodas. Darbo rezultatai. Šiame darbe panaudota medžiaga buvo surinkta 2006.04.23, ir 2006.birželio – rugsėjo mėnesiais. Atlikus stebėjimus buvo pastebėti akivaizdūs skirtumai tarp namų ir lauko bandymo rezultatų. Kambario sąlygos, šiluma ir temperatūra nulėmė buožgalvių greitesnį vystymąsi, nei lauko sąlygomis. Namų sąlygomis buožgalvių metamorfozė nuo embriono iki buožgalvio trunka 4 dienas. Lauko sąlygomis buožgalviai vystosi panašiai, kaip ir natūraliomis sąlygomis , metamorfozė nuo embriono iki buožgalvio trunka 12 dienų. Smailiasnukės varlės ( Rana arvalis) gausiai sutinkamos pušyne. Paprastasis tritonas (Titrus vulgaris) aptinkamas tik sausuose pušynuose. Mišriame lapuočių miške – pievinės varlės (Rana temporaria). Glitėtų beržyne gausiai sutinkamos varlės ežerinė varlė (Rana ridisbunda) ir kūdrinė varlė (Rana esculenta). Senvagėje ir užtvankoje varlių pasiskirstymas nėra būdingas vienai ar kitai gyvenamajai aplinkai. Krekenavos regioniniame parke gausiausiai sutinkamos rudosios varlės, o iš jų – pievinė varlė (Rana temporaria); ji mažiausiai išranki savo gyvenamajai vietai. / This master work analyses the development of amphibians and their distribution in Krekenava regional park. The object of this work – the amphibians in Krekenava regional park. The goal of this work – to determine the variety of amphibian species in Krekenava regional park, their abundance and distribution. The objectives of this work – experiment, natural observation, measurement, route method. The results of this work. The material used in this work was collected in 2006.04.23 and June ) September period of 2006. After observation there were noticed big differences between the results achieved in experiment within outside and inside conditions. Inside conditions, warmth and temperature have caused faster development of tadpoles than within outside conditions. The methamorphosis of tadpoles within inside conditions takes 4 days. The development of tadpoles within outside conditions in their natural habitat is very similar, only in takes 12 days to develop from embryo to tadpoles. Rana arvalis are very common in pine forest. Triturus vulgaris are found only in dry pine forest. Rana temporaria are very common in leaf – bearing forests. Rana esculenta and Rana ridibunda are very common in birch forest. The distribution of frogs in the old riverbed and the, pond isn’t common for one or the other natural habitat. The most common frog species in Krekenava regional park is the brown frog species - Rana temporaria , which is the least fastidious for its natural habitat.

I studied two aspects of the ecology of amphibians in southwestern Quebec, an area characterized by a mosaic of small forests interspersed by cultivated land and by the presence of rare species at the northern limits of their distribution. One aim was to determine how forest age after clearcutting affected woodland amphibians. Path analysis was used to compare different causal effects of forest age on Plethodon cinereus density in 22 deciduous forests of 30, 60 and $>$90 years old. Repopulation of Plethodon followed forest litter recovery, 30 to 60 years after clearcutting. However, the effect of forest age was overridden by that of microtopography and soil texture. Rana sylvatica seemed also sensitive to clearcutting while Bufo americanus, Ambystoma maculatum and A. laterale seemed much less sensitive. / A second aim was to determine the status and habitat of stream salamanders at the northern edge of the Adirondacks. Sixty stream sections were sampled. Eurycea bislineata was widespread (in 47 sites) and abundant, especially where rocks were numerous on the shore. The distributions of Gyrinophilus porphyriticus (8 sites) and, to a lesser extent, of Desmognathus fuscus (11 sites) were positively correlated with altitude and the presence of forest. It is proposed that these locations might offer the temperate and oxygenated waters needed by these species during winter and summer. (Abstract shortened by UMI.)

Identifying the ecological mechanisms that determine food web structure is critical for understanding the causes and consequences of diversity. The objective of this thesis was to identify the mechanisms structuring aquatic food webs across environmental gradients from a multi-level perspective (individual to ecosystem) using integrative methodology and field experiments to test classic ecological theory. My results demonstrate support for the dynamic constraints hypothesis, which predicts habitats with greater disturbance should have shorter food chains, but are not consistent with the ecosystem size hypothesis that predicts larger ecosystems have longer food chains. Insect and amphibian richness increased with increasing pond size and hydroperiod, indicating that insertion of new consumers into pond communities was driving variation in food-chain length. A multivariate analysis testing the influence of physicochemical variables on food-web characteristics revealed that hydroperiod and pond area had a strong influence on amphibian and invertebrate assemblages, trophic diversity and 15N range. Food-chain length did not respond strongly to any one variable, but instead responded weakly to multiple environmental variables, suggesting interacting influences on food-web structure. Conversely, the trophic niche of amphibian larvae was not influenced by pond hydroperiod, but did exhibit ontogenetic diet shifts. Populations of amphibian larvae with broader niche widths also had increased individual variation, supporting the niche variation hypothesis. In addition, I assessed whether species diversity influenced the magnitude of cross-habitat resource flow between aquatic and terrestrial habitats via emerging aquatic insects, metamorphosing amphibians, and litter deposition. Deposition into ponds far exceeded carbon exported via insect and amphibian emergences. We found a negative relationship between resource flux and the diversity of amphibians and insects, which contradicts the general pattern of positive biodiversity-ecosystem function relationships. My research strongly suggests environmental variation is a key process in shaping food-web structure and function and that multiple methodologies are needed to understand temporal and spatial dynamics of aquatic ecosystems.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Chemistry, 2000. / Copies of author's previously published articles inserted. Includes bibliographical references.

Thesis (Ph.D.) -- La Trobe University, 2006. / "A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy, Dept. of Zoology, School of Life Sciences, La Trobe University". Research. Includes bibliographical references (p. 445-481). Also available via the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 115-128). Also available on the World Wide Web.