The genetic structuring of populations can be influenced by present processes and past events. One of the largest historical events to affect the distribution and genetic characteristics of present-day North American biota is the Pleistocene glaciation. Thus, the study of post-glacial colonization patterns of species in northern landscapes can relay important ecological information, as species had to expand their range extensively following the retreat of the glaciers and are often at the terminal end of their expansion. These species consequently exhibit the genetic fingerprints of sequential founder events, in turn decreasing the genetic variation available for adaptation. Using amphibians to investigate post-glacial range expansion is advantageous, as they have limited dispersal abilities revealing fine-scale patterns and they are thought to be one of the first vertebrates to colonize post-glacial habitat. Therefore, to model the phylogeography of a primary colonizer and the population structure of anurans in northern landscapes, population genetics analyses of wood frogs (Lithobates sylvaticus) were performed in the James Bay area. Wood frogs were sampled from 17 localities around James Bay and genetic analyses were conducted with seven microsatellite loci and mitochondrial DNA sequences of the ND2/tRNATRP genes. Results show that the post-glacial recolonization of the James Bay area by wood frogs originated from the putative refugium in western Wisconsin, an area known as the Driftless Area. Two routes were taken by founders to colonize the James Bay area: one north-west of Lake Superior, colonizing western Ontario, and one through the Upper Peninsula of Michigan, colonizing southern and eastern Ontario and western Québec. Interestingly, the meeting of the two lineages south-west of James Bay led to the establishment of a zone of higher genetic variation than expected under the founder effect hypothesis. Additionally, population structure analyses revealed the segregation of three genetic populations east, north-west, and south-west of the bay, the latter showing the highest genetic variation and likely representing a zone of secondary contact. This study shows that past events such as post-glacial range expansions can explain present patterns of genetic variation and population structure, and that studies in northern landscapes may be very useful in understanding genetic patterns throughout the range of a species.

Using GIS-based tools and a review of the relevant geological and climatic literature, I attempt to identify the key implications of Quaternary glacial cycles for drainage evolution in eastern Patagonia. In doing so, the stage is set for the proper integration of existing biogeographic and phylogeographic ideas to develop a suite of inferences aimed at elucidating how these processes influenced aquatic biodiversity of Patagonian Argentina. A primary finding of this research is that the southern mainland and/or Tierra del Fuego served as an important cryptic refuge for cold-adapted species, including aquatic taxa. At least one additional aquatic refuge is likely to have existed in either central or northern Patagonia. The low position of the Atlantic shoreline during glacial periods also revealed a much larger and inter-connected drainage network in southern Patagonia. During sea-levels stands below 100m, two new drainage coalescence points on the exposed continental shelf can be recognized among the Chico/Santa Cruz, Coyle and Gallegos river basins and between the Grande and Fuego rivers. Enhanced hydrological discharge during the deglaciation period of Late-Quaternary cycles is expected to have facilitated extensive inter-drainage connections within each of the northern and southern regions of eastern Patagonia via proglacial lake and/or stream coalescence. A large proglacial lake in the Nahuel Huapi Lake region is also recognized as the most likely temporary gateway for aquatic organisms to disperse between the Neuquen and Northern Patagonian Tablelands. I also recognize climate-induced drainage reversals as a bidirectional mechanism of trans-Andean dispersal and an important factor in determining the biogeography of widespread aquatic organisms in Patagonia.

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This Ph.D. thesis presents new facts about a paleoenvironmental development of the northern part of the Bohemian Forest (area of Černé Lake and Čertovo Lake) in the Late Pleistocene and Early Holocene. The main goals of the research are: characterize the glacier landforms in the Bohemian Forest and define the variance of these landforms; determine factors influencing formation and development of the glaciation in the study area; describe environmental settings and its changes during deglaciation and in Early Holocene by using environmental proxies. This research proceeds from original data obtained by geomorphological mapping, morphometric analysis and proxy data analyses originated from a sediment sequence in a peat bog in the Černé Lake vicinity. The common attributes of the Bohemian Forest cirques and cirque variability was determined using morphometric and morphologic characteristics of the cirques on the Bavarian and Czech side of the mountain range. These characteristics were compared with other cirques of the Bohemian Massif and other chosen mountain ranges of the world. The cirque overdeepening was defined on the basis of headwall shapes and it emerged that overdeepening of the cirques in the Bavarian Forest and in the High Sudetes reflects a different extent of the Pleistocene glaciation....