Thesis (Ph. D.)--University of Chicago, Committee on Evolutionary Biology, December 1999. / Appendices on CD-ROM. Includes bibliographical references. Also available on the Internet.

No description available.

Dissertation (PhD)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

La leptospirose est une zoonose d’importance médicale majeure dans les îles du Sud-Ouest de l’Océan Indien (SOOI) dont certaines enregistrent des incidences parmi les plus élevées au monde. Durant la dernière décennie, les données épidémiologiques moléculaires obtenues avec une approche « One Health » ont mis en évidence une grande diversité de lignées de leptospires ainsi que différentes chaines de transmission sur les différentes îles de la région. Les données moléculaires montrent la présence de leptospires pathogènes et de réservoirs animaux introduits ou endémiques de cette région. La distribution de ces différentes lignées de leptospires est associée à (i) un contraste épidémiologique incluant des différences dans la sévérité des cas humains et (ii) des niveaux de spécificité d’hôtes différents selon les leptospires considérés. Plus particulièrement, les leptospires endémiques du SOOI semblent être moins pathogènes chez les humains et montrent une plus forte affinité pour leur réservoir que les leptospires cosmopolites. Pour compléter nos connaissances sur l’histoire évolutive des leptospires du SOOI, nous avons produit des données provenant de chauves-souris de l’Afrique de l’Est. Ces données confirment la spécificité de certaines lignées de leptospires envers leurs hôtes chiroptères et suggèrent que les chauves-souris d’Afrique ont colonisé Madagascar tout en étant infectées par leurs leptospires. Afin de mieux comprendre le rôle des différents leptospires dans l’épidémiologie régionale de la leptospirose, nous avons mesuré la pathogénicité de trois souches de leptospires retrouvées dans cette région à l’aide d’un modèle hamster. Des souches de Leptospira mayottensis et Leptospira borgpetersenii ont été isolés respectivement de Tenrec ecaudatus (tenrec) et Triaenops menamena (chauve-souris), deux mammifères endémiques du SOOI. Une souche de Leptospira interrogans, dont le génotype est retrouvé dans la majorité des cas humains graves à la Réunion, a été isolée de Rattus rattus (rat). En cohérence avec les données épidémiologiques humaines de Mayotte et de La Réunion, les leptospires endémiques se sont révélées être significativement moins pathogènes que la souche L. interrogans. La spécificité d’hôte des deux souches isolées de mammifères endémiques a été mise à l’épreuve par des infections expérimentales de Rattus norvegicus, connu comme un réservoir important de leptospires. Les rats ont été infectés avec les trois isolats précédemment utilisés. Les rats infectés par les souches endémiques n’ont pas développé d’infection rénale chronique contrairement à la souche cosmopolite. Ces résultats montrent que la spécificité d’hôte des leptospires endémiques observée in natura est probablement due à des facteurs génétiques plutôt qu’à des facteurs écologiques, comme un manque de contacts physiques entre les réservoirs animaux endémiques et introduits. Enfin, le séquençage complet de souches de leptospires du SOOI a été réalisé afin d’identifier des caractéristiques génétiques pouvant être associées à la pathogénicité et la spécificité d’hôte des leptospires pathogènes. Une classification précise de souches de leptospires du SOOI a pu être réalisée sur la base des génomes complets. La comparaison de ces génomes a permis d’identifier des gènes spécifiques à un groupe ou une espèce de leptospires. Cependant des modifications génomiques complexes rendent difficiles l’identification de caractéristiques génomiques responsables d’un phénotype particulier tel que la virulence ou la spécificité d’hôte. / Leptospirosis is a zoonosis of main medical concern on several islands of southwestern Indian Ocean (SWIO), some of which recording among the highest human incidence worldwide. Over the last decade, molecular epidemiology investigations carried out under a One Health framework have revealed a wide variety of Leptospira lineages and distinct transmission chains throughout the islands of the region. These islands are home to pathogenic Leptospira lineages and animal reservoirs that are either introduced or endemic to the SWIO region. Interestingly, the regional distribution of Leptospira diversity is associated with (i) a contrasted severity of human cases and (ii) distinct levels of specificity of Leptospira towards their mammalian hosts. Specifically, endemic Leptospira appear less pathogenic in humans and display higher specificity towards their animal reservoirs than their cosmopolitan counterparts. To complete the dataset of Leptospira diversity in the SWIO region, we produced data from bats of eastern Africa. Results support the previously observed pattern of host specificity of Leptospira towards their bats hosts and, overlaid upon the biogeographic history of Malagasy bats, suggest that these volant mammals have colonized Madagascar from continental Africa while hosting pathogenic Leptospira. To better understand the role of distinct Leptospira lineages in the contrasted epidemiology observed in the SWIO, we investigated the pathogenicity of three Leptospira isolates from this region using a hamster model. Leptospira mayottensis and Leptospira borgpetersenii isolates were obtained from Tenrec ecaudatus (tenrec) on Mayotte and Triaenops menamena (bat) in Madagascar, respectively, both mammals endemic to the SWIO region. A Leptospira interrogans strain, which genotype has been reported in the majority of human acute cases on La Réunion, was isolated from the introduced Rattus rattus (rat). In keeping with a distinct severity of the disease on Mayotte and La Réunion, endemic bat-borne and tenrec-borne Leptospira were significantly less pathogenic than the control cosmopolitan rat-borne isolate. The host specificity of the isolates obtained from endemic hosts was addressed using experimental infection of Rattus norvegicus, a known reservoir of pathogenic Leptospira. This animal model was challenged with all three isolates and mostly failed in supporting chronic infection with bat-borne and tenrec-borne Leptospira. Hence, the strong host-specificity of endemic Leptospira toward their hosts observed in the wild likely results from genetic determinants shaped by long-term co-evolutionary processes rather than from ecological constraints such as a lack of physical contact between introduced and endemic animal reservoirs. Finally, we undertook full genome sequencing of regional strains in order to highlight genomic features that may be associated with virulence and host specificity. Whole genome sequencing allowed the accurate classification of Leptospira isolates obtained on SWIO islands. Comparative genomics allowed to identify genes specific to a group or species of Leptospira but complex changes in Leptospira genome make difficult the identification of genomic elements responsible for specific traits such as virulence and host specificity.

Thesis (PhD (Botany and Zoology)) -- University of Stellenbosch, 2008. / Afrosoricida is a 65 million years old (my) eutherian order that together with the Tubulidentata (aardvark) and Macroscelidea (elephant shrews) form the Afroinsectiphillia, a subclade of Afrotheria. It includes two families – Chrysochloridae (nine genera of golden moles) and Tenrecidae (11 genera of tenrecs) – that collectively represent ~59% of the afrotherian generic diversity. This study presents the first comprehensive cytogenetic comparison between members of these two families (seven genera and 11 species/subspecies of golden moles, and two genera and 11 species of tenrecs) using G- and C-banding and chromosome painting. All detected rearrangements are interpreted in a strict cladistic framework. In the case of Chrysochloridae, this provides evidence for a sister relationship between Chrysochloris and Cryptochloris, the monophyly of the Amblysomus genus, and for the elevation of A. hottentotus meesteri to specific rank. The detection of telomeric-like repeats in the centromeres of all chromosomes of the Amblysomus species/subspecies but not in those of A. h. meesteri further strengthens its recognition as a distinct species. Parsimony analysis of chromosomal rearrangements within Tenrecidae, the second Afrotheria assemblage studied, showed that rearrangements which could be interpreted as Whole Arm Reciprocal Translocations (WARTs) were more likely to be the result of Robertsonian translocations. Four interspecific associations are recovered within Microgale that are consistent with morphological and molecular characters. It was also possible to infer ancestral karyotypes for the Chrysochloridae, Oryzorictinae and the two tenrecid genera, Oryzorictes and Microgale. Given the relatively high karyotypic diversity observed among some Microgale species and the prevailing debates on chromosomal evolution and regional palaeoenvironmental fluctuations, it is suggested that Microgale be added to the list of taxa where structural rearrangements are likely to have played a role in speciation. Using Genbank sequences and a relaxed Bayesian clock method, we estimate the age of the family Chrysochloridae at ~28.5 my and that of the genus Microgale at ~9.9 my. Based on these dates, it can be shown that most of the evolutionary branches are characterized by a slow rate of chromosomal change, but that markedly high rates are observed in some Microgale species and to a lesser extent in the lineage leading to A. robustus. The rates of chromosomal evolution and other cytogenetic features highlighted in this study are discussed in light of recent advances in understanding the molecular mechanims that underpin changes to genomic architecture.

Madagascar is one of the world's top conservation priorities due to the intense anthropogenic pressures on its diverse and endemic wildlife. There have been very few studies conducted in the largest protected area complex in Madagascar, the Masoala-Makira landscape (northeastern Madagascar). My goal was to examine the response of ground-dwelling forest birds, tenrecs (Lipotyphla: Tenrecidae) and lemurs to habitat degradation and the presence of exotic predators, and monitor population trends at resurveyed sites from 2008 to 2013. Using camera trap surveys and distance sampling, we observed 26 bird species (n = 4,083 observations), three spiny tenrec species (n = 244 observations) and 12 lemur species (n = 1,172 observations). Out of 13 focal species (seven bird, three tenrec and three lemur species), seven had higher point estimates of occupancy or density at intact forests when compared to intermediately degraded or degraded forest sites. Common tenrecs (Tenrec ecaudatus) and cathemeral lemurs changed their activity patterns, becoming more nocturnal in degraded forests. Feral cat (Felis sp.) trap success was negatively related to the detection of three bird species (red-breasted coua, Coua serriana; scaly ground-roller, Geobiastes squamiger; and Madagascar crested ibis, Lophotibis cristata). At two resurveyed sites (S02 and S05), out of 19 and 17 species, only four and eight species did not show consistent declines in occupancy or encounter rates, respectively, over a six-year period. This research highlights the urgent need for immediate conservation action in the Masoala-Makira protected area complex in order to protect one of the world's biodiversity hotspots. / Master of Science