The neotropical genus Exostema comprises 25 species of trees and shrubs, ranging in distribution from Bolivia to Mexico and throughout the West Indies, with most species endemic to the Greater Antilles. Infrageneric relationships and species-level patterns of evolution were investigated in phylogenetic analyses using morphological, molecular, and combined data sets. All data sets resolved three main species groups which correspond to the three sections recognized by McDOWELL (1996). However, the analyses of ITS sequence data placed the two South American species basal to the three main clades. Otherwise, the morphological and molecular data are highly compatible, and produce a more robust yet consistent phylogeny in the combined data analysis. Morphological evolution in Exostema involves many specializations for xeric habitats, reflecting repeated ecological shifts from moist forest to exposed, seasonally dry environments during the diversification of the genus. Both moth and bee pollination syndromes are found in Exostema, and shifts in pollination ecology appear pivotal to the differentiation of the three sections. Biogeographically, Exostema likely originated in South America and migrated via Central America to the Greater Antilles, where the morphological diversification and speciation are most extensive.

The Central American Isthmus has had profound effects on the evolution and distribution of larger marine organisms, but the impacts on meiobenthic animals have received little attention. Tardigrades are microscopic metazoan lobopodians that are ubiquitous in benthic communities worldwide, but little is known about marine tardigrades in Central America. Only two marine tardigrades have been identified to species level in all of Central America, and these came from a single sample of barnacles from El Salvador collected in 1953. Additionally, multiple haplotypes of Echiniscoides were reported from Costa Rica and Panama, but species names were not assigned. Here we report an extensive survey of both intertidal and subtidal marine tardigrades from both the Caribbean and Pacific coasts of Costa Rica. We found 701 individuals in 65 samples. There was a total of 19 taxa, including seven species with a sufficient quality and quantity of specimens to describe here as new to science. The new species are Archechiniscus murilloi sp. nov., Batillipes homocercus sp. nov., Batillipes ichthyocercus sp. nov., Echiniscoides costaricensis sp. nov., Echiniscoides ritavargasae sp. nov., Styraconyx vargasi sp. nov. and Tanarctus breedyae sp. nov. Ten taxa were found only in the Caribbean, six were found only in the Pacific, and three were found on both coasts. We discuss the three species with trans-isthmus distributions and note two additional candidate geminate species pairs that warrant further investigation.

The study of population biology and genetic diversity provides insights to the potential for colonization and can detect geographic patterns of invasion and range expansion, which is essential to predict how species might react to dynamic environments and the global climate change. An outstanding example for a successful colonizer is the Shepherd’s Purse (Capsella bursa-pastoris (L.) Medik.). It is closely related to Arabidopsis thaliana, the “lab rat“ of plant scientists, and originated 100-300 kya from the hybridization between an ancestral C. orientalis and an ancestor from the C. grandiflora/rubella lineage according to the current literature (Douglas et al., 2015). Many species invasions are the direct or indirect consequence of human activities, and the worldwide distribution of the Shepherd’s Purse is partially associated with prehistorical human migration (e.g. Neuffer & Hurka, 1999; Cornille et al., 2016). With the novel genome-wide restriction site-associated DNA sequencing (RADseq) it is possible to perform population genetic studies of unprecedented depth and complexity and allowed the exploration of evolutionary history, range expansion and invasion patterns of this plant species. I will show here that a large number of loci and a wide global sampling area, using seed collections from nearly all over the world covering a large part of the whole distribution area of this ubiquitous weed, reveal finer-scale population structure of C. bursa-pastoris than has previously been detected. The work proposed here generates a comprehensive picture of phenotypic diversity in relationship to genetic variation within C. bursa-pastoris. Genetic variation is clearly geographically structured and split into two lineages apparently adapted to different environments, with one population predominantly distributed in Mediterranean climate regions and the other predominantly in temperate climate regions. The worldwide distribution patterns of the genetic variation can be explained by intra- and intercontinental migration, but environmental filtering due to climate pre-adaption seems also involved. The two clusters point to an early diversification into two lineages or may even suggest multiple origins of the species.This dissertation consists of three papers and manuscripts written during my time as a doctoral student at the Osnabrück University.

This research was designed to investigate cougar response to urbanization, habitat fragmentation, and exploitation from behavioral, demographic, and landscape perspectives. The source-sink model has been proposed as an alternative framework for the management of exploited cougar populations. I addressed the basic question of whether cougars conform behaviorally to the predictions of the source-sink model, and consequently, the applied question of whether the model could be used for the conservation of this species. To achieve this I evaluated three scale-specific questions using radio-telemetry and hunter-harvest data collected from 1996-2010. At the subpopulation scale, I tested the hypothesis that cougars are wildland obligates by measuring cougar response to a suite of anthropogenic land uses. At the meso scale I compared cougar dispersal patterns from two populations under different management. Lastly, at the statewide scale I examined the distribution of human-induced de facto refugia and ecological traps in relation to the species range within Utah. Cougars show a strong proclivity for wildland over rural or suburban habitats, but all cougars used anthropogenic landscapes to some degree, and appear capable of surviving in highly disturbed, human-impacted environments. Cougar dispersal was correlated with maternal estrus; once young animals emigrated, natural and anthropogenic barriers directed movement into habitats marked by frequent human-caused mortality, with females selecting areas of lower conspecific density relative to males. Anthropogenic cougar mortality was disproportionately distributed in accessible, high quality habitats within the core of the species statewide range. Conversely, ecological traps were primarily situated within marginal habitats in remote settings on the periphery of the range. The source-sink model predicts that subordinate animals from saturated populations disperse to habitat with the highest suitability. Cougars of both sexes display behaviors that largely conform to these predictions. Based on the patchy but predictable distribution of cougar exploitation, Utah may already have a quasi source-sink system, which could be formalized through management action. In general, cougars are adaptable, behaviorally plastic, generalist carnivores, and as such defy broad habitat generalizations. These investigations have implications for sustainable hunting and long-term conservation of cougars in the multiple-use landscapes of the Intermountain West.

The Eurasian steppe belt is the vastest grassland region worldwide, stretching approximately 8000 km from the Pannonian Basin in the west to the Amur river in the east, altogether covering more than 8 million km2. Due to its size and location, the vegetation of this biome was under strong influence of past climatic fluctuations that reached their peak in the Pleistocene. Fossil record of different steppe-associated flora and fauna places the onset of Eurasian open grasslands into Central Asia from which the grasslands spread westwards around 20 MYA and reached the East European Plain first in the Late Miocene around 8 MYA. However, while useful as a proxy to infer past vegetation patterns, fossils suffer from low-resolution power and thus fail to elucidate more detailed picture of the onset and the development of the Eurasian steppe belt flora. The working hypothesis driving the whole project was that molecular signals in typical steppe plant species reflect the climate-landscape history of the steppe and the biogeographic dynamics of steppe taxa and thus allow for a much finer resolution of the history of the steppe belt in comparison to floristic and fossil-based methods. By applying a plethora of different phylogenetic, phylogeographic and biogeographic methods, I first investigated the evolutionary history of four unrelated Brassicaceae taxa that can be nowadays found in the Eurasian steppe belt. Second, I tried to draw parallels with the climate-landscape history of the Eurasian steppe belt as inferred from the fossil record to test the above-mentioned working hypothesis. The first case study dealt with the economically important Brassicaceae genus Camelina, with an emphasis on C. microcarpa, which can be found across the whole Eurasian steppe belt. I uncovered that this taxon’s contemporary uninterrupted distribution was split along the north coast of the Caspian Sea approximately 1 MYA, dating back to the Apsheron and Baku transgression events. During this time period, a polyploidisation event took place giving rise to a new hexaploid taxon and subsequently preventing gene flow after the regression of the Caspian Sea. The second case study investigated the evolutionary history of Schivereckia, which exhibits a highly disjunct distribution along the East European Plain and the Balkans and the whole Schivereckia clade that can be nowadays found either at higher latitudes in the subarctic zone or mountain ranges of the northern hemisphere. My analyses placed the radiation of this clade at the beginning of Pleistocene, when low temperatures promoted speciation and radiation of cold-adapted flora and fauna. The study showed that the highly disjunct distribution of Schivereckia podolica mirrors the Pleistocene refugial areas of different ages and points towards a close evolutionary relationship between contemporary steppe and tundra flora. A third case study focussed on Sisymbrium. I uncovered that while Sisymbrium did not evolve in the Eurasian steppe belt, it invaded this area as well as the Mediterranean several times independently throughout the Pleistocene in the south-north and east-west trajectory, respectively. This study proved yet again how variable the Eurasian steppe flora is in terms of evolutionary onset and that many of steppe elements originated in its adjacent areas in the south. These then subsequently migrated to the Eurasian steppe belt only after it was already fully developed either towards the west into the Euro-Siberian steppe or to the east into the Mongol-Chinese steppe. The fourth case study investigated the evolutionary history of Capsella. A GBS-based approach was proven successful for inferring biological history of young taxa. I showed that contemporary steppe element Capsella orientalis invaded the Eurasian steppe belt long after it was already developed in the south-north trajectory. I acquired further insights in the evolutionary history of its cosmopolitan sister tetraploid C. bursa-pastoris and placed the origin of the whole genus into the late Pliocene continental Asia. All studies showed the importance of a taxon sample and offered an alternative nesting dating approach for reliable calibration in cases where no fossil record could be obtained. In conclusion, evolutionary history of all four investigated taxa were shaped by the same environmental changes that played a major role in the biological history of the Eurasian steppe belt. Overall, our working hypothesis that molecular signals in typical steppe plant species reflect the climate-landscape history of the steppe and the biogeographic dynamics of steppe taxa, turned out to be correct.

The legume-rhizobia relationship is an important symbiosis. Studies have found variation in specificity and the functionality of symbiotic specificity can vary among plants of the same species and among rhizobia, as well as in concert with geographical variation. Here, we examined the diversity and geographic structure of rhizobia nodulating Chamaecrista fasciculata, which grows throughout the east-central U.S. and is symbiotic with Bradyrhizobium species. We investigated the association of geography and soil variables on rhizobial diversity by sampling plant nodules and soil across Mississippi and evaluated variation in rhizobia housed in different nodules of individual plants. Using nifH and truA, we conducted phylogenetic analyses and mantel tests but did not find that geography correlates with genetic diversity. However, soil variables and genetic distance were significantly correlated. Lastly, we found that rhizobia across nodules of the same plant varied substantially. These results contribute to the knowledge of rhizobial assemblages in natural populations.

Paratetramitus jugosus, a vahlkampfiid amoebomastigote, was isolated into monoprotist/monobacterial (Bacillus sp.), cultures from laminated microbial mats (Laguna Figueroa, Baja California Norte, Mexico) and muds (Eel Pond, Woods Hole, Massachusetts). Chromidia, roughly spherical (2-4 µm in diameter) were released from both walled spherical cysts (10-12 µm) and phagocytotic amoebic forms. Desiccation-resistant walled chromidia, at first spherical, resorb their walls and develop into small pleiomorphic phagocytotic amoeba. Small amoebae feed and mature into typical monopodial vahlkampfiid adults confirming previous work (Dobell, 1913, and especially the analysis of a larger encysting vahlkampfiid amoeba associated with Long Island oyster disease studied at Woods Hole by Mary Jane Hogue, 1914). I show here that P. jugosus reproduces and develops through its life history stages of chromidia, mature monopodial amoebae, and cysts as rapidly and abundantly under low oxygen levels as at ambient atmospheric oxygen concentrations. Anoxia was achieved in the laboratory by incubation of entirely desiccated inocula from old mat or mud samples in Brewer jars with or without gas packs to control atmospheric conditions. Three sets of experiments yielded the same results: vigorous growth on bacillus food occurred on manganese acetate media by two weeks on the surface of agar plates under ambient oxic or hypoxic to anoxic conditions. Preliminary investigations of similar amoeba from geographically distinct field sites in Europe, North America, and the Caribbean were made. From them, I suggest it is likely these coastal amoebomastigotes that propagate by small desiccation resistant, oxygen-independent, manganese tolerant chromidia are genuinely cosmopolitan in its distribution.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24456号 / 理博第4955号 / 新制||理||1707(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 渡辺 勝敏, 教授 曽田 貞滋, 教授 中務 真人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24457号 / 理博第4956号 / 新制||理||1707(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 中野 隆文, 教授 本川 雅治, 教授 森 哲 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The biogeography of Central America is considered a classical case study in understanding the impact of vicariant events on patterns of biotic dispersal. While many biogeographers have focused on community composition and geographic limits of species at broad scales across Central America, much less work has focused on post-colonization diversification patterns at finer scales. The livebearing freshwater fish Xenophallus umbratilis presents an ideal system for determining the impact of recent earth history events on biodiversity in northern Costa Rica. Here, we test the hypothesis that marine inundation of the San Carlos and Northern Limón basins during the Miocene has caused genetic fragmentation among X. umbratilis populations, despite contemporary freshwater connections across this region. To test this idea, we collected mitochondrial (cytb) and nuclear (Xmrk-2) DNA sequence data from up to 162 individuals taken from 27 localities across northern Costa Rica. We employed a variety of analytical approaches, including: maximum parsimony (MP) and maximum likelihood (ML), analysis of molecular variance (AMOVA), nested clade phylogeographic analysis (NCPA), and demographic analysis of population size through time. We found four major clades within X. umbratilis, each geographically isolated with no shared haplotypes across drainages. Oddly, clades that occupy adjacent drainages are not always sister taxa in the phylogeny, suggesting that colonization in this species is more complex than a simple model of isolation by distance. All our results are consistent with the hypothesis that changes in sea level associated with glacial eustatic cycles have had an important effect in shaping diversification patterns in this species.