The thistle Cirsium palustre exists over most of lowland Britain as a predominantly purple flowered species. However the populations of seacliffs and mountains exhibit a flower colour polymorphism, occurring as homozygous white morphs, homozygous and heterozygous intermediate morphs, and homozygous and heterozygous purple morphs. The degree of polymorphism of the seacliff populations of the Gower Peninsula is correlated with population size, the larger populations being less polymorphic. This might be interpreted as indicating chance fixation of the white alleles. Such an explanation would gain support from the very small size of the more polymorphic populations and from the drastic fluctuations in population size which have been demonstrated as having occurred in these populations over a period of four consecutive seasons. However other explanations based on selective effects are possible. On seacliffs the frequency of the white morphs is inversely related to exposure, and decreases in population size are accompanied by differential survival of the purple morphs. On mountains the distribution of the polymorphism is markedly correlated with altitude. For the mountains of southern Mid Wales, populations below 1000 ft. are strongly monomorphic purple. Above 1000 ft. the degree of polymorphism increases abruptly, with white frequencies reaching over 80%. Morph frequencies among North Wales populations bear a similar relation to altitude but the increase in polymorphism occurs at about 1200 ft. In each case the general trend is that purple frequency declines with increase in white frequency, and that the frequency of intermediates shows a unimodal distribution with a quite precise peak. For both sets of populations this peak occurs at an altitude about 250 ft. higher than that at which the increase in white frequency occurs. It is possible that the occurrence of the polymorphism on seacliffs and mountains may be related to a limitation of cross pollination consequent upon the exposure of seacliffs and the combined climatic characteristics of mountains, which include increase in exposure, mist and rain and decrease in temperature. Evidence on the levels of outbreeding in these populations was inconclusive but evidence in other species suggested that pollination might indeed be limited in these conditions. An increase in homozygosity consequent upon inbreeding would promote the frequency of the white morphs. Moreover the white morphs were subject to preferential pollination and both this and certain forms of heterogeneity in morph distribution were likely to promote the frequency of inbreeding among white morphs. However in conditions of limited pollination the degree of general outbreeding of the white morphs will be increased by preferential pollination and this may be assumed to be a fitness advantage which may be of particular importance in the maintenance of the polymorphism. In addition it is likely that the presence of white morphs within a population may result in the attraction of higher numbers of pollinators or encourage foraging for longer periods in which case the polymorphism may be said to be adaptive in the sense of Fisher (1930). Other selective effects are also apparent. The occasional presence of highly polymorphic populations in valley bases and the regular occurrence of predominantly purple populations in mountain forests may both to some extent provide evidence for an effect of temperature other than upon pollination. Some evidence suggests that both exposure and moisture may also be of individual importance. Selection was apparent even by the arrangement of morph types within a population subject to no obvious environmental heterogeneity. It is possible that the polymorphism is maintained by a physiological heterozygous advantage and that this may be responsible for the maintenance of white and intermediate morphs in low frequency in the predominantly purple populations of inland lowland regions. The maintenance of the polymorphism imposed a significant selective mortality upon the species. This was indicated by the above instance of selection within a uniform community and also in several instances in which intrapopulational selection occurred between segments of population subject to differing exposure. However the growth in cultivation of seeds set in natural populations revealed that the complexity of the genetic system was sufficient to allow widely different morph frequencies to be maintained in different populations without the necessity of high selection in each generation.

<p>Examining the genetic basis across repeated origins of the same phenotypic adaptation allows us to address several questions pertaining to the genetic basis of adaptation. First, whether the genes and types of mutations that are involved in adaptation are predictable. Second, whether the underlying genetic changes can constrain future evolutionary trajectories. Here, I have focused on the genetics of blue to red flower color shifts, an adaptive shift that has repeatedly occurred across angiosperms. First, I review the literature and determine the relative contribution of functional vs. regulatory mutations to the evolution of red flowers can be predicted both on the mutational target size of each type of mutation and the degree of their associated deleterious pleiotropy. Chapter 2 characterizes the genetic basis of red flowers in Penstemon barbatus using a combination of gene expression and protein function assays. I demonstrated that multiple inactivating mutations to one anthocyanin pathway enzyme, F3'5'h, have occurred, but no mutations to any other component of the anthocyanin pathway have contributed to the evolution of red flowers. This suggests that F3'5'h may be a particularly favorable target for selection and also that evolutionary reversal to blue flowers would be highly unlikely. Chapter 3 investigates the genetic basis of an additional 12 origins of red flowers within Penstemon. Again, using a combination of gene expression and enzyme function assays, I found the genetic basis of these additional origins red flowers in Penstemon is highly predictable, involving redundant inactivating mutations to F3'5'h, and tissue-specific regulatory mutations to a second gene F3'h. Thus, the genetics of red flowers in Penstemon often involves inactivation of a non-pleiotropic gene, F3'5'h, but tissue-specific regulatory mutations to the pleiotropic gene F3'h. Furthermore, the presence of redundant inactivating mutations in many red-flowered Penstemon species indicates that the evolutionary reversal to blue flowers would be unlikely.</p> / Dissertation

How specialist bees distinguish their host plants from co-blooming non-hosts is not well understood, but it is thought that they may be physiologically limited in their ability to recognize the majority of visual and olfactory cues presented by flowering plants. Species in the genus Diadasia collect pollen from just one of five plant families: Cactaceae, Malvaceae, Onagraceae, Asteraceae, and Convolvulaceae. Assuming a common ancestor for all Diadasia specialized on just one plant, this indicates host-switches in the past, and an ability to recognize more than one flowering plant. I hypothesized that host plants of Diadasia share the same visual and olfactory cues, thus enabling past host-switching to novel plant families, and that co-blooming non-hosts are highly dissimilar in terms of scent and visual appearance. I determined the compounds associated with the scent of Malvaceae and Cactaceae host flowers of North American Diadasia. I also evaluated visual cues for these flowers by measuring their full spectrum of reflected wavelengths, as well as select morphometric characters. I determined whether host flowers, regardless of taxa, were more similar to each other than non-hosts that were co-blooming and attractive to other bee species. Finally, I performed electroantennographic and behavioral experiments to assess the relative importance of these cues (visual and olfactory) in natural settings. Diadasia host plants share some chemical and visual characteristics that may in part explain the radiation of this group onto these particular hosts. First, host plants share a suite of scent compounds that are among the least variable across species. Many of these elicited antennal responses and did not decrease visitation when applied to host flowers. In contrast, some compounds produced by non-host flowers are detectable to Diadasia, but Diadasia are repelled by them when they are applied to host flowers. Diadasia host flowers do not share a color profile in common, but there is more reflectance in the bee-uv range as compared to other regions of the light spectrum. Also, Diadasia host flowers have a more contrasting central area that is relatively larger than in non-hosts.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第21875号 / 人博第904号 / 新制||人||215(附属図書館) / 2018||人博||904(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 瀬戸口 浩彰, 教授 加藤 眞, 教授 市岡 孝朗, 准教授 西川 完途 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20958号 / 理博第4410号 / 新制||理||1633(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 川北 篤, 教授 工藤 洋, 教授 永益 英敏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

<p>One of the major goals of evolutionary biology is understanding the process of species formation. There is particular interest in how selection can favor species formation through the process of reinforcement. When two diverging taxa produce maladaptive hybrids, selection will favor greater reproductive isolation between the taxa. Reinforcement often results in a pattern of reproductive character displacement, which is defined as two species having greater reproductive isolation in sympatry then in allopatry. Floral-color divergence in the native Texas wildflower, Phlox drummondii, constitutes one of the best documented cases of reinforcement in plants. P. drummondii and a closely related species, P. cuspidata produce similar light-blue flowers throughout the allopatric parts of their ranges. However, in the area of sympatry P. drummondii has dark-red flowers, which has been shown to decrease hybridization between the two species. In the following work, I investigate the causes and consequences of the process of reinforcement and the pattern of character displacement in P. drummondii. First, I identify the genetic basis of the flower color variation as regulatory changes in two genes controlling the type and amount of anthocyanin floral pigments. I then evaluate neutral genetic variation across the range of P. drummondii and conclude there is extensive gene flow between allopatric and sympatric areas of the range, which indicates that selection and not genetic drift is responsible for the flower color variation. By investigating genetic variation at the loci underlying flower color variation I find a molecular signature of a selective sweep at one of the two flower color loci, further indicating that selection is responsible for this flower color variation. Finally, I measure selection on flower color in both sympatry and allopatry. I find no evidence that flower color variation is a response to ecological character displacement or local adaptation in the area of sympatry. I find evidence of pollinator preference for the ancestral allopatric flower color in allopatry, which may explain the persistence of the pattern of character displacement. These investigations of reproductive character displacement and reinforcement address important areas of research in evolutionary biology including the genetic basis of adaptation, the formation of species, and pleiotropy and conflicting selection pressures in species.</p> / Dissertation

<p>The evolution of selfing from outcrossing is one of the most frequent mating system transitions in angiosperms. Plants that are highly selfing typically exhibit a suite of morphological traits termed a "selfing syndrome," including reduced corollas and reproductive structures, loss of corolla pigmentation, little anther-stigma separation, and a low pollen/ovule ratio. The overall consensus among scientist is that the morphological changes that accompany the transition to selfing are adaptive and thus a product of natural selection. Few attempts, however, have been made to determine whether traits of the selfing syndrome are truly an operation of natural selection or if genetic drift could be the acting force. My dissertation examines the roles that natural selection and genetic drift played in the evolution of the selfing syndrome in Ipomoea lacunosa. With the use of field observations, crossing data, and molecular analyses, I show that I. lacunosa has evolved increased selfing ability, decreased anther-stigma distance and smaller, white flowers, compared to its closest relative I. cordatotriloba. Furthermore, using a standard QST - FST comparison, I evaluated the relative importance of selection and drift in the evolution of the selfing syndrome in I. lacunosa. I also identified the genetic basis of flower color divergence between I. lacunosa (white) and I. cordatotriloba (purple) and examined patterns of variation to determine if selection or genetic drift caused the divergence. Analyses revealed that the traits of I. lacunosa characteristic of the selfing syndrome have evolved as a product of natural selection, not genetic drift.</p> / Dissertation

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13017号 / 論農博第2827号 / 新制||農||1042(附属図書館) / 学位論文||H28||N4964(農学部図書室) / 32945 / 京都大学大学院農学研究科農学専攻 / (主査)教授 土井 元章, 教授 裏出 令子, 教授 奥本 裕 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Am "Max-Planck-Institut für Züchtungsforschung Köln-Vogelsang" wurde Mitte der achtziger Jahre in eine weißblühende Linie von Petunia hybrida Hort. (Vilm.) ein Anthocyansynthese-Gen von Zea mays L. transferiert. Unter den nach diesem Gentransfer entstandenen ziegelrot blühenden Pflanzen befand sich auch ein Typ, der ein Sternmuster in der Blüte zeigt. In der vorliegenden Arbeit konnte diese Musterbildung auf eine chimärische Konstitution zurückgeführt werden: Die Instabilität des A1-Gens in der Petunie resultiert in einen Farbstoffausfall in der alleinig farbstofführenden Epidermis, die von der ersten Scheitelschicht (L1) des Sproßscheitels gebildet wird. Subepidermale Gewebe können als genetisch intakt im Sinne einer potentiellen Fähigkeit zur Farbstoffsynthese charakterisiert werden. Deutlich wird das unter anderem an den partnerinduktiven Wirkungen, die von subepidermalem, L2-bürtigen Gewebe ausgehen und die Anthocyanbildung in der benachbarten, farbstoffdefekten Epidermis veranlaßt. Da die L1 am Kronblattrand alle Gewebe, also auch das Mesophyll bildet, bleiben diese Bereiche weiß gefärbt. Nur im Binnenfeld der Petalen, wo L2-bürtiges, intaktes Gewebe an die Epidermen anschließt, treten diese partnerinduktiven Wirkungen auf. Das Resultat ist ein Sternmuster der aus fünf Petalen zusammengewachsenen Kronröhre. Spontan und nach in-vitro-Kalluskultur entmischen die Pflanzen in ihre einzelnen Komponenten, so daß rot und weiß blühende Typen entstehen, die mit ihrer Blütenfarbe und ihrem Ploidiegrad (unterscheidbar bei Ploidiemarkierung) die jeweilige Scheitelschicht repräsentieren, von der sie abstammen. Bei Kreuzung spaltet die Nachkommenschaft in rot und weiß blühende Pflanzen auf. Aufgrund der Instabilität des transferierten A1-Gens ergibt sich kein Mendelsches Aufspaltungsverhältnis für die Blütenfarbe, wie das dem heterozygotem Zustand entsprechen würde. Auch existieren (wie bei den Entmischungsprodukten) gesprenkelte Blütentypen. Die Instabilität konnte als licht- und temperaturabhängig erkannt werden. Sie ist gleichzeitig der Grund dafür, daß sich an weiß blühenden Kallusregeneraten bzw. Sämlingen, die das A1-Gen in inaktiver Form besitzen, ein Sternmuster jederzeit neu bilden kann. Aufgrund dieses modifikativen Charakters dieser Sternmuster-Chimäre wird der Begriff "Epigenetische Periklinalchimäre" vorgeschlagen. In Sorteneinkreuzungen konnten Instabilitäten bis in die F2-Generation verfolgt werden, möglicherweise übertragen sich die Ursachen der Farbstoffausfälle der transgenen Form auch auf die Farbkomponente des Kreuzungspartners. Weiterhin enthält die Arbeit einen vorläufigen Bestimmungsschlüssel zur generellen Einordnung von Blütenfarbvariation nach ihren Ursachen.