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Orientador: Maria das Graças Sajo / Coorientador: Fábio de Barros / Banca: Ludmila Mickellumas Pansarin / Banca: Claudio Nicoletti de Fraga / Banca: Poliana Ramos Cardoso / Banca: Silvia Rodrigues Machado / Resumo: / Abstract: / Doutor

The gynoecia of all three species considered in this study originate not as individual carpel primordia but rather as a continuous ring. Processes of continued radial expansion and differential zonal growth give rise to the mature body of the gynoecium with no observable fusion taking place. Later manifestations of distinctness and separation of carpels represent secondarily acquired traits. Consequently, the mature gynoecia of the Malvaceae cannot be reliably used to infer early developmental events. The physical environment in which carpels originate is proposed to play a role in determining carpel number. Carpel size at inception does not vary considerably among the different species surveyed here. Ring size, however, does and this presumably dictates carpel number by the upward limit of what its circumference can ultimately accommodate. The uniovulate condition appears to be derived from the pluriovulate one through several interrelated developmental events. On the basis of acropetal initiation of ovules in Abutilon species and the precocious development of style primordia in Malacothamnus fasciculatus, a mechanism for the origin of the uniovulate carpel is proposed. Here, early style growth may limit zonal growth of the gynoecial base so that the acropetal series of ovule initiations is disrupted, leaving only a single basal one. The study of gynoecial development in this group has been hindered by certain problems of interpretation (e.g., Duchartre, 1845; Klotz, 1975; present account). These include difficulties in conceptualization of developmental processes and their reconciliation with preconceived views of the evolutionary origin of gynoecia. Consideration of relative size among successive stages is crucial, since the affect of radial growth is otherwise easily overlooked. Despite the differences of their mature gynoecia, the three species studied were determined to be strikingly similar in development, thereby supporting the close affinities attributed to them. In the final analysis, however, conclusive statements regarding the systematic implications of the ontogenetic patterns observed would be premature. Too few taxa have been studied and those that have should be reassessed in light of the developmental phenomena presented here. / M.S.

Our understanding of bird pollination systems has changed dramatically in the last few years. A long-standing paradigm was that hummingbirds and passerine birds select for different nectar properties in flowers (phylogenetic hypothesis). However, specialist passerines, such as sunbirds, have similar nectar preferences to hummingbirds and nectar in plants pollinated by these two bird groups is strongly convergent. Thus, as an alternative to the existing paradigm, it has been argued that the most useful distinction that can be drawn is that between specialist and generalist avian nectarivores (feeding niche hypothesis). This was supported by phylogenetically-controlled analyses that show that nectar in plants pollinated by specialist avian nectarivores (whether hummingbird or passerine) tends to have a lower volume, higher concentration and higher sucrose content than that in plants pollinated by generalist avian nectarivores. The aim of this thesis was to determine if these trends can be explained by the nectar preferences of avian nectarivores, and to determine whether the generalist-specialist dichotomy can be applied to Kniphofia, a largely bird-pollinated African plant genus. This thesis consists of two sections. In the first, I present data from equicaloric choice experiments to determine sugar preferences of both specialist and occasional nectar feeding birds across a range of concentrations. In addition, I determine apparent sugar assimilation efficiencies and concentration preferences for a range of occasional nectar feeding birds. Using Malachite Sunbirds (Nectarinia famosa), Dark-capped bulbuls (Pycnonotus tricolor), Speckled Mousebirds (Colius striatus) and Red-winged Starlings (Onychognathus morio) (plus Village Weavers (Ploceus cucullatus) in an appendix) as representatives of the major groups of nectar feeding birds in South Africa, I show that some differences occur between occasional nectar feeding birds and all specialist nectar feeding birds studied so far. Specialists show a switch from hexose preference at low (5%) concentrations, exhibit no preference at medium concentrations (10-20%) and prefer sucrose or show no preference at high concentrations (25%). However, specialists are unable to maintain energy balance at low concentrations, and always select the higher concentration when given choices within this range. Occasional nectar feeding birds prefer hexose solutions at low and medium concentrations (5 and 10%), but show varied preferences at higher concentrations. Occasional nectar feeding birds are able to maintain energy balance at low concentrations, and either show no concentration preference, or a preference for lower concentrations when given a choice. Occasional nectar feeding birds show a range in ability to digest sucrose, although some species, like the Dark-capped Bulbul, are quite proficient at it. Surprisingly, no significant difference is found between specialist and occasional nectarivores sugar preferences when analysed globally, even when phyllogeny is accounted for. Instead, I found a significant relationship between body size and bird sugar preference at different concentrations, from which I build the body size hypothesis, which I suggest is a better predictor to use than bird diet type (specialist or occasional nectarivores – feeding niche hypothesis). In the second section of the thesis, I examine the associations between plant traits and nectarivore nectar preferences. This section focuses on flower morphology and nectar characteristics in Kniphofia species, and ecotypes within species, pollinated by specialist versus occasional avian nectarivores. I show that apart from sugar type, which appears to be phylogenetically constrained, flower morphology and nectar characteristics appear to diverge according to whether plants are pollinated by generalist or specialist nectar feeding birds. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.