Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: It is thought that a large proportion of the great variety of floral structures in flowering plants reflect adaptations to different biotic pollen vectors. Divergence in flower traits and pollinators is linked to speciation. Pollinator-driven speciation is thought to have played a large role in the spectacular floral diversity found in South African Iridaceae and the genus Tritoniopsis is a particularly good example of this. This study focuses on Tritoniopsis revoluta, a pink irid occurring in the Swartberg and Langeberg Mountains, as well as Potberg Mountain. I tested the hypothesis that variation in flower tube-lengths of Tritoniopsis revoluta are related to the geographic distribution of pollinators and the variation of their tongue lengths. It was determined that this species is highly variable in respect to corolla tube-length and is pollinated by different fly species across its range. Also, the tongue-lengths of the fly pollinators corresponded almost exactly with the tube-length of the flowers they were pollinating in each population. In some populations, where long-proboscid flies were absent, bees were observed visiting T. revoluta flowers. This presents evidence for pollinator-driven floral variation within a single plant species, and most of this vast diversification in floral morphology has probably been driven by morphological variation found within a single fly family. In one population I found variable tube-lengths which appeared to exhibit a bimodal distribution of corolla tubelengths. I hypothesized that the two Tritoniopsis revoluta ecotypes at this population are pollinated by two different pollinators, leading to assortative mating, and ultimately strong inter-ecotype incompatibility. Tritoniopsis revoluta is self-incompatible and exists as two discrete entities (morphotypes) at the Gysmanshoek Pass site, and these entities differ in tubelength, color, nectar volume and sugar content. These morphotypes were not pollinated by long-proboscid flies, but seems to represent a recent shift to pollination by Amegilla bees. However, ecotypes are not reproductively isolated as short and long flowers can produce offspring, rather tube-length differences are possibly maintained through spatial separation. To compliment the correlatory data between flower tube-lengths and pollinator tongue-lengths, I used molecular tools (chloroplast markers and AFLPs) to elucidate the patterns of tube-length evolution in Tritoniopsis revoluta. I aimed to determine the directionality and frequency of transitions between tube-length categories. Tube-length transitions would be suggestive of flower morphology being labile, and together with the tube-tongue length correlation it suggests pollinator shifts may drive the changes in tube length. Character state reconstructions using tube-length as character determined that four evolutionary transitions to shorter tube-length categories and two transitions to longer categories occurred. I also tested whether morphological divergence between populations corresponds to patterns of divergence from neutral genetic markers. Population genetic structure in this system showed that the different populations of T. revoluta are vicariant and tube-length differences between them could have evolved through selection. / AFRIKAANSE OPSOMMING: Dit is ‘n algemene gedagte dat die groot verskeidenheid blom strukture in die angiosperme dui op aanpassings tot verskillende biotiese stuifmeel draers. Die diverse blom strukture in baie van die groot Kaapse genera kan verduidelik word deur aanpassings tot veranderinge in bestuiwings-sisteme. ‘n Aantal studies hieroor stel voor dat bestuiwers nie net die veranderinge in blom morfologie bewerkstellig nie, maar ook ‘n rol speel in die aanpassende uiteenlopendheid van blomplant kenmerke. Spesiasie bewerkstellig deur bestuiwers het moontlik ‘n groot rol gespeel in die blom-diversiteit wat gevind word in die Suid-Afrikaanse Iridaceae familie, en die genus Tritoniopsis is ‘n baie goeie voorbeeld hiervan. Hierdie studie fokus spesifiek op Tritoniopsis revoluta, ‘n pienk iris wat voorkom in die Swart- en Langeberge, asook by Potberg. Die hipotese dat die variasie in buis-lengtes van T. revoluta verwant is aan die geografiese verspreiding van bestuiwers en die variasie in hul tong-lengtes is hier getoets. Dit is bepaal dat hierdie spesie groot variasie toon in terme van buis-lengtes en bestuif word deur verskillende vlieg spesies regoor sy verspreiding. Die tong-lengtes van hierdie vlieë korrespondeer ook met die buis-lengtes van die blomme wat hul bestuif in elkeen van die T. revoluta populasies. In sommige van die populasies, waar lang-tong vlieë afwesig was, is bye wat die T. revoluta blomme besoek, opgemerk. Hierdie resultate lewer bewyse vir die hipotese dat bestuiwers blom morfologie kan beïnvloed; die interessante hiervan is dat die variasie in buis-lengtes in hierdie spesie heel moontlik te danke is aan die morfologies variasie wat gevind word in ‘n enkele lang-tong vlieg familie. In een van die populasies het ek ‘n bimodale verspreiding van buis-lengtes gevind. ‘n Logiese afleiding is dat hierdie twee verskillende buislengtes – ekotipes – deur twee verskillende bestuiwers besoek word, en dat dit lei tot sterk onversoenbaarheid tussen ekotipes. Tritoniopsis revoluta is nie instaat tot self-bestuiwing nie en die twee ekotipes verskil in terme van buis-lengtes, kleur, nektar volume en suiker inhoud. Kort- en lang-buis blomme word nie eksklusief bestuif deur lang-tong vlieë in die Gysmanshoek Pas nie, maar word in die algemeen ook bestuif deur bye van die genus Amegilla. Die twee ekotipes is in staat om te reproduseer met mekaar, so die buis-lengte verskille word moontlik in stand gehou deur hul geografiese skeiding. Om die korrelasie analise tussen blom buislengtes en vlieg tong-lengtes te komplimenteer, het ek molekulêre tegnieke (chloroplast merkers en AFLPs) gebruik om die patrone van buis-lengte evolusie in Tritoniopsis revoluta duidelik te maak. Ten eerste het ek bepaal of verkortings en verlengings van buis-lengtes een keer in die verlede gebeur het, of as meermalige gebeurtenisse. Meermalige veranderinge in buis-lengtes kan moontlik dui op verskuiwings tussen verskillende bestuiwers, asook taksonomiese verdelings wat korrespondeer met bestuiwer veranderinge. Ek het ook bepaal of die buis-lengte verskille in die verskillende populasies toegeskryf kan word aan seleksie prosesse. Deur buis-lengte as karakter te gebruik, het ek karakter-status rekonstruksies gedoen en bepaal dat vier ewolutionêre transisies na korter buis-lengte kategorieë, en twee transisies na langer kategorieë plaasgevind het. Populasie genetiese struktuur in die sisteem dui daarop dat T. revoluta populasies geïsoleer is deur afstand. Die konklusie wat ek trek gebasseer op hierdie resultate is dat verskille in buis-lengtes in hierdie sisteem moontlik ontstaan het as gevolg van die verskillende bestuiwers wat aktief is in die verskillende T. revoluta populasies, en dat natuurlike prosesse nie die hoofrol spelers in hierdie sisteem is ten opsigte van buis-lengte evolusie nie.

The social mole-rats have often been typecast as extreme examples of mammalian sociality. With their pronounced reproductive skew, status-related contrasts in lifespan and morphology, and the suggestion of a division of labour amongst helpers, mole-rat societies have repeatedly been likened to the structurally complex societies of some eusocial insects. However, because few studies of mole-rats have quantified individual variation in growth and behaviour across long periods of development, it has remained unclear the extent to which mole-rat societies, and the features of individuals within them, should be considered unique amongst social vertebrates. In this thesis, I examine life history variation in Damaraland mole-rats Fukomys damarensis from three perspectives- growth, behaviour, and ageing- to explore how individual developmental trajectories contribute to, and are influenced by, the structure of mole-rat societies. First, I use a large longitudinal dataset to test for the presence of behavioural specialisation in non-breeding mole-rat helpers. I find no indication of individual specialisation in cooperative activities. Instead, individual differences in helping behaviour are largely the result of age-related changes in the extent to which individuals commit to all forms of helping (Chapter 3); refuting the notion of helper castes. I then focus on the variation in growth across non-breeders, developing a novel biphasic model to accurately quantify sex differences in growth and explore the influence of social effects on growth trajectories (Chapter 4). Despite the proposition of intense intrasexual competition in mole-rat societies, there was no clear signature of sex-specific competition on helper growth trajectories. A more conspicuous form of socially-mediated growth in mole-rats is the secondary growth spurt displayed by females that have acquired the dominant breeding position, causing them to become larger and more elongated. By experimentally controlling reproduction in age-matched siblings, I show that rather than being stimulated by the removal from reproductive suppression, this adaptive morphological divergence is achieved through a lengthening of the lumbar vertebrae when breeding is commenced (Chapter 5). With contrasts in size and shape following the acquisition of the breeding role, this status-related growth pattern shares similarities with growth in naked mole-rats and other social vertebrates. Breeders also show a twofold greater lifespan than non-breeders in Fukomys mole-rats, prompting the suggestion that the transition to dominance also sets individuals onto a slower ageing trajectory. To date, there is little evidence to support a physiological basis to lifespan extension in breeders. This assertion is bolstered by the absence of longer telomeres or slower rates of telomere attrition in breeding females compared to non-breeding females residing in groups (Chapter 6), each of which might be expected if breeders age more slowly. I argue that previous studies exploring status-related ageing in captive Fukomys mole-rats have overlooked the importance of demographic processes (and associated behavioural influences) on mortality schedules. Irrespective of the proximate basis of the longer lifespan of breeders, at an interspecific level the social mole-rats are unusually long-lived for their size. A recent large-scale comparative analysis concluded that prolonged lifespan is a general characteristic of all mammalian cooperative breeders, but this conclusion is premature, as in most of the major clades containing both cooperative and non-cooperative species there is no consistent trend towards lifespan extension in cooperative species (Chapter 7). In the case of mole-rats, it seems more likely that their exceptional longevity arises principally from their subterranean habits and related reductions in extrinsic mortality. Overall, these findings demonstrate that cooperative breeding has important consequences for individual life histories, but there is no strong basis for the claim that Damaraland mole-rat societies are markedly different in form than other cooperative breeding societies.

So far, research on inter- and intraspecific teleost brain plasticity across different freshwater environments has been widely conducted. However, insights of brain morphological variation on social and predator avoidance behaviours are lacking. Here, we investigated variation in shape and size of the brain and its six major regions of European minnows (Phoxinus phoxinus) inhabiting Lake Ånnsjön and its tributaries, using geometric morphometrics methods. We also experimentally compared stream and lake fish activity and social behaviour under different feeding and predation regimes. Contrary to our predictions of lake minnows having evolved smaller brains because of living in habitats with reduced environmental complexity compared to their conspecifics in the streams, we found that overall brain size generally did not differ between locations. Instead, brain morphology differed between minnows caught in the lake and streams, with stream minnows showing larger dorsal medulla, telencephalon and olfactory bulbs, and lake minnows presenting larger optic tecta and hypothalamus. Experimental results showed that lake minnows were more likely to engage in social behaviour than those from streams. Our results indicate that while overall allocation of energy to the brain does not change, habitat-specific differences in activity and trophic divergence might predict specialization for different senses, allocating more resources towards different brain regions. In addition, we show how various ecological factors, such as environmental complexity and social organization seem to be reflected in brain shape.