Aciphylla species (wild spaniard/speargrass) are an iconic component of the Australasian high country flora, but their reproductive system is enigmatic. They are insect-pollinated dioecious mast seeders (synchronous highly variable seed production), which seems maladaptive. The resource supply to pollinators is highly variable, yet dioecious plants are dependent on pollinators, and dioecious masting requires male and female plants to flower synchronously. Floral display in Aciphylla is relatively large, with tall inflorescences bearing thousands of flowers, suggesting that plants would not have the resources to produce such large stalks every year. But why do they have such huge inflorescences in the first place? I tested whether pollinator attraction is providing an economy of scale which favours intermittent production of very large inflorescences, by manipulating floral display size during a high-flowering year and measuring insect visitation rates and seed set (female reproductive success). Using space-for-time substitution and selective removal of male inflorescences, I also tested whether female seed set was affected by distance to flowering male plants (i.e. changes in local pollen availability) to see if flowering asynchrony would reduce pollination success. Bags were used to exclude pollination by insects and test for wind pollination, and hand pollination was done to test for pollen limitation. Insect surveys suggest that Aciphylla has a generalist pollination system (to avoid satiating a specialist pollinator during 'mast' years'). Male inflorescences received significantly more visits than females, and some seeds were set inside bags (although only 20-30%), suggesting wind pollination may occur at low levels. Seed set rate was higher for taller inflorescences with greater flowering length in A. aurea but tall inflorescences with excess flowers led to a decrease in seed set rates in A. scott-thomsonii. Hand pollination significantly increased seed set rates although these effects were not as large as expected (e.g. 10% increases from natural to hand-pollinated inflorescences were typical). There was no evidence for resource limitation in any species. Female plants in dense flowering populations had higher seed set rates, and individual floral display size in females was particularly important when females were 'isolated' from males. Insect visitation rates were generally higher on inflorescences with a larger floral display, suggesting that display size is important for pollinator attraction. Overall, these results suggest that the pollinator-attraction benefits of such a large floral display (at both the plant and population level) are possibly providing an economy of scale, although the relative effects are small.

Aciphylla species (wild spaniard/speargrass) are an iconic component of the Australasian high country flora, but their reproductive system is enigmatic. They are insect-pollinated dioecious mast seeders (synchronous highly variable seed production), which seems maladaptive. The resource supply to pollinators is highly variable, yet dioecious plants are dependent on pollinators, and dioecious masting requires male and female plants to flower synchronously. Floral display in Aciphylla is relatively large, with tall inflorescences bearing thousands of flowers, suggesting that plants would not have the resources to produce such large stalks every year. But why do they have such huge inflorescences in the first place? I tested whether pollinator attraction is providing an economy of scale which favours intermittent production of very large inflorescences, by manipulating floral display size during a high-flowering year and measuring insect visitation rates and seed set (female reproductive success). Using space-for-time substitution and selective removal of male inflorescences, I also tested whether female seed set was affected by distance to flowering male plants (i.e. changes in local pollen availability) to see if flowering asynchrony would reduce pollination success. Bags were used to exclude pollination by insects and test for wind pollination, and hand pollination was done to test for pollen limitation. Insect surveys suggest that Aciphylla has a generalist pollination system (to avoid satiating a specialist pollinator during 'mast' years'). Male inflorescences received significantly more visits than females, and some seeds were set inside bags (although only 20-30%), suggesting wind pollination may occur at low levels. Seed set rate was higher for taller inflorescences with greater flowering length in A. aurea but tall inflorescences with excess flowers led to a decrease in seed set rates in A. scott-thomsonii. Hand pollination significantly increased seed set rates although these effects were not as large as expected (e.g. 10% increases from natural to hand-pollinated inflorescences were typical). There was no evidence for resource limitation in any species. Female plants in dense flowering populations had higher seed set rates, and individual floral display size in females was particularly important when females were 'isolated' from males. Insect visitation rates were generally higher on inflorescences with a larger floral display, suggesting that display size is important for pollinator attraction. Overall, these results suggest that the pollinator-attraction benefits of such a large floral display (at both the plant and population level) are possibly providing an economy of scale, although the relative effects are small.

Made available in DSpace on 2016-06-02T19:31:51Z (GMT). No. of bitstreams: 1 3112.pdf: 4538374 bytes, checksum: de855e1830eb260ab2d2aa15c63fa695 (MD5) Previous issue date: 2007-05-30 / Financiadora de Estudos e Projetos / Guadua tagoara (Nees) Kunth is a large sized bamboo native of the Brazilian Atlantic Rain Forest, with a semi-scandent habitat, pachymorphic rhizome and thorns for fixation on trees. Nowadays this bamboo is considered an invasive species in secondary forests, where its populations are supposedly in expansion. The general objective of this study, developed in Parque Nacional da Serra dos Órgãos (PARNASO), RJ, was to investigate the life history of G. tagoara from two perspectives: (a) to know the ecological basis of its supposed invasive potential and (b) to discuss it in the context of theoretical ecology and evolution of mast seeding plants. This dissertation was based primarily on three moments of the G. tagoara life cycle, studied in the scales of clump, genet and ramet. The investigated aspects of its life history were: mast seeding followed by parental death (monocarpy), regeneration from seed, synchrony and reproductive interval, development, morphological plasticity and intra and infra-specific diversity. At least at PARNASO, the life cycle of G. tagoara is strictly monocarpic, its regeneration from seeds occurred mainly in the interior of the senescent clumps. The majority of reproductive events were concentrated in 2004, suggesting a pattern known as flowering distribution for this region. The spatial gregarism of G. tagoara seems to be associated to the intra-clump reproductive synchrony, and the selective advantage of monocarpy seems to be the creation of regeneration sites for the following cohort. The same seems to be valid for other monocarpic species of Guadua with a tendency for gregarism. It was not possible to establish a reproductive interval for G. tagoara, but four possible flowering patterns were proposed for its life history. Although the adult genets have long spacers (necks), the rhizomes in the 2004 and 2006 cohorts did not present this character. Culm ramification occurred before rhizome ramification, and the thorns appeared just in the second year of the young genets. These cohorts (2004 and 2005) differed among them in structural characters, except in the number of living culms per genet, and presented characteristics here considered to be adaptations for the regeneration inside the clumps or other kinds of gaps. The morphological plasticity presented by the different patterns of ramification, by the reiterative growth and by the deviance from obstacles during elongation was observed in the culms of adult genets. The reiterative growth was also seen in the 2004 and 2005 cohorts, as well as articulated culms and the presence of invertebrates in their interior, including the internodes filled with water. Climatic seasonality doesn t restrict the growth of G. tagoara, but it is potentialized in the rainy season. Adult genets of this bamboo seem to grow during the whole year in PARNASO. Morphological plasticity observed in their culms can be considered a foraging behavior searching for light and space in the canopy. G. tagoara also has a large opportunistic growing behavior, expressed in ramets and genets, and can be considered a structural parasite of trees. Morphological elasticity, potential for clonal growth and integration of phalanx and guerilla strategies seem to be key aspects of its life history and its expansion and dominance in secondary forests. The results of this study support the hypothesis that the expansion of G. tagoara in secondary forests is facilitated by activities altering the structure of the forest. I suggest that the selfperpetuating disturbance cycle proposed to explain the formation and expansion of forests dominated by Guadua spp. in the Amazon forest must also act in the G. tagoara dominated forests, but in this latter case the anthropogenic activities seem to be very important for the origin and expansion of dominance. Some possible causes of its intra and infraspecific diversity of G. tagoara were discussed, based on the knowledge acquired about its life history, as well as some possible relations between its life cycle and the forest dynamics. The need and viability of the management of its populations were also discussed. / Guadua tagoara (Nees) Kunth é um bambu de grande porte nativo da Floresta Atlântica, de hábito semi escandente, rizoma paquimórfico e dotado de espinhos para fixação nas árvores. Atualmente este bambu é considerado uma espécie invasiva em áreas de florestas secundárias, onde suas populações supostamente estariam em expansão. O objetivo geral deste estudo, desenvolvido no Parque Nacional da Serra dos Órgãos (PARNASO), RJ, foi investigar a história de vida de Guadua tagoara sob duas perspectivas: (a) conhecer a base ecológica do seu suposto potencial invasiso e (b) discuti-la no contexto teórico da ecologia e evolução das plantas mast seeding. Esta dissertação baseou-se principalmente em três momentos do ciclo vital de G. tagoara, abordados nas escalas de taquaral, geneta e rameta: frutificação maciça seguida de morte parental (monocarpia), regeneração por sementes e desenvolvimento dos genetas adultos. Os aspectos estudados em sua história de vida foram: frutificação maciça, monocarpia, regeneração por sementes, sincronia e intervalo reprodutivos, desenvolvimento, plasticidade morfológica e diversidade intra e infra - específica. Pelo menos no PARNASO, o ciclo de vida de G. tagoara é estritamente monocárpico, e sua regeneração por sementes ocorreu principalmente no interior dos taquarais senescentes. O florescimento foi assincrônico em escala populacional, mas marcadamente sincrônico dentro dos taquarais. O ano de 2004 concentrou a maior parte dos taquarais reprodutivos, sugerindo para esta região um padrão conhecido como distribuição do florescimento. O gregarismo espacial de G. tagoara parece associado à sincronia reprodutiva intra taquaral, e a vantagem seletiva da monocarpia parece ser a criação de sítios de regeneração para a coorte seguinte. O mesmo parece valer para outras espécies monocárpicas de Guadua com tendência ao gregarismo. Não foi possível estabelecer um intervalo reprodutivo para G. tagoara, mas quatro possíveis padrões de florescimento foram propostos para sua história de vida. Embora os genetas adultos possuam espaçadores (pescoços) longos, nas coortes de 2004 e 2005 o rizoma não apresentou esta característica. A ramificação dos colmos ocorreu antes da ramificação do rizoma, e o surgimento dos espinhos ocorreu a partir do segundo ano de vida destes genetas. Estas coortes diferiram entre si em termos estruturais, com exceção do número de colmos vivos por geneta, e apresentaram características interpretadas aqui como adaptações à regeneração no interior dos taquarais ou em outras clareiras. A plasticidade morfológica representada por distintos padrões de ramificação, pelo crescimento reiterativo e pelo desvio de obstáculos durante o elongamento foi observada nos colmos de genetas adultos. O crescimento reiterativo também foi observado nos colmos das coortes de 2004 e 2005, nas quais também foram observados colmos articulados e a presença de raízes nos nós aéreos. Tanto nas coortes jovens quanto nos genetas adultos foram observadas perfurações nos colmos e a presença de invertebrados em seu interior, inclusive nos entrenós preenchidos com água. A sazonalidade climática não restringe o desenvolvimento de G. tagoara, mas o potencializa na época mais chuvosa do ano. Os genetas adultos deste bambu parecem crescer durante todo o ano no PARNASO. A plasticidade morfológica observada nos seus colmos pode ser considerada como um comportamento forrageador por espaço e luz no dossel da floresta. G. tagoara possui grande potencial de crescimento oportunista, o qual pode se expressar nas escalas de rametas e genetas, e pode ser considerado um parasita estrutural de árvores. A plasticidade morfológica, o potencial de crescimento clonal e a integração das estratégias falangeal e guerrilheira parecem ser aspectos-chave da sua história de vida e da sua expansão e dominância em florestas secundárias. Os resultados deste estudo dão suporte à hipótese de que a expansão de G. tagoara em florestas secundárias seja facilitada por atividades antrópicas que alterem a estrutura da floresta. Eu sugiro que o ciclo de distúrbios auto-perpetuante proposto para explicar a formação e expansão das florestas dominadas por Guadua spp. na Amazônia também deve atuar nas florestas dominadas por G. tagoara, mas nesse caso as ações antrópicas parecem ter grande relevância na origem e expansão da dominância. A partir dos conhecimentos obtidos sobre a história de vida de G. tagoara, foram discutidas algumas possíveis causas da sua diversidade intra e infraespecífica, e algumas possíveis relações entre o seu ciclo de vida e a dinâmica florestal. A necessidade e a viabilidade do manejo de suas populações também foram discutidas.

Chionochloa, a genus of snow tussock grasses native to New Zealand, exhibits pronounced mast seeding. Chionochloa suffers very high levels of pre-dispersal flower and seed predation by three main insects: Eucalyptodiplosis chionochloae, a cecidomyiid midge, which is formally described here; Megacraspedus calamogonus, a gelechiid moth and Diplotoxa similis, a chloropid fly. Seven species of parasitoids that attack these seed predators were discovered. Four species parasitize M. calamogonus (one tachinid fly and three hymenopteran wasps), one parasitizes D. similis (Hymenoptera: Eulophidae) and two parasitize E. chionochloae, (a pteromalid wasp Gastrancistrus sp. and a platygastrid wasp Zelostemma chionochloae, which is given a formal description here). The abundance, predation levels by each of the insect species, and interactions between all the organisms in the community were studied across three elevations at Mount Hutt over three summer seasons. M. calamogonus was most abundant at 450 m altitude during all three seasons. D. similis was most common at 1070 m altitude, while its predation levels peaked in low flowering seasons and decreased in high seasons. E. chionochloae was abundant in all three altitudes and increased its predation levels with increasing flowering intensity. E. chionochloae was confirmed to use prolonged diapause of at least three years. Prolonged diapause was also confirmed in its two parasitoids. Chionochloa plants were manipulated with various treatments to test the effect on diapause in E. chionochloae and its two parasitoids. Treatments included plant warming, root pruning, gibberellic acid sprayed on the plants and combinations of these treatments. All three insects changed their emergence in response to some treatments and therefore it was suggested that combined with risk-spreading diapause, they may use some predicting to emerge from prolonged diapause. E. chionochloae control their diapause following some of the cues that Chionochloa use for flowering, while Z. chionochloae and Gastrancistrus in some cases follow their host’s cues and in others use similar cues as Chionochloa plants. Emergence or diapause predictions differed across elevations and plant species in all three insect seed/flower predators. E. chionochloae had female-biased sex ratios in different populations even after prolonged diapause. There was week evidence that both parasitoid species are female-biased in the first emergence year and male-biased after more than one year in diapause. Therefore it was suggested that diapause is not more costly for females of E. chionochloae and its parasitoid than for males. Females of all three species were not found to be better predictors (i.e, more likely to respond to treatments by not entering extended diapause) than males. The complex interactions of all the organisms in this web are thought to be sensitive to climate, and it was suggested that the global climate change may alter this sensitive system.

Chionochloa, a genus of snow tussock grasses native to New Zealand, exhibits pronounced mast seeding. Chionochloa suffers very high levels of pre-dispersal flower and seed predation by three main insects: Eucalyptodiplosis chionochloae, a cecidomyiid midge, which is formally described here; Megacraspedus calamogonus, a gelechiid moth and Diplotoxa similis, a chloropid fly. Seven species of parasitoids that attack these seed predators were discovered. Four species parasitize M. calamogonus (one tachinid fly and three hymenopteran wasps), one parasitizes D. similis (Hymenoptera: Eulophidae) and two parasitize E. chionochloae, (a pteromalid wasp Gastrancistrus sp. and a platygastrid wasp Zelostemma chionochloae, which is given a formal description here). The abundance, predation levels by each of the insect species, and interactions between all the organisms in the community were studied across three elevations at Mount Hutt over three summer seasons. M. calamogonus was most abundant at 450 m altitude during all three seasons. D. similis was most common at 1070 m altitude, while its predation levels peaked in low flowering seasons and decreased in high seasons. E. chionochloae was abundant in all three altitudes and increased its predation levels with increasing flowering intensity. E. chionochloae was confirmed to use prolonged diapause of at least three years. Prolonged diapause was also confirmed in its two parasitoids. Chionochloa plants were manipulated with various treatments to test the effect on diapause in E. chionochloae and its two parasitoids. Treatments included plant warming, root pruning, gibberellic acid sprayed on the plants and combinations of these treatments. All three insects changed their emergence in response to some treatments and therefore it was suggested that combined with risk-spreading diapause, they may use some predicting to emerge from prolonged diapause. E. chionochloae control their diapause following some of the cues that Chionochloa use for flowering, while Z. chionochloae and Gastrancistrus in some cases follow their host’s cues and in others use similar cues as Chionochloa plants. Emergence or diapause predictions differed across elevations and plant species in all three insect seed/flower predators. E. chionochloae had female-biased sex ratios in different populations even after prolonged diapause. There was week evidence that both parasitoid species are female-biased in the first emergence year and male-biased after more than one year in diapause. Therefore it was suggested that diapause is not more costly for females of E. chionochloae and its parasitoid than for males. Females of all three species were not found to be better predictors (i.e, more likely to respond to treatments by not entering extended diapause) than males. The complex interactions of all the organisms in this web are thought to be sensitive to climate, and it was suggested that the global climate change may alter this sensitive system.