Much work on sex ratios in dioecious plants has involved the genus Silene. The classic literature indicates that female-biased sex ratios result from excess pollen because pollen tubes from female-determining pollen reach the ovary more quickly, on average, than pollen tubes from male-determining pollen. I proposed the "weak male hypothesis" to account for female-biased ratios from limited amounts of pollen. This hypothesis assumes that male-determining pollen either germinates at a lower rate or experiences greater pollen tube attrition than female-determining pollen. To test this hypothesis, limited numbers of pollen grains were placed at one of three positions along the style. According to the hypothesis, if male-determining pollen is handicapped in germination, seed set and progeny sex ratios, which should all be female biased, should not be affected by where on the style the pollen is placed. If handicapping occurs during pollen tube growth, seed set should decrease and sex ratios should become increasingly female biased as the distance traveled by the pollen tubes increases. Seed set exhibited a nonsignificant decrease as style distance increased; none of the sex ratios was female biased. Therefore, the weak male hypothesis is rejected. In another experiment, pollen from individual anthers was separated into nonoverlapping small and large size classes. Sex ratios resulting from the two size classes did not differ, indicating that there is no sex-related bimodality for pollen size. In two other experiments, excess pollen was placed at one of two positions on the style. Of 48 resulting sex ratios, only six deviated significantly from 1:1; of these six, three were female biased and three were male biased. Style position had a significant effect in one experiment (progeny from distant pollinations contained excess males), but not the other. Sex ratios were not affected by either parent in these experiments. The data indicate that female-biased sex ratios do not necessarily result from excess pollen. Therefore, gametophytic competition cannot be assumed to explain the preponderance of females in natural populations. Reasons for the differences between my results and results of early experiments are discussed.

<p> The unique nature of island ecosystems have fascinated generations of naturalists, ecologists, and evolutionary biologists. Studying island systems led to the development of keystone biological theories including: Darwin and Wallace's theories of natural selection, Carlquist's insights into the biology of adaptive radiations, MacArthur and Wilson's theory of island biogeography, and many others. Utilizing islands as natural laboratories allows us to discover the underlying fabric of ecology and evolutionary biology. This dissertation represents my attempt to contribute to this long and storied scientific history by thoroughly investigating two aspects of island biology: 1. the role of island climate in shaping drought tolerance of woody plants, and 2. the absence of mammalian herbivores from insular environments and its effects on woody plant defenses. </p><p> These goals were accomplished by quantifying functional trait patterns, seasonal water relations, and plant defenses among closely-related species pairs of chaparral shrubs from matched field sites on Santa Catalina Island and the adjacent Santa Ana Mountains in southern California. This experimental design allowed me to test for &#65532;repeated evolutionary divergences across island and mainland environments and to examine the evolutionary trade-offs between traits. </p><p> Chapter 1 focuses on differences in dry season water availability and hydraulic safety between island and mainland chaparral shrubs by measuring seasonal water relations and cavitation resistance. My results suggest that island plants are more buffered than mainland relatives from the harsh summer drought conditions that characterize the Mediterranean type climate region of California. Furthermore, island plants exhibit increased hydraulic safety margins that suggest island plants may fare better than mainland relatives during episodes of increasing aridity. </p><p> Chapter 2 examines an exhaustive suite of 12 functional traits that characterize the drought-related functional strategies of island and mainland chaparral shrubs. Island plants have more mesomorphic leaf and canopy traits than mainland relatives. However, stem hydraulic traits are surprisingly similar between the island and mainland environments despite large differences in seasonal water relations. The differences between patterns at the leaf and stem levels may be related to the existence of evolutionary correlations for leaf traits but not for stem traits. Multivariate principal component analyses suggest that island plants are employing a very different suite of functional traits than their mainland relatives that allows them to take advantage of the more moderate conditions that characterize the island environment without sacrificing increased vulnerability to drought at the stem level. </p><p> Chapter 3 tests the hypothesis that the absence of mammalian herbivores throughout most of Santa Catalina Island's history has selected for plants that are less defended and more palatable than mainland relatives that have experienced more consistent browsing pressure. My results confirm that island plants have fewer morphological defenses and are more preferred by mammalian herbivores compared to close relatives from the mainland. These findings also suggest that island plants are more vulnerable to browsing by introduced mammalian herbivores. This vulnerability should be taken into account when making management decisions concerning introduced herbivores on islands. </p><p> In conclusion, chaparral shrubs on Santa Catalina Island have different levels of drought tolerance and herbivore defenses compared to mainland relatives that affect how they are likely to be impacted by climate change and other anthropogenic alterations of the insular environment. Furthermore, the pattern of evolutionary divergences between island and mainland plants reported in this dissertation offer new insights into how drought tolerance and herbivore defenses are shaped by environmental factors. </p>

<p> Tallgrass prairie once extended from Manitoba south to Texas and southeast to Indiana covering 100 million hectares prior to European settlement. Today less than 0.1% remains in Illinois, Indiana, Iowa, and Wisconsin. Tallgrass prairie is a diverse ecosystem with small remnants (1&ndash;2 ha) containing a large number of plant species (> 100). With most of the ecosystem lost, active efforts to replant tallgrass prairie began in the 1930s. Unfortunately, even the oldest restorations do not have plant communities similar to native prairies. My research attempts to understand the factors limiting successful restoration of native plant diversity by focusing on intensive surveys of three native and two restored prairies in Iowa. In each prairie, I sampled seven 0.5 m² plots using a frame with 49 grid points 10 cm apart and resurveyed these plots across successive years. I also collected soil cores and biomass and litter measurements in each plot. I analyzed plant community composition with a nonmetric multidimensional scaling ordination and fine-scale community structure with point richness and similarity metrics. Native prairies differed from restorations in plant community composition and had higher total carbon, nitrogen, and phosphorous, while restorations had higher plant available phosphorous. Native prairies also had higher richness from plot to point scales and lower similarity of neighboring plants at distances of centimeters. Restorations differ from native prairies at coarse and fine scales, and there was no indication that these restorations became more similar to native prairies over time. My work is the first to document fine-scale structure of plant diversity in native and restored prairies. By identifying that contemporary restoration practices do not result in plant communities that develop toward native prairies in composition, my work highlights our current limited understanding of the elements structuring plant communities and our ability to recreate this structure.</p><p>

Calcareous wetlands are rare in New England due to the limited occurrence of limestone-rich bedrock. Because of their great floristic diversity and their support of numerous rare and uncommon plant species, these habitats are targeted for conservation. Little is known about the intricate workings of these ecosystems. This research contributes significantly to understanding the complex biogeochemical relationships that exist between the plant and soil systems in calcareous freshwater wetland environments as a whole. A 3-year field study was initiated in May 1996, to collect data on soils, geochemistry, and hydrology along a 250-m-long transect. Monitoring was concentrated within the rooting zone. Field monitoring and water sampling were conducted biweekly across three growing seasons. Measurements were made for soil-water pH, conductivity, total iron, alkalinity and several dissolved metals. Strong seasonal patterns were observed for several parameters including calcium and iron. Seasonal changes in geochemistry were evaluated using Solmineq.88, a thermodynamic model. In July 1997, soils were sampled adjacent to each replicate instrumentation cluster and standard analyses conducted. Significant differences were measured between the stations for pH, cation exchange capacity, exchangeable calcium, phosphorus, manganese, and biologically available iron. A detailed vegetation analysis was completed in July 1997. High species richness and turnover were measured across the site. Ordination and cluster techniques were used to analyze the vegetation patterns and relate these to environmental site variables. The ordinations suggest that gradients in both soil chemistry (e.g., pH, exchangeable calcium, phosphorus, and iron) and geochemistry (e.g., pH and dissolved calcium) may have strong influences on the vegetation patterns observed in this study. These research results will serve as a baseline for the geochemistry in the greater watershed region, representing a relatively undisturbed system. No fen studies currently exist (for any geographical region) that monitored soil and geochemical parameters throughout the growing season. This research demonstrates the importance of seasonal sampling to describe the cycles present in site biogeochemistry accurately, and it defines several geochemical parameters that strongly influence plant species occurrence and distribution within these environments. This detailed analysis provides valuable information for conservation managers seeking to identify areas for future conservation, preservation, or restoration efforts.

This study uses habitats that have been naturally fragmented throughout the Holocene to examine the effects of habitat fragmentation on a much longer time scale. To investigate the long-term effects of habitat fragmentation on population genetic structure of Carex bigelowii, Diapensia lapponica , and Minuartia groenlandica, isozyme variation in fragmented patches of alpine tundra was compared to variation in sites from continuous alpine tundra. The questions posed by this study include: Is genetic variation reduced in fragmented habitat? Does gene flow occur between habitat fragments? What is the effect of fragment size on genetic variation? Have populations from fragments diverged more than populations separated by a similar distance in continuous habitat? Some of the results agree with the predictions of population genetic theory, and some do not. Dipensia lapponica and C. bigelowii have significantly less genetic variation in fragmented habitat. Contrary to theoretical predictions, M. groenlandica has significantly more genetic variation in fragmented habitat. Gene flow between populations of D. lapponica and C. bigelowii in fragmented habitat appears to be absent or reduced compared to unfragmented habitat. Gene flow between populations of M. groenlandica does not seem to have been affected by the scale of habitat fragmentation in this study. Correlation of genetic variation with fragment size is positive for C. bigelowii, not significant for D. lapponica and negative for M. groenlandica. Contrary to theoretical predictions, populations of M. groenlandica have significantly more genetic variation in small habitat patches than in large ones. Populations of D. lapponica and C. bigelowii have diverged more in fragmented habitat than in unfragmented habitat, possibly as a result of genetic drift. Minuartia groenlandica populations have not diverged more in fragmented than in unfragmented habitat. Diapensia lapponica, C. bigelowii, and M. groenlandica have virtually identical distributions in the northeast, and must have migrated into the region contemporaneously (on a geologic time scale) from southern refugia, yet have strikingly different patterns of genetic variation. This observation should serve as a cautionary note in attempts to infer past migration patterns from current patterns of genetic variation. (Abstract shortened by UMI.)

Made available in DSpace on 2014-06-11T19:30:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-10-25Bitstream added on 2014-06-13T20:21:30Z : No. of bitstreams: 1 alberti_lf_dr_rcla.pdf: 1362214 bytes, checksum: 9ba6f4be07cb47f723a731eb9d4a912a (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Comparação entre borda antrópica, clareiras naturais e o interior da floresta quanto à fenologia de árvores na floresta semidecídua e quanto à fenologia do arbusto Psychotria nuda na Floresta Atlântica). O objetivo da presente tese foi verificar se: (a) nos fragmentos do Morro do Elefante (400 ha, grande), Morro do Cerrito (20 ha, pequeno) e Morro Tabor (15 ha, pequeno) localizados em Santa Maria - RS (29°43'S e 53°47'W), grupos de posições de copa dominantes, co-dominantes, dominadas e oprimidas diferem quanto à intensidade das fenofases botões florais, antese, frutos imaturos e maduros (fenofases reprodutivas); (b) os três fragmentos diferem entre si quanto à intensidade das fenofases reprodutivas, sem considerar e considerando a densidade populacional das espécies. Uma vez que os morros do Cerrito e Tabor não diferiram significativamente quanto à intensidade das fenofases reprodutivas de suas árvores os mesmos foram tratados como um único fragmento (fragmento pequeno) nos capítulos seguintes (c em diante); (c) no fragmento pequeno, borda antrópica e interior da floresta diferem quanto à luz incidente e às variáveis reprodutivas número de flores, número de frutos, taxa de conversão de flores em frutos (sucesso reprodutivo) e tamanho de frutos de Myrocarpus frondosus; (d) na borda e no interior da floresta, há relação entre as variáveis reprodutivas e entre estas com as variáveis individuais altura, índice de esbelteza (circunferência a altura do peito/altura) e distância entre indivíduos de M. frondosus; (e) borda e interior da floresta diferem quanto à luz incidente e às variáveis reprodutivas em indivíduos de Nectandra megapotamica nos fragmentos grande e pequeno; (f) no fragmento pequeno, uma trilha clara difere de uma trilha escura quanto à luz incidente e às variáveis reprodutivas medidas... / Comparison of anthropogenic edge, natural gaps and the forest interior in relation to tree phenology in the semideciduous forest and in relation to the phenology of the shrub Psychotria nuda in the Atlantic forest). The present thesis aimed to verify if: (a) in the forest fragments of Morro do Elefante (400 ha, large), Morro do Cerrito (20 ha, small) and Morro Tabor (15 ha, small) located in Santa Maria - RS (29°43'S and 53°47'W), the dominants, co-dominants, dominated and oppressed canopy position groups differ in relation the intensity of phenophases flower buds, anthesis, immature and mature fruits (reproductive phenophases); (b) the three fragments differ one from another concerning the intensity of phenophase, considering and not considering the population size of species. Since the Morro Cerrito and Morro Tabor did not differ about the intensity of reproductive phenophases of their trees both fragments were considered a single one fragment (small fragment) in the following chapters (c and so on); (c) in the small fragment, there was a difference between edge and forest interior with respect to the light intensity and the reproductive variables number of flowers, number of fruits, ratio of conversion of flowers into fruits (reproductive success) and fruit size of Myrocarpus frondosus; (d) in the edge and forest interior, are the reproductive variables of M. frondosus related to one another and to the individual variables height, slenderness index (height/circumference at breast height), and distance between trees; (e) in the large and small fragments, edge and forest interior differ concerning light intensity and reproductive variables of Nectandra megapotamica individuals; (f) in the small fragment, a lighter trail differ from a darker one concerning the light intensity and reproductive variables measured in the canopy of Gymnanthes concolor individuals... (Complete abstract click electronic access below)

Orientador: Leonor Patrícia Cerdeira Morellato / Banca: Flavio Nunes Ramos / Banca: Silvana Buzato / Banca: Dalva Maria da Silva Matos / Banca: Rodrigo Augusto Santinelo Pereira / Resumo: Comparação entre borda antrópica, clareiras naturais e o interior da floresta quanto à fenologia de árvores na floresta semidecídua e quanto à fenologia do arbusto Psychotria nuda na Floresta Atlântica). O objetivo da presente tese foi verificar se: (a) nos fragmentos do Morro do Elefante (400 ha, grande), Morro do Cerrito (20 ha, pequeno) e Morro Tabor (15 ha, pequeno) localizados em Santa Maria - RS (29°43'S e 53°47'W), grupos de posições de copa dominantes, co-dominantes, dominadas e oprimidas diferem quanto à intensidade das fenofases botões florais, antese, frutos imaturos e maduros (fenofases reprodutivas); (b) os três fragmentos diferem entre si quanto à intensidade das fenofases reprodutivas, sem considerar e considerando a densidade populacional das espécies. Uma vez que os morros do Cerrito e Tabor não diferiram significativamente quanto à intensidade das fenofases reprodutivas de suas árvores os mesmos foram tratados como um único fragmento (fragmento pequeno) nos capítulos seguintes (c em diante); (c) no fragmento pequeno, borda antrópica e interior da floresta diferem quanto à luz incidente e às variáveis reprodutivas número de flores, número de frutos, taxa de conversão de flores em frutos (sucesso reprodutivo) e tamanho de frutos de Myrocarpus frondosus; (d) na borda e no interior da floresta, há relação entre as variáveis reprodutivas e entre estas com as variáveis individuais altura, índice de esbelteza (circunferência a altura do peito/altura) e distância entre indivíduos de M. frondosus; (e) borda e interior da floresta diferem quanto à luz incidente e às variáveis reprodutivas em indivíduos de Nectandra megapotamica nos fragmentos grande e pequeno; (f) no fragmento pequeno, uma trilha clara difere de uma trilha escura quanto à luz incidente e às variáveis reprodutivas medidas... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Comparison of anthropogenic edge, natural gaps and the forest interior in relation to tree phenology in the semideciduous forest and in relation to the phenology of the shrub Psychotria nuda in the Atlantic forest). The present thesis aimed to verify if: (a) in the forest fragments of Morro do Elefante (400 ha, large), Morro do Cerrito (20 ha, small) and Morro Tabor (15 ha, small) located in Santa Maria - RS (29°43'S and 53°47'W), the dominants, co-dominants, dominated and oppressed canopy position groups differ in relation the intensity of phenophases flower buds, anthesis, immature and mature fruits (reproductive phenophases); (b) the three fragments differ one from another concerning the intensity of phenophase, considering and not considering the population size of species. Since the Morro Cerrito and Morro Tabor did not differ about the intensity of reproductive phenophases of their trees both fragments were considered a single one fragment (small fragment) in the following chapters (c and so on); (c) in the small fragment, there was a difference between edge and forest interior with respect to the light intensity and the reproductive variables number of flowers, number of fruits, ratio of conversion of flowers into fruits (reproductive success) and fruit size of Myrocarpus frondosus; (d) in the edge and forest interior, are the reproductive variables of M. frondosus related to one another and to the individual variables height, slenderness index (height/circumference at breast height), and distance between trees; (e) in the large and small fragments, edge and forest interior differ concerning light intensity and reproductive variables of Nectandra megapotamica individuals; (f) in the small fragment, a lighter trail differ from a darker one concerning the light intensity and reproductive variables measured in the canopy of Gymnanthes concolor individuals... (Complete abstract click electronic access below) / Doutor

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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The morphology, phenology and stem demography of devil's club and thimbleberry were examined to elucidate their niche utilization strategies. The study was conducted in the Kitimat River valley in west central B.C. during the 1986 and 1987 growing seasons. Thimbleberry was sampled in a girdled alder site and a nongirdled alder site, whereas devil's club was sampled in an old growth forest. The variation in the plant characters, as summarized by principal components axes, was apportioned within and among clones, between sites, years, and species. Except for the thimbleberry vegetative phenology, within-sites differences accounted for most variation and variation between-sites often exceeded that between years. Moreover, between-species differences accounted for less variation than within-species differences for morphology and phenology. The variation in plant characters was also examined in relation to canopy cover, soils and adjacent vegetation using multivariate methods. The rate of vegetative development for devil's club in 1986 increased as canopy cover decreased; other environmental measures were uncorrelated with devil's club. Both vegetative and reproductive rates of development increased with disturbance due to girdling and increasing moisture for the combined girdled and ungirdled thimbleberry data set. Similarly, morphdodcal size was greater for the combined thimbleberry data set with increasing moisture and dsturbance. Environmental correlations were reflected differently within-sites, however, with rates of development, plant size and the number of flowers decreasing with increasing moisture at the nongirdled thimbleberry site. The relationship between plant characters was also assessed. Phenology and morphology were correlated for both devil's dub and thimbleberry; stem development began earlier and was more rapid with increasing stem size. Demography and phenology were unrelated. Both species displayed different niche utilization strategies; thimbleberry being more flexible than devil's club. In contrast to devil's dub, thimbleberry is morphologically a phenologically responsive to disturbance and is mizomatous rather man stoloniterous. Stems and lateral branches also had several phonological and developmental possibilities. This flexibility imparted an advantage to thimbleberry in the fluctuating conditions of its earlier successional niche. The differing correlation structure between and within thimbleberry sites suggests that several scales of observation are necessary to clarify plant-environment relationships. Moreover, as environmental characters interact differently with plants from site to site, management must be site specific. Alder girdling may be a judicious management technique at drier sites, where thimbleberry is not as prolific under an open canopy. / Science, Faculty of / Botany, Department of / Graduate