A novel interpretation of leaf mass variation in plants has been recently proposed based on its relationship with variation in leafing intensity – number of leaves produced per unit remaining above-ground dry mass. It is now widely established that between species variation in these two traits is strongly, negatively (and isometrically) correlated for woody and herbaceous species. Possible fitness advantages of higher leafing intensity (requiring smaller leaf size) can be interpreted in terms of the greater concentration of axillary meristems (larger ‘bud bank’), which may provide greater potential deployment flexibility for growth or reproduction. However, no research to date has addressed how these two traits are related at different scales, specifically at the between-individual (within-species) level, or between sexes in dioecious species. For the majority of 24 herbaceous angiosperms studied here, between-individual (within species) co-variation in leaf size and leafing intensity displayed as an isometric trade-off. For the few species with allometric trade-offs, plants with smaller body size produced disproportionately more leaves, indicating a possible mechanism for promoting reproductive economy when plant size is suppressed (e.g. by competition). For two out of three woody dioecious species, and two out of three herbaceous dioecious species, males tended to produce more, smaller leaves than females, possibly promoting pollen dispersal through a more broadly-spaced floral display (developing from more numerous axillary meristems). In contrast, the larger (but fewer) leaves in females may serve to maximize local photosynthetic resources available for axillary fruit and seed maturation. Males and females did not differ in branching rates associated with differences in leafing intensities, but in one herbaceous species, higher leafing intensity in males was associated with higher flower production than in females. In the larger 24-species data set, there was no evidence that species with higher leafing intensity (providing more axillary meristems) was associated with either a greater magnitude or a greater flexibility in branching or flowering intensity. Additional studies are required to explore the possibility that large ‘bud banks’ of axillary meristems (conferred by high leafing intensity) may promote effective mechanisms for tolerating environmental variability, responding to damage (e.g. from herbivory), and/or maximizing reproductive economy. / Thesis (Master, Biology) -- Queen's University, 2009-10-27 21:20:03.509

Trade-offs in resource allocation underlie key life history traits of organisms. My dissertation focuses on the size-number trade-off in clonal broods of offspring using the polyembryonic wasp, Copidosoma bakeri parasitizing immature stages of the moth Agrotis ipsilon. I aim to characterize responses of wasp brood size and individual body mass by manipulating the environments in order to understand the allocation pattern in the size number trade-off. In reviewing the functional forms of trade-off relationships in relation to resource constraints, I distinguish among three main trade-off types based on graphical representations of the relationship between the trade-off variables: linear, convex (inverse), and concave. The size-number trade-off in C. bakeri shows convex relationship. Characteristics of the trade-off are sex specific: female broods have larger body mass but smaller brood size than do male broods. When food intake of the host was increased, the trade-off between wasp body mass and brood size for both sexes shifts toward both higher wasp brood size and higher body mass. When the host has better access to food late in development, the size-number trade-off curve moves up and to the right on the graph. However, the trait combinations shift along the same trade-off curve toward greater wasp body mass but smaller brood size when the host development time is shorter due to more resources in early in development. I also investigate temperature effects on the size-number trade-off. C. bakeri brood size significantly increases with high temperature early in host development. There is no shift in the allocation pattern of the size-number trade-off with temperature. Finally, I test effects of body mass on longevity, fecundity, and mating competitiveness of C. bakeri. Larger body size increases female longevity, and mated females produce more eggs than unmated females. There are no significant relationships between male body mass and longevity or mating competitiveness. Mating reduces male longevity independent of body mass. The different impact of body mass on fitness between male and female wasps suggests the observed sex-specific allocation patterns of the size-number trade-off. Implications of the experiments and possible follow-up work are discussed.

The scope of this thesis was to identify, describe and quantify important life-history traits for the pseudoannual aquatic plant Ranunculus lingua in different ecological settings, by comparing populations from geographically marginal vs. central habitats. Results from a four-year field study showed that abiotic factors (water-level fluctuations and associated processes) tended to have a greater influence in marginal populations, whereas biotic factors (competition, insect grazing and fungal infections) dominated in central populations. This was reflected in different depth distribution of ramet numbers and ramet sizes between the areas, and In different dynamic patterns, with a higher flux of ramets in marginal populations. In a reciprocal transplant experiment, marginal ramets produced more but smaller rhizomes, whereas central ramets produced Individually larger but fewer rhizomes, irrespective of transplant site. A possible selection for genotypes producing large rhizomes in the central habitat was supported by the fact that initially smaller ramets were more likely to be diseased by the fungal pathogen Peronospora gigantea and damaged by insect grazing. In the marginal population, where density-independent mortality factors tend to dominate, a high reproductive output, expressed in production of high numbers of rhizomes, was suggested to be a favoured life-history trait. In a glasshouse experiment, ramets from marginal and central populations were grown in low and high densities and under three contrasting nutrient levels. The allocation to sexual structures was generally very low, and did not incur any costs in terms of reduced rhizome production. Rhizome production showed strong positive allometrical relationships to mother ramet size. Increasing mother ramet size resulted in a larger increase in rhizome numbers for the marginal than for the central population, whereas the increase in mean rhizome mass was more pronounced for the centred population. Both populations showed similar reductions in rhizome production in response to increased density and lowered nutrient levels, which could not be explained by size-dependent effects adone. The dispersal, dynamics and distribution of R. lingua were studied in a marginal river population in northern Sweden, where the only means of dispersal is by vegetative diaspores, i.e. floating rhizome fragments. Stranding occurred mainly in river curves and at obstacles, and the distribution of established stands was also highly correlated with these features. Relative changes in ramet numbers were correlated with water-level fluctuations during the present and previous growing seasons, with winter low-water, and with duration of spring-flood. The predictability of change was high within but low between stands. It was concluded that the patterns and mechanisms of dispersal are fundamental for local distribution patterns as well as variation in regional abundance in R. lingua / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 4 uppsatser</p> / digitalisering@umu