No abstract

Abstract. Invasive species have the potential to alter trade-offs leading to selection in the populations they invade. Here we quantify the demographic and selective effects of herbivory by native insects and the introduced floral feeder Rhinocyllus conicus on Platte thistle (Cirsium canescens), a sparse monocarpic thistle endemic to North America. Rhinocyllus first invaded the Platte thistle population in 1993. Since then, its numbers have increased exponentially, while the Platte thistle population size has decreased. Data from 11 years were analyzed to determine how demographic rates varied with plant size and damage by native insects and Rhinocyllus. Individual growth, survival, flowering probability, and seed set were all size dependent. Damage to vegetative structures did not influence demographic rates; damage to flower heads did because Platte thistle is seed limited. These analyses were used to parameterize a series of integral projection models (IPMs) that investigated the effects of floral herbivory on the population growth rate , equilibrium population size, and the evolutionary stable (ES) flowering strategy. The IPMs showed that native insects have significant impact on the equilibrium population size and , but not the ES flowering strategy, because they use the flowers of different-sized plants indiscriminately. In contrast, Rhinocyllus has the potential to drive Platte thistle extinct. Rhinocyllus preferentially fed and oviposited on the flowers of larger plants and therefore selected for a reduction in flowering size. However, as the thistle population went into decline, this pattern reversed. Thus, selection imposed by an invader may be complex and will reflect behavioral interactions between herbivore and host, as well as demographic changes in the host population.

Understanding why individuals delay reproduction is a classic problem in evolutionary biology. In plants, the study of reproductive delays is complicated because growth and survival can be size and age dependent, individuals of the same size can grow by different amounts and there is temporal variation in the environment. We extend the recently developed integral projection approach to include size-and age-dependent demography and temporal variation. The technique is then applied to a long-term individually structured dataset for Carlina vulgaris, a monocarpic thistle. The parameterized model has excellent descriptive properties in terms of both the population size and the distributions of sizes within each age class. In Carlina, the probability of flowering depends on both plant size and age. We use the parameterized model to predict this relationship, using the evolutionarily stable strategy approach. Considering each year separately, we show that both the direction and the magnitude of selection on the flowering strategy vary from year to year. Provided the flowering strategy is constrained, so it cannot be a step function, the model accurately predicts the average size at flowering. Elasticity analysis is used to partition the size-and agespecific contributions to the stochastic growth rate, s . We use s to construct fitness landscapes and show how different forms of stochasticity influence its topography. We prove the existence of a unique stochastic growth rate, s , which is independent of the initial population vector, and show that Tuljapurkar's perturbation analysis for log( s ) can be used to calculate elasticities.

Conducting child- and parent-centred qualitative research allows exploration of the perceptions and understanding of type 1 diabetes mellitus and the meaning ascribed by children and their parents who live with the condition. Diabetes is a lifelong, life-threatening condition that has a significant impact on children's and parents' lives. Developing a deeper understanding of their lives and experiences will enable the delivery of nursing care to meet their specific needs.

We explore the evolution of delayed age- and size-dependent flowering in the monocarpic perennial Carlina vulgaris, by extending the recently developed integral projection approach to include demographic rates that depend on size and age. The parameterized model has excellent descriptive properties both in terms of the population size and in terms of the distributions of sizes within each age class. In Carlina the probability of flowering depends on both plant size and age. We use the parameterized model to predict this relationship, using the evolutionarily stable strategy (ESS) approach. Despite accurately predicting the mean size of flowering individuals, the model predicts a step-function relationship between the probability of flowering and plant size, which has no age component. When the variance of the flowering-threshold distribution is constrained to the observed value, the ESS flowering function contains an age component, but underpredicts the mean flowering size. An analytical approximation is used to explore the effect of variation in the flowering strategy on the ESS predictions. Elasticity analysis is used to partition the agespecific contributions to the finite rate of increase (lambda) of the survival-growth and fecundity components of the model. We calculate the adaptive landscape that defines the ESS and generate a fitness landscape for invading phenotypes in the presence of the observed flowering strategy. The implications of these results for the patterns of genetic diversity in the flowering strategy and for testing evolutionary models are discussed. Results proving the existence of a dominant eigenvalue and its associated eigenvectors in general size- and age-dependent integral projection models are presented.

We explore the effects of temporal variation in multiple demographic rates on the joint evolution of delayed reproduction and seed dormancy using integral projection models (IPMs). To do this, we extend the standard IPM to include a discrete state variable representing the number of seeds in the seed bank, density-dependent recruitment, and temporal variation in demography. Parameter estimates for Carlina vulgaris and Carduus nutans are obtained from long-term studies. Carlina is relatively long lived and has a short-lived seed bank, whereas most Carduus plants flower in their first year and the seed bank is long lived. Using the evolutionarily stable strategy (ESS) approach, we predict the observed flowering and germination strategies. There is excellent agreement between the predictions and the field observations. The effects of temporal variation on the joint ESS are partitioned into components arising from nonlinear averaging (systematic changes in the mean resulting from the interaction between variability and nonlinearity) and nonequilibrium dynamics (fluctuations in fitness caused by temporal variation). This shows that temporal variation can have substantial effects on the observed flowering and germination strategies and that covariance between demographic processes is important. We extend the models to include spatial population structure and assess the robustness of the results from the nonspatial models.

Growth rates play a fundamental role in many areas of biology (Q. Rev. Biol., 67, 1992, 283; Life History Invariants. Some Explorations of Symmetry in Evolutionary Biology, 1993; Philos. Trans. R. Soc. Lond. B Biol. Sci., 351, 1996Sci., 351, , 1341 Plant Strategies, Vegetation Processes, and Ecosystem Properties, 2002; Trends Ecol. Evol., 18, 2003, 471; Q. Rev. Biol., 78, 2003, 23; J. Ecol., 95, 2007, 926.) but the cost and benefits of different growth rates are notoriously difficult to quantify (Q. Rev. Biol., 72, 1997, 149; Funct. Ecol., 17, 2003, 328). This is because (1) growth rate typically declines with size and yet the most widely used growth measure -relative growth rate or RGR (conventionally measured as the log of the ratio of successive sizes divided by the time interval) -is not size-corrected and so confounds growth and size, (2) organisms have access to different amounts of resource and (3) it is essential to allow for the long-term benefits of larger size. Here we experimentally demonstrate delayed costs and benefits of rapid growth in seven plant species using a novel method to calculate size-corrected RGR. In control treatments, fast-growing plants benefited from increased reproduction the following year; however, fast-growing plants subjected to an experimental stress treatment (defoliation) showed strongly reduced survival and reproduction the following year. Importantly, when growth was estimated using the classical RGR measure, no costs or benefits were found. These results support the idea that life-history trade-offs have a dominant role in life-history and ecological theory and that the widespread failure to detect them is partly due to methodological shortcomings. (Arendt 1997(Arendt , 2003. This is because 1) growth rate typically declines with size and yet the most widely used growth measure -relative growth rate or RGR (conventionally measured as the log of the ratio of successive sizes divided by the time interval) -is not size-corrected and so confounds growth and size, 2) organisms have access to different amounts of resource and 3) it is essential to allow for the long-term benefits of larger size. Here we experimentally demonstrate delayed costs and benefits of rapid growth in seven plant species using a novel method to calculate size-corrected RGR. In control treatments, fast-growing plants benefited from increased reproduction the following year; however, fastgrowing plants subjected to an experimental stress treatment (defoliation) showed strongly reduced survival and reproduction the following year. Importantly, when growth was estimated using the classical RGR measure, no costs or benefits were found. These results support the idea that life-history trade-offs have a dominant role in life-history and ecological theory and that the widespread failure to detect them is partly due to methodological shortcomings. The Costs and Benefits of Fast

Background-The safety and predictability of refractive surgery for all degrees of myopia is now becoming established. It is therefore appropriate to evaluate whether there is a patient driven demand for such treatments and, if so, to establish guidelines for its provision within the National Health Service (NHS). Methods-A comparative study was designed to assess the eVect of degree of myopia on quality of life ("high" (n = 30) -10.00D, worse eye; "moderate" (n = 40) -4.00 to -9.75D, worse eye; "low" (n = 42) <-4.00D, worse eye) compared with a group of patients with keratoconus (n = 30) treated by optical correction. Data collection included binocular logMAR visual acuity, Pelli-Robson low contrast letter sensitivity, questionnaires to assess subjective visual function (VF-14) and eVect on quality of life (VQOL), and semistructured interviews. Results-There were no significant diVerences in any of the measures between patients with a high degree of myopia and those with keratoconus, or between those with a low and those with a moderate degree of myopia. However, those with a high degree of myopia had highly significantly poorer logMAR, VF-14, and VQOL scores than those with low and moderate myopia (p<0.001). Interview data supported these findings with patients with a high degree of myopia and those with keratoconus reporting that psychological, cosmetic, practical, and financial factors aVected their quality of life. Conclusion-Compared with low and moderate myopia, patients with a high degree of myopia experience impaired quality of life similar to that of patients with keratoconus. Criteria should therefore be identified to enable those in suYcient need to obtain refractive surgical treatment under the NHS. (Br J Ophthalmol 2000;84:1031-1034 Myopia aVects 25% of the population in western industrialised societies and has a potentially negative eVect on self-esteem, career choice, and ocular health.