The lifetime fitnesses of individuals comprising a population determine its numerical dynamics, and genetic variation in fitness results in evolutionary change. The dual importance of individual fitness is well understood, but empirical fitness records generally generally violate the assumptions of standard statistical approaches. This problem has plagued comprehensive study of fitness and impeded empirical study of the link between numerical and genetic dynamics of populations. Recently developed aster models address this problem by explicitly modeling the dependence of later expressed components of fitness (e.g. fecundity) on those expressed earlier (e.g. survival to reproduce). Moreover, aster models employ different sampling distributions for components of fitness, as appropriate (e.g. binomial for survival over a given interval and Poisson for fecundity). The analysis is conducted by maximum likelihood, and the resulting compound distributions for lifetime fitness closely approximate the observed data. We illustrate the breadth of aster's utility with three examples demonstrating estimation of the finite rate of increase, comparison of mean fitness among genotypic groups, and phenotypic selection analysis. Aster models offer a unified approach to address the breadth of questions in evolution and ecology for which life history data are gathered.

Clonal diversity within plant populations is affected by factors that influence genet (clone) survival and seed recruitment, such as resource availability, disturbance, seed dispersal mechanism, propagule predation and the age of the population. Here we studied a population of Potamogeton pectinatus, a pseudo-annual aquatic macrophyte. Within populations reproduction appears to be mainly asexually through subterranean propagules (tubers), while recruitment via seeds is believed to be relatively unimportant. RAPD markers were used to analyse clonal diversity and genetic variation within the population. Ninety-seven genets were identified among 128 samples taken from eight plots. The proportion of distinguishable genets (0.76) and Simpson's diversity index (0.99) exhibited high levels of clonal diversity compared to other clonal plants. According to an analysis of molecular variance (amova) most genetic variation occurred between individuals within plots (93-97%) rather than between plots (8-3%). These results imply that sexual reproduction plays an unexpectedly important role within the population. Nevertheless, autocorrelation statistics revealed a spatial genetic structure resulting from clonal growth. In contrast to genetic variation, clonal diversity was affected by several ecological factors. Water depth and silt content had direct negative effects on clonal diversity. Tuber predation by Bewick's swans had an unexpected indirect negative effect on clonal diversity through reducing the tuber-bank biomass in spring, which on its turn was positively correlated to clonal diversity. The disturbance by swans, therefore, did not enhance seed recruitment and thus clonal diversity; on the contrary, heavily foraged areas are probably more prone to stochastic loss of genets leading to reduced clonal diversity.

Despite fundamental importance to population dynamics, mating system evolution, and conservation management, the fitness consequences of breeding patterns in natural settings are rarely directly and rigorously evaluated. We experimentally crossed Echinacea angustifolia, a widespread, perennial prairie plant undergoing radical changes in distribution and abundance due to habitat fragmentation. We quantified the effects of both biparental inbreeding and crossing between remnant populations on progeny survival and reproduction in the field over the first eight years. Lifetime fitness is notoriously difficult to assess particularly for iteroparous species because of the long sequence and episodic nature of selection events. Even with fitness data in hand, analysis is typically plagued by nonnormal distributions of overall fitness that violate the assumptions of the usual parametric statistical approaches. We applied aster modeling, which integrates the measurements of separate, sequential, nonnormally distributed annual fitness components, and estimated current biparental inbreeding depression at 68% in progeny of sibling-mating. The effect of between-remnant crossing on fitness was negligible. Given that relatedness among individuals in remnant populations is already high and dispersal very limited, inbreeding depression may profoundly affect future dynamics and persistence of these populations, as well as their genetic composition. K E Y W O R D S :Aster life-history analysis, Echinacea angustifolia, genetic rescue, habitat fragmentation, inbreeding depression, outbreeding depression, restoration, self-incompatibility, tallgrass prairie.

Summary 1We studied local adaptation to substrate type within a population of the clonal aquatic macrophyte Potamogeton pectinatus and the role that genotypic variation in propagule-provisioning plays therein. 2 P. pectinatus reproduces mainly by means of subterranean asexual propagules (tubers), whose survival and sprouting success depends on the interaction of factors such as the size of tubers, substrate type and predation risk by Bewick's swans. 3 We studied a population of P. pectinatus in which genotypes producing large tubers predominate at the sandy shore and those producing small tubers at the clay-rich shore. Clonal lines originating from different shores were grown on a sandy and a clay-rich substrate in a common-garden. Plants from all clonal lines were grown from tubers of a comparable size range, but the various clones from within each shore differed in the average size of tubers they are genetically determined to produce. 4 The performance of all clones was much lower on sandy substrate than on clay-rich substrate, indicating that the former is a stressful (nutrient-poor) environment. The reaction norms of morphological traits varied significantly among clones, revealing genetic variation in phenotypic plasticity. However, these differences were not related to our correlates of fitness (total tuber biomass, tuber size and tuber number). We found no evidence of local adaptation independent of genotypic tuber size. Instead, tuber size mediated local adaptation: clones producing larger tubers had a higher fitness in sandy substrate, while clones producing smaller tubers had a higher fitness in clay-rich substrate. 5 Our results imply that diversifying selection for tuber size takes place between the two substrate types and confirms the importance of tuber-size provisioning for local adaptation to substrate heterogeneity.