Microsatellite data are widely used to test ecological and evolutionary hypotheses in wild populations. In this paper, we consider three typical sources of scoring errors capable of biasing biological conclusions: stuttering, large-allele dropout and null alleles. We describe methods to detect errors and propose conventions to mitigate scoring errors and report error rates in studies of wild populations. Finally, we discuss potential bias in ecological or evolutionary conclusions based on data sets containing these scoring errors. AbstractMicrosatellite data are widely used to test ecological and evolutionary hypotheses in wild populations. In this paper, we consider three typical sources of scoring errors capable of biasing biological conclusions: stuttering, large-allele dropout and null alleles. We describe methods to detect errors and propose conventions to mitigate scoring errors and report error rates in studies of wild populations. Finally, we discuss potential bias in ecological or evolutionary conclusions based on data sets containing these scoring errors.

The differences in phenotypic plasticity between invasive (North American) and native (German) provenances of the invasive plant Lythrum salicaria (purple loosestrife) were examined using a multivariate reaction norm approach testing two important attributes of reaction norms described by multivariate vectors of phenotypic change: the magnitude and direction of mean trait differences between environments. Data were collected for six life history traits from native and invasive plants using a split-plot design with experimentally manipulated water and nutrient levels. We found significant differences between native and invasive plants in multivariate phenotypic plasticity for comparisons between low and high water treatments within low nutrient levels, between low and high nutrient levels within high water treatments, and for comparisons that included both a water and nutrient level change. The significant genotype 3 environment (G 3 E) effects support the argument that invasiveness of purple loosestrife is closely associated with the interaction of high levels of soil nutrient and flooding water regime. Our results indicate that native and invasive plants take different strategies for growth and reproduction; native plants flowered earlier and allocated more to flower production, while invasive plants exhibited an extended period of vegetative growth before flowering to increase height and allocation to clonal reproduction, which may contribute to increased fitness and invasiveness in subsequent years. Abstract. The differences in phenotypic plasticity between invasive (North American) and native (German) provenances of the invasive plant Lythrum salicaria (purple loosestrife) were examined using a multivariate reaction norm approach testing two important attributes of reaction norms described by multivariate vectors of phenotypic change: the magnitude and direction of mean trait differences between environments. Data were collected for six life history traits from native and invasive plants using a split-plot design with experimentally manipulated water and nutrient levels. We found significant differences between native and invasive plants in multivariate phenotypic plasticity for comparisons between low and high water treatments within low nutrient levels, between low and high nutrient levels within high water treatments, and for comparisons that included both a water and nutrient level change. The significant genotype 3 environment (G 3 E) effects support the argument that invasiveness of purple loosestrife is closely associated with the interaction of high levels of soil nutrient and flooding water regime. Our results indicate that native and invasive plants take different strategies for growth and reproduction; native plants flowered earlier and allocated more to flower production, while invasive plants exhibited an extended period of vegetative growth before flowering to increase height and allocation to clonal reproduction, which may contribute to increased fitness and invasiveness in subsequent ...

We studied variation in flowering phenology, fruit and seed set, and the abundance of the pollinators of four species of night-blooming Sonoran Desert columnar cacti for up to eight years at one site in Mexico and one year at one site in Arizona. We determined how spatiotemporal variation in plant-pollinator interactions affects the evolution of generalized pollination systems. We conducted pollinator exclusion and hand pollination experiments to document annual variability in pollinator reliability and to determine whether pollination systems were redundant (different species are partially or totally substitutable) or complementary (different species have an additive effect on fruit set). The cacti we studied included three species with generalized pollination systems involving bats, birds, and bees (cardon, Pachycereus pringlei; saguaro, Carnegiea gigantea; and organ pipe, Stenocereus thurberi) and one specialized moth-pollinated species (senita, Lophocereus schottii). We predicted that the migratory lesser long-nosed bat, Leptonycteris curasoae, is a less reliable pollinator than birds and bees, and that cacti with generalized pollination systems have more variable flowering phenologies than the specialized species.Annual time of peak flowering and mean size of flower crops were relatively invariant in saguaro and organ pipe. Time of peak flowering in cardon varied by as much as six weeks, and mean flower crop size varied threefold over six years. In senita, peak flowering varied by as much as 5-8 wk among years. Peak numbers of the nectar bat L. curasoae varied among years, and bat density (0.9/ha) was an order of magnitude lower than that of cactus-visiting birds at both study sites. The abundance of migratory hummingbirds was also highly variable among years.Pollinator exclusion experiments indicated that bats were major pollinators of cardon, whereas diurnal visitors accounted for most fruit set in saguaro (except in 1995 when bats were most important) and organ pipe at our Mexican site; honeybees accounted for 64-87% of diurnal fruit set in these species. Annual variation in the contribution to fruit set by bats was substantially higher than that of diurnal pollinators in saguaro and organ pipe, but not in cardon. There was little geographic variation in the relative importance of nocturnal vs. diurnal pollinators in saguaro and senita, but bats were much more important for fruit set in organ pipe in Arizona than in Mexico. We generally detected no effect of different pollinators on number of seeds per fruit in any species.Annual variation in fruit set was lowest in saguaro, the species with the most diurnal pollination system, and highest in organ pipe, the species with the most generalized pollination system. Fruit set was strongly pollen limited only in females of cardon (a trioecious species) and in organ pipe (at both sites). The ''missing'' pollinators in both species are likely Leptonycteris bats. The pollination systems of saguaro and cardon were partially redundant, whereas that of organ pipe was...

The genetic structures of the Iowa Corn Borer Synthetic #1 (CB) and Iowa Stiff Stalk Synthetic (SS) maize (Zea mays L.) populations are important because these populations serve as the model for development of modern commercial hybrids. In 1949, CB and SS were used to start a reciprocal recurrent selection (RRS) breeding program at Iowa State University. This study was conducted to analyze more thoroughly the genetic diversity within this RRS program and illustrate how the RRS program has changed over time at the molecular level. The progress of this program was measured by analyzing the variation at 86 SSR loci among 28 progenitor lines and 30 plants sampled from each of seven cycles (Cycle 0, Cycle 1, Cycle 3, Cycle 6, Cycle 9, Cycle 12, and Cycle 15) in each population. The progenitors of these populations show a high amount of variation on the basis of expected heterozygosity (0.557). As the RRS program proceeded, this variation decreased (Cycle 15, 0.245). In total, a larger amount of genetic variation was found among plants within cycles (66%) than among cycles (13%) or between populations (21%). The repartitioning of variation from within populations (96% in progenitors) to between populations (58% in Cycle 15) over time is consistent with theoretical expectations of divergence between the populations. By sampling intermediate time points, we gained a comprehensive genetic view of CB and SS permitting evaluation of the molecular-level changes occurring as a result of reciprocal recurrent selection. Population Genetic Diversity in a Maize Reciprocal Recurrent Selection ProgramLori L. Hinze,* Stephen Kresovich, John D. Nason, and Kendall R. Lamkey ABSTRACTto selection for yield has increased through Cycle 11, while genetic variance within populations showed aThe genetic structures of the Iowa Corn Borer Synthetic #1 (CB)

This study was conducted to determine if Brassica germplasm bulks created and maintained by the USDA-ARS North Central Plant Introduction Station (NCRPIS) were made with genetically indistinguishable component accessions and to examine newly identified putative duplicate accessions to determine if they can be bulked. Using ten microsatellite primer pairs, we genotyped two bulks of B. rapa L. ssp. dichotoma (Roxb.) Hanelt comprising four accessions and three bulks of B. rapa L. ssp. trilocularis (Roxb.) Hanelt comprising fourteen accessions, as well as four pairs of putatively duplicate accessions of B.␣napus L. Assignment tests on ten individual plants per accession were conducted using a model-based clustering method to arrive at probabilities of likelihood of accession assignment. The assignment tests indicated that one of the two bulks of B. rapa ssp. dichotoma involves genetically heterogeneous accessions. It was observed in the B. rapassp. trilocularis bulks that the component accessions could be differentiated into groups, with misassignments observed most frequent within groups. In B. napus, only one of the four pairs of putative duplicates showed significant genetic differentiation. The other three pairs of putative duplicates lack differences and support the creation of bulks. The results of the assignment tests were in agreement with cluster analyses and tests of population differentiation. Implications of these results in terms of germplasm management include the maintenance and/or re-creation of someBrassica germplasm bulks by excluding those accessions identified as being unique in this study. Abstract This study was conducted to determine if Brassica germplasm bulks created and maintained by the USDA-ARS North Central Plant Introduction Station (NCRPIS) were made with genetically indistinguishable component accessions and to examine newly identified putative duplicate accessions to determine if they can be bulked. Using ten microsatellite primer pairs, we genotyped two bulks of B. rapa L. ssp. dichotoma (Roxb.) Hanelt comprising four accessions and three bulks of B. rapa L. ssp. trilocularis (Roxb.) Hanelt comprising fourteen accessions, as well as four pairs of putatively duplicate accessions of B. napus L. Assignment tests on ten individual plants per accession were conducted using a model-based clustering method to arrive at probabilities of likelihood of accession assignment. The assignment tests indicated that one of the two bulks of B. rapa ssp. dichotoma involves genetically heterogeneous accessions. It was observed in the B. rapa ssp. trilocularis bulks that the component accessions could be differentiated into groups, with misassignments observed most frequent within groups. In B. napus, only one of the four pairs of putative duplicates showed significant genetic differentiation. The other three pairs of putative duplicates lack differences and support the creation of bulks. The results of the assignment tests were in agreement with cluster analyses and tests of population differen...