TY - JOUR A1 - Neuhauser, C. A1 - Andow, D.A. A1 - Heimpel, G.E. A1 - May, G. A1 - Shaw, R.G. A1 - Wagenius, S. PY - 2003 TI - Community genetics: expanding the synthesis of ecology and genetics SP - 545 EP - 558 JF - Ecology VL - 84 IS - 3 KW - anthropogenic disturbance; Bt maize; community genetics; Echinacea angustifolia; evolution of resistance; genetic engineering; habitat fragmentation; nonequilibrium dynamics; plant– insect interactions; plant–pathogen interactions; Ustilago maydis. N2 - Community genetics synthesizes community ecology and population genetics and yields fresh insights into the interplay between evolutionary and ecological processes. A community genetics framework proves especially valuable when strong selection on traits results from or impinges on interspecific interactions, an increasingly common phenomenon as more communities are subject to direct management or anthropogenic disturbances. We draw illustrations of this perspective from our ongoing studies of three representative communities, two managed and one natural, that have recently undergone large perturbations. The studied communities are: (1) insect pests of crop plants genetically engineered to produce insecticidal toxins; (2) insect-pollinated plants in habitats severely fragmented by agriculture and urbanization; and (3) a pathogen and its crop host now grown extensively outside their native ranges. We demonstrate the value of integrating genetic and ecological processes to gain a full understanding of community dynamics, particularly in nonequilibrium systems that are subject to strong selection. [References: 121] UR - http://echinacea.umn.edu/pdf/neuhauser_etal_2003.pdf ER - TY - JOUR AU - Wagenius, S. PY - 2004 TI - Style persistence, pollen limitation, and seed set in the common prairie plant Echinacea angustifolia (Asteraceae) SP - 595 EP - 603 JF - International Journal of Plant Sciences VL - 165 IS - 4 KW - Echinacea KW - pollen limitation KW - pollination KW - prairie KW - reproductive success KW - fecundity KW - style persistence N2 - Pollen limitation of seed set in flowering plants has important ramifications for the population dynamics, evolution, and conservation of plant populations. I conducted a pollen addition and exclusion experiment demonstrating that style persistence signifies pollen limitation in the narrow-leaved purple coneflower Echinacea angustifolia, a species native to the North American prairie and plains. I developed a measure of style persistence, SP, a novel way to quantify pollen limitation in individual plants during the flowering season. Using this measure, I investigated the relationship between pollen limitation and seed set over two years in 19 and 27 natural remnant populations in an agricultural landscape. Population mean rates of seed set per plant varied from 0% to 54% in 1997 and from 0% to 63% in 1998. I found that pollen limitation reduced annual reproductive fitness within and among the populations studied. An analysis of the relationship between floret production and the rate of seed set provided no evidence that resource limitation influenced the rate of seed set. I estimated annual fecundity per plant as the product of the rate of seed set per floret, a pollen-limited process, and floret production per plant, likely a resource-limited process. Population means of individual annual fecundity ranged from 0 to 182 in 1997 and from 0 to 156 in 1998 and were predicted by population means of SP and the rate of seed set, but not by floret production. The effect of pollen limitation, as quantified by SP, overrides the strong, fundamental relationship between fecundity and floret production. This finding shows that populations consisting of large plants with large floral displays do not necessarily produce more seeds per plant. UR - http://echinacea.umn.edu/pdf/wagenius2004.pdf ID - 4109 ER - TY - JOUR AU - Wagenius, S. PY - 2006 TI - Scale dependence of reproductive failure in fragmented Echinacea populations SP - 931 EP - 941 JF - Ecology VL - 87 IS - 4 KW - Allee effect KW - bee KW - density dependence KW - Echinacea angustifolia KW - habitat fragmentation KW - isolation KW - pollen limitation KW - resource limitation KW - self-incompatibility KW - spatial scale KW - style persistence N2 - I investigated reproduction in a three-year study of Echinacea angustifolia, purple coneflower, growing in a fragmented prairie landscape. I quantified the local abundance of flowering conspecifics at individual-based spatial scales and at a population-based spatial scale. Regression analyses revealed that pollen limitation increased while seed set and fecundity decreased with isolation of individual plants. Isolation, defined as the distance to the kth nearest flowering conspecific, was a good predictor of pollen limitation, for all nearest neighbors considered (k = 1–33), but the strength of the relationship, as quantified by R2, peaked at intermediate scales (k = 2–18). The relationship of isolation to seed set and fecundity was similarly strongest at intermediate scales (k = 3–4). The scale dependence of individual density effects on reproduction (density of flowering plants within x meters) resembled that of isolation. Analyses at a population-based scale showed that pollen limitation declined significantly with population size. Seed set and fecundity also declined with population size, but significantly so only in 1998. Whether quantifying local abundance with population- or individual-based measures, reproductive failure due to pollen limitation is a consistent consequence of Echinacea scarcity. However, individual-based measures of local abundance predicted pollen limitation from a wider sample of plants with a simpler model than did population size. Specifically, the largest site, a nature preserve, is composed of plants with intermediate individual isolation and, as predicted, intermediate pollen limitation, but its large population size poorly predicted population mean pollen limitation. UR - http://echinacea.umn.edu/pdf/wagenius2006.pdf ER - TY - JOUR AU - Wagenius, Stuart AU - Lonsdorf, Eric AU - Neuhauser, Claudia PY - 2007 TI - Patch aging and the S-Allee effect: breeding system effects on the demographic response of plants to habitat fragmentation SP - 383 EP - 397 JF - American Naturalist VL - 169 IS - 3 KW - self-incompatibility KW - pollen limitation KW - Echinacea angustifolia KW - spatially explicit model KW - prairie KW - mating system N2 - We used empirical and modeling approaches to examine effects of plant breeding systems on demographic responses to habitat fragmentation. Empirically, we investigated effects of local flowering plant density on pollination and of population size on mate availability in a common, self-incompatible purple coneflower, Echinacea angustifolia , growing in fragmented prairie habitat. Pollination and recruitment increased with weighted local density around individual flowering plants. This positive density dependence is an Allee effect. In addition, mean mate compatibility between pairs of plants increased with population size. Based on this empirical study, we developed an individual-based, spatially explicit demographic model that incorporates autosomal loci and an S locus. We simulated habitat fragmentation in populations identical except for their breeding system, self-incompatible (SI) or self-compatible (SC). Both populations suffered reduced reproduction in small patches because of scarcity of plants within pollination distance (potential mates) and inbreeding depression. But SI species experienced an additional, genetic contribution to the Allee effect ( S -Allee effect) caused by allele loss at the S locus, which reduces mate availability, thereby decreasing reproduction. The strength of the S -Allee effect increases through time (i.e., patches age) because random genetic drift reduces S -allele richness. We investigate how patch aging influences extinction and discuss how the S -Allee effect influences communities in fragmented habitat. UR - http://echinacea.umn.edu/pdf/wagenius_etal_2007.pdf ER -