Measuring Fitness and Natural Selection in Wild Plant Populations

Primack, Richard B.; Kang, Hyesoon

doi:10.1146/annurev.es.20.110189.002055

Cited by 170 publications

(80 citation statements)

References 143 publications

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“…Can the divergence of the high-and low-flow populations be explained by limited gene flow (maintained by limited gamete dispersal or by incompatible gametes of the 2 morphotypes; Endler 1977, Gottlieb 1984, Barton & Hewitt 1989, Primack & Kang 1989? Kelp spores are capable of dispersing many kilometers from the point of release (Reed et al 1988, Gaylord et al 2002, but little is known about the dispersal capabilities of Eisenia arborea.…”

Section: Discussionmentioning

confidence: 99%

Variation in blade morphology of the kelp Eisenia arborea: incipient speciation due to local water motion?

Roberson

Coyer²

2004

Mar. Ecol. Prog. Ser.

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The southern sea palm kelp Eisenia arborea produces wide, bullate (bumpy) blades in low-flow areas, whereas in adjacent high-flow areas blades are flat and narrow. Here we determine if morphological differences in these 2 closely associated populations are correlated with physical factors in the environment, and whether this response is a genetically fixed or plastic trait. Both phenotypes were subjected to morphometric analysis, field and laboratory transplant experiments, and genetic analysis (M13 DNA fingerprinting). Physical variables (water motion, temperature, and light) were monitored simultaneously in the field. Results indicate that the 2 populations, separated by <10 m, are genetically distinct and transplants in the field and lab remained similar to individuals from the original collection location, regardless of the imposed flow environment. Water motion varied significantly between the 2 populations and was the single physical variable that correlated with morphology. Based on bump heights and water velocities in the field, bullate blades could increase turbulent transport of nutrients 4-fold that of flat blades. The thicker blades and large holdfasts of the flat morph may impart higher survivorship under high-flow conditions. This suggests water motion selects for 2 distinct morphotypes of E. arborea that represent adaptations to enhance fitness under different nutrient availability and drag force regimes. Thus, blade morphology is not a plastic response to the local environment but a genetically fixed trait and may be indicative of nascent speciation in the face of strong selection by water motion over spatial scales smaller than observed previously in kelps.

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Section: Discussionmentioning

confidence: 99%

Variation in blade morphology of the kelp Eisenia arborea: incipient speciation due to local water motion?

Roberson

Coyer²

2004

Mar. Ecol. Prog. Ser.

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“…"Finegrained" variation in fitness favors generalist strategies and slows the selective elimination of genotypes whereas "coarse-grained" variation in fitness favors local adaptation. There has been much work measuring genetic variation for ecologically important characters and documenting fitness variation in natural populations (Endler, 1986;Primack and Kang, 1989). However, the variability of those processes in space and time is less well known, for the obvious reason that the size of an experiment increases in proportion to the number of sites that are sampled.…”

Section: Introductionmentioning

confidence: 99%

Measuring spatial variation in natural selection using randomly‐sown seeds of Arabidopsis thaliana

Stratton

Bennington

1996

J of Evolutionary Biology

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We describe a simple method of measuring spatial variation in fitness using randomly sown seeds. Given a random initial distribution of seeds, any spatial variation in the final distribution of genotypes must be the result of spatial variation in natural selection. Departures from spatial randomness are tested using a modification of join-count statistics, based on the probability that two randomly chosen plants separated by a given distance carry the same genetic marker. Monte Carlo simulations showed that for the randomly sown seeds design the join-count test had higher power to detect spatial variation in fitness than analysis of variance. The power was relatively independent of the number of genotypes used or the number of microsites sampled. The method was tested in the field using three standard lines of Arabidopsis thuliuna. At the end of the life cycle, adjacent plants were significantly more likely to be the same line than randomly chosen pairs and the spatial dependence extended to distances of nearly 50 cm. Simple experiments like this may be especially useful for "comparative ecological genetics", allowing systematic studies of natural selection among many species or habitats.

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“…From an evolutionary viewpoint, it is the differences among individuals in reproductive success that is of interest. Several authors have warned about the potential biases inherent in the use of relative measures of reproductive success, instead of absolute figures expressed on a per individual basis (Wyatt 1980, Herrera 1982, 1988a, Zimmerman and Gross 1984, Andersson 1988; see also Primack and Kang 1989). If individual variation in rate-based estimates of reproductive success (describing the relative success of structures) is poorly correlated with individual variation in fecundity, then evolutionary inferences drawn from studies based on the former may be misleading or even erroneous.…”

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confidence: 99%

Dissecting Factors Responsible For Individual Variation in Plant Fecundity

Herrera¹

1991

Ecology

142

131

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Abstract. This paper analyses, on an individual plant basis, the various components determining seed production in the evergreen shrub Lavandula latifolia (Labiatae), in order to estimate their relative contributions to individual differences in fecundity. The relationships between fecundity and age, size, and growth rate are also examined. Experimental pollination and watering were done in an attempt to alter natural patterns of partial fecundity components. Fecundity of individual plants is partitioned into its absolute (number of inflorescences, number of flowers per inflorescence) and relative (fruits/flower and seeds/ fruit) partial components, and the following questions are addressed: (1) Are there individual differences in relative components of fecundity? (2) What are the proportional contributions of relative and absolute components of fecundity to individual variation in seed production? (3) Are relative measures of reproductive success reliable predictors of individual differences in fecundity? (4) When induced experimentally, do changes in partial fecundity components translate into modifications of the population's ranking of absolute fecundities?Fecundity depended more on plant size than age, was unrelated to growth rate, and was limited by water, but not pollen, availability. Individual plants differed in all components of fecundity examined, and differences were consistent among years. The proportional contributions of the various components to individual differences in fecundity were very unequal. Almost all variation among plants in seed production (-90% of variance) was explained by the variances and covariances of number of inflorescences and number of flowers per inflorescence. Variation among plants in the two relative components (fruit and seed set), even though statistically significant, had a negligible influence on individual differences in fecundity. These patterns remained invariant despite significant modification of flower production and fruit set induced by artificially watering a part of the study population. Fruit and seed set alone are unreliable indicators of individual differences in the maternal component of fitness in L. latifolia, and a review of relevant literature indicates that this probably applies to other polycarpic plants as well. Plant reproductive biology studies may make erroneous inferences if they consider exclusively data on relative fruit and seed set, and neglect the absolute components of individual differences in fecundity. It is proposed that, to circumvent these potential problems, demographic aspects and absolute estimates of seed output on a per individual basis should be examined in addition to the customarily employed fruit and seed set measures.Key words: fecundity components; flower production; fvuit set; individual variation; Lavandula latifolia; Mediterranean scrublands; plant demography; reproductive biology; seed production; size hierarchy; water limitation. contributions in Bentley and Elias 1983, Jones andRecent studies on plant reproductive ...

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Measuring Fitness and Natural Selection in Wild Plant Populations

Cited by 170 publications

References 143 publications

Variation in blade morphology of the kelp Eisenia arborea: incipient speciation due to local water motion?

Variation in blade morphology of the kelp Eisenia arborea: incipient speciation due to local water motion?

Measuring spatial variation in natural selection using randomly‐sown seeds of Arabidopsis thaliana

Dissecting Factors Responsible For Individual Variation in Plant Fecundity

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