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Updated: May 9, 2026
08:16
Experimental Protocol for Manipulating Plant-induced Soil Heterogeneity
Published on: March 13, 2014
Phenotypic selection favors missing trait combinations in coexisting annual plants.
Sarah Kimball1, Jennifer R Gremer, Travis E Huxman
1Center for Environmental Biology, School of Biological Sciences, University of California, Irvine, CA 92697, USA. skimball@uci.edu
The American Naturalist
|July 16, 2013
Summary
Trade-offs between plant growth rate and water-use efficiency are key to biodiversity. Natural selection favors traits not seen in the community, suggesting genetic constraints shape these plant trait trade-offs.
Area of Science:
- Ecology
- Evolutionary Biology
- Plant Science
Background:
- Trait trade-offs are crucial for biodiversity maintenance.
- The role of natural selection in shaping these trade-offs is often unclear.
- Potential mechanisms include fundamental constraints or selection on redundant traits.
Purpose of the Study:
- Investigate the role of natural selection in constructing trait trade-offs.
- Examine the trade-off between relative growth rate and water-use efficiency in Sonoran Desert winter annual plants.
- Determine if within-species trait correlations align with the among-species trade-off.
Main Methods:
- Measured selection on water-use efficiency and relative growth rate in four plant species across two distinct climate sites.
- Analyzed phenotypic trait correlations within populations.
- Compared within-species correlations to the observed among-species trade-off.
Main Results:
- Identified an among-species trade-off: high relative growth rate correlated with low water-use efficiency, and vice versa.
- Within-species correlations did not consistently mirror the among-species trade-off.
- Observed positive directional selection for both water-use efficiency and relative growth rate in all populations.
- Selection intensity varied by site climate, with stronger selection on water-use efficiency in warmer/drier conditions and on relative growth rate in cooler/wetter conditions.
Conclusions:
- Directional natural selection favors phenotypes not currently present among the species.
- The observed among-species trade-off may result from genetic constraints.
- Community assembly processes might interact with genetic constraints to shape trait trade-offs.
Related Concept Videos
01:21Frequency-dependent Selection
When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
01:46Types of Selection
Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
01:43Incomplete Dominance
Gregor Mendel's work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid cell has two variants called alleles inherited from each parent. He suggested that amongst these two alleles, one allele is dominant in character and the other recessive. The combination of alleles determines the phenotype of a gene in an organism.
02:27Trihybrid Crosses
Trihybrid Crosses
Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
The F1 generation plants of a trihybrid cross are heterozygous for all three traits and produce eight gametes. Upon self-fertilization, these gametes have an equal chance to...
Some of Mendel’s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A trihybrid cross is a combination of three individual monohybrid crosses. For example, plant height (tall vs. short), seed shape (round vs. wrinkled), and seed color (yellow vs. green).
The F1 generation plants of a trihybrid cross are heterozygous for all three traits and produce eight gametes. Upon self-fertilization, these gametes have an equal chance to...
01:18Dihybrid Crosses
Overview
02:03Law of Independent Assortment
While Mendel’s Law of Segregation states that the two alleles for one gene are separated into different gametes, a different question of how different genes are inherited remains. For example, is the gene for tall plants inherited with the gene for green peas? Mendel asked this question by experimenting with a dihybrid cross; a cross in which both parents are homozygous for two distinct traits resulting in an F1 generation that are heterozygous for both traits.