Related Experiment Video
Updated: Jul 5, 2026
08:16
Experimental Protocol for Manipulating Plant-induced Soil Heterogeneity
Published on: March 13, 2014
Environmental heterogeneity generates fluctuating selection on a secondary sexual trait
Matthew R Robinson1, Jill G Pilkington2, Tim H Clutton-Brock3
1Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, United Kingdom; Macaulay Institute, Craigiebuckler, Aberdeen AB15 8QH, United Kingdom.
Current Biology : CB
|May 20, 2008
Summary
Resource allocation to reproduction can impact survival. In Soay sheep, male horn growth favored reproduction in good conditions but reduced survival in poor conditions, demonstrating fluctuating selection.
Area of Science:
- Evolutionary biology
- Behavioral ecology
- Population genetics
Background:
- Resource allocation trade-offs between reproduction and survival are critical in limiting environments.
- Sexually selected traits involve a balance between fecundity and viability, influenced by environmental conditions.
- Environmental heterogeneity can lead to varying optimal strategies for reproduction versus survival.
Purpose of the Study:
- To investigate how ecological conditions influence the opposing selection pressures on a secondary sexual trait.
- To examine the relationship between male horn growth and lifetime reproductive success in fluctuating environments.
- To understand the role of fluctuating selection in maintaining genetic variation in sexual traits.
Main Methods:
- Studied a wild population of Soay sheep (Ovis aries).
- Analyzed phenotypic and genetic associations between male horn growth and lifetime reproductive success.
- Assessed the impact of varying environmental conditions (good vs. poor) on these associations.
Main Results:
- Selection on male horn growth acted in opposing directions for viability and fecundity.
- The relative strength of these selection pressures varied with environmental conditions, causing fluctuating selection.
- In good environments, horn growth positively correlated with reproductive success; in poor environments, it negatively correlated due to reduced survival.
Conclusions:
- Fluctuating selection, driven by environmental conditions, impacts the balance between reproduction and survival.
- High investment in early sexual trait development (horn growth) is a gamble in unpredictable environments.
- Fluctuating selection may prevent the loss of genetic variance in secondary sexual traits.
Related Concept Videos
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...
01:21Frequency-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.Positive Frequency-Dependent SelectionIn positive...
01:06Natural Selection and Mating Preferences
The principle of natural selection posits that organisms better adapted to their environment are more likely to survive and reproduce. This principle is closely intertwined with mating preferences, a key aspect of sexual selection, which evolutionary psychologists believe is driven by instincts to propagate one's genes. Such instincts significantly influence mating behaviors and preferences between genders.
Females, due to their biological roles in conception, pregnancy, and nursing, inherently...
Females, due to their biological roles in conception, pregnancy, and nursing, inherently...
01:20Mate Choice
Mate choice—the decision about whom to mate with—is a type of natural selection, since animals must reproduce to pass down their genes. Mate choice is also called intersexual selection because the behavior occurs between the sexes.
03:33Genetic Drift
Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can...
02:27Background and Environment Affect Phenotype
Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...