Related Experiment Video
Updated: May 28, 2026
06:44
Induction and Evaluation of Inbreeding Crosses Using the Ant, Vollenhovia Emeryi
Published on: October 5, 2018
Polyandry reduces sperm length variation in social insects.
John L Fitzpatrick1, Boris Baer
1Centre for Evolutionary Biology, School of Animal Biology, University of Western Australia, WA 6009, Australia. jfitzpat@cyllene.uwa.edu.au
Evolution; International Journal of Organic Evolution
|October 5, 2011
Summary
Postcopulatory sexual selection reduces sperm variation in social insects. This indicates sperm competition favored higher quality sperm, explaining the evolution of sperm morphology in ants and bees.
Area of Science:
- Evolutionary biology
- Animal reproduction
- Insect behavior
Background:
- Postcopulatory sexual selection, including sperm competition and cryptic female choice, drives sperm morphology variation across species.
- Intraspecific variation in sperm morphology and the role of postcopulatory sexual selection are understudied in invertebrates.
Purpose of the Study:
- To investigate if postcopulatory sexual selection reduces sperm morphology variation within and between males.
- To test this hypothesis in 27 species of eusocial ants and bees, which lack haploid-diploid conflict in sperm production.
Main Methods:
- Comparative analysis of sperm morphology variation across 27 eusocial ant and bee species.
- Examination of sperm morphology in relation to mating systems (polyandry) in these species.
Main Results:
- Males of polyandrous ant and bee species exhibit significantly reduced variation in sperm morphology.
- This finding supports the hypothesis that sperm competition selects for sperm of superior quality.
Conclusions:
- Postcopulatory sexual selection, specifically sperm competition, plays a crucial role in shaping sperm morphology variation within species.
- The study provides evidence for the evolution of high-quality sperm in social insects, influenced by sexual selection.
Related Concept Videos
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.
01:17What is a Species?
Overview
02:45The Ratio of X Chromosome to Autosomes
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
01:21Nondisjunction
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...
01:29Nondisjunction
During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.
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.