Selection in Natural Populations

By Jeffry B. Mitton | Go to book overview

All the very large mammals have fecundities of approximately 25. Small mammals, such as house mice and deer mice, have fecundities that are approximately twice as great as those in large mammals, providing a greater potential for the occurrence of balancing selection. In mammals, as in all other groups of species, the opportunity for balancing selection increases with fecundity, but in mammals, size and fecundity are negatively correlated. Together, these patterns may explain the weak negative correlation between heterozygosity and size in mammals ( Nevo et al. 1984; Wooten and Smith 1985). If someone will point to an immense homeotherm with high fecundity, I will predict that it will have lots of genetic variation.

Whereas the largest animals have little genetic variability, the largest plants have the highest level of heterozygosity of any group of species. Conifers have more genetic variation than do Drososphila, marine invertebrates, or amphibians ( Hamrick, Mitton, and Linhart 1979; Mitton 1983, 1995b; Nevo, Beiles, and Ben-Shlomo 1984). Again, size is probably irrelevant. Multivariate analyses of life-history variables revealed that many aspects of ecology and life history covaried among the 113 taxa of plants examined ( Hamrick, Linhart, and Mitton 1979). Principal-components analysis was used to examine the patterns of variation in the data, which included 15 variables for each species. The first principal axis explained 30% of the variation in the data, and this axis was most strongly associated with three measures of genetic variation. Other variables associated with this axis were generation length, mating system, pollination mechanism, fecundity, seed dispersal, and successional status. Species that were long lived and wind pollinated and had high fecundities tended to have the highest levels of genetic variation. This suite of characteristics is common to conifers.

Fecundity, geographic range, and the population size ( Soulé 1976) covary among species; species with large population sizes (or populations with high densities) also tend to have large geographic ranges, and it is these species that most commonly have high levels of genetic variation. This coordinated set of axes can be used to predict rates of molecular evolution and rates of speciation. These predictions are presented in chapter 10).


Summary

Genetic variation varies dramatically among species of both plants and animals; fruit flies, marine mussels, and conifers have lots of genetic variation, whereas large vertebrates and weeds have much less. Widespread species tend to have more genetic variation than do species with small geographic ranges. Genetic variation increases with niche width in some studies but not in others. Neutral theory predicts that genetic variation will increase with population size, and empirical data are usually consistent with this prediction. Both the opportunity for selection and genetic variation increase with fecundity.

-156-

Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this book

This book has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this book

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this page

Cited page

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited page

Bookmark this page
Selection in Natural Populations
Table of contents

Table of contents

  • Title Page iii
  • Preface vii
  • Contents ix
  • 1 - Natural Selection, Fitness Determination, and Molecular Variation 3
  • Summary 12
  • 2 - Classes of Abundant Genetic Variation 14
  • 3 - Environmental Variability and Enzyme Polymorphism 29
  • Summary 37
  • 4 - The Impact of a Single Gene 39
  • Summary 57
  • 5 - Patterns of Variation Among Loci 58
  • Summary 71
  • 6 - The Axis of Individual Heterozygosity: Theory 73
  • Summary 86
  • 7 - The Axis of Individual Heterozygosity: Empirical Data 87
  • Summary 126
  • 8 - Female Choice and Male Fitness 127
  • Summary 142
  • 9 - Patterns Among Species 144
  • Summary 156
  • 10 - The Sisyphean Cycle 157
  • Summary 166
  • 11 - Comments on Natural Selection 167
  • Appendices 175
  • Bibliography 199
  • Index 233
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen
/ 246

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.