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Formation of Species

Formation of Species

Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the parent species, and barriers to reproduction will typically exist. There are two primary mechanisms, speciation with and without geographic isolation—allopatric and sympatric speciation, respectively.Allopatric SpeciationIn allopatric speciation, gene flow between two populations of the same species is prevented by a geographic barrier, like...

Genetics of Speciation

Genetics of Speciation

Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.The genetics of speciation involves the different traits or isolating mechanisms preventing gene exchange, leading to reproductive isolation. Reproductive isolation can be due to reproductive barriers that have effects either before or after the formation of a zygote. Pre-zygotic mechanisms prevent fertilization from occurring, and post-zygotic mechanisms...

Types of Selection

Types 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...

Speciation Rates

Speciation Rates

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.

Frequency-dependent Selection

Frequency-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...

Mate Choice

Mate 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.

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Related Experiment Video

Updated: Jun 16, 2026

Determination of the Mating Efficiency of Haploids in Saccharomyces cerevisiae

Determination of the Mating Efficiency of Haploids in Saccharomyces cerevisiae

Published on: December 2, 2022

Selective loss of polymorphic mating types is associated with rapid phenotypic evolution during morphic speciation.

Ammon Corl¹, Alison R Davis, Shawn R Kuchta

¹Department of Ecology and Evolutionary Biology, EMS A316, University of California, Santa Cruz, CA 95064, USA. corl@biology.ucsc.edu

Proceedings of the National Academy of Sciences of the United States of America

|February 18, 2010

Summary

This summary is machine-generated.

Polymorphism loss in side-blotched lizards can drive rapid evolution and speciation. This study details how losing distinct morphs leads to new subspecies and species formation.

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Area of Science:

Evolutionary Biology
Speciation Research
Herpetology

Background:

Polymorphism is a key factor in speciation, but the exact mechanisms are unclear.
Distinct morphs within populations may lead to the origin of new species.
Understanding how morph loss drives speciation is crucial for evolutionary studies.

Purpose of the Study:

To investigate the role of throat color polymorphism in speciation.
To detail the evolutionary history and geographic variation of this polymorphism in Uta stansburiana.
To understand the process by which morph loss contributes to species formation.

Main Methods:

Studied geographic variation and evolutionary history of throat color polymorphism.
Utilized phylogenetic reconstruction to analyze polymorphism.
Examined the association between polymorphism loss and morphological evolution.

Main Results:

The throat color polymorphism in Uta stansburiana is geographically widespread and ancient.
Polymorphism has been independently lost eight times, often resulting in distinct subspecies/species.
Loss of the 'sneaker' morph allele was consistent across all loss events.
Polymorphism loss correlated with accelerated evolution in male size, female size, and sexual dimorphism.

Conclusions:

Polymorphism loss can promote rapid population divergence and aid in species formation.
Selection likely drives the loss of specific morphs, such as the 'sneaker' morph.
This study provides insights into the microevolutionary processes underlying macroevolutionary changes like speciation.