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Genetics of Speciation

Genetics of Speciation

Speciation is the evolutionary process resulting in the formation of new, distinct species—groups of reproductively isolated populations.

Speciation Rates

Speciation Rates

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.

Hybrid Zones

Hybrid Zones

Hybrid zones are narrow regions where two closely related species interact, mate, and produce hybrids. Relative to either parent species, hybrids may possess distinct phenotypic or genetic differences that impact their survival and reproductive success. The genetic variances introduced by hybridization influence species diversity and speciation processes within the hybrid zone.

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...

Limits to Natural Selection

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.

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Thermal Limits Determination for Zooplankton Using a Heat Block

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Environmental harshness, latitude and incipient speciation.

¹Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada, M1C 1A4.

Molecular Ecology

|May 27, 2015

Summary

Speciation rates may not be highest in the tropics. Environmental harshness, not latitude, predicts subspecies richness, suggesting speciation opportunities are greatest in less diverse, harsher regions.

Keywords:

environmental harshness latitudinal diversity gradients speciation subspecies richness

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Area of Science:

Ecology
Evolutionary Biology
Biogeography

Background:

The latitudinal diversity gradient is a key pattern in ecology.
A prominent theory, the speciation pump model, posits that the tropics generate species faster than temperate regions.
This model suggests higher speciation rates in the tropics drive greater biodiversity.

Purpose of the Study:

To test the speciation pump model's predictions regarding speciation rates and diversity.
To investigate environmental factors, rather than latitude alone, as drivers of subspecies richness.
To assess if subspecies richness, as a proxy for speciation opportunity, is highest in the tropics.

Main Methods:

Analyzed subspecies richness patterns for over 9000 bird and mammal species.
Examined environmental correlates of latitude (e.g., harshness) as predictors of subspecies richness.
Used subspecies richness as an indicator of incipient speciation opportunity.

Main Results:

Environmental harshness was a significant positive predictor of subspecies richness.
High subspecies richness was found in environmentally harsh areas, suggesting increased speciation opportunities.
These harsh areas generally occur at higher latitudes, contrary to the speciation pump model.

Conclusions:

The findings challenge the view of the tropics as the primary cradle of diversity.
Environmental harshness, leading to range fragmentation or faster trait evolution, appears to drive speciation.
Results support the idea that speciation and reproductive isolation may occur fastest at higher latitudes.