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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.

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...

Conservation of Declining Populations

Conservation of Declining Populations

Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.

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...

The Evidence for Evolution

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.The collection of fossils within sedimentary rocks give a record of common ancestry and often depicts the history of evolution.

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.For one, natural selection can only act upon existing genetic variation. Hypothetically, redtusks may enhance elephant survival by deterring ivory-seeking poachers. However, if there are no gene variants—or alleles—for redtusks, natural selection cannot increase the prevalence of...

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A Push-pull Protocol to Reduce Colonization of Bird Nest Boxes by Honey Bees

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Published on: September 4, 2016

Consistent ecological selectivity through time in Pacific Island avian extinctions.

Alison G Boyer¹

¹Division of Birds, MRC-116, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington, D.C. 20013-7012, USA. agboyer@ucsd.edu

Conservation Biology : the Journal of the Society for Conservation Biology

|October 22, 2009

Summary

Ancient avian extinctions reveal key ecological traits linked to bird extinction risk. Understanding these patterns, like endemism and body size, aids modern conservation efforts for endangered species.

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Area of Science:

Paleoecology
Conservation Biology
Avian Ecology

Background:

Understanding ecological mechanisms driving extinction is crucial for conservation.
Ancient extinction events offer insights into predicting future biodiversity loss.

Purpose of the Study:

To determine ecological traits associated with avian extinction risk using historical and paleoecological data.
To assess the utility of ancient extinction patterns for predicting modern bird endangerment.

Main Methods:

Classification trees were employed to analyze paleoecological and historical island data.
Ecological traits, including endemism, body size, and feeding guilds, were evaluated as predictors of extinction.

Main Results:

Intrinsic species traits such as endemism and large body size were strongly correlated with extinction risk over the past 3500 years.
Species ecology and phylogeny proved more significant predictors of extinction than extrinsic or abiotic factors.
Modern endangered birds exhibit similar ecological characteristics to species that experienced past extinctions.

Conclusions:

Paleoecological data provides valuable insights for modern conservation biology.
Identifying species at risk of extinction can be improved by studying past avian extinction events.
Conservation strategies can benefit from understanding the long-term ecological drivers of bird extinctions.