Evolutionary ecology is the study of the relationship between evolutionary processes and ecological processes. It is a subfield of ecology that focuses on how the traits and behaviors of organisms evolve in response to environmental pressures and how these traits and behaviors influence the distribution and abundance of species within an ecosystem.
Evolutionary ecologists may study a wide range of topics, including the impacts of natural selection on the evolution of species, the role of genetic drift in shaping the evolution of populations, and the ways in which species adapt to changing environments. They may also study the impacts of human activities on evolutionary processes and the ways in which these impacts can be managed or mitigated.
To study evolutionary processes, evolutionary ecologists may use a variety of methods, including field observations, experiments, and data analysis. They may also use techniques such as molecular genetics to understand the genetic basis of evolutionary change.
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Evolutionary ecology is an important field for understanding the mechanisms of evolutionary change and for informing conservation efforts to protect and preserve species and their habitats. It is also important for understanding the impacts of human activities on evolutionary processes and the ways in which these impacts can be managed or mitigated.
When we talk about evolutionary ecology, the name itself gives its general idea, as it intersects the knowledge of ecology and evolutionary biology. Evolutionary ecology has different subfields like life history evolution, sociobiology, the evolution of interspecific interactions, and the evolution of biodiversity and ecological communities. The environment is incredibly dynamic as we ourselves have witnessed many climatic changes in the past few years.
Evolution depends upon the origin of new species that have greater adaptive efficiency than their ancestors. Speciation is the process of the creation of new kinds of plant or animal species. It occurs when a group within a species separates from the other member of its species and develops its own unique characteristics. According to Mayr (1970), the speciation or multiplication of species can occur through two methods: gradual speciation (through population) and instantaneous speciation (through individuals).
- Gradual speciation: It has been mainly divided into four types: allopatric speciation, peripatric speciation, parapatric speciation, and sympatric speciation.
- Allopatric speciation: The type of speciation that involves the environmental or geographical barriers is known as allopatric speciation. This speciation separates a population into two or more evolutionary units due to reproductive isolation caused by the geographic separation of two sub-populations. In sexually reproducing animals, when a population is geographically isolated from other populations of its parental species and reproductive isolation occurs after the external breakdown, this results in the development of a new species. The allopatric speciation was of special interest to Darwin as he saw the species of finches on Galapagos Island. The finches were found to have the characteristic of polymorphism. This also occurs when two or more clearly distinct individuals of a species occur in the same ecosystem, for example, a jaguar and a common leopard. Polymorphism also occurs in the case of humans due to the presence of polymorphic traits of blood groups. Biologists have been able to find out the model of the ABO histo-blood group, which is the critical determinant of transfusion compatibility and the first genetic polymorphism discovered in humans. The blood group of humans can be A, B, AB, and O.
- Sympatric speciation: It refers to the speciation which occurs in a subpopulation in the midst of its parent populations. There is no geographical separation or isolation. Reproductive isolation occurs between the segments of a single population. The gene flow between the parent and daughter population is inhibited by intrinsic factors than extrinsic factors. This speciation can occur either due to vital mutation or Polyploidy. Sympatric speciation is observed in bees, hummingbirds, etc.
- Peripatric speciation: This type of speciation occurs when a very small subpopulation becomes isolated from a larger population. As the isolated subpopulation is very small, divergence can happen rapidly, resulting from the ‘Founder Effect .’The Founder Principle states that the gene pool of an isolated new population is not similar to that of the parent population because of the sampling error; this leads to genetic variation. The small populations often undergo bottlenecks, become more sensitive to genetic drift, and natural selection act upon a small gene pool.
- Parapatric speciation: This type of speciation occurs when a small subpopulation remains within the habitat of an original population but enters a different niche. It prevents interbreeding between the two separated populations.
- Instantaneous speciation: It produces a single individual or the offspring of a single mate that is reproductively isolated from the species to which the parental stock belongs. The individual is reproductively and ecologically capable of establishing a new species of population. This type of speciation occurs by either one of the methods: Ordinary mutation, Macrogenesis, Chromosomal aberration, and Polyploidy.
- Ordinary mutation: This type of mutation cannot produce new species in the sexually reproducing species but can produce new species in the vegetative reproduction by growth and splitting. This type of reproduction only occurs in some of the lowest groups of animals, like sponges, coelenterates, etc.
- Macrogenesis is the sudden origin of new species and higher taxa. However, it is said to be a poor source of speciation.
- Chromosomal aberration is also known as chromosomal rearrangements, which produces speciation only in a few cases. In this type, speciation occurs due to the change in various kinds of chromosomes.
- Polyploidy: It is the multiplication of normal chromosome numbers. It is an important and widespread method of speciation in the plant kingdom.
Evolutionary Ecologists
The trend of evolution was first explained by Lamarck, whereas the concept of evolution was first given by Empedocles and Buffon.
- Charles Darwin: His theories of ‘natural selection’ and ‘population dynamics’ have been the basis for the principles of evolutionary ecology and explain how populations of a species change over time.
His most significant contributions to evolutionary ecology are as follows:
Modern Concept of Evolution
Branching Evolution which implies that all the species of living beings have a common descent from a single unique origin.
- George Evelyn Hutchinson: He is also known as the father of ‘modern ecology. He constructed the mathematical models of populations, the changing proportions of individuals of various ages, birthrates, the ecological niche, and the population interaction in this technical introduction to population ecology.
- Robert Mac Arthur: He is best known for his work on ‘the theory of Island Biogeography’, in which he and his coauthors stated that ‘the number of species on any island reflects a balance between the rate at which new species colonize it and the rate at which populations of established societies become extinct.
- Eric Pianka: His contribution to evolutionary ecology includes foraging strategies, reproductive tactics, competition and niche theory, community structure and organization, species diversity, and understanding rarity.
- Michael Rosenzweig: His creation ‘Reconciliation Ecology’ shows that the designated nature reserves would not be enough to conserve the biodiversity of the earth as human beings have used up so much of land that has not only affected the biogeochemical cycles but the ecosystem as a whole.
- R. A. Fisher: He gave the fundamental theorem of natural selection.
- David Lack: He worked to merge the field of evolutionary biology and ecology, focusing mainly on birds and evolution.
- Thierry Lode: His work focused on how the sexual conflict in species populations impacts evolution.
Organic Evolution
The main steps of the origin of life in sequence have been summarized in short as follows:
Presence of atoms (H, C, N, O, etc.) in a free state.
The molecules and simple inorganic compounds (H2, H2O, NH3, etc.) originated.
Chemogeny: Simple organic compounds originated (CH4, HCN, simple sugars, fatty acids, glycerol, amino acid, nitrogenous bases).
Complex organic compounds originated (polysaccharides, fats, proteins, nucleotides, nucleic acids).
Biogeny: Prebiotic molecules originated (having the ability to grow and divide aggregates of complex organic compounds).
Origin of Prokaryotes (without organized nucleus)
Origin of Eukaryotes (with an organized nucleus)
Types of Organic Evolution
- Progressive evolution: More complex and specialized structures are formed from the simpler ones. Example: the sequential development of bryophyte, pteridophyte, gymnosperm, and angiosperm.
- Retrogressive evolution: Simple and less specialized structures are formed from the complex ones. Example: a tadpole larva undergoing retrogressive changes during metamorphosis to become adult in the tunicates and amphibians. (The free-swimming tadpole larva shows advanced chordate characters that become lost during metamorphosis).
- Microevolution: Gene mutations and recombinations result in the development of minute changes below the species level. Examples: pesticide resistance, herbicide resistance, and antibiotic resistance.
- Parallel evolution: Related groups of organisms form similar traits independently. Example: similar traits shown by marsupial mammals of Australia and the placental mammals
- Convergent evolution: Unrelated groups of organisms form similar traits, for example, wings of insects, birds, and bats.
- Divergent evolution (adaptive radiation): formation of different structures from a common ancestral form. Example: forelimbs in the horse, bats, and human beings.
- Macroevolution: Development of large changes like the formation of new species and genera due to mutation causing large-scale changes in chromosomes. Examples: the origin of eukaryotic life forms, the origin of human beings, the extinction of dinosaurs, etc.
- Mega evolution: Large change giving rise to new families, orders, classes, etc. Example: the Cambrian explosion or Cambrian radiation resulted in the rapid appearance of most major animal phyla around 530 million years ago. Coevolution: Evolutionary changes in one or more species in response to changes in other species of the same community. Example: predator-prey relationships like the one existing between the African honey badger and the African honey bee.
Darwin’s theory of Natural Selection
Charles Darwin and Alfred Russel Wallace jointly propounded the ‘Theory of Natural Selection’. In 1858, Darwin and Wallace jointly published a paper entitled ‘Origin of Species’. Darwin’s theory of evolution by natural selection had the following postulates:
Overproduction: More organisms are produced than the number survival.
Struggle for existence: Competition between the organisms for limited environmental resources like nutrients, living space, or light. It may be interspecific (between individuals of the same species), intraspecific (between different species), and extraspecific (between individuals and the environment).
Heredity and evolution: Organisms with inherited traits favor survival and reproduction. It will cause the traits to increase in frequency over generations.
Due to evolution, organisms change over time as a result of changes in heritable physical or heritable traits.
Natural selection (Darwin) or survival of the fittest (Spencer): Natural selection is the process of nature in which the organisms have to adapt to their changing environment; those who have better adapted survive as well as reproduce more than those less adapted to their environment. The organisms that have best adjusted to their environment are the most successful in surviving and reproducing.
Variations: The differences that an organism shows from its parent or from its related species. An animal that has developed a favorable variation has a higher chance of survival, and its offspring are likely to inherit these variations.
Origin of species: the formation of new species as a result of geographic, physiological, anatomical, or behavioral factors.
The main Neo-Darwinians are August Weismann, Gregor John Mendel and Hugo de Vries.
According to the Neo-Darwinians, both mutations and natural selection are responsible for evolution. One major criticism of Darwin’s theory was his failure to explain the variations.
FAQs on Evolutionary Ecology
What is ecosystem evolution?
Ecosystem evolution is the understanding of the evolutionary processes in the ecosystem and the replacement of an ecosystem by another ecosystem that have occurred as a result of natural selection. The evolutionary processes give rise to diversity at every level of biological organization including species, individual organisms and molecules such as DNA and RNA. There are five basic processes which bring evolution: mutations, gene recombinations, gene flow, genetic drift (all causing genetic variations) and natural selection followed by isolation.
1. Mutations: These are the permanent heritable changes in the genetic material of the individuals. They are caused by the
Change in chromosome number (polyploidy and aneuploidy)
Chromosome aberrations (deletion, duplication, inversion, translocation) and
Change in genes (number and sequence of nucleotides).
New alleles and sometimes even new genes are formed by the gene mutations. The alleles that are removed by the evolutionary agents are restored by the mutations. Mutations create and maintain variations within population. New alleles and genes are added into the gene pool. In this way, mutations are raw material for evolutionary change.
Very few mutations are useful. Most of the mutations are neutral or harmful and recessive. However, with the change in the environment, many neutral or harmful and recessive mutations may change into beneficial ones as these mutations are also the source of pre-adaptations and basis to natural selection.
The pre-adaptive mutations appear without exposure to the environment, they are beneficial to the organism. The pre-adaptive mutations express themselves only in the new environment and they result in the natural selection.
2. Gene recombinations: They are variations produced due to coming together of different alleles and parts of alleles of genes during sexual reproduction in recombination which doesnot exist in parents. No two individuals of a species are similar due to the genetic recombinations (except the case of monozygotic twins). Gene recombinations occur due to different reasons like dual parentage, random union of gametes, chance separation of chromosomes and crossing over.
i. Dual parentage: Gene recombinations occur as each individual receives half of its genes from one parent and the remaining half from the other parent.
ii. Random union of gametes: After fertilization and formation of zygote, each new individual comes to have its own gene recombination or genotype as any male gamete can fuse with any female gamete.
iii. Chance separation of chromosomes: Out of the two homologous chromosomes, anyone can pass into a gamete because of their random separation.
iv. Crossing over: It refers to the exchange of segments between non sister chromatids of a homologous pair and production of a new linkage (new combination of existing genes and alleles) by bringing together alleles together alleles that developed in different chromosomes at different time and places. Crossing over occur during pachytene stage of meiosis. The addition of new alleles, genes and combination of alleles to the gene pool result in recombinations which function as agents of evolution.
3. Gene Flow (Gene Exchange): A species may consist of many populations. The entry or exit of a section of population result in the addition or loss of alleles. Regular mixing of populations due to migrations, emigration and immigration decreases the differences between the separated populations and reduces the chances of formation of new species. Gene migration occurs which involves the occasional migration of a section of population to the area of another population of the species adding new alleles to the local gene pool. It will change the phenotype of the individuals which are likely to be acted upon by natural selection. A closely related species also may immigrate into the area causing interspecific mating and producing fertile hybrids. These hybrids carry gene from species to species.
4. Genetic Drift: It is random change in allele number and frequency in a gene pool caused by chance like small size of population. It is caused by sampling error, genetic bottle neck effect Sewall wright effect or error in gene pool sample that is to form the next generations.
The sampling gene pool is generally small in size. Certain alleles are fixed whereas others are eliminated. In new habitat, the colonisers also called as founders are generally few. There is increase in inbreeding, decrease in heterozygosity and increase in homozygosity. Mutations produce entirely new alleles and genes. This produces a different gene pool and a different population. Thus, changes in phenotypes form new species and such mechanism of speciation is called ‘founder effect’.
Certain species like mosquitoes, houseflies, etc. show seasonal flush and crash in their population which causes survival of only small populations and result in shrinkage of gene pool. As the population grows in size, a random genetic drift takes place. The reduction in allele frequencies during the brief reduction in size of population is called bottle neck effect or Sewall Wright effect. It protects the organism from extinction.
5. Natural Selection: According to Darwin, natural selection is the survival in the struggle for existence and reproductive success of the fittest surviving individuals. Depending upon the type of environmental pressure, natural selection is of three types: stabilizing or centripetal selection (selection of the average of the species), directional selection (selection of one of the two extremes of a trait, not average of species) and disruptive or centrifugal selection (selection of both the extremes but not average of the species).
What is the relationship between ecology and evolution?
The vegetation, plant and animal communities have been changing from time to time in the nature. If the replacement of an old plant community occurs in a same place by a new plant community, it is called vegetation succession. But, when an ecosystem is replaced by another ecosystem in a course of time period, it is called as ecosystem evolution.
Ecology and evolution have been interconnected with each other since the time immemorial. If we talk about their relation, one cannot resist in the absence of the other. The history of earth is divided into four great eons (Hadean, Archean, Proterozoic and Phanerozoic) starting around more than 4 million years ago with the planet formation. Each eon observed the most dynamic changes in the composition, climate and life on the earth. This means the abiotic and biotic components i.e. collectively called ecology.
The Hadean eon represents the time before the reliable record of fossils. It began with the planet formation and ended 4 billion years ago. Its features are absence of life, extremely hot temperatures with frequent volcanic cavity, nebular atmosphere and possibly presence of early oceans or liquid water bodies. 
The succeeding Archean and Proterozoic eons produced the beginning of life on the earth and its earliest evolution. Archean eon had the abiogenesis i.e. origin of prokaryotic life, the first form of life. The atmosphere was surrounded by greenhouse and volcanic gases in the Archean eon.
The Proterozoic eon had the origin of the eukaryotic life. The features of this eon are ‘snowball earth’ having freezing temperatures below zero degree, production of oxygen by bacteria, formation of plants, animals and possible earlier forms of fungiThe next is Phanerozoic eon, the eon of arthropods, fishes, the first life on land, the rise, reign and extinction of the dinosaurs and rise of mammals. Main feature of this eon is ‘Cambrian explosion’ which expanded the life on land. Recognizable human beings and animal species also emerged almost 2 million years ago in this eon.
A biome is a community of organisms characterized by specific adaptation to a certain environment. Biome includes the desert, tundra, rainforests, grassland, etc. Biomes are continuous as they gradually lead from one to the next. The intermediate area in biome is known as an ecotone. For example, between an African forest and an open Savanna, there might be a tress savanna as ecotone where the trees are sparser than in the forest but more prevalent than in the Savanna. In the desert ecosystem, the animals have developed different types of adaptations like body modification in order to conserve water, modified fur, feathers or skin to reflect the sunlight, they might have nocturnal behavior as it is cooler in the night than during the day. On the contrast, organisms of the Tundra have modified body structures or adapted features like blubber, thick fur, feathers, etc. in order to conserve heat. The communities of organisms display continuous gradient known as ‘ecocline’. One example is the ring species like Ensatina lizard species.
The biome can be regarded as ‘theatres of evolution’ if we focus on long-term evolutionary processes shaping both the taxonomic and trait pools.
Why is evolution important to ecology?
Evolution is important to ecology due to the following reasons:
The evolution has a very long history of around 4 billion years which has resulted in the rich biodiversity we see today around us.
Understanding evolution is also very important. For example, evolution helps in solving the biological problems which impact our lives.
The knowledge of evolutionary patterns of pathogens (disease causing organisms) helps the researchers find the ways to get rid of them and stop them from being epidemics.
The knowledge of evolution has helped us know that we share a common ancestor with animals like monkeys, dogs and rats. This provides us a big advantage in the sense that new drugs and vaccines can be tested on the animals without hampering human life.
The evolution has also helped scientists in the discovery of new life saving drugs.
What are the 5 levels of ecology?
The five levels of ecology are population, community, ecosystem, biomes and biosphere.
What are examples of ecology?
The examples of ecology are study of food chain in a wetland area, population estimation and study of spatio-temporal distribution of tiger in a National Park, diversity and abundance of birds in a forest etc.
What are the types of ecology?
The types of ecology are population ecology, community ecology, landscape ecology, ecosystem ecology, evolutionary ecology, molecular ecology, organismal ecology and global ecology.
What is definition of evolution?
Evolution refers to the change in the inherited characteristic of biological populations over successive generations.
What ecology means?
Ecology means the study of inter-relationship between the living organisms and the environment.
Who created the ecosystem?
Sir Arthur G. Tansley coined the term ecosystem in 1935.
What is another word for ecology?
Environmental biology is another word for ecology.
Who is the father of Evolutionary Ecology?
Jean Baptiste de Lamarck is the father of Evolutionary Ecology.
What are the two main branches of ecology?
Autecology and Synecology are the two main branches of ecology.