EVO-DEVO (EVOLUTIONARY DEVELOPMENTAL BIOLOGY) - BIOLOGY - 2024

The evolutionary biology of development, commonly abbreviated as evo-devo for its acronym in English, is a new field of evolutionary biology that integrates development branch in evolution. One of the most promising objectives of this discipline is to explain morphological diversity on earth.

The modern synthesis sought to integrate Darwin's theory of evolution by natural selection and the mechanisms of inheritance proposed by Mendel. However, he left out the possible role of development in evolutionary biology. For this reason, evo-devo arises from the lack of integration of development in synthesis.

Source: Romanes, GJ; uploaded to Wikipedia by en: User: Phlebas; authors of the description page: en: User: Phlebas, en: User: SeventyThree, via Wikimedia Commons The development of molecular biology achieved the sequence of genomes and the visualization of genetic activity, allowing to fill this gap in evolutionary theory.

Thus, the discovery of the genes involved in these processes gave rise to the origin of evo-devo. Evolutionary developmental biologists are responsible for comparing the genes that regulate developmental processes in a wide range of multicellular organisms.

What is evo-devo?

One of the fundamental questions in evolutionary biology - and in the biological sciences in general - is how the extraordinary biodiversity of the organisms that today inhabit the planet arose.

Different branches of biology, such as anatomy, paleontology, developmental biology, genetics and genomics provide information to find the answer to this question. However, within these disciplines, development stands out.

Organisms begin their life as a single cell and, through the processes of development, the formation of the structures that compose it occurs, call it head, legs, tails, among others.

Development is a central concept, since through this process all the genetic information contained in an organism is translated into the morphology that we observe. Thus, the discovery of the genetic bases of development has revealed how changes in development can be inherited, giving rise to evo-devo.

Evo-devo seeks to understand the mechanisms that have led to the evolution of development, in terms of:

- The development processes. For example, how a new cell or new tissue is responsible for novel morphologies in certain lineages

- Evolutionary processes. For example, which selective pressures promoted the evolution of these novel morphologies or structures.

Historical perspective

Before the genes

Until the mid-1980s, most biologists assumed that diversity in forms had arisen thanks to significant changes in the genes that controlled the development of each lineage.

Biologists knew that a fly looked like a fly, and a mouse looked like a mouse, thanks to their genes. However, it was thought that the genes between such morphologically disparate organisms must reflect these abysmal differences at the gene level.

After the genes

Studies in mutants of the fruit fly, Drosophila, led to the discovery of genes and gene products that participate in the development of the insect.

These pioneering works by Thomas Kaufman led to the discovery of the Hox genes - those responsible for controlling the pattern of body structures and the identity of segments in the anteroposterior axis. These genes work by regulating the transcription of other genes.

Thanks to comparative genomics, it can be concluded that these genes are present in almost all animals.

In other words, although metazoans differ greatly in morphology (think of a worm, a bat, and a whale), they share common developmental pathways. This discovery was shocking to biologists of the time and led to the proliferation of the science of evo-devo.

Thus, it was concluded that species with very different phenotypes have very few genetic differences and that genetic and cellular mechanisms are extremely similar throughout the tree of life.

What does evo-devo study?

Evo-devo has been characterized by the development of multiple research programs. Muller (2007) mentions four of them, although he warns that they overlap each other.

Morphology and comparative embryology

This type of study seeks to clarify the morphogenetic differences that distinguish primitive ontogeny from derived ones. The information can be complemented with what is found in the fossil record.

Following this line of thought, different patterns of morphological evolution can be characterized on large scales, such as the existence of heterochronies.

These are variations that occur in development, either in the time of appearance in the rate of formation of the trait.

Biology of genetic development

This approach focuses on the evolution of the genetic machinery of development. Among the techniques used is the cloning and visualization of the expression of genes involved in regulation.

For example, the study of the Hox genes and their evolution through processes such as mutation, duplication and divergence.

Experimental epigenetics

This program studies the interaction and the molecular, cellular and tissue dynamics affect evolutionary changes. It studies developmental properties that are not contained in the genome of the organism.

This approach allows corroborating that, although the same phenotype exists, it can be expressed differentially depending on the environmental conditions.

Computer programs

This program focuses on the quantification, modeling and simulation of development evolution, including mathematical models for data analysis.

Eco-evo-devo

The emergence of evo-devo gave rise to the formation of other disciplines that sought to continue with the integration of different branches of biology in evolutionary theory, thus eco-evo-devo was born.

This new branch seeks the integration of the concepts of developmental symbiosis, developmental plasticity, genetic accommodation, and niche construction.

In general terms, developmental symbiosis states that organisms are built, in part, thanks to interactions with their environment and are persistent symbiotic relationships with microorganisms. For example, in various insects, the existence of symbiotic bacteria produces reproductive isolation.

There is no doubt that symbiosis has had an impressive impact on the evolution of organisms, from the origin of the eukaryotic cell to the origin of multicellularity itself.

In the same way, plasticity in development consists in the ability of organisms to generate different phenotypes, depending on the environment. Under this concept, the environment is not exclusively a selective agent, without also shaping the phenotype.

References

1. Carroll, SB (2008). Evo-devo and an expanding evolutionary synthesis: a genetic theory of morphological evolution. Cell, 134 (1), 25-36.
2. Gilbert, SF, Bosch, TC, & Ledón-Rettig, C. (2015). Eco-Evo-Devo: developmental symbiosis and developmental plasticity as evolutionary agents. Nature Reviews Genetics, 16 (10), 611.
3. Müller, GB (2007). Evo – devo: extending the evolutionary synthesis. Nature reviews genetics, 8 (12), 943.
4. Raff, RA (2000). Evo-devo: the evolution of a new discipline. Nature Reviews Genetics, 1 (1), 74.
5. Sultan, SE (2017). Eco-Evo-Devo. In Evolutionary Developmental Biology (pp. 1-13). Springer International Publishing.