What is Convergent Evolution?

Convergent evolution is an evolutionary concept that explains the evolution of anatomically different trait or structure that performs the same function in phylogenetically independent organisms.

Such anatomical structures are referred to as analogous that have evolved the same function as an adaptive measure to similar environmental pressures, even though these structures belong to evolutionary distinct and unrelated species. These do not involve a common ancestor and differ anatomically and have different embryonic origins.

Convergence, Homoplasy, and Reversal

The homoplasty or homoplasy phenomenon refers to the process through which similar morphological traits are acquired by unrelated organisms not by inheritance but rather due to an evolutionary process. Such similarities in these organisms develop gradually with time even though they have different evolutionary lineages.

One of the reasons can be their similar habitats and other environmental factors that result in similar adaptive tactics or mechanisms. This type of parallel or convergent evolution can lead to homoplasy.

Evolutionary reversal is another evolutionary concept that is seen when a trait seen in the ancestral lineage is lost in recent ones but is observed later in related species.

Convergent Evolution Examples

Convergent evolution examples include wings of the insects, birds, and bats. Their wings differ anatomically but the function is similar that is flight. They have no evolutionary relatedness and emerge from different phylogenetic lines but exploit their wings to soar through the air.

The eyes of cephalopods, vertebrates, arthropods, and cubozoan jellyfish are another example. These eye structures have different embryonic origins and differ in anatomical features in these organisms that evolved separately. The eyes of all these organisms serve the function of sight. Similarly, the olfactory organs are also examples in unrelated species are also analogous structures.

For instance, consider the smelling organs sensilla of insects and the terrestrial coconut crab that perform a similar function of detecting odors. The shells of unrelated brachiopods and bivalve mollusks also show certain resemblances. Different aquatic organisms like fish and dolphins have a streamlined structure that enables efficient swimming.

An antifreeze compound that is formed of a protein and sugar that helps fishes like Arctic cod and the Antarctic toothfish to survive in extreme conditions. The gene that codes for this antifreeze glycoprotein had a different function like digestion in ancient times but evolved for adaptation.

Fruitafossor resembles the pangolins and anteaters in having long sticky tongues that made them myrmecophagous, even though they are phylogenetically related in any manner. Mimicry comprises a defense strategy employed by many organisms.

They are of 2 types: Batesian vs Mullerian. Mullerian mimicry occurs when the organisms copy another one morphologically. While in the case of Batesian mimicry, a non-poisonous animal mimics a harmful organism. For instance, Heliobolus lugubris is a sand lizard that mimics a ground beetle Anthia sp. that sprays formic acid in its defense.

The former lizard is non-toxic but by mimicry, it deceives its predators. This evolutionary process can also be observed in plants. Various analogous structures like spines, thorns, and prickles can be seen as an adaptive defensive measure.

Convergent vs Parallel Evolution

Convergent evolution and parallel evolution both result in analogous structures in unrelated species in the process of evolution. In the case of parallel evolution, the species are adapting to the same environment, while in convergent evolution the organisms face similar environmental selection pressures leading to similar adaptive mechanisms. An example of parallel evolution is African euphorbia and North American cactus that live in hot arid regions and as a result, have sharp quills and thicker stems as a result of adaptation.

Convergent Evolution vs Divergent Evolution

The evolutionary process where related species diverge due to different selection pressures and different adaptation measures is called divergent evolution. In this, the organisms belonging to a common lineage diverge in the process of evolution. This divergence occurs due to the evolution of a novel function in an anatomical structure.

They diversify with time and become more dissimilar from their ancestors. Such an evolutionary process can be observed in Darwin finches that showed adaptive radiation. They diversified to decrease competition by specializing their beaks that restricted them to a particular diet. Bat’s forelimbs are another example.

Bat has the same mammalian anatomic forelimb features and the forelimb is comprised of ulna and radius. But in bats, the forelimb acquired a new function that is gliding by the evolution of patagia that is the wing membranes. These structures that have the similar embryonic origin and same anatomical features are homologous.

Potential causes of this evolutionary process include interbreeding, migration, differential selection pressures. As in Darwin’s finches that became selected for a particular niche by the process of Natural selection.