HOME

TheInfoList




Convergent evolution is the independent
evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The
cladistic Cladistics (; ) is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically ...
term for the same phenomenon is
homoplasy Homoplasy, in biology and phylogenetics, is when a Phenotypic trait, trait has been gained or lost independently in separate lineages over the course of evolution. This is different from Homology (biology), homology, which is the similarity of trait ...
. The
recurrent evolution Recurrent evolution is the repeated evolution of a particular trait, character, or mutation (biology), mutation. Most evolution is the result of Genetic drift, drift, often interpreted as the random chance of some alleles being passed down to the ...
of flight is a classic example, as flying
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
s,
bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

bird
s,
pterosaurs Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptile Reptiles are tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes ...

pterosaurs
, and
bat Bats are mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meanin ...

bat
s have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are ''analogous'', whereas '' homologous'' structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur
wings A wing is a type of fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust Thrust is a reaction (physics), reaction force (physics), force describ ...

wings
are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is
divergent evolution Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to speciation Speciation is the evolution Evolution is change in the Heredity, heritable Phenoty ...
, where related species evolve different traits. Convergent evolution is similar to
parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and parall ...
, which occurs when two independent species evolve in the same direction and thus independently acquire similar characteristics; for instance, gliding frogs have evolved in parallel from multiple types of
tree frog A treefrog, or tree frog, is any species of frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (literally ''without tail'' in Ancient ...

tree frog
. Many instances of convergent evolution are known in
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s, including the repeated development of
C4 photosynthesis
C<sub>4</sub> photosynthesis
,
seed dispersal Seed dispersal is the movement, spread or transport of seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The ban ...
by fleshy
fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

fruit
s adapted to be eaten by animals, and
carnivory A carnivore , meaning "meat Meat is animal flesh that is eaten as food. Humans have hunted and killed animals for meat since prehistoric times. The advent of civilization allowed the domestication of animals such as chickens, sheep, rabbi ...

carnivory
.


Overview

In morphology, analogous traits arise when different species live in similar ways and/or a similar environment, and so face the same environmental factors. When occupying similar
ecological niche In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms ...

ecological niche
s (that is, a distinctive way of life) similar problems can lead to similar solutions. The British anatomist
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Despite being a controversial figure, Owen is generally considered to have been an outstanding naturalist with a remark ...

Richard Owen
was the first to identify the fundamental difference between analogies and homologies. In biochemistry, physical and chemical constraints on have caused some
active site Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records Active Records was a record label, record sublabel of RCA Records founded in 1980. The label focused mainly on heavy metal music. The label was disso ...

active site
arrangements such as the
catalytic triad A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes (e.g. proteases, amidases, esterases, acylases, lipas ...

catalytic triad
to evolve independently in separate
enzyme superfamiliesA protein superfamily is the largest grouping (clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common anc ...
. In his 1989 book '' Wonderful Life'',
Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start ...
argued that if one could "rewind the tape of life the same conditions were encountered again, evolution could take a very different course."
Simon Conway Morris Simon Conway Morris (born 1951) is an English palaeontologist Paleontology, also spelled palaeontology or palæontology (), is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene The ...
disputes this conclusion, arguing that convergence is a dominant force in evolution, and given that the same environmental and physical constraints are at work, life will inevitably evolve toward an "optimum" body plan, and at some point, evolution is bound to stumble upon intelligence, a trait presently identified with at least
primates A primate ( ) (from Latin , from 'prime, first rank') is a eutherian mammal constituting the Taxonomy (biology), taxonomic order (biology), order Primates (). Primates arose 85–55 million years ago first from small Terrestrial animal, ...
,
corvids Corvidae is a cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 ...
, and
cetaceans Cetaceans (from la, cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the ...

cetaceans
.


Distinctions


Cladistics

In cladistics, a homoplasy is a trait shared by two or more
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
for any reason other than that they share a common ancestry. Taxa which do share ancestry are part of the same
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic – that is, composed of a common ancestor and all its lineage (evolution), lineal descendants - on a phylogenetic tree. R ...

clade
; cladistics seeks to arrange them according to their degree of relatedness to describe their
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram A diagram is a symbolic representation Representation may refer to: Law a ...

phylogeny
. Homoplastic traits caused by convergence are therefore, from the point of view of cladistics, confounding factors which could lead to an incorrect analysis.


Atavism

In some cases, it is difficult to tell whether a trait has been lost and then re-evolved convergently, or whether a gene has simply been switched off and then re-enabled later. Such a re-emerged trait is called an
atavism In biology, an atavism is a modification of a biological structure whereby an ancestral genetic Trait (biological), trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways; one ...
. From a mathematical standpoint, an unused gene () has a steadily decreasing
probability Probability is the branch of mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained ...

probability
of retaining potential functionality over time. The time scale of this process varies greatly in different phylogenies; in mammals and birds, there is a reasonable probability of remaining in the genome in a potentially functional state for around 6 million years.


Parallel vs. convergent evolution

When two species are similar in a particular character, evolution is defined as parallel if the ancestors were also similar, and convergent if they were not. Some scientists have argued that there is a continuum between parallel and convergent evolution, while others maintain that despite some overlap, there are still important distinctions between the two. When the ancestral forms are unspecified or unknown, or the range of traits considered is not clearly specified, the distinction between parallel and convergent evolution becomes more subjective. For instance, the striking example of similar placental and marsupial forms is described by
Richard Dawkins Richard Dawkins (born 26 March 1941) is a British evolutionary biology, evolutionary biologist and author. He is an Oxford fellow, emeritus fellow of New College, Oxford and was Simonyi Professor for the Public Understanding of Science, Prof ...

Richard Dawkins
in ''
The Blind Watchmaker ''The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design'' is a 1986 book by , in which the author presents an explanation of, and argument for, the theory of by means of . He also presents arguments to refute ...
'' as a case of convergent evolution, because mammals on each continent had a long evolutionary history prior to the extinction of the dinosaurs under which to accumulate relevant differences.


At molecular level


Proteins


Protease active sites

The
enzymology Enzymes () are protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958 ...
of
proteases A protease (also called a peptidase or proteinase) is an enzyme that catalysis, catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of n ...
provides some of the clearest examples of convergent evolution. These examples reflect the intrinsic chemical constraints on enzymes, leading evolution to converge on equivalent solutions independently and repeatedly. Serine and cysteine proteases use different amino acid functional groups (alcohol or thiol) as a
nucleophile In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...

nucleophile
. In order to activate that nucleophile, they orient an acidic and a basic residue in a
catalytic triad A catalytic triad is a set of three coordinated amino acids that can be found in the active site of some enzymes. Catalytic triads are most commonly found in hydrolase and transferase enzymes (e.g. proteases, amidases, esterases, acylases, lipas ...

catalytic triad
. The chemical and physical constraints on
enzyme catalysis Enzyme catalysis is the increase in the rate of a process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and managem ...

enzyme catalysis
have caused identical triad arrangements to evolve independently more than 20 times in different
enzyme superfamiliesA protein superfamily is the largest grouping (clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common anc ...
.
Threonine protease Threonine proteases are a family of proteolytic enzymes harbouring a threonine (Thr) residue within the active site. The prototype members of this class of enzymes are the catalysis, catalytic subunits of the proteasome, however the acyltransferas ...
s use the amino acid threonine as their catalytic
nucleophile In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during a ...

nucleophile
. Unlike cysteine and serine, threonine is a
secondary alcohol upright=0.8, The bond angle between a hydroxyl group (-OH) and a chain of carbon atoms (R) In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, ...

secondary alcohol
(i.e. has a methyl group). The methyl group of threonine greatly restricts the possible orientations of triad and substrate, as the methyl clashes with either the enzyme backbone or the histidine base. Consequently, most threonine proteases use an N-terminal threonine in order to avoid such steric clashes. Several evolutionarily independent
enzyme superfamiliesA protein superfamily is the largest grouping (clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common anc ...
with different
protein foldA protein superfamily is the largest grouping (clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common anc ...

protein fold
s use the N-terminal residue as a nucleophile. This commonality of
active site Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records Active Records was a record label, record sublabel of RCA Records founded in 1980. The label focused mainly on heavy metal music. The label was disso ...

active site
but difference of protein fold indicates that the active site evolved convergently in those families.


Cone snail and fish insulin

'' Conus geographus'' produces a distinct form of
insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets; it is considered to be the main Anabolism, anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats and p ...

insulin
that is more similar to fish insulin protein sequences than to insulin from more closely related molluscs, suggesting convergent evolution.


Na+,K+-ATPase and Insect resistance to cardiotonic steroids

Many examples of convergent evolution exist in insects in terms of developing resistance at a molecular level to toxins. One well-characterized example is the evolution of resistance to cardiotonic steroids (CTSs) via amino acid substitutions at well-defined positions of the α-subunit of Na+,K+-ATPase (ATPalpha). Variation in ATPalpha has been surveyed in various CTS-adapted species spanning 6 insect orders. Among 21 CTS-adapted species, 58 (76%) of 76 amino acid substitutions at sites implicated in CTS resistance occur in parallel in at least two lineages. 30 of these substitutions (40%) occur at just two sites in the protein (positions 111 and 122). CTS-adapted species have also recurrently evolved neo-functionalized duplications of ATPalpha, with convergent tissue-specific expression patterns.


Nucleic acids

Convergence occurs at the level of
DNA Deoxyribonucleic acid (; DNA) is a molecule A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically Electricity is the set of physical ...

DNA
and the
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
sequences produced by structural genes into
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
s. Studies have found convergence in amino acid sequences in echolocating bats and the dolphin; among marine mammals; between giant and red pandas; and between the thylacine and canids. Convergence has also been detected in a type of
non-coding DNA Non-coding DNA sequences are components of an organism's DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of ...
,
cis-regulatory element ''Cis''-regulatory elements (CREs) or ''Cis''-regulatory modules (CRMs) are regions of non-coding DNA Non-coding DNA sequences are components of an organism's DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) ...
s, such as in their rates of evolution; this could indicate either
positive selection upThree types of selection In population genetics, directional selection, or positive selection is a mode of natural selection Natural selection is the differential survival and reproduction of individuals due to differences in pheno ...
or relaxed
purifying selection In natural selection, negative selection or purifying selection is the selective removal of alleles that are Mutation#Harmful mutations, deleterious. This can result in stabilizing selection through the purging of deleterious genetic polymorphisms ...
.


In animal morphology


Bodyplans

Swimming animals including
fish Fish are aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

fish
such as
herring Herring are forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish fee ...

herring
s,
marine mammals Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their ...
such as
dolphins Dolphin is a common name of aquatic mammals within the infraorder Cetacea Cetaceans (from la, Cetus (mythology), cetus, lit=whale, from grc, κῆτος, translit=Cetus (mythology), kētos, lit = huge fish, sea monster) are aquatic mamma ...

dolphins
, and
ichthyosaur Ichthyosaurs (Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period (), and the period (). Ancient ...
s ( of the Mesozoic) all converged on the same streamlined shape. A similar shape and swimming adaptations are even present in molluscs, such as '' Phylliroe''. The fusiform bodyshape (a tube tapered at both ends) adopted by many aquatic animals is an adaptation to enable them to travel at high speed in a high
drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adja ...
environment. Similar body shapes are found in the
earless seal The earless seals, phocids or true seals are one of the three main groups of mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of comm ...
s and the eared seals: they still have four legs, but these are strongly modified for swimming. The marsupial fauna of Australia and the placental mammals of the Old World have several strikingly similar forms, developed in two clades, isolated from each other. The body and especially the skull shape of the
thylacine The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including t ...

thylacine
(Tasmanian tiger or Tasmanian wolf) converged with those of
Canidae Canidae (; from Latin, ''canis'', "dog") is a biological family Family ( la, familia, plural ') is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order (biology), order and genus. A famil ...
such as the red fox, ''
Vulpes vulpes The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanli ...

Vulpes vulpes
''. marsupial Marsupials are any members of the mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ' ...
and
placental The infraclass In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mole ...
mammals"> File:Vulpes vulpes skeleton.JPG,
Red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanli ...

Red fox
skeleton File:Beutelwolf fg01.jpg, Skulls of
thylacine The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including t ...

thylacine
(left),
timber wolf
timber wolf
(right) File:Beutelwolfskelett brehm.png,
Thylacine The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct Extinction is the termination of a kind of organism In biology Biology is the natural science that studies life and living organisms, including t ...

Thylacine
skeleton


Echolocation

As a sensory adaptation,
echolocation
echolocation
has evolved separately in
cetaceans Cetaceans (from la, cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus (mythology), Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the ...

cetaceans
(dolphins and whales) and bats, but from the same genetic mutations.


Eyes

One of the best-known examples of convergent evolution is the camera eye of
cephalopods A cephalopod is any member of the mollusca Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are ...
(such as squid and octopus),
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...
s (including mammals) and
cnidaria Cnidaria () is a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of ...

cnidaria
(such as jellyfish). Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the progressive refinement of camera eyes — with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates. As a result, cephalopods lack a blind spot.


Flight

Birds Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With ...

Birds
and
bat Bats are mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meanin ...

bat
s have homologous limbs because they are both ultimately derived from terrestrial
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a sp ...
s, but their flight mechanisms are only analogous, so their wings are examples of functional convergence. The two groups have powered flight, evolved independently. Their wings differ substantially in construction. The bat wing is a membrane stretched across four extremely elongated fingers and the legs. The airfoil of the bird wing is made of
feather Feathers are epidermal growths that form a distinctive outer covering, or plumage Plumage ( "feather") is a layer of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avi ...

feather
s, strongly attached to the forearm (the ulna) and the highly fused bones of the wrist and hand (the
carpometacarpus The carpometacarpus is the fusion of the carpal and metacarpal In human anatomy, the metacarpal bones or metacarpus, form the intermediate part of the skeleton, skeletal hand located between the phalanges of the fingers and the carpal bones of the ...

carpometacarpus
), with only tiny remnants of two fingers remaining, each anchoring a single feather. So, while the wings of bats and birds are functionally convergent, they are not anatomically convergent. Birds and bats also share a high concentration of
cerebroside Cerebrosides is the common name for a group of glycosphingolipids called monoglycosylceramides which are important components in animal muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein Proteins are la ...

cerebroside
s in the skin of their wings. This improves skin flexibility, a trait useful for flying animals; other mammals have a far lower concentration. The extinct
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptiles of the extinct clade or Order (biology), order Pterosauria. They existed during most of the Mesozoic: from the late Triassic to the end of the Cretac ...
s independently evolved wings from their fore- and hindlimbs, while
insects Insects (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

insects
have
wings A wing is a type of fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust Thrust is a reaction (physics), reaction force (physics), force describ ...
that evolved separately from different organs.
Flying squirrel Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant usage of the term is in the discipline of ant ...

Flying squirrel
s and
sugar glider The sugar glider (''Petaurus breviceps'') is a small, omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores di ...

sugar glider
s are much alike in their body plans, with gliding wings stretched between their limbs, but flying squirrels are placental mammals while sugar gliders are marsupials, widely separated within the mammal lineage.
Hummingbird hawk-moth The hummingbird hawk-moth (''Macroglossum stellatarum'') is a species of hawk moth The Sphingidae are a family of Moth, moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as ...

Hummingbird hawk-moth
s and
hummingbird Hummingbirds are Bird, birds native to the Americas and comprise the Family (biology), biological family Trochilidae. With about 360 species, they occur from Alaska to Tierra del Fuego, but the vast majority of the species are found in the tropi ...

hummingbird
s have evolved similar flight and feeding patterns.


Insect mouthparts

Insect mouthparts show many examples of convergent evolution. The mouthparts of different insect groups consist of a set of homologous organs, specialised for the dietary intake of that insect group. Convergent evolution of many groups of insects led from original biting-chewing mouthparts to different, more specialised, derived function types. These include, for example, the
proboscis Convolvulus hawk-moth (''Agrius convolvuli'') feeding with extended proboscis">Agrius_convolvuli.html" ;"title="Convolvulus hawk-moth (''Agrius convolvuli">Convolvulus hawk-moth (''Agrius convolvuli'') feeding with extended proboscis A probosci ...

proboscis
of flower-visiting insects such as
bee Bees are flying insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', m ...

bee
s and
flower beetle Flower chafers are a group of scarab beetles, comprising the subfamily Cetoniinae. Many species are diurnal and visit flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering ...

flower beetle
s, or the biting-sucking mouthparts of blood-sucking insects such as
flea Flea, the common name for the order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, tr ...
s and
mosquito Mosquitoes are members of a group of almost 3,600 species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defin ...

mosquito
s.


Opposable thumbs

Opposable thumb The thumb is the first digit of the hand A hand is a prehensile, multi- fingered appendage located at the end of the forearm The forearm is the region of the upper limb between the Elbow-joint, elbow and the wrist. The term forearm is us ...
s allowing the grasping of objects are most often associated with
primates A primate ( ) (from Latin , from 'prime, first rank') is a eutherian mammal constituting the Taxonomy (biology), taxonomic order (biology), order Primates (). Primates arose 85–55 million years ago first from small Terrestrial animal, ...
, like humans, monkeys, apes, and lemurs. Opposable thumbs also evolved in giant pandas, but these are completely different in structure, having six fingers including the thumb, which develops from a wrist bone entirely separately from other fingers.


Primates

Convergent evolution in humans includes blue eye colour and light skin colour. When humans migrated
out of Africa ''Out of Africa'' is a memoir A memoir (; , ) is any nonfiction Nonfiction (also spelled non-fiction) is any document A document is a writing, written, drawing, drawn, presented, or memorialized representation of thought, often the manif ...
, they moved to more northern latitudes with less intense sunlight. It was beneficial to them to reduce their
skin pigmentation Afghan children with fair skin Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigment A pigment is a colored material that is completely or nearly i ...
. It appears certain that there was some lightening of skin colour ''before'' European and East Asian lineages diverged, as there are some skin-lightening genetic differences that are common to both groups. However, after the lineages diverged and became genetically isolated, the skin of both groups lightened more, and that additional lightening was due to ''different'' genetic changes.
Lemurs Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are wet-nosed primates of the superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid se ...

Lemurs
and
humans Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...
are both primates. Ancestral primates had brown eyes, as most primates do today. The genetic basis of blue eyes in humans has been studied in detail and much is known about it. It is not the case that one gene locus is responsible, say with brown dominant to blue
eye colour Eye color is a polygenicA polygene is a member of a group of non-epistatic gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Mendelian units of heredity.. ...
. However, a single locus is responsible for about 80% of the variation. In lemurs, the differences between blue and brown eyes are not completely known, but the same gene locus is not involved.


In plants


Carbon fixation

While convergent evolution is often illustrated with animal examples, it has often occurred in
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
evolution. For instance, , one of the three major carbon-fixing biochemical processes, has arisen independently up to 40 times. About 7,600 plant species of angiosperms use carbon fixation, with many monocots including 46% of grasses such as Zea mays, maize and sugar cane, and dicots including several species in the Chenopodiaceae and the Amaranthaceae.


Fruits

A good example of convergence in plants is the evolution of edible
fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

fruit
s such as apples. These pomes incorporate (five) carpels and their accessory tissues forming the apple's core, surrounded by structures from outside the botanical fruit, the receptacle (botany), receptacle or hypanthium. Other edible fruits include other plant tissues; for example, the fleshy part of a tomato is the walls of the pericarp. This implies convergent evolution under selective pressure, in this case the competition for seed dispersal by animals through consumption of fleshy fruits. Seed dispersal by ants (myrmecochory) has evolved independently more than 100 times, and is present in more than 11,000 plant species. It is one of the most dramatic examples of convergent evolution in biology.


Carnivory

Carnivory has evolved multiple times independently in plants in widely separated groups. In three species studied, ''Cephalotus, Cephalotus follicularis'', ''Nepenthes alata'' and ''Sarracenia purpurea'', there has been convergence at the molecular level. Carnivorous plants secrete enzymes into the digestive fluid they produce. By studying Purple acid phosphatases, phosphatase, Glycoside hydrolase family 19, glycoside hydrolase, glucanase, RNASET2, RNAse and chitinase enzymes as well as a pathogenesis-related protein and a thaumatin-related protein, the authors found many convergent
amino acid Amino acids are organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, a ...

amino acid
substitutions. These changes were not at the enzymes' catalytic sites, but rather on the exposed surfaces of the proteins, where they might interact with other components of the cell or the digestive fluid. The authors also found that homologous genes in the non-carnivorous plant ''Arabidopsis thaliana'' tend to have their expression increased when the plant is stressed, leading the authors to suggest that stress-responsive proteins have often been co-opted in the repeated evolution of carnivory.


Methods of inference

Phylogenetic reconstruction and Ancestral reconstruction, ancestral state reconstruction proceed by assuming that evolution has occurred without convergence. Convergent patterns may, however, appear at higher levels in a phylogenetic reconstruction, and are sometimes explicitly sought by investigators. The methods applied to infer convergent evolution depend on whether pattern-based or process-based convergence is expected. Pattern-based convergence is the broader term, for when two or more lineages independently evolve patterns of similar traits. Process-based convergence is when the convergence is due to similar forces of natural selection.


Pattern-based measures

Earlier methods for measuring convergence incorporate ratios of phenotypic and phylogenetic distance by simulating evolution with a Brownian motion model of trait evolution along a phylogeny. More recent methods also quantify the strength of convergence. One drawback to keep in mind is that these methods can confuse long-term stasis with convergence due to phenotypic similarities. Stasis occurs when there is little evolutionary change among taxa. Distance-based measures assess the degree of similarity between lineages over time. Frequency-based measures assess the number of lineages that have evolved in a particular trait space.


Process-based measures

Methods to infer process-based convergence fit models of selection to a phylogeny and continuous trait data to determine whether the same selective forces have acted upon lineages. This uses the Ornstein–Uhlenbeck process, Ornstein-Uhlenbeck (OU) process to test different scenarios of selection. Other methods rely on an ''A priori knowledge, a priori'' specification of where shifts in selection have occurred.


See also

*: the presence of multiple alleles in ancestral populations might lead to the impression that convergent evolution has occurred. *


Notes


References


Further reading

* {{Authority control Evolutionary biology concepts