Anagenesis

Anagenesis, also known as "phyletic transformation", is when the new morphospecies is a result of rapid evolution in the ancestral form without speciation taking place, such that there are no remaining other populations of the ancestor species and the species can be considered extinct. The ancestor species is therefore superseded by the new species it morphs into. Anagenesis is in contrast to the branching speciation known as cladogenesis. Anagenesis rejects animals related by convergent evolution and unlike the study of behavioral homologies permits the inclusion of animals related by parallel evolution (Yarczower & Hazlett 1977).

However, the Punctuated Equilibria Hypothesis was proposed, which explained the gradual direction of phyletic change. Under this hypothesis, phyletic transformation is almost meaningless, because if it is correct, lineages do not change during its lifetime, they remain static until speciation occurs so that anagenesis is not possible (Gutman & Altava 2008).

Recent evolutionary studies are looking at anagenesis and cladogeneis for possible answers in developing the hominin phylogenetic tree to understand morphological diversity and the origins of "Australopithecus anamensis", and this case could possibly show anagenesis in the fossil record (Kimbel et al. 2006).

When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population, a new species name may be assigned. A series of such species is collectively known as an evolutionary lineage.^[1]^[2] The various species along an evolutionary lineage are chronospecies. If the ancestral population of a chronospecies does not go extinct, then this is cladogenesis, and the ancestral population represent a paraphyletic species or paraspecies, being an evolutionary grade. This situation is quite common in species with widespread populations.

It is easy to see from this definition how controversy can arise among taxonomists as to when the differences are significant enough to warrant a new species classification: Anagenesis may also be referred to as "gradual evolution". Attempts to distinguish different forms of speciation as anagensis or cladogenesis are controversial, and some academics question the necessity of the terms altogether.^[3]

The philosopher of science Marc Ereshefsky argues that paraphyletic taxa are the result of anagenesis.^{[citation needed]} The lineage leading to birds has diverged significantly from lizards and crocodiles, allowing evolutionary taxonomists to classify birds separately from lizards and crocodiles, which are grouped as reptiles.^[4]

Regarding social evolution, it has been suggested that social anagenesis/aromorphosis be viewed as universal or widely diffused social innovation that raises social systems' complexity, adaptability, integrity, and interconnectedness.^[5]

Notes

^ The University of California, Berkeley resource on understanding evolution defines a lineage as "A continuous line of descent; a series of organisms, populations, cells, or genes connected by ancestor/descendent relationships." Understanding Evolution, Glossary of Terms
^ The Oxford English Dictionary defines biological lineage as "a sequence of species each of which is considered to have evolved from its predecessor."OED definition of lineage
^ Vaux, F; Trewick, SA; Morgan-Richards, M (2016). "Lineages, splits and divergence challenge whether the terms anagenesis and cladogenesis are necessary". Biol J Linnean Soc. 117 (2): 165–176. doi:10.1111/bij.12665.
^ Ereshefsky, M. (2001), "Philosophy of Biological Classification", Encyclopedia of Life Sciences, Wiley-Blackwell, doi:10.1038/npg.els.0003447, ISBN 0470016175
^ Leonid Grinin & Andrey Korotayev. Social Macroevolution: Growth of the World System Integrity and a System of Phase Transitions. World Futures, Volume 65, Issue 7 October 2009 , pages 477 - 506; Aromorphoses in Biological аnd Social Evolution: Some General Rules for Biological and Social Forms of Macroevolution in Social Evolution & History (Vol. 8 No. 2, September 2009: 6-50).

External links

Diagram contrasting Anagenesis and Cladogenesis from the University of Newfoundland

This evolution-related article is a stub. You can help Wikipedia by expanding it.

[1] The University of California, Berkeley resource on understanding evolution defines a lineage as "A continuous line of descent; a series of organisms, populations, cells, or genes connected by ancestor/descendent relationships." Understanding Evolution, Glossary of Terms

[2] The Oxford English Dictionary defines biological lineage as "a sequence of species each of which is considered to have evolved from its predecessor."OED definition of lineage

[3] Vaux, F; Trewick, SA; Morgan-Richards, M (2016). "Lineages, splits and divergence challenge whether the terms anagenesis and cladogenesis are necessary". Biol J Linnean Soc. 117 (2): 165–176. doi:10.1111/bij.12665.

[4] Ereshefsky, M. (2001), "Philosophy of Biological Classification", Encyclopedia of Life Sciences, Wiley-Blackwell, doi:10.1038/npg.els.0003447, ISBN 0470016175

[5] Leonid Grinin & Andrey Korotayev. Social Macroevolution: Growth of the World System Integrity and a System of Phase Transitions. World Futures, Volume 65, Issue 7 October 2009 , pages 477 - 506; Aromorphoses in Biological аnd Social Evolution: Some General Rules for Biological and Social Forms of Macroevolution in Social Evolution & History (Vol. 8 No. 2, September 2009: 6-50).

[1]

[2]

[3]

[4]

[5]

v t e Evolutionary biology
Introduction Outline Timeline of evolution History of life Index
Evolution	Abiogenesis Adaptation Adaptive radiation Altruism Cheating Reciprocal Baldwin effect Cladistics Coevolution Mutualism Common descent Convergence Divergence Earliest known life forms Evidence of evolution Evolutionary arms race Evolutionary pressure Exaptation Extinction Event Homology Last universal common ancestor Macroevolution Microevolution Mismatch Non-adaptive radiation Origin of life Panspermia Parallel evolution Signalling theory Handicap principle Speciation Species Species complex Taxonomy Unit of selection Gene-centered view of evolution
Population genetics	Artificial selection Biodiversity Evolutionarily stable strategy Fisher's principle Fitness Inclusive Gene flow Genetic drift Kin selection Parental investment Parent–offspring conflict Mutation Population Natural selection Sexual dimorphism Sexual selection Flowering plants Fungi Mate choice Social selection Trivers–Willard hypothesis Variation
Development	Canalisation Evolutionary developmental biology Genetic assimilation Inversion Modularity Phenotypic plasticity
Of taxa	Bacteria Birds origin Brachiopods Molluscs Cephalopods Dinosaurs Fish Fungi Insects butterflies Life Mammals cats canids wolves dogs hyenas dolphins and whales horses Kangaroos primates humans lemurs sea cows Plants pollinator-mediated Reptiles Spiders Tetrapods Viruses
Of organs	Cell DNA Flagella Eukaryotes symbiogenesis chromosome endomembrane system mitochondria nucleus plastids In animals eye hair auditory ossicle nervous system brain
Of processes	Aging Death Programmed cell death Avian flight Biological complexity Cooperation Color vision in primates Emotion Empathy Ethics Eusociality Immune system Metabolism Monogamy Morality Mosaic evolution Multicellularity Sexual reproduction Gamete differentiation/sexes Life cycles/nuclear phases Mating types Meiosis Sex-determination Snake venom
Tempo and modes	Gradualism/Punctuated equilibrium/Saltationism Micromutation/Macromutation Uniformitarianism/Catastrophism
Speciation	Allopatric Anagenesis Catagenesis Cladogenesis Cospeciation Ecological Hybrid Non-ecological Parapatric Peripatric Reinforcement Sympatric
History	Renaissance and Enlightenment Transmutation of species David Hume Dialogues Concerning Natural Religion Charles Darwin On the Origin of Species History of paleontology Transitional fossil Blending inheritance Mendelian inheritance The eclipse of Darwinism Neo-Darwinism Modern synthesis History of molecular evolution Extended evolutionary synthesis
Philosophy	Darwinism Alternatives Catastrophism Lamarckism Orthogenesis Mutationism Saltationism Structuralism Spandrel Theistic Vitalism Teleology in biology
Related	Biogeography Ecological genetics Evolutionary medicine Group selection Cultural evolution Cultural group selection Dual inheritance theory Hologenome theory of evolution Missing heritability problem Molecular evolution Astrobiology Phylogenetics Tree Polymorphism Protocell Systematics Transgenerational epigenetic inheritance
Category Portal

See also

Notes

External links