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{{Afd-merge to|Evolutionary developmental biology|Developmental Drive|15 December 2017}} |
{{Afd-merge to|Evolutionary developmental biology|Developmental Drive|15 December 2017}} |
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To show the involvement of developmental drive, it is necessary to compare existent and nonexistent [[Morphology (biology)|morphologies]].<ref name=":1">{{Cite journal|last=Arthur|first=W.|date=July 2001|title=Developmental drive: an important determinant of the direction of phenotypic evolution|url=https://www.ncbi.nlm.nih.gov/pubmed/11478524|journal=Evolution & Development|volume=3|issue=4|pages=271–278|pmid=11478524}}</ref> |
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'''Developmental drive''' is characterized by positive biases toward other trajectories or phenotypes. Developmental drive is a type of biased developmental reprogramming of ontogenetic trajectory within a lineage in favor of certain changes. Developmental drive can have a powerful influence on the direction of evolutionary change along with [[natural selection]]. |
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<ref name=":1">{{Cite journal|last=Arthur|first=W.|date=July 2001|title=Developmental drive: an important determinant of the direction of phenotypic evolution|url=https://www.ncbi.nlm.nih.gov/pubmed/11478524|journal=Evolution & Development|volume=3|issue=4|pages=271–278|issn=1520-541X|pmid=11478524}}</ref><ref name=":2">{{Cite journal|last=Arthur|first=W.|date=October 2002|title=The interaction between developmental bias and natural selection: from centipede segments to a general hypothesis|url=https://www.ncbi.nlm.nih.gov/pubmed/12242638|journal=Heredity|volume=89|issue=4|pages=239–246|doi=10.1038/sj.hdy.6800139|issn=0018-067X|pmid=12242638}}</ref> |
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== Developmental Drive in the Real World == |
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To show the involvement of developmental drive, it is necessary to compare existent and nonexistent [[Morphology (biology)|morphologies]]. This is a difficult step and causes a problem since there must be a decision made about which nonexistent morphologies to compare with the actual existent morphology.<ref name=":1" /> In this, there is a broad scope for uninformative comparisons to be made so it must be done with careful consideration. |
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=== Centipede Segments === |
=== Centipede Segments === |
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There exists at least 3000 species of [[centipede]] with trunk segment numbers that range from 15 to 191. There are two orders of centipedes in which developmental drive is evident.<ref>{{Cite journal|last=Chipman|first=Ariel D|last2=Arthur|first2=Wallace|last3=Akam|first3=Michael|date=2004-07-27|title=A Double Segment Periodicity Underlies Segment Generation in Centipede Development|url=http://www.sciencedirect.com/science/article/pii/S0960982204005184|journal=Current Biology|volume=14|issue=14|pages=1250–1255|doi=10.1016/j.cub.2004.07.026}}</ref> |
There exists at least 3000 species of [[centipede]] with trunk segment numbers that range from 15 to 191. There are two orders of centipedes in which developmental drive is evident.<ref>{{Cite journal|last=Chipman|first=Ariel D|last2=Arthur|first2=Wallace|last3=Akam|first3=Michael|date=2004-07-27|title=A Double Segment Periodicity Underlies Segment Generation in Centipede Development|url=http://www.sciencedirect.com/science/article/pii/S0960982204005184|journal=Current Biology|volume=14|issue=14|pages=1250–1255|doi=10.1016/j.cub.2004.07.026}}</ref> |
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[[File:Stone Centipede, Lithobiomorpha - Flickr - GregTheBusker.jpg|thumb|Centipede: Lithobiomorpha]] |
[[File:Stone Centipede, Lithobiomorpha - Flickr - GregTheBusker.jpg|thumb|Centipede: Lithobiomorpha]] |
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The order [[Lithobiomorpha]] consists of about 1100 species. All have 15 trunk segments at their adult stage. However, these centipedes hatch from the egg with fewer than 15 segments. The segments are added with age through a series of moults through which the hatchling grows towards adulthood. Lithobiomorph centipedes with an even number of trunk segments exist, but only as juveniles. However, given the role of [[heterochrony]] in evolution, there have been no shifts of relative timing so that reproductive maturity and a cessation of segment addition have occurred in an even-numbered trunk segment juvenile in at least one of the many lithobiomorph species. It is more plausible that there is a drive towards odd-numbered trunk segments than a constraint of even-numbered trunk segments.<ref name=":2" /> |
The order [[Lithobiomorpha]] consists of about 1100 species. All have 15 trunk segments at their adult stage. However, these centipedes hatch from the egg with fewer than 15 segments. The segments are added with age through a series of moults through which the hatchling grows towards adulthood. Lithobiomorph centipedes with an even number of trunk segments exist, but only as juveniles. However, given the role of [[heterochrony]] in evolution, there have been no shifts of relative timing so that reproductive maturity and a cessation of segment addition have occurred in an even-numbered trunk segment juvenile in at least one of the many lithobiomorph species. It is more plausible that there is a drive towards odd-numbered trunk segments than a constraint of even-numbered trunk segments.<ref name=":2">{{Cite journal|last=Arthur|first=W.|date=October 2002|title=The interaction between developmental bias and natural selection: from centipede segments to a general hypothesis|url=https://www.ncbi.nlm.nih.gov/pubmed/12242638|journal=Heredity|volume=89|issue=4|pages=239–246|doi=10.1038/sj.hdy.6800139|issn=0018-067X|pmid=12242638}}</ref> |
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[[File:Chilipoda- Geophilomorpha (3309242471).jpg|thumb|Centipede: Geophilomorpha]] |
[[File:Chilipoda- Geophilomorpha (3309242471).jpg|thumb|Centipede: Geophilomorpha]] |
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The order [[Geophilomorpha]] consists of about 1000 species with variable trunk segment numbers. The overall range of segment number for the order is from 27 to 191. Within this range almost all odd numbers are represented in individuals whereas all even numbers are completely absent. Despite the larger number of segments in geophilomorphs, all are formed during embryonic development. The tiny hatchling has its full adult complement of segments. There are no segments added in any series of moults in any geophilomorph species in postembryonic growth.<ref name=":2" /> |
The order [[Geophilomorpha]] consists of about 1000 species with variable trunk segment numbers. The overall range of segment number for the order is from 27 to 191. Within this range almost all odd numbers are represented in individuals whereas all even numbers are completely absent. Despite the larger number of segments in geophilomorphs, all are formed during embryonic development. The tiny hatchling has its full adult complement of segments. There are no segments added in any series of moults in any geophilomorph species in postembryonic growth.<ref name=":2" /> |
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It is always possible to go back in evolutionary time to an ancestor in which those characters did not exist. There must have been a gastropod without a typical gastropod shell form. The mutations of developmental genes that initiated the first shells and opened up whole new areas of morphospace were perhaps based on the first kind of developmental drive, while the numerous wanderings within such morphospace were most likely based on the type of drive that utilizes pre-existing within-population variation. The direction of evolutionary change at the phenotypic level may be as much a product of the within-individual dynamics of development as of the within-population dynamics of natural selection.<ref name=":1" /> |
It is always possible to go back in evolutionary time to an ancestor in which those characters did not exist. There must have been a gastropod without a typical gastropod shell form. The mutations of developmental genes that initiated the first shells and opened up whole new areas of morphospace were perhaps based on the first kind of developmental drive, while the numerous wanderings within such morphospace were most likely based on the type of drive that utilizes pre-existing within-population variation. The direction of evolutionary change at the phenotypic level may be as much a product of the within-individual dynamics of development as of the within-population dynamics of natural selection.<ref name=":1" /> |
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== References == |
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{{reflist}} |
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{{Uncategorized|date=December 2017}} |
Revision as of 14:31, 15 December 2017
To show the involvement of developmental drive, it is necessary to compare existent and nonexistent morphologies.[1]
Centipede Segments
There exists at least 3000 species of centipede with trunk segment numbers that range from 15 to 191. There are two orders of centipedes in which developmental drive is evident.[2]
The order Lithobiomorpha consists of about 1100 species. All have 15 trunk segments at their adult stage. However, these centipedes hatch from the egg with fewer than 15 segments. The segments are added with age through a series of moults through which the hatchling grows towards adulthood. Lithobiomorph centipedes with an even number of trunk segments exist, but only as juveniles. However, given the role of heterochrony in evolution, there have been no shifts of relative timing so that reproductive maturity and a cessation of segment addition have occurred in an even-numbered trunk segment juvenile in at least one of the many lithobiomorph species. It is more plausible that there is a drive towards odd-numbered trunk segments than a constraint of even-numbered trunk segments.[3]
The order Geophilomorpha consists of about 1000 species with variable trunk segment numbers. The overall range of segment number for the order is from 27 to 191. Within this range almost all odd numbers are represented in individuals whereas all even numbers are completely absent. Despite the larger number of segments in geophilomorphs, all are formed during embryonic development. The tiny hatchling has its full adult complement of segments. There are no segments added in any series of moults in any geophilomorph species in postembryonic growth.[3]
All variant centipede ontogenies, from whatever starting point, are driven into odd-segment-number character states. Therefore, there is absolute drive in this direction, and equivalently absolute constraint regarding even numbers of segments.
Gastropod Shells
Gastropods are a clade that consist of about 65,000 to 80,000 species [4][5] which exhibit a huge variety of shell form. All gastropod shells are built, during development, in the same basic way. Each shell is a tube that extends in length and increases in diameter.[1]
One possible kind of developmental drive in shell form within a hypothetical gastropod species, the within-population variation in tube length and diameter takes a downward-sloping form, indicating a trade-off between growth in the two directions. Given such a biased range of phenotypes, some local fitness optima may be reachable, others not, on the basis of selection on the existing variation, despite being equally distant from the population mean. The march of the population toward a reachable optimum rather than an unreachable one is a joint result of selection and drive.[1] This is an example of developmental drive from pre-existing phenotypic variation.
It is always possible to go back in evolutionary time to an ancestor in which those characters did not exist. There must have been a gastropod without a typical gastropod shell form. The mutations of developmental genes that initiated the first shells and opened up whole new areas of morphospace were perhaps based on the first kind of developmental drive, while the numerous wanderings within such morphospace were most likely based on the type of drive that utilizes pre-existing within-population variation. The direction of evolutionary change at the phenotypic level may be as much a product of the within-individual dynamics of development as of the within-population dynamics of natural selection.[1]
- ^ a b c d Arthur, W. (July 2001). "Developmental drive: an important determinant of the direction of phenotypic evolution". Evolution & Development. 3 (4): 271–278. PMID 11478524.
- ^ Chipman, Ariel D; Arthur, Wallace; Akam, Michael (2004-07-27). "A Double Segment Periodicity Underlies Segment Generation in Centipede Development". Current Biology. 14 (14): 1250–1255. doi:10.1016/j.cub.2004.07.026.
- ^ a b Arthur, W. (October 2002). "The interaction between developmental bias and natural selection: from centipede segments to a general hypothesis". Heredity. 89 (4): 239–246. doi:10.1038/sj.hdy.6800139. ISSN 0018-067X. PMID 12242638.
- ^ Appeltans W., Bouchet P., Boxshall G.A., Fauchald K., Gordon D.P., Hoeksema B.W., Poore G.C.B., van Soest R.W.M., Stöhr S., Walter T.C., Costello M.J. (eds) (2011). World Register of Marine Species. Accessed at marinespecies.org on 2011-03-07.
- ^ Solem, A.G. "Gastropod". Encyclopaedia Britannica. Encyclopaedia Britannica Inc. Retrieved 6 March 2017.