Donald I. Williamson
Encyclopedia
Donald Irving Williamson is a British
planktologist
and carcinologist, born 8 January 1922, Alnham
, Northumberland
, England
. He gained his first degree from the Durham University
in 1942, his Ph.D.
from the same university in 1948, and a D.Sc.
from the Newcastle University in 1972. He worked at the Port Erin Marine Laboratory of the University of Liverpool
from 1948 to 1997, and has published on the Irish Sea
plankton, crustacean behaviour and taxonomy, and crustacean larvae.
: Larvae and Evolution (a book forwarded by Lynn Margulis
and Alfred I. Tauber
), The Origins of Larvae (a revised and extended edition of Larvae and Evolution, not to be confounded with his 2007 article of same title published in the magazine American Scientist
), and some articles on the same subject.
In Larvae and Evolution Williamson developed a controversial hypothesis proposing the acquisition of larval stages in some marine organisms by hybridisation between two distant animal species (a speciation process referred to as hybridogenesis by Williamson). The fraction of the genome of one of the contributor species would be restricted to lead the developmental program of a newly acquired larva whereas the genome of the other contributor would drive the development of most of the adult anatomical structures. During the following years he would generalize his theory to other animal groups featuring a holometabolous
development.
According to Williamson, these successful hybridisations would most likely occur in organisms with external fertilisation or male gamete dispersal. He acknowledges in his work Larvae and Evolution to have borrowed the idea of hybridogenesis from the well-known process of interspecific hybridisation that take place in plants. Hybrid plants generated from phylogenetically distant species can often give rise to new species if the hybrids become reproductively isolated from the progenitor populations.
In one of his articles Williamson contends that
Williamson's hypothesis has been reviewed in the companion website for the eighth edition of Developmental Biology (a principal textbook of reference in the field of Developmental Biology
). The review can be found in the chapter 23, section 10: Alternative Mechanisms for Evolutionary Developmental Biology, subsection: alt.evodevo: Reticulate Evolution and Sequential Chimeras, under the header Sequential Chimerism.
(online in August 2009, in print in November 2009), Williamson claimed that the body plan
of the adult butterfly and its caterpillar larval stage would have evolved separately in different organisms; then, their phylogenies would eventually merge by hybridisation at a more recent point of their evolutionary history. The study was communicated by Lynn Margulis
, via a submission route that at that time allowed academy members of the United States National Academy of Sciences
to manage the peer review of a colleague's manuscript. The acceptance for publication led to accusations of "nepotism" and "nonsense" science. Margulis maintained that Williamson's paper was scientifically sound and was only being censured because it didn't adhere to Darwinian orthodoxy. '"We don't ask anyone to accept Williamson's ideas — only to evaluate them on the basis of science and scholarship, not knee-jerk prejudice," said Margulis.
In a subsequent paper published in print in the same issue of the journal, the biologists Michael W. Hart and Richard K. Grosberg rebutted Williamson's hypothesis. The same issue also included another communication sent by Gonzalo Giribet (at that time Curator of Invertebrates in the Museum of Comparative Zoology
at Harvard University
) rebutting Williamson's paper, together with Williamson's reply to Giribet's letter. In the issue of December 2009 of the same journal another letter submitted by Arnab De, Ram K. Mathur and Rituparna Bose was published. Even though the authors rectified some of the signs considered by Williamson as molecular evidence of an ancestral hybridogenesis, they recommended a laboratory hybridisation study between an onychophore and a cockroach
, as proposed by Williamson.
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
planktologist
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
and carcinologist, born 8 January 1922, Alnham
Alnham
Alnham is a village in Northumberland, England. It is about to the west of Alnwick.To the west of the Church of St Michael, Alnham Vicars Pele is a 14th century pele tower, restored from a ruinous state in the 19th century....
, Northumberland
Northumberland
Northumberland is the northernmost ceremonial county and a unitary district in North East England. For Eurostat purposes Northumberland is a NUTS 3 region and is one of three boroughs or unitary districts that comprise the "Northumberland and Tyne and Wear" NUTS 2 region...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. He gained his first degree from the Durham University
Durham University
The University of Durham, commonly known as Durham University, is a university in Durham, England. It was founded by Act of Parliament in 1832 and granted a Royal Charter in 1837...
in 1942, his Ph.D.
Doctor of Philosophy
Doctor of Philosophy, abbreviated as Ph.D., PhD, D.Phil., or DPhil , in English-speaking countries, is a postgraduate academic degree awarded by universities...
from the same university in 1948, and a D.Sc.
Doctor of Science
Doctor of Science , usually abbreviated Sc.D., D.Sc., S.D. or Dr.Sc., is an academic research degree awarded in a number of countries throughout the world. In some countries Doctor of Science is the name used for the standard doctorate in the sciences, elsewhere the Sc.D...
from the Newcastle University in 1972. He worked at the Port Erin Marine Laboratory of the University of Liverpool
University of Liverpool
The University of Liverpool is a teaching and research university in the city of Liverpool, England. It is a member of the Russell Group of large research-intensive universities and the N8 Group for research collaboration. Founded in 1881 , it is also one of the six original "red brick" civic...
from 1948 to 1997, and has published on the Irish Sea
Irish Sea
The Irish Sea separates the islands of Ireland and Great Britain. It is connected to the Celtic Sea in the south by St George's Channel, and to the Atlantic Ocean in the north by the North Channel. Anglesey is the largest island within the Irish Sea, followed by the Isle of Man...
plankton, crustacean behaviour and taxonomy, and crustacean larvae.
Works
He is also author of some speculative works on hybridization in evolutionEvolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
: Larvae and Evolution (a book forwarded by Lynn Margulis
Lynn Margulis
Lynn Margulis was an American biologist and University Professor in the Department of Geosciences at the University of Massachusetts Amherst. She is best known for her theory on the origin of eukaryotic organelles, and her contributions to the endosymbiotic theory, which is now generally accepted...
and Alfred I. Tauber
Alfred I. Tauber
Alfred I. Tauber , Zoltan Kohn Professor emeritus of Medicine and Professor emeritus of Philosophy at Boston University, is a philosopher and historian of science, who, from 1993 to 2010, served as Director of the Boston University Center for Philosophy and History of Science at Boston University...
), The Origins of Larvae (a revised and extended edition of Larvae and Evolution, not to be confounded with his 2007 article of same title published in the magazine American Scientist
American Scientist
American Scientist is the bimonthly science and technology magazine published since 1913 by Sigma Xi. Each issue includes four to five feature articles written by scientists and engineers. These authors review research in all fields of science...
), and some articles on the same subject.
In Larvae and Evolution Williamson developed a controversial hypothesis proposing the acquisition of larval stages in some marine organisms by hybridisation between two distant animal species (a speciation process referred to as hybridogenesis by Williamson). The fraction of the genome of one of the contributor species would be restricted to lead the developmental program of a newly acquired larva whereas the genome of the other contributor would drive the development of most of the adult anatomical structures. During the following years he would generalize his theory to other animal groups featuring a holometabolous
Holometabolism
Holometabolism, also called complete metamorphism, is a term applied to insect groups to describe the specific kind of insect development which includes four life stages - as an embryo or egg, a larva, a pupa and an imago or adult. Holometabolism is a monophyletic trait that all insects in the...
development.
According to Williamson, these successful hybridisations would most likely occur in organisms with external fertilisation or male gamete dispersal. He acknowledges in his work Larvae and Evolution to have borrowed the idea of hybridogenesis from the well-known process of interspecific hybridisation that take place in plants. Hybrid plants generated from phylogenetically distant species can often give rise to new species if the hybrids become reproductively isolated from the progenitor populations.
In one of his articles Williamson contends that
- there were no true larvaLarvaA larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e until after the establishment of classesClass (biology)In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
in the respective phylaPhylumIn biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
, - early animalAnimalAnimals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s hybridized to produce chimerasChimera (genetics)A chimera or chimaera is a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction. If the different cells have emerged from the same zygote, the organism is called a mosaic...
of parts of dissimilar species, - the Cambrian explosionCambrian explosionThe Cambrian explosion or Cambrian radiation was the relatively rapid appearance, around , of most major phyla, as demonstrated in the fossil record, accompanied by major diversification of other organisms, including animals, phytoplankton, and calcimicrobes...
resulted from many such hybridizations, - modern animal phyla and classes were produced by such early hybridizations, rather than by the gradual accumulation of specific differences.
Williamson's hypothesis has been reviewed in the companion website for the eighth edition of Developmental Biology (a principal textbook of reference in the field of Developmental Biology
Developmental biology
Developmental biology is the study of the process by which organisms grow and develop. Modern developmental biology studies the genetic control of cell growth, differentiation and "morphogenesis", which is the process that gives rise to tissues, organs and anatomy.- Related fields of study...
). The review can be found in the chapter 23, section 10: Alternative Mechanisms for Evolutionary Developmental Biology, subsection: alt.evodevo: Reticulate Evolution and Sequential Chimeras, under the header Sequential Chimerism.
Controversy
In an article published in the journal Proceedings of the National Academy of SciencesProceedings of the National Academy of Sciences
The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences...
(online in August 2009, in print in November 2009), Williamson claimed that the body plan
Body plan
A body plan is the blueprint for the way the body of an organism is laid out. An organism's symmetry, its number of body segments and number of limbs are all aspects of its body plan...
of the adult butterfly and its caterpillar larval stage would have evolved separately in different organisms; then, their phylogenies would eventually merge by hybridisation at a more recent point of their evolutionary history. The study was communicated by Lynn Margulis
Lynn Margulis
Lynn Margulis was an American biologist and University Professor in the Department of Geosciences at the University of Massachusetts Amherst. She is best known for her theory on the origin of eukaryotic organelles, and her contributions to the endosymbiotic theory, which is now generally accepted...
, via a submission route that at that time allowed academy members of the United States National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...
to manage the peer review of a colleague's manuscript. The acceptance for publication led to accusations of "nepotism" and "nonsense" science. Margulis maintained that Williamson's paper was scientifically sound and was only being censured because it didn't adhere to Darwinian orthodoxy. '"We don't ask anyone to accept Williamson's ideas — only to evaluate them on the basis of science and scholarship, not knee-jerk prejudice," said Margulis.
In a subsequent paper published in print in the same issue of the journal, the biologists Michael W. Hart and Richard K. Grosberg rebutted Williamson's hypothesis. The same issue also included another communication sent by Gonzalo Giribet (at that time Curator of Invertebrates in the Museum of Comparative Zoology
Museum of Comparative Zoology
The Museum of Comparative Zoology, full name "The Louis Agassiz Museum of Comparative Zoology", often abbreviated simply to "MCZ", is a zoology museum located on the grounds of Harvard University in Cambridge, Massachusetts. It is one of three museums which collectively comprise the Harvard Museum...
at Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
) rebutting Williamson's paper, together with Williamson's reply to Giribet's letter. In the issue of December 2009 of the same journal another letter submitted by Arnab De, Ram K. Mathur and Rituparna Bose was published. Even though the authors rectified some of the signs considered by Williamson as molecular evidence of an ancestral hybridogenesis, they recommended a laboratory hybridisation study between an onychophore and a cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
, as proposed by Williamson.
External links
- alt.evodevo: Reticulate Evolution and Sequential Chimeras (8e.devbio.com) Gilbert, Scott, F. DevBio: A Companion to Developmental Biology, Eighth Edition (Sinauer Associates). Chapter 23.10: Alternative Mechanisms for Evolutionary Developmental Biology (retrieved on 23 June 2010).