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Topic: Heterochrony

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	Heterochrony - Wikipedia, the free encyclopedia
		In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape.
		Heterochronies are easily identifyable when comparing phylogenetically close species, for example a group of different bird species whose legs differ in their average length.
		This particular type of heterochrony is named neoteny and involves a delay in the offset of a developmental process, or what is the same, the presence of an early developmental process in later stages of development.
	en.wikipedia.org /wiki/Heterochrony (374 words)

	Fall 99 GSA Abstracts (Site not responding. Last check: 2007-10-14)
		Heterochrony has been defined as the evolutionary consequences of changes in developmental timing or rate, from ancestor to descendant; identifying heterochrony requires information on growth rates, shape change, and phylogenetic relationships.
		Heterochrony in thecideidines is not limited to paedomorphosis: along with increases in size, the median septum (functions in lophophore support) often becomes more elaborate, by extending or increasing its rate of development.
		Heterochrony is best evaluated character by character, with reference to a specific phylogenetic hypothesis, rather than by whole organism or taxon, and often reveals a complex mosaic of developmental processes in evolution.
	www.wvup.edu /ecrisp/gsaabstractcarlsonbrachs.html (376 words)

	Shapes of Time (Kenneth McNamara) - book review
		Heterochrony constrains natural selection; it also provides it with raw material, allowing small genetic changes to have big phenotypic effects.
		Heterochrony is "all-pervasive" in the generation of sexual dimorphism, from simple size differences to extreme cases with males that are little more than "parasitic" sperm sacs.
		And heterochrony can play a key role in speciation, often combining with environmental gradients to separate populations; examples include Darwin's finches, brachiopods, and bushbucks.
	dannyreviews.com /h/Shapes_Time.html (688 words)

	The Botanical Review: Heterochrony in Plant Evolutionary Studies through the Twentieth Century.@ HighBeam Research (Site not responding. Last check: 2007-10-14)
		Heterochrony in Plant Evolutionary Studies through the Twentieth Century.
		Heterochrony, the evolutionary change in developmental rate or timing, is a major cause of ontogenetic modification during evolution.
		This paper discusses and reviews the role of heterochrony in plant evolution at the organismal, organ, tissue, cellular, and molecular...
	www.highbeam.com /library/doc0.asp?DOCID=1G1:63300306&refid=ip_encyclopedia_hf (187 words)

	Newsletter 29 Book Reviews (Site not responding. Last check: 2007-10-14)
		Whereas the basic ideas and terminology of heterochrony are made clear in the preface and elsewhere, the concepts discussed in the various papers are very largely new.
		Heterochrony concerns the effect of alterations to the timing and rate of development of particular structures or organs, relative to others in the body, during ontogeny.
		Moya Smith's Heterochrony in the evolution of enamel in vertebrates builds not only on a detailed synthesis of how enamel, enameloid, and dentine are secreted and develop anatomically, but is based also on how control and regulation of their development works at the genetic and molecular level.
	www.palass.org /pages/archive/bookreviews29.html (6295 words)

	EconPapers: Multivariate Approaches to Development and Evolution
		Dissociated heterochrony (McKinney and McNamara 1991) and heterotopy (Zelditch and Fink 1996) are natural consequences of the modular nature of most organisms, and they have often been documented.
		Heterochrony is a powerful mechanism of evolutionary change in development.
		While multivariate heterochrony will inevitably surface in the discussions, this paper will mostly be concerned with the general utility of multivariate approaches to developmental change, on the one hand, and with the possibility of, through them, studying evolution and development in novel ways, on the other.
	econpapers.repec.org /paper/wopsafiwp/99-05-035.htm (992 words)

	Heterochrony
		Gould (7) and others (26) have suggested that analyses of heterochrony may provide a vital link between studies of morphological evolution and regulatory genetics.
		Shea definition "Heterochrony, or changes in morphology resulting from shifts in the rate or timing of ancestral developmental patterns,..." (Shea, B.T. (1989) Heterochrony in human evolution: the case for neoteny reconsidered.
		Moreover, the hormonal basis of several metamorphoses has been established (Jenkin, 1970) and heterochronies can be produced and replicated experimentally (though biologists have rarely discussed this experimental research in the context of relationships between ontogeny and phylogeny).
	www.neoteny.org /a/heterochrony2.html (7990 words)

	American Zoologist: Shapes of Time. The Evolution of Growth and Development
		It argues for heterochrony as an evolutionary force by discussing numerous examples related to a series of issues presented in twelve chapters.
		In this chapter, McNamara introduces the term "sequential" heterochrony which is applied to portions of ontogenies that are changing relative to other portions.
		Those versed in heterochrony and allometry will find the book frustratingly confusing, yet interesting; those not so well-versed in the field may find the book interesting, and never know why it is confusing.
	www.findarticles.com /p/articles/mi_qa3746/is_199812/ai_n8824376 (1106 words)

	Constancea 83.2: Besa papillaeformis Setchell: An Example of Progenetic Heterochrony
		Heterochrony, in particular progenesis — the process by which sexual maturity is accelerated relative to somatic development — is inferred as the mechanism for the evolutionary origin of Besa, in which perennating crusts give rise to uprights that become reproductive while remaining miniaturized.
		One of the processes postulated to play an important role in evolution is heterochrony, the phenomenon of change in the relative rate or timing of specific developmental events in a descendant relative to its ancestor (Gould 1977, McKinney and McNamara 1991, Friedman and Carmichael 1998, Li and Johnston 2000).
		McKinney, M.L. and McNamara, K.J. Heterochrony: The Evolution of Ontogeny.
	ucjeps.berkeley.edu /constancea/83/fredericq_lopez/besa.html (4293 words)

	Heterochrony (quotes from Stephen J. Gould and others)
		This is an example of dissociated heterochrony, whereby different organs (or growth fields) can undergo heterochronies (or remain uneffected) independent of what is going on elsewhere.This process had long been known as "mosaic evolution"...
		This has proved to be one of the major stumbling blocks in studies of heterochrony for over a century.
		By comparing the ontogenies of certain species to such a sequence, she found, for example, some groups that are clearly paedomorphic, in singing continuous songs and other traits (ratain memicry and have many syllable types).
	www.neoteny.org /a/stephenjgould.html (7921 words)

	PAST - Case study 5 - Heterochrony in a fossil rhynchosaur reptile (Site not responding. Last check: 2007-10-14)
		Heterochrony involves differences in the timing of developmental processes; thus detailed, preferably statistical, analyses of ontogenetic series are of considerable value in unravelling and identifying the track and mode of heterochronic trends in phylogeny.
		Benton & Kirkpatrick (1989) have studied heterochrony in the rhynchosaur Scaphonyx.
		Benton & Kirkpatrick (1989) used some of the allometric trends in their sample to illustrate a peramorphic evolutionary cline towards a broader skull type (for example SKULL vs. FRONW and PARW).
	folk.uio.no /ohammer/past/study5.html (327 words)

	RedNova News - Science - Teaching the new baby to talk with biologists! (Site not responding. Last check: 2007-10-14)
		Heterochrony involves three kinds of evolutionary changes in the timing of development: 'changes in rate, changes in onset time, and changes in offset time.
		Understanding heterochrony is a prerequisite for applying these powerful constructs to comparative developmental psychology.
		Incidentally, heterochrony is a subfield of evolutionary developmental biology (that is, 'evodevo') that uses cladistic methodology for comparing developmental patterns of closely related species [Raff, 1996].
	www.rednova.com /news/stories/2/2003/10/02/story110.html (2479 words)

	ScienceWeek
		Although Ernst Haeckel (1834-1919) coined the term as a complement to heterochrony in 1866, few studies have detected heterotopy or even considered the possibility that it might play a role in morphological evolution.
		Heterochrony is of interest in part because it can produce novelties constrained along ancestral ontogenies, and hence result in parallelism between ontogeny and phylogeny.
		3) The authors argue that the study of heterochrony has been bound to an analytical formalism that virtually precludes the recognition of heterotopy, so the authors provide a new framework for the construction of ontogenetic trajectories and illustrate their analysis in a phylogenetic context.
	scienceweek.com /2003/sa031226-4.htm (807 words)

	mca-heterochrony
		The material object itself, the sword, functions in these processes, both long-term and short-term, not simply through its material affordances – the heirloom sword will do just as well or better to cut off a head and is already in hand – but also through the meanings and value it bears.
		But it is not just obviously textual records of past events that can function semiotically to mediate heterochrony and the integration of social activities over very different timescales.
		Semiotic mediation and heterochrony as the ground of social integration across time and space did not begin with literate texts, or even most likely with specialized record-keeping.
	www-personal.umich.edu /~jaylemke/webs/time/mca-heterochrony.htm (1236 words)

	Intraspecific heterochrony and life history evolution: decoupling somatic and sexual development in a facultatively ...
		Intraspecific heterochrony and life history evolution: decoupling somatic and sexual development in a facultatively paedomorphic salamander.
		We question the primacy of morphological data in studies of heterochrony, and instead suggest that principal sources of fitness, such as life history characteristics, are not only the chief targets of selection, but changes in them may necessitate changes in other (subordinate) elements of the organism.
		Increased attention to the intimate connection between life history evolution and heterochrony is the most promising route to a better understanding of both.
	www.uga.edu /srel/Reprint/2268.htm (303 words)

	Evolutionary patterns in ontogenetic transformation: from laws to regularities (Site not responding. Last check: 2007-10-14)
		The term heterochrony is now used to refer to a developmental process as well as to an evolutionary pattern.
		We propose to reduce the dependence of current thinking about heterochrony on the concept of "timing" and instead focus on the organization of sequences of developmental events in ontogeny.
		Current reductionist attempts to apply the morphological terminology and postulates of classical heterochrony concepts to cellular and molecular (genetic) aspects of morphogenesis are problematic.
	www.ijdb.ehu.es /9604/a845.htm (312 words)

	Natural Selection (Site not responding. Last check: 2007-10-14)
		Natural selection can employ this range of shape and the process of growth by which it arises to produce evolutionary changes in size and shape by changing the rate of growth or the timing of growth.
		Evolutionary change in the rate or timing of growth (or both) that leads to differences in size or shape between individuals of an ancestral population and their descendents is heterochrony.
		Allometry, heterochrony, and evolutionary trends in the Jurassic oyster Gryphaea.
	www.geology.buffalo.edu /sprg/heterochrony.html (1083 words)

	Behavioral and morphological correlates of heterochrony in Hispaniolan Palm-Tanagers
		We documented the occurrence of heterochrony for morphological and behavioral characters in two species of Hispaniolan Palm-Tanager.
		Phaenicophilus palmarum is age-dimorphic in morphology and foraging behavior with 55% (n = 126) of specimens classified as juveniles.
		Behavioral and morphological correlates of heterochrony in Hispaniolan Palm-Tanagers.
	www.uga.edu /srel/Reprint/1863.htm (304 words)

	Evolutionary divergence of populations (Site not responding. Last check: 2007-10-14)
		It was found that different forms (morphotypes) of these barbs acquire their specific characters at different stages of ontogenesis, and that in a number of forms it happens unusually late, in the period of sexual maturation (Mina, 2001; Mina et al.,1996, 1996b, 2001; Dgebuadze et al., 1999).
		Regarding populations as hierarchically organized selfreproducing groups of individuals able to repair localized damages, a concept of conservation of freshwater fishes was proposed based on consideration of faunas of isolated regions as principal units of conservation (Mina,1992a; Mina, Golubtsov, 1995; Golubtsov et al., 2002).
		Alekseyev S.S. [On the role of heterochrony in appearance of morphological differences between"large" and "small" African barbs (Barbus, Cyprinidae) (in accordance with data obtained in studies of species of Ethiopian fauna)].
	idbras.idb.ac.ru /POSTNAT/micro.htm (1107 words)

	Powell's Books - Shapes of Time: The Evolution of Growth and Development by Ken Mcnamara (Site not responding. Last check: 2007-10-14)
		Kenneth J. McNamara delves into the living and fossil worlds to show how animals and plants have evolved when the carefully orchestrated pattern of embryological development is gently nudged off-course — producing species that may have developed beyond their ancestors, or others that have developed less, looking more like overgrown juveniles.
		Heterochrony accounts for the Peter Pan syndrome, in which some species look like their ancestors' children.
		Central to his inquiry is the phenomenon known as heterochrony, changes in the rate and timing of the growth and development of individuals.
	www.powells.com /rau?s=71&d=20050201&i=17-0801855713-0 (289 words)

	Developmental heterochrony
		Each curve in the upper graph is an instance of the developmental distribution function for an individual at a particular age.
		Note: I refer to developmental heterochrony as 'internal heterochrony' to distinguish it from 'external heterochrony' which refers to the heterarchical connections between levels of a complex dynamical system across widely different (non-adjacent) timescales of its organizational processes.
		In the particular case of human development, the N+1 timescale is that of the community and change in the distribution function for the community as a whole.
	academic.brooklyn.cuny.edu /education/jlemke/papers/devel-heterochrony.htm (927 words)

	Gerd HP (Site not responding. Last check: 2007-10-14)
		At a first level primary pattern formation is altered through heterochrony in terms of pedomorphic truncations of skeletogenic processes.
		Diffusable morphogens have an influence on the symmetries of limb patterning and could thus underlie some of the changes of primary patterns, but the chemical model alone cannot account for the patterns of secondary change, nor can it explain homology of limb elements.
		A heterochrony and fusion mechanism based on branching and segmentation processes is the only model that allows to be predictive about evolutionary transformations of limb patterns and these predictions can be empirically tested.
	www.univie.ac.at /morphology/proj/limbpatt.htm (368 words)

	Disruption of the Hoxd-13 gene induces localized heterochrony leading to mice with neotenic limbs. (Site not responding. Last check: 2007-10-14)
		Vertebrate Hoxd genes are sequentially activated during the morphogenesis and pattern formation of the limb.
		In limbs, abnormalities such as a reduction in the length of some bony elements, loss of phalanges, bone fusions, and the presence of an extra element were observed.
		We propose that the mutation induces local heterochrony, as illustrated by an important retardation in limb morphogenesis.
	www.bioscience.org /knockout/ref/dolle2.htm (165 words)

	Ontogeny and Phylogeny (Stephen Jay Gould) - review
		He couples a grasp of the broad sweep of the history of ideas with an eye for the finest detail.
		He then discusses the evolutionary and ecological significance of heterochrony.
		He stresses the need to consider the immediate advantages to organisms of developmental changes, as well as long term and retrospective macroevolutionary explanations.
	dannyreviews.com /h/Ontogeny_and_Phylogeny.html (492 words)

	246 HETEROCHRONY AND PAEDOMORPHOSIS (Site not responding. Last check: 2007-10-14)
		The standard techniques of allometry do not provide an optimal metric for heterochrony because they subtly reinforce a prejudice directed against the dissociability upon which heterochrony depends.
		Heterochrony is no longer the disruption of a primary correlation, but rather the simple expression of differential changes in the independent vectors of size and shape.
		The bivariate regression is not "truth"; it is a valid picture that directs thought in ways that are rarely appreciated because alternatives are not presented.
	www.stephenjaygould.info /library/text/ontogeny/p0246.htm (320 words)

	Time’s arrow: heterochrony and the evolution of development (Site not responding. Last check: 2007-10-14)
		ABSTRACT The concept of heterochrony, which denotes a change in the relative timing of developmental events and processes in evolution, has accompanied attempts to link evolution and development for well over a century.
		During this time the definition of heterochrony and the application of the concept have varied and by the late 1990’s, many questioned the usefulness of the concept.
		However, in the past decade studies of heterochrony have been revitalized by a new focus on developmental sequence, an examination of heterochrony in explicit phylogenetic contexts and increasing tendencies to examine the heterochrony of many kinds of events, including cellular, molecular and genetic events.
	www.ijdb.ehu.es /abstract.03078/a613.htm (161 words)

	228 HETEROCHRONY AND PAEDOMORPHOSIS (Site not responding. Last check: 2007-10-14)
		Thus, in this second category of heterochrony, de Beer mixed an aspect of acceleration with one of retardation.
		De Beer's four admissible categories of heterochrony reduce to two processes with a common basis: acceleration and retardation.
		We simplify de Beer's complexities by distinguishing true heterochrony from the introduction of new features, and by focusing on processes instead of results.
	www.stephenjaygould.info /library/text/ontogeny/p0228.htm (352 words)

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