Hypermorphosis

Hypermorphosis

 

(hyperspecialization), a type of phylogenetic development leading to disruption of the relationship of an organism to its environment as a result of hypertrophy of certain organs. Examples of hypermorphosis are the upper canine teeth of the fossil saber-toothed tiger (Machairodus), the horns of the giant reindeer, and the tusks of the contemporary boar (the babirusa). A frequent case of hypermorphosis is the general enlargement of body dimensions, resulting in disruption of the coordination of certain organs. Hypermorphosis indicates a lag in the evolution of the organism to adapt to changes in the conditions of its existence. When there is considerable manifestation of hypermorphosis, the consequence is extinction.

REFERENCE

Shmal’gauzen, I. I. Puti i zakonomernosti evoliutsionnogo prot-sessa. Moscow-Leningrad, 1940.
References in periodicals archive ?
Kelly CD, Adams DC (2010) Sexual selection, ontogenetic acceleration, and hypermorphosis generates male trimorphism in Wellington tree weta.
agilis via hypermorphosis. However, without relevant information about the morphology and development of ancestral and extant Caddo,this matter will remain an exercise in speculation.
Of these processes, we found neoteny (decreased developmental rate in descendant), progenesis (earlier offset), and acceleration (increased rate) to be more commonly reported than hypermorphosis (delayed offset) or predisplacement (earlier onset).
Another example of both paedomorphosis and peramorphosis shaping the evolution of a single character is the derivation of larger sepals of Veronica chamaedrys by a slower development (neoteny) and a delayed offset (hypermorphosis) from the smaller sepals of Veronicastrum virginicum (Kampny et al., 1993).
Thus, it was suggested that populations of subalpine hay meadows are the peramorphic variants derived from populations of alpine grassland by predisplacement in vegetative gr owth and that populations of subalpine limestone grassland are peramorphic variants derived from populations of alpine grassland by hypermorphosis in vegetative growth.
There is thus a later developmental offset (hypermorphosis) in small homostylous flowers.
Despite the general acceptance of the theoretical framework, its implementations differ widely, and this has led to new confusion in terminology and underlying concepts, and to contradictory interpretations of the same evolutionary events [e.g., the controversy about the relative role of neoteny or hypermorphosis in human evolution (McKinney and McNamara 1991)].
Therefore, in a particular case, the question is not whether there is, for example, either neoteny or hypermorphosis, but what the relative importance of these processes is for the observed evolutionary change.
In a bivariate allometric plot of a trait against size, an extension of the ancestral allometric trajectory to larger sizes in a descendant species is called "allometric hypermorphosis," whereas termination of growth at smaller sizes is "allometric progenesis." Increase or decrease in slope is "allometric acceleration" or "allometric neoteny," respectively, and a larger or smaller y-intercept is termed "allometric predisplacement" or "allometric postdisplacement," respectively.
For neoteny and acceleration, the expected patterns result only if the trait alone is affected, and for progenesis and hypermorphosis if both the trait and size are affected by the heterochronic change.
These do not represent dimensional allometry but may be the result of developmental hypermorphosis in which a developmental growth pattern is played out at the same rate (or rate of increase) over a lengthened period of time (either the entire lifespan or just the juvenile stage) (Gould, 1977).
However, descriptive developmental studies of inflorescences (as opposed to flowers) are few (e.g., Grimes, 1996), and the possibility of differences in onset or offset of growth (i.e., predisplacement, postdisplacement, hypermorphosis, progenesis sensu McKinney & McNamara, 1991) cannot be ruled out.