Clinal variation

Lachaise D, Lemeunier F, Veuille M (1981) Clinal variation in male genitalia in Drosophila teissieri Tsacas. Am Nat 117 600-608... 

An extensive survey of the essential oils from populations of Junipems virginiana from Texas to Ontario indicates that clinal variation occurs. Further, the proposed introgression between J. virginiana and J. ashei which had been thought to occur widely in Texas in areas of overlap between the two species does not appear to exist, based on analysis of the essential oils. This was also confirmed by analysis of micromorphological characters (von Rudloff, 1975). 

Kokkini, S., E. Hanlidou, R. Karousou. and T. Lanaras. 2004. Clinal variation of Mentha pulegium essential oils along the climatic gradient of Greece. LEsserU OilR., 16 588-593. 

The variation ranges of all the torsion angles are very wide from 145 ° for T5-T8, through 172°-180° for T3, T4 up to 225 °-228 ° for T2 and Tl. This means that individual enamine fragments may adopt, in respect of particular torsion angles, any conformation from syn-c ina through sjw-periplanar to anti-clinal, obviously, some of these conformations are observed more frequently than others. 

A knowledge of the stereochemistry of an elimination reaction is of major importance not only to a more complete understanding of the mechanism but also in connection with the use of beta-eliminations in synthetic processes. A variation in the dihedral angle between the bonds undergoing fragmentation not only influences the rate but can also modify the yield of olefin and influence the direction of elimination in secondary and tertiary structures. The terms anti-clinal and "syn-clinal" are used to describe the stereochemistry of the transition state when the dihedral angle between the parts being eliminated is 180°, 0°, 120° and 60°, respectively (761. The stereochemistry of beta-eliminations, the subject of numerous papers, has been extensively reviewed . ... 

Variation - or biodiversity as it now tends to be called - may occur at the individual, intraspecific, specific or community/ecosystem level, or in DNA, cell, phenotype or population. It is inseparable from the effective study of biology. In past centuries, advances in biology were limited by the assumption that organisms were analogous to physical machines, and this restriction persisted until the thrall of Plato s essences were lifted and the invariant species of Carl Linnaeus became first the polytypic species of the late nineteenth century, and thence the clinally varying, highly polymorphic metapopulation of the mid twentieth century (Mayr,... 

Monoterpene composition also does not conform to clinal patterns of variation. Chang and Hanover (1991) separated range-wide populations into 2 east-west clusters, with the dividing line east of the Ontario-Manitoba border. The authors suggested that the clusters represented a branching of populations during the last glaciation. 

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