scholarly journals Unit Character Variation in Rodents

1921 ◽  
Vol 2 (3) ◽  
pp. 125 ◽  
Author(s):  
L. C. Dunn
Keyword(s):  
Unit Character ◽  
Character Variation

scholarly journals Phenotypic Dimensions of Reproductive Isolation Between Northern and Melissa Blue Butterflies in the Rocky Mountains

2011 ◽  
Vol 33 ◽  
pp. 101-105
Author(s):  
Zachariah Gompert
Keyword(s):  
Reproductive Isolation ◽  
Biological Diversity ◽  
Butterfly Species ◽  
General Importance ◽  
Greater Yellowstone Area ◽  
Single Character ◽  
Character Variation ◽  
Greater Yellowstone ◽  
Species Speciation

Biological diversity results from speciation, which generally involves the splitting of an ancestral species into descendant species due to adaptation to different niches or the evolution of reproductive incompatibilities (Coyne and Orr 2004). The diverse flora and fauna of the world, including the native inhabitants of the Greater Yellowstone Area (GYA), exist as a result of the speciation process. The central role speciation plays in generating biological diversity imbues importance to our understanding of this process. The general importance of a thorough understanding of speciation is amplified because of the current high rates of extinction on the planet. This is because a long term solution to the present extinction crisis will require maintaining the processes that create species (speciation) not simply preventing extinction. However, many central questions regarding speciation remain to be answered. One fundamental question in speciation research is whether diverging species are isolated (i.e., prevented from interbreeding) due to differences in one, a few, or many characters and whether each of these character differences results from different alleles at a few or many genes. For example, speciation and reproductive isolation might involve divergence along multiple phenotypic axes, such as mate preference, habitat use or preference, and phenology (the timing of life-cycle events). Alternatively, isolation could result from differentiation of a single character. I propose to address this question by assessing patterns of variation for a suite of characters across a hybrid zone between two butterfly species. This is possible because patterns of character variation across hybrids zones allow for inferences about reproductive isolation (Barton and Hewitt 1985).

scholarly journals Phenotypic Dimensions of Reproductive Isolation Between Northern and Melissa Blue Butterflies in the Rocky Mountains

2009 ◽  
Vol 32 ◽  
pp. 97-100
Author(s):  
Zachariah Gompert
Keyword(s):  
Reproductive Isolation ◽  
Biological Diversity ◽  
Butterfly Species ◽  
General Importance ◽  
Greater Yellowstone Area ◽  
Single Character ◽  
Character Variation ◽  
Greater Yellowstone ◽  
Species Speciation

Biological diversity results from speciation, which generally involves the splitting of an ancestral species into descendant species due to adaptation to different niches or the evolution of reproductive incompatibilities (Coyne and Orr 2004). The diverse flora and fauna of the world, including the native inhabitants of the Greater Yellowstone Area (GYA), exist as a result of the speciation process. The central role speciation plays in generating biological diversity imbues importance to our understanding of this process. The general importance of a thorough understanding of speciation is amplified because of the current high rates of extinction on the planet. This is because a long term solution to the present extinction crisis will require maintaining the processes that create species (speciation) not simply preventing extinction. However, many central questions regarding speciation remain to be answered. One fundamental question in speciation research is whether diverging species are isolated (i.e., prevented from interbreeding) due to differences in one, a few, or many characters and whether each of these character differences results from different alleles at a few or many genes. For example, speciation and reproductive isolation might involve divergence along multiple phenotypic axes, such as mate preference, habitat use or preference, and phenology (the timing of life-cycle events). Alternatively, isolation could result from differentiation of a single character. I propose to address this question by assessing patterns of variation for a suite of characters across a hybrid zone between two butterfly species. This is possible because patterns of character variation across hybrids zones allow for inferences about reproductive isolation (Barton and Hewitt 1985).

Individuals, hierarchies and processes: towards a more complete evolutionary theory

Paleobiology ◽  
1984 ◽  
Vol 10 (2) ◽  
pp. 146-171 ◽  
Author(s):  
Elisabeth S. Vrba ◽  
Niles Eldredge
Keyword(s):  
Downward Causation ◽  
Species Selection ◽  
Process Selection ◽  
Term Selection ◽  
Hierarchical Levels ◽  
Character Variation ◽  
Long Term Trend ◽  
Interlevel Causation ◽  
Selection Of

Hierarchy is a central phenomenon of life. Yet it does not feature as such in traditional biological theory. The genealogical hierarchy is a nested organization of entities at ascending levels. There are phenomena common to all levels: (1) Entities such as genomic constituents, organisms, demes, and species are individuals. (2) They have aggregate characters (statistics of characters of subparts), but also emergent characters (arising from organization among subparts). Character variation changes by (3) introduction of novelty and (4) sorting by differential birth and death. Causation of introduction and sorting of variation at each level may be (5) upward from lower levels, (6) downward from higher levels, or (7) lodged at the focal level. The term “selection” applies to only one of the possible processes which cause sorting at a focal level. Neo-Darwinian explanations are too narrow, both in the levels (of genotypes and phenotypes) and in the directive process (selection) which are stressed. The acknowledgment of additional, hierarchical phenomena does not usually extend beyond lip service. We urge that interlevel causation should feature centrally in explanatory hypotheses of evolution. For instance, a ready explanation for divergence in populations is “selection of random mutants.” But upward causation from genome dynamics (or downward causation from the hierarchical organism) to the directed introduction of mutants may be more important in a given case. Similarly, a long-term trend is traditionally explained as additive evolution in populations. But sorting among species may be the cardinal factor, and the cause may not be species selection but upward causation from lower levels. A general theory of biology is a theory of hierarchical levels—how they arise and interact. This is a preliminary contribution mainly to the latter question.

Colorimetric analysis of the dorsal plumage of the red-eyed vireo (Aves: Vireonidae) in Canada

1971 ◽  
Vol 49 (3) ◽  
pp. 417-419 ◽  
Author(s):  
Jon C. Barlow ◽  
Nikki Williams
Keyword(s):  
Boreal Forest ◽  
Test Procedure ◽  
Sums Of Squares ◽  
Climatic Variable ◽  
Colorimetric Analysis ◽  
Dominant Wavelength ◽  
Simultaneous Test ◽  
Character Variation ◽  
Recording Spectrophotometer ◽  
East West

The red-eyed vireo is widely distributed across Canada in the boreal forest. Collections were made at seven localities from central Alberta to central Quebec and potential variation in the olive-green dorsal plumage was analyzed with a recording spectrophotometer equipped with a reflectance attachment. The trichromatic coefficients x (dominant wavelength) and y (purity) and Y (the percentage luminous reflection or brightness) were subjected to an overall analysis of variance, and means were treated with Gabriel's sums of squares simultaneous test procedure. Significant differences were demonstrated among locality samples for Y and x but the STP revealed discordant variation among locality samples, i.e. no east–west clines in character variation were shown. Regressions of Y and x on precipitation were nearly significant and could suggest a weak clinal relationship between color and this climatic variable as predicted by the ecogeographic rule of Gloger.

Australian Ogeria Distant (Heteroptera : Schizopteridae)

1990 ◽  
Vol 4 (4) ◽  
pp. 697 ◽  
Author(s):  
L Hill
Keyword(s):  
Character Variation

Ogeria Distant is redefined in comparison with Pachyplagia Gross. Thirteen species are newly described from Australia: O. spinera, O. convexicauda, O. quadridentata, O. illumata, O. obliquicauda, O. multidentata, O. dentispina, O. arcuata, O. parallela, O. bifurca, O. biprojecta, O. cavatica, and O. quadrivenata. The species are keyed. The occurrence of Ogeria outside Australia is outlined. A cryptic arboreal inquiline niche is suggested. Character variation in the genus is discussed.

Variation in morphology of Teucrium polium aggr. populations in Bulgaria

2010 ◽  
Vol 5 (6) ◽  
pp. 880-887 ◽  
Author(s):  
Dolja Pavlova ◽  
Magdalena Vasileva
Keyword(s):  
Corolla Tube ◽  
Leaf Length ◽  
Tube Length ◽  
Serpentine Soils ◽  
Stem Height ◽  
Multivariate Statistical ◽  
Discriminant Ability ◽  
Character Variation ◽  
Teucrium Polium ◽  
Vegetative Characters

AbstractThe aim of this study was to investigate natural serpentine and non-serpentine populations of Teucrium polium aggr. and to document the differences in their morphological traits, as well as estimate which characters are most likely contributing to differentiation of the populations. Nine populations distributed both on and off serpentine soils were investigated, and 12 different morphological features of 270 individuals were studied by univariate and multivariate statistical analyses. The results did not demonstrate clear delimitation of the serpentine from the non-serpentine populations. Using these ecotypes as classification factors in the discriminant analysis, it can be stated that stem height, leaf length in the fifth leaf pair, internode length between the fourth and the fifth leaf pairs, and corolla tube length are features with the greatest discriminant ability. The character variation was generally higher for the vegetative features, while reproductive features failed to demonstrate clear differences. The similarity groupings indicated by the cluster analysis were synchronous with groups distinguished by both the discriminant and PCA analyses. Significant differences were observed between sets of vegetative characters in all populations investigated.

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