scholarly journals Correlated evolution and independent contrasts

1997 ◽  
Vol 352 (1352) ◽  
pp. 519-529 ◽  
Author(s):  
Trevor Price
Keyword(s):  
Adaptive Radiation ◽  
Related Species ◽  
Past History ◽  
Evolutionary Model ◽  
Closely Related Species ◽  
Correlated Evolution ◽  
Mean Values ◽  
Contrast Method ◽  
Independent Contrast

The use of the independent contrast method in comparative tests is studied. It is assumed that: (i) the traits under investigation are subject to natural selection; (ii) closely related species are similar because they share many characteristics of their niche, inherited from a common ancestor; and (iii) the current adaptive significance of the traits is the focus of investigation. The main objection to the use of species values in this case is that third variables which are shared by closely related species confound the relationship between the focal traits. In this paper, I argue that third variables are largely not controlled by the contrast methods, which are designed to estimate correlated evolution. To the extent that third variables also show correlated evolution, the true relationship among the traits of interest will remain obscured. Although the independent contrast method does not resolve the influence of third traits it does, in principle, provide a greater resolution than the use of the species mean values. However, its validity depends on the applicability of an evolutionary model which has a substantial stochastic component. To illustrate the consequences of relaxing this assumption I consider an alternative model on an adaptive radiation, where species come to fill a fixed niche space. Under this model, the expected value for the contrast correlation differs from that for the species correlation. The two correlations differ because contrasts reflect the historical pattern of diversification among species, whereas the species values describe the present–day relationships among the species. If the latter is of interest, I suggest that assessing significance based on the species correlations can be justified, providing that attention is paid to the role of potentially confounding third traits. Often, differences between contrast and species correlations may be biologically informative, reflecting changes in correlations between traits as an adaptive radiation proceeds; contrasts may be particularly useful as a means of investigating past history, rather than current utility of traits.

Evolution of primate orphan proteins

2009 ◽  
Vol 37 (4) ◽  
pp. 778-782 ◽  
Author(s):  
Macarena Toll-Riera ◽  
Robert Castelo ◽  
Nicolás Bellora ◽  
M. Mar Albà
Keyword(s):  
Related Species ◽  
Sequence Divergence ◽  
Orphan Genes ◽  
Closely Related Species ◽  
Protein Coding ◽  
Rapid Sequence ◽  
Adaptive Processes ◽  
Mechanisms Of Formation ◽  
Novel Protein

Genomes contain a large number of genes that do not have recognizable homologues in other species. These genes, found in only one or a few closely related species, are known as orphan genes. Their limited distribution implies that many of them are probably involved in lineage-specific adaptive processes. One important question that has remained elusive to date is how orphan genes originate. It has been proposed that they might have arisen by gene duplication followed by a period of very rapid sequence divergence, which would have erased any traces of similarity to other evolutionarily related genes. However, this explanation does not seem plausible for genes lacking homologues in very closely related species. In the present article, we review recent efforts to identify the mechanisms of formation of primate orphan genes. These studies reveal an unexpected important role of transposable elements in the formation of novel protein-coding genes in the genomes of primates.

Niche conservatism predominates in adaptive radiation: comparing the diversification of Hawaiian arthropods using ecological niche modelling

2019 ◽  
Vol 127 (2) ◽  
pp. 479-492 ◽  
Author(s):  
Anna E Hiller ◽  
Michelle S Koo ◽  
Kari R Goodman ◽  
Kerry L Shaw ◽  
Patrick M O’Grady ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Phylogenetic Signal ◽  
Niche Overlap ◽  
Oceanic Islands ◽  
Niche Conservatism ◽  
Environmental Niche ◽  
Niche Modelling ◽  
Closely Related Species ◽  
Species Comparisons

Abstract The role of the environmental niche in fostering ecological divergence during adaptive radiation remains enigmatic. In this study, we examine the interplay between environmental niche divergence and conservatism in the context of adaptive radiation on oceanic islands, by characterizing the niche breadth of four Hawaiian arthropod radiations: Tetragnatha spiders (Tetragnathidae Latreille, 1804), Laupala crickets (Gryllidae Otte, 1994), a clade of Drosophila flies (Drosophilidae Fallén, 1823) and Nesosydne planthoppers (Delphacidae Kirkaldy, 1907). We assembled occurrence datasets for the four lineages, modelled their distributions and quantified niche overlap. All four groups occupy the islands in distinct ways, highlighting the contrasting axes of diversification for different lineages. Laupala and Nesosydne have opposite environmental niche extents (broad and narrow, respectively), whereas Tetragnatha and Drosophila share relatively intermediate tolerances. Temperature constrains the distributions of all four radiations. Tests of phylogenetic signal suggest that, for Tetragnatha and Drosophila, closely related species exhibit similar environmental niches; thus, diversification is associated with niche conservatism. Sister species comparisons also show that populations often retain similar environmental tolerances, although exceptions do occur. Results imply that diversification does not occur through ecological speciation; instead, adaptive radiation occurs largely within a single environment.

scholarly journals Comparative analyses for adaptive radiations

2000 ◽  
Vol 355 (1403) ◽  
pp. 1599-1605 ◽  
Author(s):  
Paul H. Harvey ◽  
Andrew Rambaut
Keyword(s):  
Brownian Motion ◽  
Adaptive Radiation ◽  
Related Species ◽  
Character Evolution ◽  
Motion Model ◽  
Closely Related Species ◽  
Branch Lengths ◽  
Character Variation ◽  
Brownian Motion Model ◽  
Adaptive Radiations

Biologists generally agree that most morphological variation between closely related species is adaptive. The most common method of comparative analysis to test for co–evolved character variation is based on a Brownian–motion model of character evolution. If we are to test for the evolution of character covariation, and we believe that characters have evolved adaptively to fill niches during an adaptive radiation, then it is appropriate to employ appropriate models for character evolution. We show here that under several models of adaptive character evolution and coevolution during an adaptive radiation, which result in closely related species being more similar to each other than to more distantly related species, cross–species analyses are statistically more appropriate than contrast analyses. If the evolution of some traits fits the Brownian–motion model, while others evolve to fill niches during an adaptive radiation, it might be necessary to identify the number of relevant niche dimensions and the modes of character evolution before deciding on appropriate statistical procedures. Alternatively, maximum–likelihood procedures might be used to determine appropriate transformations of phylogenetic branch lengths that accord with particular models of character evolution.

scholarly journals A comparative study of the gastric ossicles of Trichodactylidae crabs (Brachyura: Decapoda) with comments on the role of diet and phylogeny in shaping morphological traits

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5028 ◽  
Author(s):  
Débora A. Carvalho ◽  
Pablo A. Collins ◽  
Renata Lima-Gomes ◽  
Célio Magalhães ◽  
Maria Victoria Torres ◽  
...  
Keyword(s):  
Comparative Study ◽  
Related Species ◽  
Morphological Traits ◽  
Closely Related Species ◽  
Natural Diet ◽  
Freshwater Crabs ◽  
The Family ◽  
Feeding Structure ◽  
And Function

The gastric armature of decapod foregut is a feeding structure that sparks controversial debates about the role dietary and historical components have in shaping its morphological traits. Having previous information about the natural diet is an interesting way to gather evidence on this issue. For the present study, we analyzed the morphological traits of gastric ossicles involved directly in the maceration of food in nine species of freshwater crabs of the family Trichodactylidae (Brachyura: Decapoda) representing five genera, three tribes and two subfamilies. The analyzed gastric ossicles were quite consistent among closely related species, suggesting that the observed traits had a clear phylogenetic component. However, it was also noted that the morphological traits of the gastric teeth of trichodactylid crabs match well with the natural diet and presented likeness with general features of other species with a similar trophic habit. We discuss the influence of phylogeny and function on the design of morphological traits and propose to quantify the role of phylogeny and function in shaping morphological traits through the analysis of phylogenetic signals.

The influence of testosterone on cognitive performance in bonobos and chimpanzees

Behaviour ◽  
2015 ◽  
Vol 152 (3-4) ◽  
pp. 407-423 ◽  
Author(s):  
Victoria Wobber ◽  
Esther Herrmann
Keyword(s):  
Related Species ◽  
Cognitive Abilities ◽  
Comparative Research ◽  
Pan Paniscus ◽  
Steroid Hormone ◽  
Cognitive Tasks ◽  
Closely Related Species ◽  
Proximate Mechanisms ◽  
And Performance

Levels of the steroid hormone testosterone have been found to impact diverse features of cognition from spatial memory to decision-making regarding risk, both in humans and other animals. However less is known about whether closely-related species differ in their testosterone-cognition relationships in line with pressures shaping each species’ cognitive evolution. We therefore examined relationships between testosterone and cognition in two-closely related species that differ markedly in their social behaviour, cognition, and patterns of testosterone production: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We presented individuals of both species with a battery of 16 cognitive tasks and determined whether performance on these tasks correlated with average testosterone level. We found that among male chimpanzees, high levels of testosterone correlated with higher performance in numerous tasks, including tasks assessing spatial cognition and physical cognitive abilities more broadly. Meanwhile, in male bonobos we found no correlations between testosterone and performance on the cognitive tasks, and found no correlations in females of either species. Building on prior comparative research, these results suggest that bonobos and chimpanzees differ critically in the proximate mechanisms influencing their cognitive capacities, and that in particular the role of testosterone in shaping behaviour and cognition differs dramatically between the two species.

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