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Pro bonum publico: Eu já destaquei aqui neste blog o Journal of Biology. Open-access [acesso grátis], com muitos bons artigos. Fator de impacto do JoB: 3.50.

Recentemente eu li dois bons artigos no JoB:

“Cryptic biodiversity in a changing world”, por Luciano B Beheregaray e Adalgisa Caccone.

Journal of Biology 2007, 6:9doi:10.1186/jbiol60

The electronic version of this article is the complete one and can be found online here.


Abstract

DNA studies are revealing the extent of hidden, or cryptic, biodiversity. Two new studies challenge paradigms about cryptic biodiversity and highlight the importance of adding a historical and biogeographic dimension to biodiversity research.

Minireview

Biodiversity, the variety of life, is one of nature's most exuberant manifestations. Scientists have long struggled to understand the evolutionary and ecological processes underlying the origin, distribution and maintenance of biodiversity. This dilemma is faced not only by researchers working in undersampled regions such as tropical rainforests and marine habitats, but also by those studying densely sampled and well characterized temperate systems. The problem is partly generated by the difficulty of detecting and measuring biodiversity solely on the basis of morphological information. Despite the central and unrivalled position of morphology-based taxonomy in biodiversity research, human visual perception will probably never quite suffice to capture natural complexity. A good example of this is the escalating number of DNA-based studies reporting cryptic species [1,2]. Cryptic, or sibling, species are discrete species that are difficult, or sometimes impossible, to distinguish morphologically and thus have been incorrectly classified as a single taxon. Cryptic species are found from the poles to the Equator and in all major terrestrial and aquatic taxonomic groups [2,3]. For example, a recent meta-analysis yielded 2,207 articles reporting cryptic species in all metazoan phyla and classes, including 996 new species in insects, 267 in mammals, 151 in fishes and 94 in birds [2]. Similarly, a recent report shows that global biodiversity in protozoa is often cryptic and significantly higher than previously considered [4].

Analysis of the genetic diversity distributed within 'species' provides a powerful framework for recognizing cryptic species. In this context, historical considerations are important, as the current genetic architectures of many species have been shaped by global climatic fluctuations, environmental gradients and the separation of populations by geographic barriers during the past 3 million years and, to a lesser extent, by more ancient physical processes [5,6].

E este aqui:

“Small changes, big results: evolution of morphological discontinuity in
Mammals”, de Rodney L Honeycutt.

Abstract

Comparative morphological and developmental studies, including a recent comparative study of tooth development among the Afrotherian mammals, are indicating the types of genetic mechanisms responsible for the evolution of morphological differences among major mammalian groups.

Mini-Review

The orders of eutherian mammals are especially characterized by morphological differences in the skull and dentition, related to different requirements for processing food, and in the postcranial skeleton, which is adapted for varied modes of locomotion. The evolutionary biologist George Gaylord Simpson [1] defined major morphological discontinuities among higher taxa, specifically the orders of mammals, as the result of macroevolution or ‘quantum evolution’. In many cases, these discontinuities lack fossil evidence of transitions, appearing as what Simpson termed ‘breaks in the fossil record’, and thus probably result from major adaptive
shifts. Along with the accepted processes of microevolutionary change at the population level, Simpson also suggested that mutations with large phenotypic effects “unquestionably provide a theoretically excellent mechanism” for large changes in morphology. These discontinuities, as well as the short time periods associated with the diversification of many mammalian orders, are still presenting a challenge to paleontologists, geneticists and developmental biologists attempting to reconstruct the ‘Mammal Tree of Life’, a first step in understanding the geological and biological processes that are responsible for mammalian diversity [2]. For many years now, differences in gene regulation rather than dramatic differences in gene structure have been proposed as the most probable explanations for morphological and functional differences, including those between ourselves and our closest living primate relative, the chimpanzee [3]. For example, genes involved in craniofacial muscle development [4], higher brain functions [5,6], and speech and language [7] have been found to show potentially significant differences in rate of evolution or pattern of expression between chimps and humans.

This paper can be found online here.

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