分子进化研究中的一些问题

本文在强调生物系统的层次结构和非线性特征的基础上,就分子进化研究中存在的某些认识上的和方法学上的问题,提出了作者的观点和简要分析。     

EVOLUTIONARY TRENDS IN THE GENUS GINKGO

Three main independent phylogenetic groups within Ginkgoales , consisting of different families, are suggested. It is considered impossible to deduce the genus Ginkgo from any other genus by means of fossil evidence known at present.
The oldest finds of Ginkgo date from the Lower Jurassic. During the Cretaceous, increasing polymorphy in foliar remains indicates the rise of new species. During the Lower Cretaceous there also appears a type of leaf known both as G. adiantoides and as G. paradiantoides. This leaf is from the gross morphological and the anatomical point of view almost identical with the Tertiary and Recent Ginkgo populations, thus making a direct ancestry between the present-day Ginkgo and those of the Lower Cretaceous likely. By Lower Tertiary times a considerable reduction has taken place leaving only one gross morphological type of leaf, that of G. adiantoides. This is suggested to be identical with G. biloba. Although there is no positive evidence, it can be assumed that the final reduction of the genus, to its present-day East Asiatic home, has taken place during the Pleistocene period.     

GENOMICS IN THE LIGHT OF EVOLUTIONARY TRANSITIONS

Molecular biology has entrenched the gene as the basic hereditary unit and genomes are often considered little more than collections of genes. However, new concepts and genomic data have emerged, which suggest that the genome has a unique place in the hierarchy of life. Despite this, a framework for the genome as a major evolutionary transition has not been fully developed. Instead, genome origin and evolution are frequently considered as a series of neutral or nonadaptive events. In this article, we argue for a Darwinian multilevel selection interpretation for the origin of the genome. We base our arguments on the multilevel selection theory of hypercycles of cooperative interacting genes and predictions that gene‐level trade‐offs in viability and reproduction can help drive evolutionary transitions. We consider genomic data involving mobile genetic elements as a test case of our view. A new concept of the genome as a discrete evolutionary unit emerges and the gene–genome juncture is positioned as a major evolutionary transition in individuality. This framework offers a fresh perspective on the origin of macromolecular life and sets the scene for a new, emerging line of inquiry—the evolutionary ecology of the genome.     

PERSPECTIVE: EVOLUTIONARY PATTERNS IN THE FOSSIL RECORD

The study of large-scale evolutionary patterns in the fossil record has benefited from a diversity of approaches, including analysis of taxonomic data, ecology, geography, and morphology. Although genealogy is an important component of macroevolution, recent visions of phylogenetic analysis as replacing rather than supplementing other approaches are short-sighted. The ability of traditional Linnaean taxa to document evolutionary patterns is mainly an empirical rather than a theoretical issue, yet the use of these taxa has been dismissed without thorough evaluation of their empirical properties. Phylogenetic analysis can help compensate for some of the fossil record's imperfections. However, the shortcomings of the phylogenetic approach have not been adequately acknowledged, and we still lack a rigorous comparison between the phylogenetic approach and probabilistic approaches based on sampling theory. Important inferences about the history of life based on nongenealogical data have later been corroborated with genealogical and other analyses, suggesting that we risk an enormous loss of knowledge and understanding if we categorically dismiss nonphylogenetic data.     

THE EVOLUTIONARY DYNAMICS OF SPITE IN FINITE POPULATIONS

Spite, the shady relative of altruism, involves paying a fitness cost to inflict a cost on some recipient. Here, we investigate a density dependent dynamic model for the evolution of spite in populations of changing size. We extend the model by introducing a dynamic carrying capacity. Our analysis shows that it is possible for unconditionally spiteful behavior to evolve without population structure in any finite population. In some circumstances spiteful behavior can contribute to its own stability by limiting population growth. We use the model to show that there are differences between spite and altruism, and to refine Hamilton’s original argument about the insignificance of spite in the wild. We also discuss the importance of fixing the measure of fitness to classify behaviors as selfish or spiteful.     

EVOLUTIONARY CHANGE IN THE MORPHOLOGICAL COMPLEXITY OF THE MAMMALIAN VERTEBRAL COLUMN

The notion that morphological complexity increases in evolution is widely accepted in biology and paleontology. Several possible explanations have been offered for this trend, among them the suggestion that it has an active forcing mechanism, such as natural selection or the second law of thermodynamics. No such mechanism has yet been empirically demonstrated, but testing is possible: if a forcing mechanism has operated, the expectation is that complexity would have increased in evolutionary lineages more frequently than it decreased. However, a quantitative analysis of changes in the complexity of the vertebral column in a random sample of mammalian lineages reveals a nearly equal number of increases and decreases. This finding raises the possibility that no forcing mechanism exists, or at least that it may not be as powerful or pervasive as has been assumed. The finding also highlights the need for more empirical tests.     

中国白垩纪被子植物花粉的宏演化

根据中国白垩纪被子植物花粉产出记录与形态构造分析以及与世界其它地区产出顺序比较,假设中国白垩纪被子植物花粉的宏演化序列,共划分为１０个发育阶段,归于７个形态演化期：１）欧特里夫期至早巴列姆期的无口器类演化期（含：１：１网纹无口器粉发育阶段）;２）晚巴列姆至晚阿普梯期的单沟类演化期（含：２：１。棒纹粉发育阶段;２．２,星粉－棒纹粉发育阶段）;３）早,中阿尔必期的三沟类演化期（含：３．１,三沟粉类－星     

EVOLUTIONARY SHIFTS IN THE SPECTRAL PROPERTIES OF SPIDER SILKS

We measured the reflectance properties of unpigmented silks spun by a systematic array of primitive (Deinopoidea) and derived (Araneoidea) aerial, web-spinning spiders, as well as silks spun by Araneomorphae and Mygalomorphae spiders that do not spin aerial webs. Our data show that all of the primitive aerial web spinners produce catching silks with a spectral peak in the ultraviolet (UV), and cladistic analysis suggests that high UV reflection is the primitive character state for silk spectral properties. In contrast, all of the derived aerial web spinners produce silks that are spectrally flat or characterized by reduced reflectance in the UV. Correlated with the evolution of these catching silks is a 37-fold increase in species number and apparent habitat expansion. This suggests that the unique silk proteins spun by the araneoids have been important to their ecological and evolutionary diversity.     

COMPLEX PALEOZOIC FILICALES IN THE EVOLUTIONARY RADIATION OF FERNS

Filicalean frond segments bearing indusiate sori with gradate development have been discovered in Pennsylvanian deposits of eastern North America. The specimens combine characters of Schizaeaceae, Gleicheniaceae, Cyatheaceae and Hymenophyllaceae, and together with data from other sources, indicate that the Filicales were in the midst of an evolutionary radiation during the late Paleozoic. Evidence from fossil and extant species prompts the hypothesis that filicalean ferns originated near the base of the Carboniferous, and have undergone three major evolutionary radiations.