Gymnosperm Phylogeny — A commentary on the views of S. V. Meyen

In his important contribution to the literature on gymnosperm phylogeny, “Basic Features of Gymnosperm Systematics and Phylogeny as Evidenced by the Fossil Record,” Meyen (1984) uses the classical comparative method of the morphologist and the “congregational” method, i.e., grouping by common characters, of the taxonomist. The latter may have led him to categorize some taxa on the basis of superficially similar, non-homologous characters because he used no apparently objective method to distinguish homoplasy. For this and other reasons, Meyen’s hypothesis of evolutionary relationship among gymnosperms cannot, at present, be accepted as any nearer the truth than several competing proposals. The major innovation of Meyen’s proposed phylogeny is the recognition of the clade, Ginkgoopsida, coordinate with Cycadopsida and Pinopsida. Ginkgoopsida encompasses Calamopityaceae, Callistophytales, Glossopteridales, Peltaspermales, Caytoniales, and Ginkgoales, among others. These taxa are considered to be related because, in Meyen’s view, they share the common character of primary platyspermy — i.e., the presumed platyspermic seed-type of the basal group, Calamopityaceae, is considered to have evolved directly from the pteridophytic condition of an ancestral form. This basis for Ginkgoopsida is weakened by the facts that no seeds have been discovered in organic connection with any calamopityacean and, except for the poorly-preserved seed-like structure,Spermolithus, all seeds that occur earlier in the geologic record than fossils of the Calamopityaceae are radiospermic. It is possible, therefore, that even if the platyspermic seed,Lyrasperma, found in association with the calamopityacean,Stenomyelon, were borne by that plant, it is secondarily platyspermic, having evolved from a radiospermic ancestor. The foundation upon which Ginkgoopsida was erected seems, therefore, to be rather tenuous. Other characters used by Meyen, both reproductive and vegetative are discussed. Some which he considers significant, are interpreted to be unimportant in denoting phylogeny, while others are interpreted to support alternative hypotheses. Meyen proposes that the Ginkgoopsida evolved from archaeopterid progymnosperms. This viewpoint seems to be based largely on his erroneous belief thatArchaeopteris was probably a seed plant that bore compound leaves. There is no definitive evidence that supports the view thatArchaeopteris bore seeds. On the other hand, there is strong evidence to support the contention thatArchaeopteris produced simple leaves (Carluccio et al., 1966; Beck, 1971), not compound leaves. Meyen’s phylogenetic proposal is based on data that can be and, in part, have been differently interpreted by others. Consequently, it deserves the careful and critical evaluation of all students of gymnosperm phylogeny.     

What shapes the range edge of a dominant African savanna tree,Colophospermum mopane? A demographic approach

Climate is widely assumed to be the primary process that limits the distribution ranges of plants. Yet, savannas have vegetation not at equilibrium with climate, instead its structure and function are shaped by interactions between fire, herbivory, climate, and vegetation. I use the rich literature of a dominant African savanna woody plant, Colophospermum mopane, to demonstrate that climate and disturbance interact with each demographic stage to shape this species range limits. This synthesis highlights that climate‐based predictions for the range of C. mopane inadequately represents the processes that shape its distribution. Instead, seed bank depletion and rainfall limitation create a demographic bottleneck at the early seedling stage. The legacy of top‐kill from disturbance changes tree stand architecture causing a critical limitation in seed supply. Exposure to top‐kill at all demographic stages causes a vigorous resprouting response and shifts tree architecture from that of 1–2 stemmed tall trees to that of a short multi‐stemmed shrub. The shorter, multi‐stemmed shrubs are below the height threshold (4 m) at which they can produce seeds, resulting in shrub‐dominated landscapes that are effectively sterile. This effect is likely most pronounced at the range edge where top‐kill‐inducing disturbances increase in frequency. The proposed mechanistic, demographic‐based understanding of C. mopane''s range limits highlights the complexity of processes that interact to shape its range edges. This insight serves as a conceptual model for understanding the determinants of range limits of other dominant woody savannas species living in disturbance limited ecosystems.     

Method of fixing the heterotic effect—implementation on plants (on the hundredth anniversary of the birth of V.A. Strunnikov)

The article is devoted to the 100th anniversary of the outstanding world-renown Russian scientist Vladimir Alexandrovich Strunnikov, Academician, Professor, Head of Group of Developmental Cytology and Sex Regulation at Koltzov Institute of Developmental Biology and Head of genetic studies on silkworms in a number of sericulture institutes in CIS. Laureate of the State Prize of the USSR (1981), Hero of Socialist Labor (1990), awarded the I.I. Mechnikov Gold Medal, Academy of Sciences of the USSR (1981), founder of the theory explaining the origin of heterosis. One of his most significant achievements is the “Methods of Fixing the Heterosis Effect,” which makes it possible to abandon the production of hybrid seed and increase the yield of many crops by 20–50%. Fixing the gene complexes that determine the heterosis effect will become the “springboard” that will allow obtaining even more productive heterotic hybrids on the basis of new-generation varieties. The efficiency of this method in plant objects at the organismal and molecular levels was shown in the All-Russia Research Institute of Rice. A modification of this method reducing its laboriousness and increasing its efficiency was developed.     

Heritability: What's the point? What is it not for? A human genetics perspective

Genetica - In this paper, we explain the concept of heritability and describe the different methods and the genotype–phenotype correspondences used to estimate heritability in the specific...     

Lymphotoxin and TNF: How it all began—A tribute to the travelers

The journey from the discoveries of lymphotoxin (LT) and tumor necrosis factor (TNF) to the present day age of cytokine inhibitors as therapeutics has been an exciting one with many participants and highs and lows; the saga is compared to that in “The Wizard of Oz”. This communication summarizes the contributions of key players in the discovery of the cytokines and their receptors, the changes in nomenclature, and the discovery of the LT family’s crucial role in secondary and tertiary lymphoid organs. The remarkable advances in therapeutics are detailed as are remaining problems. Finally, special tribute is paid to two pioneers in the field who have recently passed away: Byron H. Waksman and Lloyd Old.     

Annexin V binding perturbs the cardiolipin fluidity gradient in isolated mitochondria. Can it affect mitochondrial function?

The phosholipid bilayer fluidity of isolated mitochondria and phospholipid vesicles after calcium-dependent binding of annexin V was studied using EPR spectroscopy. The membranes were probed at different depths by alternatively using cardiolipin, phosphatidylcholine, or phosphatidylethanolamine spin labeled at position C-5 or C-12 or C-16 of the beta acyl chain. Computer-aided spectral titration facilitated observing and quantitating the EPR spectrum from phospholipid spin labels affected by annexin binding, and spectral mobility was calibrated by comparison with standard spectra scanned at various temperatures. In most cases it was found that binding of the protein to the membranes makes the inner bilayer more rigid up to acyl position C-12 than afterward, in agreement with the previously observed effect in SUVs [Megli, F. M., Selvaggi, M., Liemann, S., Quagliariello, E., and Huber, R. (1998) Biochemistry 37, 10540-10546]. Moreover, in isolated mitochondrial membranes, cardiolipin apparently is more readily affected than the other main phospholipids, while in vesicles made from mitochondrial phospholipids, the different species are affected in essentially the same way. This behavior is consistent with the existence of distinct cardiolipin pools in mitochondria, and with the already advanced hypothesis that these domains are the binding site for annexin V to the isolated organelles [Megli, F. M., Selvaggi, M., De Lisi, A., and Quagliariello, E. (1995) Biochim. Biophys. Acta 1236, 273-278]. Keeping in mind the funcional importance of cardiolipin in the mitochondrial membrane, the question is raised as to whether the observed influence of annexin V binding to this phospholipid and its consequent local fluidity alteration might affect the mitochondrial functionality, at least in vitro.     

ATP-dependent Clp Proteases in Photosynthetic Organisms— A Cut Above the Rest!

Proteases are critical regulatory factors for many metabolic cellular processes as well as being vital for degrading proteins damaged during environmental stresses. Many of those responsible for targeted protein degradation require the hydrolysis of ATP, and one class that has attracted much attention recently are the Clp proteases. They are among the best characterized proteases to date, and were the first shown to rely on an ATPase regulatory subunit possessing molecular chaperone activity, which functions both within the proteolytic complex and independently. A range of Clp proteins has been identified from many different bacteria and eukaryotes, with by far the greatest number and diversity of forms in oxygenic photobionts such as cyanobacteria and higher plants. Functionally, Clp proteins have also evolved into one of the more critical proteolytic enzymes within photobionts, and it is now somewhat of a paradox that we currently know least about Clp protease functions in the photosynthetic organisms, where they have their most important roles. This discrepancy is now being addressed, with studies on Clp protein in cyanobacteria and, in an increasing number, in higher plants.     

The search for Fort Armstrong: Dendroarchaeology of the Williamson “Snow Hill” Plantation,Cherokee County,Alabama, U.S.A.

Tree-ring dating has been applied to three historical log buildings in northeastern Alabama to determine if any of the structures could have been associated with historic Fort Armstrong. Fort Armstrong was constructed near Cedar Bluff, Alabama by militia members under the ultimate command of Andrew Jackson to support actions against the “Red Stick” faction of Creeks during the First Creek War in 1813. Comparison of tree-ring samples from the structures with reference chronologies from nearby living trees strongly indicates that none of the three buildings was constructed prior to about 1849 and therefore could not have been contemporaneous with Fort Armstrong. However, the dating does indicate that the buildings are Antebellum in age and were very likely constructed as part of the early development of Snow Hill Plantation. As such these structures provide insight into the physical and cultural patterns of an early Alabama plantation. We believe that this project represents the first dendroarchaeological research reported from Alabama.     

What about R.A. Fisher's statement of the "too good" data of J.G. Mendel's Pisum paper?

Mendel was accused by Fisher that his observed data, which corresponded to expectations, were too good to be true, and, further, that Mendel, growing only 10 plants per offspring, disregarded in his genotypical analysis the loss of recessives by assuming a ratio of 1:2 instead of 1.1126:1.8874. In contrast, it is proposed here that all chi-square statistics of genetic segregations fall short because the variance of genetic segregations is smaller and not of a binomial type as assumed. Furthermore, this variance and the corresponding chi-square statistics are not homogeneous in different segregation types. Consequently, it is not possible to summarize the different chi-square statistics as Fisher did. It is only in this way that he was able to obtain his unrealistic result (a probability of "seven times in 100,000 cases"). Regarding Fisher's second accusation, it should be taken into account that Mendel selected his 10 plants from offspring with a finite and not an infinite number of entities. Although this number is different from offspring to offspring, the average number is about 30. This means that the loss of recessives must be calculated by using a hypergeometric and not a binomial model as Fisher did. Consequently, the real deviation from the 1:2 ratio can be disregarded.     

Spinitheca gen. nov.—A new orthothecimorph hyolith genus from the Lower Cambrian of the Siberian platform

The study of the morphology of orthothecimorph hyoliths from the Atdabanian (Lower Cambrian) of the Siberian Platform allowed the recognition of the new genus and species Spinitheca sysoievi gen. and sp. nov.     

What Genomic Sequence Information Has Revealed About Vibrio Ecology in the Ocean—A Review

To date, the genomes of eight Vibrio strains representing six species and three human pathogens have been fully sequenced and reported. This review compares genomic information revealed from these sequencing efforts and what we can infer about Vibrio biology and ecology from this and related genomic information. The focus of the review is on those attributes that allow the Vibrios to survive and even proliferate in their ocean habitats, which include seawater, plankton, invertebrates, fish, marine mammals, plants, man-made structures (surfaces), and particulate matter. Areas covered include general information about the eight genomes, each of which is distributed over two chromosomes; a discussion of expected and unusual genes found; attachment sites and mechanisms; utilization of particulate and dissolved organic matter; and conclusions.