EVOLUTION AND MORPHOGENETIC RULES: THE SHAPE OF THE VERTEBRATE LIMB IN ONTOGENY AND PHYLOGENY

The notion of a “developmental constraint” has become a catchphrase for a collection of poorly defined notions about how ontogeny affects phylogeny. In this paper, we shall attempt to define this idea more precisely by examining the vertebrate limb from three viewpoints. First, theoretical models of morphogenesis suggest several generalizations about how limb geometry is laid down during development. Comparative studies and experimental manipulations of developing limbs independently confirm these generalizations, which amount to a set of “construction rules” for determining how the major features of limb architecture are established in ontogeny. Armed with these rules, we can inquire how limb morphology can be varied during evolution and suggest a more precise operational definition of “developmental constraints” on morphological evolution.     

THE GROWTH AND NUTRITION OF THE AFRICAN ELEPHANT

In order to gain information on the growth and nutrition of two populations of elephants in Murchison Falls National Park, Uganda, their urinary excretions of hydroxyproline peptides (HP) were compared. Animals from the “south bank” population had a consistently higher level of excretion than corresponding animals from the “north bank” population. This indicated a faster rate of growth and a superior nutritional status in “south bank” animals at the time of sampling. The HP output from both populations was found to run parallel to the seasonal variation in rainfall and vegetation growth. Sampling from each population was carried out at a different time of the year and evidence is presented to show that the differences in the rate of growth are a direct result of this. It is concluded that any primary differences between the populations are small enough to be obliterated by seasonal changes. The effect of the seasons on the growth of the elephant is therefore examined in more detail, and a direct influence on collagen metabolism is discussed.     

THE JUST-ABOUT-RIGHT INTENSITY SCALE: FUNCTIONAL ANALYSES AND RELATION TO HEDONICS

This study assessed the meaning of just‐about‐right (JAR) categories when used with a 5‐point intensity scale. The panelists comprised both consumer and in‐house respondents. The JAR categories have various meanings as perceived by the respondents: “prefer product,”“very good,”“I like the product,”“like it very much,”“highly favorable,”“high acceptability,”“desirable like the product,”“best for the situation” and “correct.” Thus, the JAR meanings invoke preference and acceptability. This article presents two additional analyses to help the product tested. One method of analysis divides below‐JAR deviation from the above‐JAR deviation, with standard statistical procedures applied in each data set. The second method introduces the signal‐to‐noise ratio statistic for analyzing the relation of JAR to overall liking. Both analytic methods provide new ways to look at the JAR data, especially with respect to hedonics and product improvement.     

麋鹿行为谱及PAE编码系统

以麋鹿为实例,通过辨识行为的基本单元,区别了“姿势”、“动作”和“环境”,分解了动物行为的层次,然后根据行为的适应和社群机能归类,建立了以“姿势—动作—环境”为轴心的,以生态功能为分类依据的动物行为分类编码系统（PAE编码分类系统）。PAE编码分类系统以集合论为基础,明确了动物行为的三要素：姿势、动作和生态环境之间的关系,避免了笼统地将动物的姿势、动作和行为混为一谈的做法,区分了动物行为的组成要素和结构层次。行为要素编码方法为动物行为学研究提供了一个新的生长点。在继承前人工作的基础上,记录了有关麋鹿的姿势、动作和行为达200多种,还区别了各种行为在雄性、雌性和幼体之间的相对发生频次以及发生季节。     

基于中华鲟繁殖群体数量的长江中、下游生态环境考核指标

繁殖群体数量是中华鲟能否成功繁殖的重要影响因子, 建议作为长江生态考核的重要评价指标。根据重要种群参数和历史数据, 基于稳态转换理论和方法, 确定中华鲟繁殖群体数量指标的评估基准值和等级, 670尾以上为“优”、400—670尾为“良”、200—400尾为“中”、50—200尾为“差”、50尾以下为“极差”。水声学探测结果显示, 1998—2001年中华鲟繁殖群体数量指标评级为“良”; 2004—2012年三峡工程蓄水后至向家坝蓄水前评级为“中”; 2013—2020年评级为“极差”。为了复壮中华鲟野生种群, 建议修复葛洲坝下中华鲟产卵场功能, 大规模放流性成熟亲鱼和大规格个体, 建立国家级中华鲟保育中心。     

PRINCIPLISM AND THE ETHICAL APPRAISAL OF CLINICAL TRIALS

For nearly two decades, the process of reviewing the ethical merit of research involving human subjects has been based on the application of principles initially described in the U.S. National Commission's Belmont Report, and later articulated more fully by Beauchamp and Childress in their Principles of Biomedical Ethics. Recently, the use of ethical principles for deliberating about moral problems in medicine and research, referred to in the pejorative sense as “principlism”, has come under scrutiny. In this paper we argue that these principles can provide a foundation for the source of ethical appraisal of human research, but are not themselves wholly adequate for this purpose. Therefore, we further propose that (1) principles should be understood as heuristics that can be “specified” as described by DeGrazia (1992), and (2) that the principle-based approach should be supplemented by formally incorporating “sensitivity to context” into the evaluation of clinical trials     

OBAMA AND THE BIRACIAL FACTOR: THE BATTLE FOR A NEW AMERICAN MAJORITY

Written from a “critical perspective”, four new sociologies of Israel have recently been published. This article critically reviews the strengths and weaknesses of these new books, as well as the “new orthodoxy” that they propose with regard to Israel's past and present.     

SOLVING THE PARADOX OF STASIS: SQUASHED STABILIZING SELECTION AND THE LIMITS OF DETECTION

Despite the potential for rapid evolution, stasis is commonly observed over geological timescales—the so‐called “paradox of stasis.” This paradox would be resolved if stabilizing selection were common, but stabilizing selection is infrequently detected in natural populations. We hypothesize a simple solution to this apparent disconnect: stabilizing selection is hard to detect empirically once populations have adapted to a fitness peak. To test this hypothesis, we developed an individual‐based model of a population evolving under an invariant stabilizing fitness function. Stabilizing selection on the population was infrequently detected in an “empirical” sampling protocol, because (1) trait variation was low relative to the fitness peak breadth; (2) nonselective deaths masked selection; (3) populations wandered around the fitness peak; and (4) sample sizes were typically too small. Moreover, the addition of negative frequency‐dependent selection further hindered detection by flattening or even dimpling the fitness peak, a phenomenon we term “squashed stabilizing selection.” Our model demonstrates that stabilizing selection provides a plausible resolution to the paradox of stasis despite its infrequent detection in nature. The key reason is that selection “erases its traces”: once populations have adapted to a fitness peak, they are no longer expected to exhibit detectable stabilizing selection.     

THE STABILITY OF THE SYMBIOSIS BETWEEN DIOECIOUS FIGS AND THEIR POLLINATORS: A STUDY OF FICUS CARICA L. AND BLASTOPHAGA PSENES L.

Each Ficus species depends on a specific mutualistic wasp for pollination. The wasp breeds on the fig, each larva destroying a female flower. It is, however, not known why the wasps have not evolved the ability to use all female flowers. In “dioecious” figs, the wasp can only breed in the female flowers of the “male” trees, so that pollination of a female tree is always lethal. The wasps should therefore be selected to avoid female trees. Field data is presented showing that the fruiting phenology of the dioecious fig Ficus carica is such that this selection does not occur: syconia are not receptive at the same time on “male” and female trees. Most wasps are forced to emerge from the syconia of “male” trees at a time when they will not be able to reproduce, whether they avoid female trees or not. This aspect of the life cycle of the wasp, although noticed, has been obscured in most previous studies. It is shown that the fruiting phenology of Ficus carica, which stabilizes the symbiosis, is the result of short-term selective pressures on the male function of the trees. Such selective pressures suggest a possible pathway from monoecy to dioecy in Ficus under seasonal climates.     

GROWTH AND PROBABLE GAMETE FORMATION IN THE MARINE DINOFLAGELLATE CERATIUM SCHRANKII1

Growth and formation of probable gametes in clonal cultures of Ceratium schrankii Kofoid isolated from the Gulf of Naples were monitored at 15, 20 and 25°C (12:12h LD period). Sustained division rates (k) of 0.15 div d ^?1 at 15°C and elevated ones at 20°C (0.27 div d^?1) and 25°C (0.25 div d^?1) were obtained. “Gamete” formation occurred at each temperature with few “gametes” observed at 15°C, and the greatest numbers at 20° and 25°C. This process in each parent cell involved two successive divisions with the first division forming tow “pregametes” which, within a few hours, divided again to form four motile unicells. These “gametes” remained motile for at least 24 h and normally survived for no longer tahn 48 h. Depending on the initial population at the onset of “gamete” formation, the impact on Ceratium populations was to cause either a momentary pause in log growth or a reversible decline in the populaiton.     

PHYLOGENETIC TRANSITIONS IN THE CHLOROPLASTS OF THE ANTHOCEROTALES I. THE NUMBER AND ULTRASTRUCTURE OF THE MATURE PLASTIDS

Representatives of three genera of anthooerotes were examined: Phaeoceros, Notothylas, and Megaceros. Species of the first two genera were found to exemplify the typical anthocerote plastid condition. This condition is characterized by the presence in each cell of the gametophyte of only a single large chloroplast containing a “multiple” pyrenoid. The genus Megaceros, however, proved to be quite different. In two species of Megaceros the pyrenoid was observed to be composed of a highly subdivided thylakoid system of even greater complexity than the “multiple” pyrenoids of Phaeoceros. In another species only an indistinct “pyrenoid-like” area was noted while in a fourth species no evidence was found for any internal differentiation. Associated with these changes in plastid structure there are corresponding alterations in the number and the size of the chloroplasts. Together they indicate an evolutionary trend away from a primitive, algal-like condition to a more advanced land plant form.     

REPTILIAN PHYSIOLOGY AND THE FLIGHT CAPACITY OF ARCHAEOPTERYX

Current scenarios frequently interpret the Late Jurassic bird Archaeopteryx as having had an avian-type physiology and as having been capable of flapping flight, but only from “the trees downward.” It putatively lacked capacity for takeoff and powered flight from the ground upward. Data from extant reptiles indicate that if Archaeopteryx were physiologically reptilian, it would have been capable of ground upward takeoff from a standstill, as well as “trees downward” powered flight. This conclusion is based largely on a previously unrecognized attribute of locomotory (skeletal) muscle in a variety of extant reptiles: During “burst-level” activity, major locomotory muscles of a number of active terrestrial taxa generate at least twice the power (watts kg^?1 muscle tissue) as those of birds and mammals. Reptilian physiological status also helps resolve the apparently uneven development of various flight support structures in Archaeopteryx (e.g., well-developed flight features but relatively unspecialized pectoral girdle, supracoracoideus muscles, etc.). Endothermy and capacity for longer-distance powered flight probably evolved only in Early Cretaceous birds, which were the first birds to have a keeled sternum, strap-like coracoid, and hypocleidium-bearing furcula.     

RETRODISPLACEMENT OF THE ORAL AND ANAL OPENINGS IN DENDRASTERID SAND DOLLARS

In regular echinoids, the mouth opening (or peristome) and the anal opening (or periproct) are located centrally. In irregular echinoids, the peristome tends to shift toward the anterior end of the test, whereas the periproct typically shifts toward the posterior end. This produces an anatomically polarized morphology, which is consistent with functional expectations. In the dendrasterid sand dollars, however, the peristome and periproct have been displaced in the “wrong” directions; the peristome has shifted posteriorly, whereas the periproct has shifted anteriorly. These movements, which run counter to functional expectations, may be termed “retrodisplacements.” This study presents a new model for the development of the oral surface in dendrasterids. The model assumes that the “Dendraster pattern” of development (which occurs in dendrasterids) was derived from the older “Echinarachnius pattern” (which occurs in other northern Pacific sand dollars). The Echinarachnius pattern includes two successive phases of asymmetric growth: the first phase favors anterior growth, whereas the second phase favors posterior growth. These two phases are normally balanced, and at maturity, the test appears to be symmetrical. But if the second phase of unequal growth were suppressed through a heterochronic change in development, the effects on test development would be profound. On the aboral surface, the predicted effects include posterior displacement of the apical system. On the oral surface, the predicted effects include retrodisplacement of the peristome and periproct, as well as conspicuous changes in ambulacral and interambulacral development. In fact, all of the predicted effects are characteristic features of dendrasterids. The model assumes that the oral and aboral surfaces could be simultaneously affected by the same developmental processes. This assumption is supported by empirical evidence: in dendrasterids, there is a strong correlation between the displacement of the apical system (on the aboral surface) and the displacement of the peristome (on the oral surface). The displacement of the apical system (known as “apical eccentricity”) is regarded as a valuable adaptation, because it facilitates suspension feeding. But if oral and aboral development are linked, then selective pressure for apical eccentricity would simultaneously produce new oral characters as well. Thus, the retrodisplacement of the peristome and periproct in dendrasterids may be related to developmental constraints. These unusual characters may have little or no functional significance.     

AN ACOUSTIC LINK BETWEEN BLUE WHALES IN THE EASTERN TROPICAL PACIFIC AND THE NORTHEAST PACIFIC1

Blue whale calls in the eastern North Pacific Ocean consist of a two-part call often termed the A-B call. This call has been described for regions offshore of Oregon, Washington, and California, USA and the Sea of Cortez, Mexico (reviewed in Rivers 1997). Data collected from moored hydrophones in the eastern tropical Pacific (ETP) indicate that the A-B pattern is common in this region as well. There is consistency in this call type throughout the eastern North Pacific and throughout the year. This acoustic evidence indicates continuity between blue whales in the ETP and those found west of North America. The acoustic data suggest that the population of blue whales generally referred to as the “Californi/Mexico” stock might better be termed the “northeast Pacific” stock of blue whales.     

THE EVOLUTION OF CANALIZATION AND THE BREAKING OF VON BAER'S LAWS: MODELING THE EVOLUTION OF DEVELOPMENT WITH EPISTASIS

Evolution can change the developmental processes underlying a character without changing the average expression of the character itself. This sort of change must occur in both the evolution of canalization, in which a character becomes increasingly buffered against genetic or developmental variation, and in the phenomenon of closely related species that show similar adult phenotypes but different underlying developmental patterns. To study such phenomena, I develop a model that follows evolution on a surface representing adult phenotype as a function of underlying developmental characters. A contour on such a “phenotype landscape” is a set of states of developmental characters that produce the same adult phenotype. Epistasis induces curvature of this surface, and degree of canalization is represented by the slope along a contour. I first discuss the geometric properties of phenotype landscapes, relating epistasis to canalization. I then impose a fitness function on the phenotype and model evolution of developmental characters as a function of the fitness function and the local geometry of the surface. This model shows how canalization evolves as a population approaches an optimum phenotype. It further shows that under some circumstances, “decanalization” can occur, in which the expression of adult phenotype becomes increasingly sensitive to developmental variation. This process can cause very similar populations to diverge from one another developmentally even when their adult phenotypes experience identical selection regimes.     

THE ROLES OF LIFE‐HISTORY SELECTION AND SEXUAL SELECTION IN THE ADAPTIVE EVOLUTION OF MATING BEHAVIOR IN A BEETLE

Although there is continuing debate about whether sexual selection promotes or impedes adaptation to novel environments, the role of mating behavior in such adaptation remains largely unexplored. We investigated the evolution of mating behavior (latency to mating, mating probability and duration) in replicate populations of seed beetles Callosobruchus maculatus subjected to selection on life‐history (“Young” vs. “Old” reproduction) under contrasting regimes of sexual selection (“Monogamy” vs. “Polygamy”). Life‐history selection is predicted to favor delayed mating in “Old” females, but sexual conflict under polygamy can potentially retard adaptive life‐history evolution. We found that life‐history selection yielded the predicted changes in mating behavior, but sexual selection regime had no net effect. In within‐line crosses, populations selected for late reproduction showed equally reduced early‐life mating probability regardless of mating system. In between‐line crosses, however, the effect of life‐history selection on early‐life mating probability was stronger in polygamous lines than in monogamous ones. Thus, although mating system influenced male–female coevolution, removal of sexual selection did not affect the adaptive evolution of mating behavior. Importantly, our study shows that the interaction between sexual selection and life‐history selection can result in either increased or decreased reproductive divergence depending on the ecological context.     

PHYLOGENETIC AFFINITIES OF “CHANTRANSIA” STAGES IN MEMBERS OF THE BATRACHOSPERMALES AND THOREALES (RHODOPHYTA)1

This study evaluated the phylogenetic relationship among samples of “Chantransia” stage of the Batrachospermales and Thoreales from several regions of the world based on sequences of two genes—the plastid‐encoded RUBISCO LSU gene (rbcL) and the nuclear SSU ribosomal DNA gene (SSU rDNA). All sequences of “Chantransia macrospora” were shown to belong to Batrachospermum macrosporum based on both molecular markers, confirming evidence from previous studies. In contrast, nine species are now associated with “Chantransia pygmaea,” including seven species of the Batrachospermales and two of the Thoreales. Therefore, the presence of “C. macrospora” in a stream can be considered reliable evidence that it belongs to B. macrosporum, whereas the occurrence of “C. pygmaea” does not allow the recognition of any particular species, since it is associated with at least nine species. Affinities of “Chantransia” stages to particular taxa were congruent for 70.5% of the samples comparing the rbcL and SSU analyses, which were associated with the same or closely related species for both markers. Sequence divergences have been reported in the “Chantransia” stage in comparison to the respective gametophyte, and this matter deserves further attention.     

CAENOGENESIS,DEVELOPMENTAL VARIABILITY,AND EVOLUTION IN THE CARPUS AND TARSUS OF THE MARBLED NEWT TRITURUS MARMORATUS

In this paper, after a comparative analysis of the development of Triturus marmoratus, we explore the existence of caenogenetic events and their ontogenetic and phylogenetic consequences. The adult morphology of the Triturus marmoratus limb, in terms of number and spatial arrangement of skeletal elements, agrees with the general pattern of urodeles. The congruence in the typical pattern of adult morphology does not hint at the striking differences in embryonic development. These differences can be summarized as follows: 1) Presence of a “central axis” that develops in a distal-to-proximal direction. It originates in the basale commune giving rise to the centrale and the intermedium. Thus, there is no postaxial branching as found in Ambystoma mexicanum. 2) Again, unlike in Ambystoma mexicanum, we find a postaxial structure composed of the ulnare (fibulare)-distal carpal (tarsal) 4-metacarpal (metatarsal) 4 which is independent of the “digital arch.” 3) The (forelimb) digits, in particular, digits 1, 2, and 3, undergo disproportionate elongation. For example, the second digit, composed of a thin continuous, cartilaginous rod, becomes longer than the rest of the limb. Our study of the patterns of embryonic connectivity suggests the coexistence of three directions of growth and morphogenesis in the development of the Triturus marmoratus limb. 1) A proximo-distal one that gives rise to the preaxial axis, “primary axis,” and individual digits. 2) An anterio-posterior axis of development that gives rise to the “digital arch” and determines the number of digits. 3) A disto-proximal central axis that originates in the basale commune and sequentially generates the centrale and the intermedium. We speculate that heterochronic interspecific variation in the time of onset of limb bud formation is related to the degree of precocious digital elongation. Selection for long extremities in early larval stages, associated with functional demands for locomotion and balancing, may be the cause for the above listed changes in developmental pattern. Thus, the reported system is an example of how selection during ontogeny can result in the evolution of the developmental process.     

台湾海峡晚更新世人类肱骨化石

产自台湾海峡海底的人类右肱骨石化程度高; 个体大而粗壮 ,三角肌粗隆发育 ,骨干上下两半段不在同一纵轴上 ,形成 6 5°的夹角 ,这些显示不同于新石器时代和现代人的原始性状 ,其演化水平和日本的港川人及欧洲的克罗马农人相当。与人化石一同捞出的哺乳动物化石有古菱齿象、野马、最后鬣狗、达氏四不像鹿等 ,表明其时代为晚更新世晚期。