Genetic analysis of sympatric char populations in western Alaska: Arctic char (Salvelinus alpinus) and Dolly Varden (Salvelinus malma) are not two sides of the same coin

The North Pacific Ocean has been of great significance to understanding biogeography and speciation in temperate faunas, including for two species of char (Salmonidae: Salvelinus) whose evolutionary relationship has been controversial. We examined the morphology and genetics (microsatellite and mitochondrial DNA) of Arctic char (Salvelinus alpinus) and Dolly Varden char (Salvelinus malma) in lake systems in western Alaska, the eastern and western Arctic, and south of the Alaskan Peninsula. Morphologically, each lake system contained two forms: one (Arctic char) largely confined to lake habitats and characterized by greater numbers of pyloric caeca, gill rakers, and shallower bodies, and another (Dolly Varden) predominated in adjacent stream habitats and was characterized by fewer pyloric caeca, gill rakers, and deeper bodies. MtDNA partial (550 bp) d-loop sequences of both taxa were interspersed with each other within a single 'Bering' clade and demographic inferences suggested historical gene flow from Dolly Varden to Arctic char had occurred. By contrast, the taxa were strongly differentiated in sympatry across nine microsatellite loci in both lakes. Our data show that the two taxa are highly genetically distinct in sympatry, supporting their status as valid biological species, despite occasional hybridization. The interaction between these species highlights the importance of the North Pacific, and Beringia in particular, as an evolutionary wellspring of biodiversity.     

Dental trait expression at the enamel-dentine junction of lower molars in extant and fossil hominoids

Discrete dental traits are used as proxies for biological relatedness among modern human populations and for alpha taxonomy and phylogeny reconstruction within the hominin clade. We present a comparison of the expression of lower molar dental traits (cusp 6, cusp 7, trigonid crest pattern, and protostylid) at the enamel-dentine junction (EDJ) in a variety of extant and fossil hominoid taxa, in order to assess the contribution of the EDJ to the morphology of these traits at the outer enamel surface (OES). Molars (n=44) were imaged nondestructively using high-resolution microCT, and three-dimensional surface models of the EDJ and OES were created to compare trait expression at each surface. Our results indicate that these dental traits originate at the EDJ, and that the EDJ is primarily responsible for their degree of expression at the OES. Importantly, variable trait morphology at the EDJ (often not easily recognizable at the OES) indicates that different developmental processes can produce traits that appear similar at the enamel surface, suggesting caution in intra- and intertaxonomic comparisons. The results also highlight the importance of the EDJ for understanding the morphological development of discrete traits, and for establishing graded scales of variation to compare trait frequency among groups for the purpose of taxonomic and/or phylogenetic analysis. Finally, this study demonstrates that imaging the EDJ of both worn and unworn fossil hominin teeth provides a novel source of information about tooth development and variation in crown morphology.     

The ecological effect of phenotypic plasticity — Analyzing complex interaction networks (COIN) with agent-based models

Analyzing complex dynamics of ecological systems is complicated by two important facts: First, phenotypic plasticity allows individual organisms to adapt their reaction norms in terms of morphology, anatomy, physiology and behavior to changing local environmental conditions and trophic relationships. Secondly, individual reactions and ecological dynamics are often determined by indirect interactions through reaction chains and networks involving feedback processes.

We present an agent-based modeling framework which allows to represent and analyze ecological systems that include phenotypic changes in individual performances and indirect interactions within heterogeneous and temporal changing environments. We denote this structure of interacting components as COmplex Interaction Network (COIN).

Three examples illustrate the potential of the system to analyze complex ecological processes that incorporate changing phenotypes on the individual level:

• A model on fish population dynamics of roach (Rutilus rutilus) leads to a differentiation in fish length resulting in a conspicuous distribution that influences reproduction capability and thus indirectly the fitness.

• Modeling the reproduction phase of the passerine bird Erithacus rubecula (European Robin) illustrates variation in the behavior of higher organisms in dependence of environmental factors. Changes in reproduction success and in the proportion of different activities are the results.

• The morphological reaction of plants to changes in fundamental environmental parameters is illustrated by the black alder (Alnus glutinosa) model. Specification of physiological processes and the interaction structure on the level of modules allow to represent the reaction to changes in irradiance and temperature accurately.

Applying the COIN-approach, individual plasticity emerges as a structural and functional implication in a self-organized manner. The examples illustrate the potential to integrate existing approaches to represent detailed and complex traits for higher order organisms and to combine ecological and evolutionary aspects.

乙烯利诱导网纹甜瓜主蔓两性花花芽分化的形态和解剖学研究

以网纹甜瓜(Cucumis melo L.var. reticulatus Naud.)品种’西域1号’为试验材料,于幼苗3叶1心期喷施浓度为150 mg·L^-1的乙烯利溶液进行处理,诱导主蔓形成两性花,以清水为对照,分别对处理和对照植株不同时期的主蔓和侧蔓花芽分化过程进行形态和解剖学观察。结果表明：经乙烯利处理后,幼苗植株主蔓花原基持续向两性花分化,最终发育形成两性花。未经处理植株的主蔓花原基在分化早期与两性花发育过程相同,但在雌蕊出现后,不再继续发育,最终发育形成雄花。处理植株主蔓两性花发育过程与侧蔓两性花发育过程相同。     

大花睡莲种子至种苗的发育形态学研究

为了探索睡莲目与泽泻目个体发育早期的共性,追踪观察了大花睡莲种子至种苗的发育过程。结果发现：种子胚苗端发育先于根端;萌发时首先出现下胚轴,继而末端膨大产生下胚轴毛,最后胚根分化;初生根短命;节生根后发生但较粗壮,浮水叶开始产生时根茎第一节以下部分随即烂掉;种苗的各器官中均有发达的通气组织等基本上与芡、泽泻和黑藻相似。     

中国产异蒴藓属（Lyellia）植物形态解剖比较观察

利用扫描电镜法、徒手切片法对中国产的2种异蒴藓进行观察分析。分别观察了孢子大小、颜色、叶片和茎的长度和宽度等。结果表明异蒴藓属植物叶片的一些形态学和解剖学性状表现出了金发藓科植物所共有的特征,异蒴藓属在金发藓科中气孔较明显属于进化性状,而孢壁纹饰则属于原始性状。     

Phosphatized rare star-like mouth disc of Punctatus and its functional morphology from the earliest Cambrian of the South Shaanxi China

The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion. In this prominent stage, rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped. In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi, China in 2003. By studying on functional morphology and analogy with mouthpart of Punctatus, there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth. The appearance of coelenterates marks the real beginning of metazoan evolution. Therefore, it has the prominent position in the origin and evolutionary history of organisms. Perhaps the star-like organism represents the early types of coelenterate with original tentacles. These new materials provide new evidence for the origin, evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.     

DNA barcode discovers two cryptic species and two geographical radiations in the invasive drosophilid Zaprionus indianus

Comparing introduced to ancestral populations within a phylogeographical context is crucial in any study aiming to understand the ecological genetics of an invasive species. Zaprionus indianus is a cosmopolitan drosophilid that has recently succeeded to expand its geographical range upon three continents (Africa, Asia and the Americas). We studied the distribution of mitochondrial DNA (mtDNA) haplotypes for two genes (CO‐I and CO‐II) among 23 geographical populations. mtDNA revealed the presence of two well‐supported phylogenetic lineages (phylads), with bootstrap value of 100%. Phylad I included three African populations, reinforcing the African‐origin hypothesis of the species. Within phylad II, a distinct phylogeographical pattern was discovered: Atlantic populations (from the Americas and Madeira) were closer to the ancestral African populations than to Eastern ones (from Madagascar, Middle East and India). This means that during its passage from endemism to cosmopolitanism, Z. indianus exhibited two independent radiations, the older (the Eastern) to the East, and the younger (the Atlantic) to the West. Discriminant function analysis using 13 morphometrical characters was also able to discriminate between the two molecular phylads (93.34 ± 1.67%), although detailed morphological analysis of male genitalia using scanning electron microscopy showed no significant differences. Finally, crossing experiments revealed the presence of reproductive barrier between populations from the two phylads, and further between populations within phylad I. Hence, a bona species status was assigned to two new, cryptic species: Zaprionus africanus and Zaprionus gabonicus, and both were encompassed along with Z. indianus and Zaprionus megalorchis into the indianus complex. The ecology of these two species reveals that they are forest dwellers, which explains their restricted endemic distribution, in contrast to their relative cosmopolitan Z. indianus, known to be a human‐commensal. Our results reconfirm the great utility of mtDNA at both inter‐ and intraspecific analyses within the frame of an integrated taxonomical project.     

Nitric oxide regulates axonal regeneration in an insect embryonic CNS

In higher vertebrates, the central nervous system (CNS) is unable to regenerate after injury, at least partially because of growth-inhibiting factors. Invertebrates lack many of these negative regulators, allowing us to study the positive factors in isolation. One possible molecular player in neuronal regeneration is the nitric oxide (NO)-cyclic guanosine-monophosphate (cGMP) transduction pathway which is known to regulate axonal growth and neural migration. Here, we present an experimental model in which we study the effect of NO on CNS regeneration in flat-fillet locust embryo preparations in culture after crushing the connectives between abdominal ganglia. Using whole-mount immunofluorescence, we examine the morphology of identified serotonergic neurons, which send a total of four axons through these connectives. After injury, these axons grow out again and reach the neighboring ganglion within 4 days in culture. We quantify the number of regenerating axons within this period and test the effect of drugs that interfere with NO action. Application of exogenous NO or cGMP promotes axonal regeneration, whereas scavenging NO or inhibition of soluble guanylyl cyclase delays regeneration, an effect that can be rescued by application of external cGMP. NO-induced cGMP immunostaining confirms the serotonergic neurons as direct targets for NO. Putative sources of NO are resolved using the NADPH-diaphorase technique. We conclude that NO/cGMP promotes outgrowth of regenerating axons in an insect embryo, and that such embryo-culture systems are useful tools for studying CNS regeneration.