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2. Comparison of natural and artificial hybridization in Potamogeton
- Creator:
- Kaplan, Zdeněk and Fehrer, Judith
- Type:
- article and TEXT
- Subject:
- clonality, cpDNA, hybridization, internal transcribed spacer, plant taxonomy, Potamogeton, recurrent origin, sterility, and variation
- Language:
- English
- Description:
- The first attempt to artificially hybridize species of Potamogeton resulted in the hybrid P. perfoliatus × P. gramineus. The morphological features, reproductive behaviour and molecular markers of the offspring of this experimental hybridization were compared with those of the parental species and natural hybrids of the same assumed parentage. A phenotype corresponding to that of the natural hybrid P. × nitens was acquired from an experimental cross between P. perfoliatus and P. gramineus. All plants, both natural and artificial, of this hybrid were consistently sterile. They showed the ITS variants of both parental taxa, which is consistent with biparental inheritance of nuclear DNA. The experimental hybrid was used to test the maternal inheritance of chloroplast DNA in Potamogeton. Sequences of a chloroplast intergenic spacer (rpl20- rps12) were identical with those of the female parent. Then, the directions of the crosses resulting in the natural hybrids were investigated. Of five natural populations of P. × nitens, P. gramineus was the maternal parent of two and P. perfoliatus of three populations. The frequency of hybridization events and rise of hybrids are discussed.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/
3. Maternal age and endogenous variation in maternal influence on photoperiodic response in the progeny diapause in Trichogramma embryophagum (Hymenoptera: Trichogrammatidae)
- Creator:
- Reznik, Sergey Ya., Kats, Tatyana S., Umarova, Tatsiya Ya., and Voinovich , Nataliya D.
- Type:
- article, model:article, and TEXT
- Subject:
- Parasitoids, Hymenoptera, Trichogramma, physiology, ecology, diapause, photoperiod, maternal age, and variation
- Language:
- English
- Description:
- A laboratory study was carried out on photoperiodic control of prepupal diapause in the egg parasitoid Trichogramma embryophagum (Hartig). All experiments were conducted with an isofemale parthenogenetic strain. The maternal generation was reared at 20°C and photoperiods of L:D = 3:21, 6:18, 9:15, 12:12, 15:9, 18:6, 21:3 or 24:0. The tendency to diapause in the progeny was estimated by rearing the daughter generation at 15°C in the dark. Experiments revealed a long-day type response based on maternal influence on the progeny prepupal diapause. However, significant endogenous fluctuations in the pattern of the photoperiodic curve were revealed in successive laboratory generations reared under constant conditions. The left threshold day-length was very variable, while the right threshold kept relative constancy. Experiments with individual females sequentially offered new host eggs demonstrated that the probability of the progeny entering diapause depends significantly on maternal age. At 20°C and 18L : 6D, the percentage of diapause was maximal (ca 15%) in the progeny eclosed from the eggs laid during 1st - 2nd days of maternal life. Then the proportion of diapausing progeny decreased to 0-5% at days 9-11 of female life and later slightly increased in 15-17 days old females. Thus, endogenous factors play an important role in maternal influence on progeny diapause, particularly in environments close to threshold temperature and photoperiod.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
4. Předložky v(e), na a jejich konkurence ve statických prostorověrelačních významech
- Creator:
- Ocelák, Radek
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- preposition, prepositional meaning, variation, static spatial relation, localization, předložka, předložkový význam, konkurence, statická prostorová relace, and lokalizace
- Language:
- Czech
- Description:
- The article provides a classification of the static spatial relations expressed by the prepositions v(e) and na (in most contexts translated as in and on) in contemporary Czech, based on the data of The Czech National Corpus and the internet. Both prepositions, used with a nominal phrase in the locative, may refer to several distinct relations between the determined and the determining spatial object (usually, but not necessarily, various types of localization). For each of the prepositions, these relations are classified with special attention to possible variation between the two (and some other) prepositions in describing the same situation. Such detailed analysis of prepositional meanings and variation seems useful e. g. in advanced learning of Czech as a foreign language. The description of the static spatial meanings of the prepositions is a proper basis for describing their other spatial (dynamic) as well as non-spatial (ab-stract) meanings.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
5. Standarddeutsch messen?: Frequenz und Varianz negativ-konditionaler Konnektoren
- Creator:
- Konopka, Marek and Waßner, Ulrich H.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- corpus linguistics, grammar, standard German, adverbials, variation, korpusová lingvistika, gramatika, standardní němčina, adverbiale, and varianta
- Language:
- Czech
- Description:
- Among the German negative-conditional connectors in the range of consequens markers there are the prototypical cases sonst and ansonsten. Morphological alternatives (sonsten and ansonst) are rarely mentioned in contemporary grammars and dictionaries but they actually occur with considerable frequency. The four connectors are used in two functions: as a conjunctional adverb which can occupy various positions within the sentence or as a specific kind of subordinating conjunction (Postponierer). The large IDS corpora allow us to reveal specific distributions of the lexemes and of their different ways of use. Comparing the frequencies and the distributions can indicate to which extent the phenomena are part of the standard language. The paper will report on the results and demonstrate how the findings can be deduced from the corpora. It will draw conclusions for assessing the acceptability of the variants and the extent to which they can be considered standard language additionally testing statistical instruments to visualise and calculate the variance of phenomena as association plots and DPnorm. and Prototypickými případy těchto konektorů jsou v němčině slova sonst (jinak) a ansonsten (jinak). Jejich morfologické alternativy sonsten a ansonst se v současných gramatikách a slovnících téměř nezmiňují, avšak jejich frekvence v textech není zanedbatelná. Všechny tyto čtyři konektory se užívají ve dvou funkcích: jako spojkové adverbium, jež může ve větě zaujímat různé pozice, nebo jako specifický druh subordinační konjunkce (postponent). Velké korpusy IDS umožňují odhalovat specifickou distribuci těchto lexémů a různých způsobů jejich užívání. Srovnávání frekvence a distribuce může indikovat, do jaké míry jsou tyto jevy součástí standardního jazyka. Tato studie při-náší výsledky tohoto srovnávání a ukazuje, jak lze korpusové nálezy interpretovat. Prostřednictvím testování statistických nástrojů se vyslovuje k akceptabilitě variant a míře, v níž mohou náležet standardnímu spisovnému jazyku.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
6. The range of insect dormancy responses
- Creator:
- Danks, Hugh V.
- Type:
- article, model:article, and TEXT
- Subject:
- Insect, life-cycle, development, dormancy, diapause, trade-off, constraint, variation, and plasticity
- Language:
- English
- Description:
- Insect dormancy responses, in the broad sense of modifications of development, are examined from a general perspective. The range of responses is extraordinarily wide because environments are diverse, different taxa have different evolutionary histories, adaptations are needed for both seasonal timing and resistance to adversity, and not only development but also many other aspects of the life-cycle must be coordinated. Developmental options are illustrated by examining the wide range of ways in which development can be modified, the fact that each individual response consists of several components, and the different potential durations of the life-cycle. The concepts of alternative life-cycle pathways (chosen according to current and likely future environmental conditions) and of active and passive default responses are treated. Also introduced are aspects of variation and trade-offs. Some general conclusions that help in understanding dormancy responses emerge from such an examination. Many options are available (cf. Table 1). The nature of the habitat, especially its predictability, determines the potential effectiveness of many of the developmental options. Any particular set of responses reflects evolutionary history and hence depends on past as well as current environments. It is not necessarily obvious what kinds of selection, especially requirements for timing versus resistance to adversity, explain a particular life cycle. Life-cycle pathways have multiple components, so that components cannot be analyzed in isolation. A given feature, such as delayed development, can have multiple roles. Default responses can be either active (development continues unless signalled otherwise) or passive (development stops unless signalled otherwise), making necessary a broad approach to understanding the action of environmental cues. Even relatively minor effects that fine-tune dormancy responses enhance survival, but may be difficult to detect or measure. Trade-offs are not inevitable, not only when certain resources are surplus, but also because resources in very short supply (constraints) cannot be traded off. Life-cycle components are widely, but not universally, coordinated. These conclusions confirm that the range of dormancy responses is wider, more complex and more integrated than has often been recognized.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
7. The symmetry reduction of variational integrals
- Creator:
- Tryhuk, Václav and Chrastinová, Veronika
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Routh reduction, Lagrange variational problem, Poincaré-Cartan form, diffiety, standard basis, controllability, and variation
- Language:
- English
- Description:
- The Routh reduction of cyclic variables in the Lagrange function and the Jacobi-Maupertuis principle of constant energy systems are generalized. The article deals with one-dimensional variational integral subject to differential constraints, the Lagrange variational problem, that admits the Lie group of symmetries. Reduction to the orbit space is investigated in the absolute sense relieved of all accidental structures. In particular, the widest possible coordinate-free approach to the underdetermined systems of ordinary differential equations, Poincaré-Cartan forms, variations and extremals is involved for the preparation of the main task. The self-contained exposition differs from the common actual theories and rests only on the most fundamental tools of classical mathematical analysis, however, they are applied in infinite-dimensional spaces. The article may be of a certain interest for nonspecialists since all concepts of the calculus of variations undergo a deep reconstruction.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public