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51.
Stylar micromorphological diversity of 42 Asteraceae species from Argentina was analysed considering species phylogenetic
membership and some floral reproductive functions (pollen presentation and pollen reception). In particular, the morphology
and organisation of pollen presenter (sweeping hairs) and pollen receptive structures (stigmatic papillae) were described.
Results showed that style morphology of the studied species is far more diverse than the categories previously established
for Asteraceae, and that it is problematic to relate the sweeping-hair arrangement of species to the only three modes of pollen
presentation described for the family, indicating that the hypothesised relationship could be more complex than was formerly
thought. For all species with di- or trimorphic florets, the styles of female florets were more slender and without or with
more reduced sweeping hairs than the styles of hermaphrodite florets, and divergences of sweeping hair arrangements and morphology
were higher among phylogenetically related species. These results suggest that functional aspects of floral morphology seem
to be more important than phylogenetic constraints as selective forces determining stylar pollen presentation structures.
In contrast, stigmatic-area organisation as well as the morphology of stigmatic papillae remain identical between female and
hermaphrodite florets and among phylogenetically related species. Thus, stigmatic papilla morphology seems to be a phylogenetically
constrained character in the studied species.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
52.
《L'Anthropologie》2022,126(1):102973
The lithic industries of the sites Kermek, Ciscaucasia (2.1–2.0 Ma) and Karakhach, South Caucasus (1.85–1.78 Ma) contain almost all the components of the Acheulian, indicating that this techno-complex appeared in the different areas of the Caucasus region not later than at the end of the Gelasian. Such extremely old ages of these industries as well as a number of their features due to the influence of the local raw material (tabular clasts) suggest that they were formed independently of the Early Acheulian industries known in Africa and the Near East. The very early appearance and further dispersal of Early Acheulian in the Caucasus can be explained by the presence there of raw materials with qualities supporting the production of large tools inherent of Acheulian, and by the very favorable natural conditions of the region in the final Gelazian-initial Calabrian (low or medium altitude terrain with subtropical climate and savanna-like landscape). 相似文献
53.
Soil – an underestimated biotope The soil is a biotope with high species abundances and richness. It is, furthermore, a location where important ecosystem services are realized. Recent research projects on the origin and development of soil animal communities, on the heterogeneous interactions within the soil nutrient net and the distribution of soil animals show the different ecological traits and adaptabilities of the world beneath our feet. So research contributes to maintain the eco‐resource of soil and its sustainable use. 相似文献
54.
The purpose of this article is to summarize the main elements of clinician point of view concerning the contribution of amyloid neuroimaging in the diagnostic approach of the Alzheimer's disease. The main pathological characteristics of the Alzheimer's disease are established by two types of protein aggregates: the extracellular plaques (containing Aβ aggregates) and neurofibrillary tangles (composed of aggregates of tau-protein). At present, the use of biomarkers is more and more included in the diagnostic approach of Alzheimer's disease. The possibility to highlight in vivo cortical amyloid deposits through the amyloid neuroimaging can allow the realization of an earlier diagnosis. However, the amyloid imaging is a “physiopathological” biomarker and is not correlated with the clinical evaluation. It is still difficult to differentiate the Alzheimer's disease of the other neurodegenerative diseases. 相似文献
55.
56.
This work presents two stock-effort dynamical models describing the evolution of a fish population growing and moving between two fishing zones, on which it is harvested by a fishing fleet, distributed on the two zones. The first model corresponds to the case of constant displacement rates of the fishing effort, and the second one to fish stock-dependent displacement rates. In equations of the fishing efforts, a control function is introduced as the proportion of the revenue to be invested, for each fleet. The stabilizability analysis of the aggregated model, in the neighborhood of the equilibrium point, enables the determination of a Lyapunov function, which ensures the existence of a stabilizing discontinuous feedback for this model. This enables us to control the system and to lead, in an uniform way, any solution of this system towards this desired equilibrium point. 相似文献
57.
Simulation models of the role of genetic variability in social insect task allocation 总被引:3,自引:0,他引:3
Summary A feature of some species of eusocial Hymenoptera is a high level of intra-colonial genetic diversity, and correlated diversity in the level of the stimulus required for individuals to initiate work. Here we explore the effects of intracolonial variability on the responsiveness of colonies to changing needs in task allocation using computer simulation. Our simulations show that colonies comprised of individuals of uniform task threshold are poor at adapting to changing colony needs – that is, they did not allocate the appropriate numbers of workers to tasks. On the other hand, colonies comprised of many groups of differing task threshold adapt quickly and more appropriately to changes in task need. Our simulations suggest that intracolonial genetic variability may be an important component of an efficient task allocation system for some species of social Hymenoptera. We speculate that the benefits of an improved task allocation system may have contributed to the high levels of polyandry and polygyny seen in some of these insects.Received 17 August 2001; revised 25 March and 13 October 2003; accepted 3 November 2003. 相似文献
58.
Prof. Dr. Hans Joachim Gross 《当今生物学》2012,42(4):232-237
The “magical” number four We know already since more than 140 years that humans have the inborn ability to recognize only up to four objects correctly if counting is strictly inhibited. Many vertebrates and the honeybee workers can remember up to four objects albeit they are unable to count. This inborn numerical competence common to humans and animals raises interesting questions concerning the purpose and the evolution of this ability. The “magical” number four is obviously a neurological, historical and mythological enigma. 相似文献
59.
Marie-Line Maublanc Eric Bideau Romain Willemet Clara Bardonnet Georges Gonzalez Lionel Desneux Nicolas Cèbe Jean-François Gerard 《Comptes rendus biologies》2012,335(12):735-743
We studied the ranging behaviour and spatial relationships between seven roe deer during more than 4 years in a partly wooded 14.2-ha enclosure. The animals (three young males, four adult females) were monitored with GPS telemetry collars. As expected, the surface area and overlap of the males’ bimonthly ranges decreased, and the distance between their arithmetic centres increased, as they became adult and, for two of them, territorial. Unexpectedly, females also tended to space out, the surface area and overlap of their bimonthly ranges being minimal in May to June, i.e. during the birth period. The distance between their arithmetic centres reached its maximum at the same time. Overlap between females’ ranges was consistently lower than those between males and females’ ranges, or between 1-year old males’ ranges. Our results raise the questions of female seasonal territoriality and of independence of the spacing systems of the two sexes in roe deer. 相似文献
60.
Cholesterol (CHOL), free fatty acids (FFA) and nine classes of ceramides (CER1-CER9) form the main constituents of the intercellular lipid lamellae in stratum corneum (SC), which regulate the skin barrier function. Both the presence of a unique 13-nm lamellar phase, of which the formation depends on the presence of CER1, and its dense lateral packing are characteristic for the SC lipid organisation. The present study focuses on the lipid organisation in mixtures prepared with CHOL, FFA and a limited number of synthetic CER, namely CER1, CER3 and bovine brain CER type IV (∑CERIV). The main objective is to determine the optimal molar ratio of CER3 to ∑CERIV for the formation of the 13-nm lamellar phase. CER3 contains a uniform acyl chain length, whereas ∑CERIV contains fatty acids with varying chain lengths. Using small angle X-ray diffraction (SAXD), it is demonstrated that the CER3 to ∑CERIV ratio affects the formation of the 13-nm lamellar phase and that the optimal ratio depends on the presence of FFA. Furthermore, the formation of the 13-nm lamellar phase is not very sensitive to variations in the total CER level, which is similar to the in vivo situation. 相似文献