Opakovaný a nezávislý vznik i následná rozmanitost šavlozubých predátorů náležejí mezi nejpozoruhodnější jevy historie života na Zemi. Ti tak představují jedinečný příklad konvergentní evoluce, který zahrnuje celou řadu sdílených, velmi efektivních adaptací, vedoucích k jejich mimořádnému evolučnímu úspěchu. Důvod jejich zániku, ač k tomu v průběhu kenozoika došlo vícekrát, zůstává nejasný a poskytuje tím vděčný námět k četným spekulacím. Naposledy tento zajímavý ekomorfotyp vymizel z přírody zhruba před deseti tisíci lety. Snad ne navždy., Multiple independent origins and great diversity of sabre-tooth predators are one of the most remarkable phenomena in the natural history of life. Sabre-tooth predators provide a unique example of the convergent evolution that involved many kinds of very efficient functional adaptations leading to their unprecedented evolutionary success. The reason for their demise, although occurring repeatedly during the Tertiary, remains unclear and offers a broad matter of speculation. Nevertheless, this interesting ecomorphotype completely disappeared from nature roughly 10,000 years ago, but may be not for ever., and Stanislav Knor.
V průběhu neogénu byli s výjimkou jihoamerických vačnatých thylakosmilidů po celém světě jedinými představiteli šavlozubého ekomorfotypu již pouze šelmy barbourofelidi (Barbourofelidae) a příslušníci čeledi kočkovitých (Felidae). Někteří z nich pak dosahovali značné velikosti a mimořádně robustní stavby těla, přičemž v těchto ohledech překonávali ty největší zástupce dnešních velkých koček. Zvláště šavlozubé kočky na dlouhou dobu obsadily pozici na vrcholu potravní pyramidy, než nakonec definitivně vymizely ke konci pleistocénu ze Severní a Jižní Ameriky. Ve Starém světě však vyhynuly již o něco dříve během čtvrtohor, zřejmě následkem zesílené vzájemné konkurence s velkými kočkami, především pak se lvy a tygry., During the Neogene, with the exception of thylacosmilids, barbourofelids and felids were the only representatives of the sabre--tooth ecomorphotype worldwide. Some of them attained tremendous size and were of very robust somatic constitution, exceeding in these aspects the largest contemporary cats. Especially the sabre-tooth felids occupied the top of the trophic chain for a long time before their demise at the end of the Pleistocene in both North and South America. But in the Old World these predators disappeared somewhat earlier, probably due to the strength of mutual competition with other large felids, namely the lions and tigers., and Stanislav Knor.
Sazná nemoc kůry je méně známé onemocnění způsobené houbou Cryptostroma corticale (Ascomycota), s ostrůvkovitým výskytem v Evropě. Postihuje zejména javory kleny (Acer pseudoplatanus) a jejich hromadná vymírání byla zaznamenána u stromů oslabených stresem, především po nadprůměrně suchých a horkých letních měsících. Nedávný výskyt onemocnění v České republice podnítil studium druhu C. corticale a jeho rozšíření v Praze. Výsledek naší čtyřleté studie prokázal, že napadena je minimálně čtvrtina klenů v pražských parcích., Sooty bark disease is a less known disease caused by fungal species Cryptostroma corticale (Ascomycota), with patchy incidence in Europe. It mainly affects Sycamore (Acer pseudoplatanus), and its mass dieback was observed in trees weakened by stress, especially after the exceptionally dry and hot summer months. Recent record of the disease in the Czech Republic prompted the research of C. corticale and its occurrence in Prague. The results of our four-year study showed that at least 25 % of Sycamore trees in Prague parks are infected., and Ivana Kelnarová, Ondřej Koukol, Karel Černý.
Ecosystem photosynthetic characteristics are of utmost importance for the estimation of regional carbon budget, but such characteristics are not well understood in alpine regions. We collected CO2 flux data measured by eddy covariance technique over an alpine dwarf shrubland on the Qinghai-Tibetan Plateau during years 2003-2010; and we quantified the temporal patterns of ecosystem apparent quantum yield (a), saturated photosynthetic rate (Pmax), and ecosystem dark respiration (RDe). Results showed that the strong seasonality of a and RDe was driven mainly by air temperature (Ta), whereas that of Pmax was much more determined by leaf area index rather than abiotic factors. Diurnal thermal fluctuation inhibited significantly the daytime photosynthetic capacity. Stepwise regression revealed that the seasonal deviations of a, Pmax, and RDe were significantly controlled by Ta. The annual a was regulated mainly by annual growing season Ta, which indicated that the response of ecosystem a was instant. The annual variations of Pmax correlated positively with soil temperature 5 cm below ground (Ts) of the annual nongrowing season and those of RDe related negatively with the annual nongrowing season precipitation. We suggested that a lagged response regulated the annual Pmax and the annual RDe. Annual deviations of a and RDe were both significantly controlled by annual Ts, and those of Pmax were marginally determined by annual PPFD. Thus, the future warming scenario, especially significant for nongrowing seasonal warming in the Qinghai-Tibetan Plateau, would favor ecosystem photosynthetic capacity in the alpine dwarf shrubland., H. Q. Li, F. W. Zhang, Y. N. LI, G. M. Cao, L. Zhao, X. Q. Zhao., and Obsahuje bibliografii
Seasonal changes in leaf gas exchange, assimilation response to light and leaf area were monitored in bearing and nonbearing pistachio shoots. Shoot bearing status did not directly affect leaf photosynthetic rate. However, photosynthetic light-response curves strongly varied during the season demonstrating the dominant effect of the tree’s seasonal phenology on assimilation. Early in the season low photosynthetic rates were associated with high rates of dark respiration indicating limited photosynthesis in the young leaves. As leaves matured, dark respiration decreased and assimilation reached maximum values. Photosynthetic efficiency was strongly reduced late in the season due to leaf age and senescence. Fruit load precipitated an early leaf senescence and drop that resulted in a 53% decrease in leaf area in bearing vs. nonbearing shoots, strongly decreasing the seasonal photosynthetic performance of bearing shoots. Bearing shoots produced a 26% lower seasonal carbon gain compared to nonbearing shoots., G. Marino, M. La Mantia, T. Caruso, F. P. Marra., and Obsahuje bibliografii
Seasonal polyphenism in adults may be a season-specific adaptation of the adult stage and/or a by-product of adaptive plasticity of the juvenile stages. The swallowtail butterfly Papilio xuthus L. exhibits seasonal polyphenism controlled by photoperiod. Adults emerging in spring from pupae that spend winter in diapause have smaller bodies than adults emerging in summer from pupae that do not undergo diapause. Pupal diapause is induced by short-day conditions typical of autumn. To explore the interactive effects of temperature and developmental pathways on the variation in adult body size in P. xuthus, we reared larvae at two temperatures (20°C, 25°C) under two photoperiods (12L : 12D and 16L : 8D). Pupal weight and adult forewing length were greater in the generation that did not undergo diapause and were greater at 25°C than at 20°C. Thus, body size differences were greatest between the individuals that were reared at the longer day length and higher temperature and did not undergo diapause and those that were reared at the shorter day length and lower temperature and did undergo diapause. Unlike in other Lepidoptera, larvae of individuals that undergo diapause had shorter developmental times and higher growth rates than those that did not undergo diapause. This developmental plasticity may enable this butterfly to cope with the unpredictable length of the growing season prior to the onset of winter. Our results indicate that there are unexplored variations in the life history strategy of multivoltine Lepidoptera., Shinya Komata, Teiji Sota., and Obsahuje bibliografii
Eristalis pertinax varies seasonally, with the spring morph more hairy than the summer morph. We measured the size and the venation of the wings of the seasonal morphs. Wings of the spring morph were significantly larger than those of the summer morph and those of females were larger than those of males. There were also significant differences between the morphs in wing venation and their allometric relationship. The differences between sexes were larger than differences between seasonal morphs. The allometry can account for the sexual dimorphism but not seasonal dimorphism. The differences between seasonal morphs in wing shape were relatively large with very few intermediate individuals. The differences were comparable to those between two related species of Syrphidae. Genetic analyses based on markers in nuclear and mitochondrial genomes unequivocally revealed that spring and summer morphs of E. pertinax form a single population and should not be regarded as separate taxa. Thus seasonal variability in this species is a rare example of polyphenism in Diptera., Lukasz E. Mielczarek, Andrzej Oleksa, Katarzyna Meyza, Adam Tofilski., and Obsahuje bibliografii
Seasonal variations in photosynthesis of cassava cv. Rayong 9 (RY9) under irrigated and rain-fed conditions were evaluated at the age of three and six months after planting (MAP). Photosynthetic light-response (PN/I) curves revealed that cassava leaves attained the highest maximum net photosynthetic rates (PNmax) in the rainy season, followed by the hot one, while the lowest PNmax was found in the cool season. Photosynthetic potential of the 3-month-old plants was mostly higher than that of the 6-month-old plants, and the seasonal variation in photosynthetic capacity was also more apparent in the younger plants. PN/I curves were used to predict daily net photosynthetic rate (PN) for each season based on daily average solar radiation data. The predicted PN were considerably lower than the PNmax values. This indicated that solar radiation is a limiting factor for photosynthesis, particularly in the rainy season. The data provided basic information for breeding cassava genotypes with enhanced photosynthesis during the period of unfavorable environment. Furthermore, the data are potentially useful in modeling photosynthesis and crop growth as affected by environmental factors., K. Vongcharoen, S. Santanoo, P. Banterng, S. Jogloy, N. Vorasoot, P. Theerakulpisut., and Obsahuje bibliografii