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32.
FRANCO PUPULIN DIEGO BOGARÍN 《Botanical journal of the Linnean Society. Linnean Society of London》2012,168(4):395-448
A taxonomic revision of Encyclia (Orchidaceae) in Costa Rica is presented. The taxonomic history of the genus and its phylogenetic position are discussed. Characters of vegetative and floral morphology are described and their taxonomic significance is discussed. The genus is treated as comprising nine species in the country and a key to species is provided. Each taxon is described on the basis of Costa Rican material, illustrated in a composite plate, and its distribution within the country is assessed. Distribution maps for all the taxa are given. Overall distribution, derivation of name, synonymy, notes on species ecology and diagnostic features are presented for each taxon. The names Encyclia tonduziana and Epidendrum mooreanum are typified. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 168 , 395–448. 相似文献
33.
Quantifying the activity levels and behavioural responses of butterfly species to habitat boundaries
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LOUISE MAIR CHRIS D. THOMAS ALDINA M. A. FRANCO JANE K. HILL 《Ecological Entomology》2015,40(6):823-828
1. The ability of species' to undergo climate‐driven range shifts across fragmented landscapes depends on their dispersal ability as well as the structure of the landscape. For species' range shifts to occur, individuals must first leave suitable habitat to seek new habitat; this is likely to depend on the rate of movement of individuals within habitat and the likelihood that a boundary is crossed, once it is encountered. For three species of butterfly with contrasting histories of recent range expansion, we examined the propensity of individuals to move within a habitat and their responses to habitat boundaries. 2. We quantified the extent to which Plebejus argus (Linnaeus) (a declining habitat specialist), Aricia agestis (Schiffermuller) (an expanding generalist) and Polymmatus icarus (Rottemburg) (a geographically ubiquitous generalist) crossed habitat boundaries into unsuitable habitat and moved within suitable habitat. The observed movement was then related to individual and environmental conditions. 3. Species differed in their activity levels in accordance within their recent distribution patterns (P. icarus > A. agestis > P. argus). Our results for P. argus suggest that movement may be motivated by nectar‐seeking, and that males generally move more than females. All three species tended to avoid crossing habitat boundaries; however the proportion of individuals crossing habitat boundaries did not differ significantly among species. 4. We conclude that levels of activity within a habitat, which will affect the frequency with which individuals encounter habitat boundaries, rather than behavioural responses to the boundaries, may be important drivers of distribution change. 相似文献
34.
Is nest‐site availability limiting Lesser Kestrel populations? A multiple scale approach 总被引:4,自引:0,他引:4
The Lesser Kestrel, a colonial migratory falcon, is one of the most endangered birds in Europe and, due to a sharp population decline across much of the breeding range, is globally threatened. The reasons for this decline are unclear, but reduced nest-site availability might be a major cause. To test this hypothesis we looked at nest-site availability within Portuguese colonies in rural and urban buildings. Nest holes were larger, longer, higher and older than unoccupied cavities. A typical nest cavity was approximately 29–30 cm long, 300–340 cm high and had an inner chamber 16.5–18 cm wide. Large-scale surveys of existing buildings in Portuguese villages suggested that 85% of sites lacked suitable nest cavities. The model for selection of buildings indicated that Lesser Kestrels prefer buildings with many roof and wall cavities, and that are surrounded by extensive cereal and fallow fields. The villages selected had many old buildings and monuments, were located in areas with few rivers, and a low percentage cover of cereal, olive groves and forest. The conservation implications of these results are discussed. 相似文献
35.
GIANLUCA PIOVESAN FRANCO BIONDI†‡ ALFREDO DI FILIPPO ALFREDO ALESSANDRINI MAURIZIO MAUGERI§ 《Global Change Biology》2008,14(6):1265-1281
Productivity of old‐growth beech forests in the Mediterranean Basin was measured by average stem basal area increment (BAI) of dominant trees at two mountain sites in the Italian Apennines. Both forests could be ascribed to the old‐growth stage, but they differed markedly with regard to elevation (1000 vs. 1725 m a.s.l.), soil parent material (volcanic vs. calcareous), mean tree age (less than 200 years vs. 300 years), and stand structure (secondary old‐growth vs. primary old‐growth forest). Drought at the two sites was quantified by the self‐calibrated Palmer Moisture Anomaly Index (Z‐index), and by the self‐calibrating Palmer Drought Severity Index (PDSI) for summer (June through August) and the growing season (May through September). Dendroclimatological analyses revealed a moisture limitation of beech BAI at interannual (water availability measured by Z‐index) and decadal scales (water availability measured by PDSI). Both BAI and water availability increased from 1950 to 1970, and decreased afterwards. Trees were grouped according to their BAI trends in auxological groups (growth‐type chronologies), which confirmed that growth of most trees at both sites declined in recent decades, in agreement with increased drought. Because BAI is not expected to decrease without an external forcing, the patterns we uncovered suggest that long‐term drought stress has reduced the productivity of beech forests in the central Apennines, in agreement with similar trends identified in other Mediterranean mountains, but opposite to growth trends reported for many forests in central Europe. 相似文献
36.
Drought resistance of Quercus pubescens as a function of root hydraulic conductance, xylem embolism and hydraulic architecture 总被引:3,自引:0,他引:3
Water relations, xylem embolism, root and shoot hydraulic conductance of both young plants in the field and potted seedlings of Quercus pubescens have been studied with the aim of investigating whether these variables may account for the well known adaptation of this oak species to arid habitats. Our data revealed that Q. pubescens is able to maintain high leaf relative water contents under water stress conditions. In fact, relative water contents measured in summer (July) did not differ from those recorded in April. This was apparently achieved by compensating water loss by an equal amount of water uptake. Such a drought avoidance strategy was made possible by the recorded high hydraulic efficiency of stems and roots under water stress. In fact, root hydraulic conductance of field-grown plants was maintained high in summer when the percentage loss of hydraulic conductance of stems was lowest. The hydraulic architecture of young plants of Q. pubescens measured in terms of partitioning of hydraulic resistances along the water pathway revealed that the highest hydraulic resistance was located in stems of the current year's growth. This hydraulic architecture is interpreted as consistent with the adaptation of Q. pubescens to arid habitats as a consequence of the recorded seasonal changes in water relation parameters as well as in root and stem hydraulics. 相似文献
37.
Remote sensing of sun-induced fluorescence to improve modeling of diurnal courses of gross primary production (GPP) 总被引:4,自引:0,他引:4
ALEXANDER DAMM JAN ELBERS† RÉ ERLER‡ BENIAMINO GIOLI§ KARIM HAMDI‡ RONALD HUTJES† MARTINA KOSVANCOVA¶ MICHELE MERONI FRANCO MIGLIETTA§ RÉ MOERSCH‡ JOSE MORENO ANKE SCHICKLING†† RUTH SONNENSCHEIN THOMAS UDELHOVEN‡‡ SEBASTIAN van der LINDEN PATRICK HOSTERT UWE RASCHER‡ 《Global Change Biology》2010,16(1):171-186
Terrestrial gross primary production (GPP) is an important parameter to explore and quantify carbon fixation by plant ecosystems at various scales. Remote sensing (RS) offers a unique possibility to investigate GPP in a spatially explicit fashion; however, budgeting of terrestrial carbon cycles based on this approach still remains uncertain. To improve calculations, spatio-temporal variability of GPP must be investigated in more detail on local and regional scales. The overarching goal of this study is to enhance our knowledge on how environmentally induced changes of photosynthetic light-use efficiency (LUE) are linked with optical RS parameters. Diurnal courses of sun-induced fluorescence yield ( F Syield ) and the photochemical reflectance index of corn were derived from high-resolution spectrometric measurements and their potential as proxies for LUE was investigated. GPP was modeled using Monteith's LUE-concept and optical-based GPP and LUE values were compared with synoptically acquired eddy covariance data. It is shown that the diurnal response of complex physiological regulation of photosynthesis can be tracked reliably with the sun-induced fluorescence. Considering structural and physiological effects, this research shows for the first time that including sun-induced fluorescence into modeling approaches improves their results in predicting diurnal courses of GPP. Our results support the hypothesis that air- or spaceborne quantification of sun-induced fluorescence yield may become a powerful tool to better understand spatio-temporal variations of fluorescence yield, photosynthetic efficiency and plant stress on a global scale. 相似文献
38.
GIOVANNA ROSATI GIULIO PETRONI SILVIA QUOCHI LETIZIA MODEO FRANCO VERNI 《The Journal of eukaryotic microbiology》1999,46(3):278-282
ABSTRACT. Euplotidium itoi harbors on its dorsal surface peculiar episymbionts (referred to as epixenosomes) equipped with a complex extrusive apparatus. In the laboratory. E. itoi stocks without epixenosomes behave and reproduce like symbiotized stocks. the hypothesis that epixenosomes play a defensive role against predators was tested by comparing the behavior of Litonotus lamella when preying upon Euplotes crassus, E. itoi without epixenosomes. and E. itoi with epixenosomes. Litonotus discharges its toxicysts upon direct-cell-to cell contact, and paralyzes the three types of prey with the same efficiency. Nevertheless, Litonotus can ingest Euplotes, Euplotidium without epixenosomes, and to a certain extent, Euplotidium with epixenosomes whose ejecting capability has been inhibited. while it never eats Euplotidium with unaltered epixenosomes. In each prey-type, about 60% of the individuals attacked by Litonotus toxicyst discharge are able to recover their normal behavior once transferred into pure sea water. This percentage for E. itoi with epixenosomes that are never eaten by the predator corresponds to the probability of survival. This probability is lower for the other two prey-types in which the prey engulfed by the predator do not have the chance to recover. These data support the hypothesis and suggest the involvement of the epixenosome's ejecting apparatus in a defensive function. 相似文献
39.
40.
PAULA C. ETEROVICK ISABELA LAZAROTTI BRUNA P. FRANCO CAMILA J. DIAS 《Austral ecology》2010,35(8):879-887
Phenotypic plasticity can improve fitness in unstable environments and can be expressed in many traits, such as life history attributes, growth and behavioural features. Microhabitat choice can have important consequences for development and survival of aquatic organisms and is expected to vary in response to stimuli, such as predation risk, food availability and temperature. At seasonal sites, microhabitat availability and associated benefits may change from season to season, which might lead to altered patterns of microhabitat use by tadpoles. We investigated this hypothesis in 17 streams from two localities in south‐eastern Brazil. We tested whether water level drops significantly during the dry season, whether lower water level results in altered microhabitat availability and whether predation risk changes between seasons, based on predator density. We then tested whether tadpoles change their pattern of microhabitat use, their spatial niche breadth (given by diversity of used microhabitats) and spatial niche overlap (in the case of co‐occurring species). We were able to include in our analyses tadpoles of four species of Hylidae, that occurred throughout both seasons. Stream depth decreased in the dry season, but microhabitat availability remained relatively stable in many streams, and predator density did not change significantly. Tadpoles of three out of the four species studied were more abundant during the dry season, which may be an adaptation to adjust time of metamorphosis to the rainy season. Tadpoles changed their patterns of microhabitat use between seasons, although the potential causing factors investigated did not seem to be responsible. Tadpole plasticity in microhabitat use may indicate the existence of selective pressures that vary through time and space and are still not well understood. 相似文献