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991.
Long-term pattern of population dynamics in the field vole from central Europe: cyclic pattern with amplitude dampening 总被引:1,自引:0,他引:1
Ana Gouveia Vladimír Bejček Jiří Flousek František Sedláček Karel Šťastný Jan Zima Nigel G. Yoccoz Nils Chr. Stenseth Emil Tkadlec 《Population Ecology》2015,57(4):581-589
The subject of population cycles is regarded as controversial due to a number of unsettled questions such as whether or not cyclic patterns are governed by the same processes at high and low latitudes in Europe. Recent evidence suggests that the dynamics at high and low latitudes share the common temporal pattern of vole dynamics referred to as collapsing population cycles. Despite concurrent interest, the key contention around the causal mechanisms that drive population cycles remains a hot topic in ecology. The aims of this study are to supplement information on the seasonal population dynamics of the field vole Microtus agrestis in the Czech Republic by analysing 25 years of time series data. By applying robust estimation procedures, we estimated several parameters to describe population dynamics, such as population variability, amplitude dampening, cycle period, order of the dynamics and the structure of density dependence. The parameters indicate that field vole dynamics in central Europe are highly variable, cyclic dynamics of order two, with peaks in abundance occurring regularly at intervals of 4–5 years. In addition to exhibiting population cycles, the field vole populations show a pattern of dampened amplitude as observed elsewhere in Europe, including northern latitudes. By analysing temporal trends in seasonal abundances, population growth rates and environmental temperatures, we did not obtain evidence to support the hypothesis that amplitude dampening results from the negative effect of increasingly mild winters on winter population growth rates. 相似文献
992.
4-Nitrophenol degrading bacterial strainCorynebacterium sp. 8/3 was isolated from chemically polluted soil. The product of cometabolic transformation of 4-nitrophenol was identified
as 4-nitrocatechol., Effect of immobilization (encapsulation in calcium alginate) ofCorynebacterium sp. cells on the process of 4-nitrophenol transformation was investigated. 4-Nitrophenol was converted by encapsulated cells
and encapsulation had a protective effect, on 4-nitrophenol degrading bacteria in repeated cycles of incubation. Transformation
of 4-nitrophenol to 4-nitrocatechol by encapsulated cells was influenced by pH of medium but was not influenced by concentration
of alginate and CaCl2. The count of viable cells in alginate beads declined approximately by one order of magnitude after 10 d of incubation.
Presented at the 4th Mini-Symposium on Biosorption and Microbial Degradation, Prague, Czech Republic, November 26–29, 1996. 相似文献
993.
Geosmithia spp. (Ascomycota: Hypocreales) are little-studied, dry-spored fungi that occur in galleries built by many phloeophagous bark
beetles. This study mapped the distribution and environmental preferences of Geosmithia species occurring in galleries of temperate European bark beetles. One hundred seven host tree samples of 16 tree species
infested with 23 subcortical insect species were collected from across Europe during the years 1997–2005. Over 600 Geosmithia isolates from the beetles were sorted into 17 operational taxonomic units (OTUs) based on their phenotype similarity and
phylogeny of internal transcribed spacer (ITS) region of rDNA (ITS1-5.8S-ITS2). The OTUs represent six known species and eight
undescribed taxa. Ninety-two samples infested with subcortical insects were characterized by the presence/absence of OTUs
and the similarity among the samples was evaluated. Geographically distant populations of the same beetle species host relatively
uniform Geosmithia communities across large geographic areas (ranging from southern Bulgaria to the Czech Republic). This suggests effective
dispersal of Geosmithia spp. by bark beetles. Clustering of similar samples in ordination analysis is correlated predominantly with the isolation
source (bark beetles and their respective feeding plant), but not with their geographical origin. The composition of the Geosmithia OTU community of each bark beetle species depends on the degree of isolation of the species’ niches. Thus, Geosmithia communities associated with regularly co-occurring bark beetle species are highly similar. The similarity decreases with
decreasing frequency of beetle species’ co-occurrence, a pattern resembling that of entomochoric ophiostomatoid fungi. These
findings suggest that: 1) communities of Geosmithia spp. are vector-specific; 2) at least in some cases, the association between Geosmithia OTUs and bark beetles may have been very stable and symbioses are likely to be a fundamental factor in the speciation of
Geosmithia fungi; and 3) that even nonsticky spores of Geosmithia are suitable for maintaining an insect–fungus association, contrary to previous hypotheses.
An erratum to this article can be found at 相似文献
994.
Maria Derkacheva Yvonne Steinbach Thomas Wildhaber Iva Mozgová Walid Mahrez Paolo Nanni Wilhelm Gruissem Lars Hennig 《The EMBO journal》2013,32(14):2073-2085
Polycomb group (PcG) proteins form essential epigenetic memory systems for controlling gene expression during development in plants and animals. However, the mechanism of plant PcG protein functions remains poorly understood. Here, we probed the composition and function of plant Polycomb repressive complex 2 (PRC2). This work established the fact that all known plant PRC2 complexes contain MSI1, a homologue of Drosophila p55. While p55 is not essential for the in vitro enzymatic activity of PRC2, plant MSI1 was required for the functions of the EMBRYONIC FLOWER and the VERNALIZATION PRC2 complexes including trimethylation of histone H3 Lys27 (H3K27) at the target chromatin, as well as gene repression and establishment of competence to flower. We found that MSI1 serves to link PRC2 to LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), a protein that binds H3K27me3 in vitro and in vivo and is required for a functional plant PcG system. The LHP1–MSI1 interaction forms a positive feedback loop to recruit PRC2 to chromatin that carries H3K27me3. Consequently, this can provide a mechanism for the faithful inheritance of local epigenetic information through replication. 相似文献
995.
Jindřich Chrtek jun 《Folia Geobotanica》1994,29(1):91-100
Chromosome numbers are given of 15 species of the genusHieracium L. s. str., representing seven species groups (in the sense of Flora Europaea, roughly corresponding to Zahn's “species principales”) from the Krkono?e Mts., N. Bohemia and SW Poland. For the first time chromosome numbers are reported forH. melanocephalum Tausch (2n=27),H. tubulosum Tausch (2n=36),H. schustleri Zlatník (2n=36),H. fritzei F. Schultz (2n=27),H. rohlenae Zlatník (2n=27),H. nigrescens Willd. (2n=36),H. decipiens Tausch (2n=36),H. atrellum Juxip inSchischkin etBobrov (2n=27),H. subnigrescens (Fries exNorrlin)Dahlst. (2n=36),H. sudeticum Sternberg (2n=36),H. pedunculare Tausch (2n=36),H. glandulosodentatum Uechtr. (2n=36),H. wimmeri Uechtr. (2n=27). InHieracium alpinum L. s. str. the number 2n=27 has been confirmed. The results show a high proportion of tetraploid taxa; no diploids have been found. 相似文献
996.
Jana Jersáková Sílvia Castro Nicole Sonk Kathrin Milchreit Iva Schödelbauerová Till Tolasch Stefan Dötterl 《Evolutionary ecology》2010,24(5):1199-1218
Polyploidy has played a key role in plant evolution and diversification. Despite this, the processes governing reproductive
isolation among cytotypes growing in mixed-ploidy populations are still largely unknown. Theoretically, coexistence of diploid
and polyploid individuals in sympatric populations is unlikely unless cytotypes are prezygotically isolated through assortative
pollination. Here, we investigated the pre-mating barriers involved in the maintenance of three co-occurring cytotypes from
the genus Gymnadenia (Orchidaceae): tetraploid and octoploid G. conopsea and tetraploid G. densiflora. We assessed differences in flowering phenology, floral morphology, and visual and olfactory cues, which could lead to assortative
mating. Gas chromatography coupled with electroantennographic detection was used to identify scent compounds with physiological
activity in the two main pollinators, Deilephila porcellus and Autographa gamma. The importance of olfactory cues was also assessed in the field by analysing the moths’ responses to the olfactory display
of the plants, and by following the pollinator’s behaviour on artificial arrays. Our complex approach demonstrated that the
coexistence of Gymnadenia cytotypes in mixed-ploidy populations was only partly explained by differences in floral phenology, as cytotypes with overlapping
flowering (i.e., octoploid G. conopsea and tetraploid G. densiflora) might freely exchange pollen due to only 1 mm differences in spur lengths and the lack of assortative behaviour of pollinators.
While floral colour among the cytotypes was similar, floral scent differed significantly. Though both pollinator species seemed
to physiologically detect these differences, and the floral scent alone was sufficient to attract them, pollinators did not
use this cue to discriminate the cytotypes in the field. The absence of pre-mating barriers among cytotypes, except partial
temporal segregation, suggests the existence of other mechanisms involved in the cytotypes’ coexistence. The genetic differences
in ITS sequences among cytotypes were used to discuss the cytotype’s origin. 相似文献
997.
Petr Sklenář 《Nordic Journal of Botany》2012,30(4):394-398
Research on the phylogeny of a distinct group of Andean Senecio, previously considered as Lasiocephalus, resulted in the discovery of two new species, which are here described and illustrated. Senecio josei Sklená?, which grows in rocky habitats in grass páramo in southern Ecuador, is characterized by linear leaves and a racemose or paniculate synflorescence. Senecio superparamensis Sklená? is characterized by grayish–white pubescence, solitary capitula and leafy stems, and inhabits superpáramos in northern and central Ecuador. 相似文献
998.
999.
The Ahníkov (Miocene, Czech Republic) site represents a concentration of vertebrate skeletal remains in a swamp setting. Autochthonous bone deposits were strongly altered by sedimentary processes and early diagenesis. Biting and gnawing traces recognized on hard animal tissues (bones, teeth, antlers, turtle thoraces) represent seven recurring morphotypes. The following ichnotaxa are erected: Nihilichnus nihilicus n. igen. et n. isp., Nihilichnus mortalis n. isp., Machichnus regularis n. igen. et n. isp., Machichnus multilineatus n. isp., Machichnus bohemicus n. isp., and Brutalichnus brutalis n. igen. et n. isp. Each kind of bones or similar substrates bears a specific proportion of various bite traces but no observed morphotype is specific for a single substrate. Ethologically, traces of sharpening of teeth are principally different from predation traces. The beavers Steneofiber eseri and Steneofiber depereti, the carnivore Amphicyon sp. and the crocodiles are presumed as the tracemakers. 相似文献
1000.
David Jandzik Daniel Jablonski Oleksandr Zinenko Oleg V. Kukushkin Jiří Moravec Václav Gvoždík 《Zoologica scripta》2018,47(1):21-32
Climatic changes during the Pleistocene played an instrumental role in the shaping recent distribution and diversity of the Western Palearctic biota. Range oscillations often lead to allopatric differentiation followed by the establishment of secondary contact zones. As a result, many species are composed of complex networks of phylogenetic lineages with different histories. Pseudopus apodus is the only surviving member of an ancient genus of Western Palearctic anguid lizards (Anguidae) distributed from the Balkans through Anatolia and Caucasus to central Asia. Here, we used mitochondrial and nuclear DNA sequences to reconstruct the evolutionary history of the species in phylogeographic and demographic frameworks. Our analyses revealed three main phylogenetic lineages that diverged during or shortly before the Pleistocene. Two of them more or less correspond to the known subspecies, and their low genetic variability suggests relatively recent dispersal and colonization of vast parts of the range. The third, southern, lineage is more geographically restricted and diversified than the other two. This pattern shows that the Quaternary climatic oscillations presumably caused repeated large‐scale population extinctions of the species, depleting most of its diversity. Only a few refugia located in Anatolia, Levant, and Transcaucasia served as sources for subsequent recolonization to the areas of the recent distribution. This is in contrast to many other Western Palearctic reptiles that survived unfavorable climatic conditions in numerous local refugia and sanctuaries, which resulted in more complex phylogenetic structure. 相似文献