Elevational gradients affect the production of plant secondary metabolites through changes in both biotic and abiotic conditions. Previous studies have suggested both elevational increases and decreases in host-plant chemical defences. We analysed the correlation of alkaloids and polyphenols with elevation in a community of nine Ficus species along a continuously forested elevational gradient in Papua New Guinea. We sampled 204 insect species feeding on the leaves of these hosts and correlated their community structure to the focal compounds. Additionally, we explored species richness of folivorous mammals along the gradient. When we accounted for Ficus species identity, we found a general elevational increase in flavonoids and alkaloids. Elevational trends in non-flavonol polyphenols were less pronounced or showed non-linear correlations with elevation. Polyphenols responded more strongly to changes in temperature and humidity than alkaloids. The abundance of insect herbivores decreased with elevation, while the species richness of folivorous mammals showed an elevational increase. Insect community structure was affected mainly by alkaloid concentration and diversity. Although our results show an elevational increase in several groups of metabolites, the drivers behind these trends likely differ. Flavonoids may provide figs with protection against abiotic stressors. In contrast, alkaloids affect insect herbivores and may provide protection against mammalian herbivores and pathogens. Concurrent analysis of multiple compound groups alongside ecological data is an important approach for understanding the selective landscape that shapes plant defences.

• MeSH
• alkaloidy metabolismus   MeSH
• býložravci * MeSH
• feromony analýza   MeSH
• Ficus chemie   MeSH
• flavonoidy metabolismus   MeSH
• hmyz fyziologie   MeSH
• listy rostlin chemie   MeSH
• nadmořská výška * MeSH
• potravní řetězec * MeSH
• savci fyziologie   MeSH
• společenstvo MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Papua Nová Guinea MeSH

Food preferences and exploitation are crucial to many aspects of avian ecology and are of increasing importance as we progress in our understanding of community ecology. We studied birds and their feeding specialization in the Central Range of Papua New Guinea, at eight study sites along a complete (200 to 3700 m a.s.l.) rainforest elevational gradient. The relative species richness and abundance increased with increasing elevation for insect and nectar eating birds, and decreased with elevation for fruit feeding birds. Using emetic tartar, we coerced 999 individuals from 99 bird species to regurgitate their stomach contents and studied these food samples. The proportion of arthropods in food samples increased with increasing elevation at the expense of plant material. Body size of arthropods eaten by birds decreased with increasing elevation. This reflected the parallel elevational trend in the body size of arthropods available in the forest understory. Body size of insectivorous birds was significantly positively correlated with the body size of arthropods they ate. Coleoptera were the most exploited arthropods, followed by Araneae, Hymenoptera, and Lepidoptera. Selectivity indexes showed that most of the arthropod taxa were taken opportunistically, reflecting the spatial patterns in arthropod abundances to which the birds were exposed.

• MeSH
• ptáci fyziologie   MeSH
• stravovací zvyklosti fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• Papua Nová Guinea MeSH

Background and Aims: The stress gradient hypothesis (SGH), the view that competition prevails in undisturbed and productive environments, and shifts to facilitation in disturbed or stressful environments, has become a central paradigm in ecology. However, an alternative view proposes that the relationship between biotic interactions and environmental severity should be unimodal instead of monotonic. Possible causes of discrepancies between these two views were examined in the high elevation desert of the arid Trans-Himalayas. Methods: A putative nurse species and its associated plant community was surveyed over its entire elevation range, spanning from alpine to desert vegetation belts. The results were analysed at the community level (vegetation cover and species richness), considering the distinction between the intensity and the importance of biotic interactions. Interactions at the species level (pairwise interactions) were also considered, i.e. the variation of biotic interactions within the niche of a species, for which the abundance (species cover) and probability of occurrence (presence/absence) for the most widespread species along the gradient were distinguished. Key Results: Overall, facilitation was infrequent in our study system; however, it was observed for the two most widespread species. At the community level, the intensity and importance of biotic interactions showed a unimodal pattern. The departure from the prediction of the SGH happened abruptly where the nurse species entered the desert vegetation belt at the lowest elevation. This abrupt shift was attributed to the turnover of species with contrasting tolerances. At the species level, however, facilitation increased consistently as the level of stress increases and individuals deviate from their optimum (increasing strain). Conclusion: While the stress gradient hypothesis was not supported along our elevation gradient at the community level, the strain gradient hypothesis, considering how species perceive the ambient level of stress and deviate from their optimum, provided a parsimonious explanation for the outcome of plant-plant interactions at both scales.

• MeSH
• ekosystém MeSH
• fyziologický stres * MeSH
• fyziologie rostlin * MeSH
• nadmořská výška * MeSH
• pouštní klima MeSH
• rostliny MeSH
• vývoj rostlin * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Geographic variation in body size has fascinated biologists since the 19th century as it can provide insight into the evolution of the body size of various organisms. In this study, we investigated body size variation in eight carabid species/subspecies (Coleoptera: Carabidae) along elevational gradients in six Central European mountain ranges. First, we examined elevational variation in body size and whether female and male body sizes differed in their responses to elevation. Second, we examined intrapopulation variation in body size along an elevational gradient, and we compared the degrees of intrapopulation variation between males and females. The investigated species either followed a converse Bergmann's cline (Carabus auronitens auronitens Fabricius 1792; Carabus linnei Panzer 1810; Pterostichus melanarius (Illiger, 1798); Pterostichus pilosus (Host, 1789)) or their size was unaffected by elevation (Carabus auronitens escheri Palliardi, 1825; Carabus sylvestris sylvestris Panzer, 1796; Carabus sylvestris transsylvanicus Dejean, 1826; Pterostichus burmeisteri Heer, 1838). Females were the larger sex in all the investigated species, but the degree of sexual size dimorphism differed between species. In general, the degree of sexual size dimorphism showed no change with elevation. The degree of intrapopulation variation in body size slightly increased with elevation in C. sylvestris sylvestris and P. pilosus. Overall, the intrapopulation variation in body size significantly differed among the investigated carabid species. The existing literature on intrapopulation variation in the body size of insects is limited, but further investigation of this issue could provide a better understanding of the mechanisms that generate geographical clines.

• MeSH
• brouci * MeSH
• hmyz MeSH
• pohlavní dimorfismus MeSH
• velikost těla MeSH
• zeměpis MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The usual positive inter-specific relationship between range size and abundance of local populations can have notable exceptions in Afrotropical montane areas, where range-restricted bird species are unusually abundant. We tested how the area occupied locally by passerines and their geographic range size relate to local abundances along a tropical elevational gradient of Mt Cameroon, West-Central Africa. Data on bird assemblages were collected at six forested elevations (350, 650, 1100, 1500, 1850 m, 2200 m a.s.l.) using a standardised point count at 16 locations per elevation. Elevational ranges of birds were compiled from published sources and their geographic range sizes were determined as the occupancy of 1° x 1° grid cells. The observed relationship between local abundance and geographic range size within the entire passerine assemblage on Mt Cameroon disagrees with the most frequently reported positive pattern. However, the patterns differ among elevations, with positive trends of the abundance-range size relationship in lowland changing to negative trends towards higher elevations. Interestingly, the total assemblage abundances do not differ much among elevations and population size estimates of species occupying different parts of the gradient remain relatively constant. These patterns are caused by relatively high abundances of montane species, which might be a result of long-term ecological specialization and/or competitive release in species-poor montane locations and possibly facilitated by an extinction filter. Our data suggest that montane species' abilities to maintain dense populations might compensate for less area available near mountain tops and help these populations to circumvent extinction.

• MeSH
• biodiverzita * MeSH
• extinkce biologická MeSH
• hustota populace MeSH
• lesy MeSH
• nadmořská výška MeSH
• Passeriformes fyziologie   MeSH
• rozšíření zvířat * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Kamerun MeSH

BACKGROUND: A crucial step in conserving biodiversity is to identify the distributions of threatened species and the factors associated with species threat status. In the biodiversity hotspot of the Himalaya, very little is known about which locations harbour the highest diversity of threatened species and whether diversity of such species is related to area, mid-domain effects (MDE), range size, or human density. In this study, we assessed the drivers of variation in richness of threatened birds, mammals, reptiles, actinopterygii, and amphibians along an elevational gradient in Nepal Himalaya. RESULTS: Although geometric constraints (MDE), species range size, and human population density were significantly related to threatened species richness, the interaction between range size and human population density was of greater importance. Threatened species richness was positively associated with human population density and negatively associated with range size. CONCLUSIONS: In areas with high richness of threatened species, species ranges tend to be small. The preponderance of species at risk of extinction at low elevations in the subtropical biodiversity hotspot could be due to the double impact of smaller range sizes and higher human density.

• MeSH
• biodiverzita MeSH
• ekosystém * MeSH
• hustota populace MeSH
• lidé MeSH
• nadmořská výška * MeSH
• obratlovci fyziologie   MeSH
• ohrožené druhy * MeSH
• rozšíření zvířat * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Nepál MeSH

The Ethiopian highlands are the most extensive complex of mountainous habitats in Africa. The presence of the Great Rift Valley (GRV) and the striking elevational ecological gradients inhabited by recently radiated Ethiopian endemics, provide a wide spectrum of model situations for evolutionary studies. The extant species of endemic rodents, often markedly phenotypically differentiated, are expected to possess complex genetic features which evolved asa consequence of the interplay between geomorphology and past climatic changes. In this study, we used the largest available multi-locus genetic dataset of the murid genus Stenocephalemys (347 specimens from ca 40 localities across the known distributional area of all taxa) to investigate the relative importance of disruptive selection, temporary geographic isolation and introgression in their adaptive radiations in the Pleistocene. We confirmed the four main highly supported mitochondrial (mtDNA) clades that were proposed as four species in a previous pilot study: S. albipes is a sister species of S. griseicauda (both lineages are present on both sides of the GRV), while the second clade is formed by two Afro-alpine species, S. albocaudata (east of GRV) and the undescribed Stenocephalemys sp. A (west of GRV). There is a clear elevational gradient in the distribution of the Stenocephalemys taxa with two to three species present at different elevations of the same mountain range. Surprisingly, the nuclear species tree corresponded only a little to the mtDNA tree. Multispecies coalescent models based on six nuclear markers revealed the presence of six separate gene pools (i.e. candidate species), with different topology. Phylogenetic analysis, together with the geographic distribution of the genetic groups, suggests a complex reticulate evolution. We propose a scenario that involves (besides classical allopatric speciation) two cases of disruptive selection along the elevational ecological gradient, multiple crosses of GRV in dry and cold periods of the Pleistocene, followed by hybridization and mtDNA introgression on imperfect reproductive barriers. Spatial expansion of the currently most widespread "albipes" mtDNA clade was followed by population fragmentation, lineage sorting and again by hybridization and mtDNA introgression. Comparison of this genetic structure to other Ethiopian endemic taxa highlight the geographical areas of special conservation concern, where more detailed biodiversity studies should be carried out to prevent many endemic taxa from going extinct even before they are recognized.

• MeSH
• cytochromy b chemie   klasifikace   genetika   MeSH
• ekosystém MeSH
• fylogeneze MeSH
• haplotypy MeSH
• hybridizace genetická MeSH
• karyotyp MeSH
• mitochondriální DNA chemie   izolace a purifikace   metabolismus   MeSH
• molekulární evoluce * MeSH
• Murinae anatomie a histologie   klasifikace   genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Etiopie MeSH

OBJECTIVES: This study aimed to determine anterior gradient 2 (AGR2) expression in biopsies from pancreatic ductal adenocarcinomas (PDACs) and to evaluate AGR2 as a potential independent prognostic factor. METHODS: Tissue sample sections from a cohort of 135 consecutive surgically resectable PDACs were subjected to semiquantitative immunohistochemical analysis of AGR2 and mucin 4 (MUC4) expression. RESULTS: Anterior gradient 2 was over-expressed in PDAC compared with normal ductal cells. Since tumor lesions of PDAC are heterogeneous and constitute structures with various differentiation states, expression of both AGR2 and MUC4 was evaluated in each separate component. Expression levels of both proteins reflected the degree of tumor differentiation. Generally, well differentiated regions of tumor lesions expressed high levels of both proteins, moderately differentiated regions showed less AGR2 and MUC4, and poorly differentiated structures showed only weak positivity or were entirely negative. Of particular interest were occasional cases of strong AGR2 expression in high-grade tumors, where elevated protein levels were associated with shorter patient survival. CONCLUSIONS: Anterior gradient 2 and MUC4 reflect the level of differentiation of PDACs. However, in less differentiated tumors, aberrantly elevated AGR2 expression predicts poor patient outcome.

• MeSH
• adenokarcinom metabolismus   patologie   chirurgie   MeSH
• dospělí MeSH
• duktální karcinom slinivky břišní metabolismus   patologie   chirurgie   MeSH
• hodnocení výsledků zdravotní péče statistika a číselné údaje   MeSH
• imunohistochemie MeSH
• Kaplanův-Meierův odhad MeSH
• kohortové studie MeSH
• lidé středního věku MeSH
• lidé MeSH
• mucin 4 metabolismus   MeSH
• nádory slinivky břišní metabolismus   patologie   chirurgie   MeSH
• pankreatektomie MeSH
• prediktivní hodnota testů MeSH
• prognóza MeSH
• proporcionální rizikové modely MeSH
• proteiny metabolismus   MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Many cushion plants ameliorate the harsh environment they inhabit in alpine ecosystems and act as nurse plants, with significantly more species growing within their canopy than outside. These facilitative interactions seem to increase with the abiotic stress, thus supporting the stress-gradient hypothesis. We tested this prediction by exploring the association pattern of vascular plants with the dominant cushion plant Thylacospermum caespitosum (Caryophyllaceae) in the arid Trans-Himalaya, where vascular plants occur at one of the highest worldwide elevational limits. We compared plant composition between 1112 pair-plots placed both inside cushions and in surrounding open areas, in communities from cold steppes to subnival zones along two elevational gradients (East Karakoram: 4850-5250 m and Little Tibet: 5350-5850 m). We used PERMANOVA to assess differences in species composition, Friedman-based permutation tests to determine individual species habitat preferences, species-area curves to assess whether interactions are size-dependent and competitive intensity and importance indices to evaluate plant-plant interactions. No indications for net facilitation were found along the elevation gradients. The open areas were not only richer in species, but not a single species preferred to grow exclusively inside cushions, while 39-60% of 56 species detected had a significant preference for the habitat outside cushions. Across the entire elevation range of T. caespitosum, the number and abundance of species were greater outside cushions, suggesting that competitive rather than facilitative interactions prevail. This was supported by lower soil nutrient contents inside cushions, indicating a resource preemption, and little thermal amelioration at the extreme end of the elevational gradient. We attribute the negative associations to competition for limited resources, a strong environmental filter in arid high-mountain environment selecting the stress-tolerant species that do not rely on help from other plants during their life cycle and to the fact the cushions do not provide a better microhabitat to grow in.

• MeSH
• biodiverzita * MeSH
• biologické modely * MeSH
• Caryophyllaceae růst a vývoj   fyziologie   MeSH
• chemické jevy MeSH
• druhová specificita MeSH
• fyziologický stres * MeSH
• mikroklima MeSH
• nadmořská výška * MeSH
• půda MeSH
• teplota MeSH
• vzduch MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Indie MeSH
• Tibet MeSH

Altered abiotic conditions resulting from human-induced climate change are already driving changes in the spatial and temporal distributions of many organisms. For insects, how species are distributed across elevations is relatively well known, but data on their seasonality at different elevations are lacking. Here we show seasonal variation in beetle abundance and species richness along two spatially-distinct elevational transects (350-1000 m and 100-1000 m asl) in the rainforests of northern Australia. Temperature was the best predictor of temporal abundance and species richness patterns, while rainfall had little influence. Elevation had little effect on seasonal changes in abundance or diversity. Adults of most beetle species exhibited long season-lengths (>6 months of the year) with distinct peaks in abundance during the summer wet-season. We found evidence of phenotypic variation among the more widespread species, with seasonal peaks in abundance often not coinciding across elevations or transects. Due to the wide elevational range of most species, and the lack of consistency in the seasonality of wide-spread individual species, we suggest that many beetles inhabiting the low to mid-elevation mountains in the Wet Tropics, and potentially other tropical rainforests, are not as vulnerable to extinction due to climate change as many other organisms.

• MeSH
• brouci fyziologie   MeSH
• chování zvířat fyziologie   MeSH
• deštný prales * MeSH
• lidé MeSH
• roční období * MeSH
• tropické klima * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Austrálie MeSH