In order to disentangle the contribution of host and parasite biology to host specificity, we compared the structure and population dynamics of the Gyrodactylus (von Nordmann, 1832) flatworm community living on sympatric three-spined Gasterosteus aculeatus L. and nine-spined Pungitius pungitius (L.) stickleback. Between April 2002 and March 2003, a small lowland creek was sampled monthly. Species identity of about 75% of the worms per host was determined with a genetic nuclear marker (ITS1). Each stickleback species hosted a characteristic gill- and fin-parasitic Gyrodactylus: G. arcuatus Bychowsky, 1933 and G. gasterostei Gläser, 1974 respectively infecting the three-spined stickleback, with G. rarus Wegener, 1910 and G. pungitii Malmberg, 1964 infecting the nine-spined stickleback. Host size and seasonal dynamics were strong determinants of parasite abundance. A strong interaction between host and parasite species determined infection levels and affected three levels of parasite organisation: community structure, population structure and topographical specialisation. Community and population structure were shaped by asymmetric cross-infections, resulting in a net transmission of the Gyrodactylus species typical of the nine-spined stickleback towards the three-spined stickleback. Host density was not a major determinant of parasite exchange. Aggregation and topographical specialisation of the Gyrodactylus species of the three-spined stickleback were more pronounced than that of the nine-spined stickleback.
Despite the substantial knowledge of the variation in cytotypes at large spatial scales for many plants, little is known about the rates at which novel cytotypes arise or the frequencies and distributions of cytotypes at local spatial scales. The frequency distribution, local spatial structure, and role of habitat differentiation of tetra-, penta- and hexaploid cytotypes of the bulbous geophyte Allium oleraceum were assessed in 21 populations sampled in the Czech Republic. The ploidy levels determined by flow cytometry confirmed that there was a mixture consisting of two or three cytotypes (i.e. 4x+5x, 4x+6x, 5x+6x, 4x+5x+6x). In addition, mixtures of cytotypes were found at sites previously considered to be cytotype-homogeneous. At all sites previously found to contain a mixture of two cytotypes, no plants with the third ploidy level were found. Although the relative frequencies of cytotypes varied considerably both among and within populations, mixed populations consisting of tetra- and hexaploids were usually dominated by tetraploids. This suggests that there are secondary contacts among cytotypes but there is little gene flow among them except for the rare formation of hexaploids in tetraploid populations. Cytotypes were not randomly distributed over the study area but were spatially segregated at either 47.6% or 61.9% of the sites investigated, depending on the statistical test (Mantel test or average distance test) used. When the composition of habitats at each of the sites is taken into account, cytotypes were more frequently spatially segregated at sites with a heterogeneous environment than a homogeneous environment. This implies that the cytotypes are ecologically differentiated. The frequent co-occurrence of cytotypes, with or without significant spatial segregation, at many sites with heterogeneous or homogeneous environments, however, suggests that niche differentiation alone is probably ineffective in determining co-occurrence. It is supposed that the prevailing vegetative reproduction associated with local dispersal, a high population density of the species in a landscape, and non-equilibrial processes influencing the establishment and extinction of A. oleraceum populations can also support the local co-occurrence of cytotypes.
For the understanding of shrew communities, their coexistence and competition, the knowledge of diet partitioning among sympatric shrew species is crucial. In this study, the trophic niches of three coexisting Sorex species: S. alpinus, S. araneus and S. minutus were compared for the first time. Shrews were taken from a montane forest habitat in northern Slovenia (NS). A little known species, S. alpinus, fed mostly on Insecta (50 %) and Lumbricidae (25 %), as well as Lithobiomorpha, Araneae and Opiliones. Its diet differed significantly from the diet of S. araneus
and S. minutus. On the other hand, a nearly-perfect trophic niche overlap was found for S. araneus and S. minutus suggesting their great hindrance of competition for food. For comparison, S.araneus from a montane forest habitat in southern Slovenia (SS) was considered. Sorex araneus
from SS fed on 15 taxa, while the shrew diets in NS habitat were half
as diverse. In contrast to previous studies, the nearly-perfect overlap of trophic niches in S. araneus-S. minutus indicates that in montane
forest habitat, otherwise highly competitive shrews can share trophic niches.
The invasion success of gibel carp (Carassius gibelio) depends on demographic and competitive traits. The major biological trait responsible for the invasiveness of C. gibelio is the mode of reproduction. Apart from sexual reproduction, which is typical in fish, C. gibelio is a unique cyprinid species able to reproduce through asexual gynogenesis, which is also known as sperm-dependent parthenogenesis, observed in all-female populations. Though the sexual and asexual forms of C. gibelio co-exist widely in natural habitats, the gynogenetic form has the capacity to modulate the range of effective ecological niches, which may facilitate the process of invasion. In this paper, we reviewed current knowledge of the sexual and gynogenetic forms of gibel carp along with their physiological advantages, immunological traits, and ability to withstand different environmental conditions. As parasitic infection may directly alter the immunology of hosts, and also indirectly alter their investment in reproduction, we provide some insights into the role of parasites as one of the potential drivers facilitating the coexistence of asexual and sexual forms. We highlight evidence that gibel carp have been identified as a serious threat to native species; hence, its impact on the ecosystem is also discussed.
Seasonal cycles constitute a major challenge for organisms since they may influence the genetic composition of a population, the species structure of a community and the interactions between organisms. Diapause is frequently used by insects to synchronize their life cycle with seasonal changes and is regarded as a key factor in the coexistence of competing species. Here the occurrence, abundance and emergence patterns of three poorly-known species of carnid flies (Carnus hemapterus Nitzsch, 1818, Hemeromyia anthracina Collin, 1949 and Hemeromyia longirostris Carles-Tolrá, 1992), which overwintered in the nests of several bird species at two localities, are reported and evidence of possible interspecific competition sought. Larvae of all three species were found in association with carrion and detritus. Both Hemeromyia species co-occurred in around 50% of the nests and Carnus with each of the Hemeromyia species at a lower rate (30-40% of the nests). Coexistence of all three carnid species was rare. We did not find any evidence of interspecific competition in the larval stage. Coexistence did not reduce the number of flies that emerged of any of the three species and the abundance of some species was even positively related. Species-specific emergence patterns and different habitat selection criteria (Carnus hemapterus seemed to avoid nests lined with vegetable material), which diminished the overlap between species were found. Such spatial and temporal segregation could facilitate the coexistence of these closely related species, which have similar ecological requirements, and might influence the seasonal dynamics of this poorly-known assemblage of insects inhabiting the nests of birds.
This paper analyzes two key questions: first, why nationalist parties have been dominating Bosnian politics since its declaration of independence in 1992 and, second, why this republic has been in a state of prolonged paralysis since the end of the war in 1995. Based on an analysis of the post-Dayton era, this study demonstrates that the roots of ongoing difficulties in Bosnia-Herzegovina lie in arguments about Bosnian independence and administration of the country. Because of these controversies, Bosnia-Herzegovina erupted in riots and eventually war in 1992. The Dayton Peace Agreement succeeded in reducing actual combats among the three constitutive nations, but the peacebuilding process failed to settle these arguments. Bosnian society remains divided between those who support an ethnic arrangement of the country, and those who prefer a civic arrangement. Another division is between those who are socially marginalized and those who participate effectively in the post-Dayton political system. and Studie analyzuje okolnosti, proč na politické scéně Bosny a Hercegoviny dominují od jejího vzniku nacionalisticky orientované politické strany, a proč se tento stát ve své novodobé poválečné historii setrvale točí v bludném kruhu. Analýza postdaytonského vývoje přitom jednoznačně napovídá, že kořeny potíží, v jakých se tato ex-jugoslávská republika od okamžiku svého vzniku v roce 1992 nachází, je nutno hledat především v odlišných postojích jejích občanů k otázce nezávislosti této země a jejímu vnitřnímu uspořádání. Kvůli rozporům vypukl na počátku 90. let vleklý konflikt, jehož mírové řešení dokázalo protikladné postoje bojujících stran reprezentovaných třemi konstitutivními národy k BaH pouze zredukovat, nikoliv však kompletně odstranit. Bosenskohercegovinská společnost je tak rozštěpená nejen mezi zastánce etnického a občanského přístupu k uspořádání státu, ale i mezi sociálně marginalizované občany a ty, kteří na daytonském politickém systému efektivně participují.
The present essay covers the topic of the first post-war census in Bosnia and Herzegovina. It focuses on the reasons why the census was postponed for so long, and explains why the implementation of the census was so deeply politicized. Last but not least, it sketches out other complications in preparing and executing this census. The crucial reason why the census was blocked for such a long time can be found in the different standpoints of the three constituent nationalities in Bosnia and Herzegovina and the international community's unclear stance to this issue. and Stať se zabývá problematikou prvního poválečného sčítání v Bosně a Hercegovině. Především se pokouší o analýzu příčin dlouhodobého odkladu sčítání, zdůvodnění politizace censu a v neposlední řadě nastiňuje i další komplikace, které jeho přípravu a realizaci provázely. Za stěžejní důvod, proč byl census tak dlouho blokován, lze označit rozdílná stanoviska tří konstitutivních národů Bosny a Hercegoviny a neujasněný postoj mezinárodního společenství k této otázce.
Príspevok poukazuje na životné osudy Gustáva Augustínyho, ktorý pôsobil ako novinár a publicista v poslednej tretine 19. storočia v rôznych mestách Dolnej zeme. Interpretačným spôsobom analyzuje jeho román Malý Paríž so špecifickým zreteľom na identifikáciu súdobých vzťahov národností na báze interpretačných reflexií. Vyzdvihuje najdôležitejšie atribúty dobovej národnej a národnostnej existencie z aspektu Slovákov. Poukazuje na "Bukuriašť" ako na významný geografický a kultúrny stredobod. Zdôrazňuje potrebné zmierenie a spojenectvo medzi Slovákmi a Rumunmi. Beletrizovaný cestopis ako základný kameň "literárnej tvorby" Gustáva Augustínyho spolu s jeho (v náznakoch uvádzanými) publikačnými aktivitami poukazuje na relatívne komplexnú tvorivú osobnosť autora v pozadí jeho horlivosti za práva Slovákov. Konkrétne teoretické súvzťažnosti sa konkretizujú adekvátnymi úryvkami z pôvodiny. and The contribution highlights the life of Gustáv Augustíny who has worked as a journalist and columnist in the last third of the 19th century in various cities of the Lowlands (Hungary). It analyzes his prose by means of interpretative method with specific regard to the identification of contemporary ethnic relations based on interpretive reflections. It highlights the most important attributes of contemporary national and ethnic aspect of the existence of the Slovaks. It refers to "Bukuriašť" as an important geographic and cultural centerpiece. It emphasizes the need of reconciliation and alliance between Slovaks and Romanians. Fictionalized prose as the cornerstone of Gustáv Augustíny's "literary work" along with him (in the stated indicated) publishing activity point to a relatively complex creative personality of the author behind his zeal for the rights of the Slovaks. Specifically, the theoretical correlations are gradually complemented by adequate excerpts from the original.
Dung beetle assemblages were monitored using baited pitfall traps from January to December 2006 in Northern Tunisia. 4,965 beetles belonging to 37 species were trapped. Aphodius lineolatus and Onthophagus taurus dominated the assemblages. Results showed a significant seasonal variation in assemblage composition, and diversity. There were four periods of activity during the course of the year. Temporal turnover was highest in October and in February. Temporal distribution of species shows seasonal segregation and opposite patterns in the two dominant guilds (Aphodiinae-dwellers and Scarabaeidae-tunnelers). Aphodiidae-dwellers were active from autumn to spring, although they were affected by summer drought. The Aphodius-dweller showed high temporal plasticity and phenological segregation. In contrast, Scarabaeidae-tunnelers were active all year round but mainly in the spring-summer period and less so in winter. Species in this guild showed a high degree of phenological overlap and a short ecological length. Our results suggest that coexistence in dung beetle guilds is facilitated by their phenological patterns, which reflect distinct ecological requirements and biogeographical origin of species. Geotrupidae-tunnelers and Scarabaeidae-rollers were rare and occurred mainly in the summer-autumn period, when individuals of the two other guilds were rare.