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Parasite Communities (parasite + community)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Effects of Human Exclusion on Parasitism in Intertidal Food Webs of Central Chile

CONSERVATION BIOLOGY, Issue 1 2005
GÉRALDINE LOOT
Fissurella crassa; intermareal rocoso; parasitismo; Proctoeces lintoni; reservas marinas Abstract:,Numerous ecological studies have demonstrated the dramatic effects that humans have on coastal marine ecosystems. Consequently, marine reserves have been established to preserve biodiversity. Recent reviews show that this strategy has paid off because inside reserves, most species have rapidly increased in size and abundance. Even though these studies focused on free-living organisms and paid little attention to parasite populations, numerous authors support the hypothesis that parasitism levels could be good indicators of ecosystem stability. We examined harvesting effects on the dynamics of a parasitic trematode ( Proctoeces lintoni) that completes its life cycle in intertidal mussels ( Perumytilus purpuratus), keyhole limpets (Fissurella crassa), and clingfish ( Sicyases sanguineus). All of these species are directly or indirectly affected by humans. Prevalence and abundance of the trematode P. lintoni in the three host species were compared in four study sites that differed in the intensity of human harvest. Parasitism infection in limpets and mussels was significantly higher in areas protected from human harvesting than in open-access areas, which suggests a significant change in parasite dynamics inside reserves. Yet the average parasitic biomass found in the gonads of F. crassa did not differ between protected and open-access areas. These results show, then, that the parasite system responded by increasing infection rates in marine protected areas without implication for reproductive success of the intermediate host. Our findings show that the indirect effects of harvesting by humans on the embedded parasite communities of littoral ecosystems require further scientific investigation. Resumen:,Numerosos estudios ecológicos han demostrado los efectos dramáticos de la actividad humana sobre ecosistemas marinos costeros. Consecuentemente, se han establecido las reservas marinas para preservar la biodiversidad. Revisiones recientes muestran que esta estrategia es adecuada porque la mayoría de las especies dentro de las reservas han incrementado en tamaño y abundancia rápidamente. Aunque, estos estudios se han concentrado en organismos de vida libre y han puesto poca atención a poblaciones de parásitos, numerosos autores apoyan la hipótesis de que los niveles de parasitismo pueden ser buenos indicadores de la estabilidad del ecosistema. Examinamos los efectos de pesquería artesanal sobre la dinámica de un trematodo parásito ( Proctoeces lintoni) que completa su ciclo de vida en mitíldos intermareales ( Perumytilus purpuratus), lapas ( Fissurella crassa) y Sicyases sanguineus, los cuales son afectados por humanos directa o indirectamente. La prevalencia y abundancia del trematodo P. lintoni en las tres especies de hospedadores fueron comparadas en cuatro sitios de estudio que difieren en la intensidad de recolecta por humanos. La infección parasitaria en lapas y mitíldos fue significativamente mayor en áreas protegidas que en áreas de libre acceso, lo que sugiere un cambio significativo en la dinámica del parásito dentro de las reservas, pero, la biomasa promedio de parásitos en gónadas de F. crassa no fue diferente entre áreas protegidas y de libre acceso. Por lo tanto, los resultados muestran que el sistema parásito respondió incrementando tasas de infección en áreas marinas protegidas sin consecuencias sobre el éxito reproductivo del ho spedador intermediario. Nuestros hallazgos muestran que se requiere más investigación científica de los efectos indirectos de los humanos sobre las comunidades de parásitos en ecosistemas litorales. [source]

Chemical mediation and niche partitioning in non-pollinating fig-wasp communities

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2007
MAGALI PROFFIT
Summary 1The parasitic chalcidoid wasps associated with the species-specific and obligatory pollination mutualisms between Ficus spp. and their agaonid wasp pollinators provide a good model to study the functional organization of communities. 2However, communities of non-pollinating fig wasps (NPFWs) remain little characterized, and their functioning and evolutionary dynamics are still poorly understood. 3We studied the communities of NPFWs associated with the monoecious F. racemosa and the dioecious F. hispida. Associated with these two fig species are a total of seven wasp species belonging to three genera. These species present contrasts in life history traits and in timing of oviposition. The species studied are thus broadly representative of the communities of NPFWs associated specifically with fig,pollinator mutualisms. 4In our study systems, there is temporal segregation of oviposition time among members of NPFW communities. 5We tested the role of volatile chemicals in the attraction of NPFWs associated with these two fig species, and tried to determine if chemical mediation can explain the organization of the communities. 6We conducted odour choice tests using a Y-tube olfactometer. All the NPFWs studied were shown to use volatile chemicals produced by the fig to locate their host. Furthermore, the signals used by each species depended on the phenological stage of the fig they exploit. 7Results demonstrated that the pattern of oviposition results from the utilization of volatile signals produced by figs that vary in their composition at different stages of fig development. Thus, chemical mediation allows resource partitioning in the NPFW communities associated with fig,pollinator mutualisms, and suggests hypotheses to explain coexistence in other parasite communities. [source]

Not everything is everywhere: the distance decay of similarity in a marine host,parasite system

JOURNAL OF BIOGEOGRAPHY, Issue 2 2009
Ana Pérez-del-Olmo
Abstract Aim, We test the similarity,distance decay hypothesis on a marine host,parasite system, inferring the relationships from abundance data gathered at the lowest scale of parasite community organization (i.e. that of the individual host). Location, Twenty-two seasonal samples of the bogue Boops boops (Teleostei: Sparidae) were collected at seven localities along a coastal positional gradient from the northern North-East Atlantic to the northern Mediterranean coast of Spain. Methods, We used our own, taxonomically consistent, data on parasite communities. The variations in parasite composition and structure with geographical and regional distance were examined at two spatial scales, namely local parasite faunas and component communities, using both presence,absence (neighbour joining distance) and abundance (Mahalanobis distance) data. The influence of geographical and regional distance on faunal/community divergence was assessed through the permutation of distance matrices. Results, Our results revealed that: (1) geographical and regional distances do not affect the species composition in the system under study at the higher scales; (2) geographical distance between localities contributes significantly to the decay of similarity estimated from parasite abundance at the lowest scale (i.e. the individual host); (3) the structured spatial patterns are consistent in time but not across seasons; and (4) a restricted clade of species (the ,core' species of the bogue parasite fauna) contributes substantially to the observed patterns of both community homogenization and differentiation owing to the strong relationship between local abundance and regional distribution of species. Main conclusions, The main factors that tend to homogenize the composition of parasite communities of bogue at higher regional scales are related to the dispersal of parasite colonizers across host populations, which we denote as horizontal neighbourhood colonization. In contrast, the spatial structure detectable in quantitative comparisons only, is related to a vertical neighbourhood colonization associated with larval dispersal on a local level. The stronger decline with distance in the spatial synchrony of the assemblages of the ,core' species indicates a close-echoing environmental synchrony that declines with distance. Our results emphasize the importance of the parasite supracommunity (i.e. parasites that exploit all hosts in the ecosystem) to the decay of similarity with distance. [source]

Richness and diversity of helminth communities in tropical freshwater fishes: empirical evidence

JOURNAL OF BIOGEOGRAPHY, Issue 4 2000
Anindo Choudhury
Abstract Aim Published information on the richness and diversity of helminth parasite communities in tropical freshwater fishes is reviewed in response to expectations of species-rich parasite communities in tropical regions. Location Areas covered include the tropics and some subtropical areas. In addition, the north temperate area of the nearctic zone is included for comparison. Methods Data from 159 communities in 118 species of tropical freshwater fish, summarized from 46 published studies, were used for this review. Parasite community descriptors used in the analyses included component community richness and calculated mean species richness. Data from 130 communities in 47 species of nearctic north temperate freshwater fish were summarized from 31 studies and used for comparison. Results The component helminth communities of many tropical freshwater fish are species-poor, and considerable proportions of fish from certain parts of the tropics, e.g. West African drainages, are uninfected or lightly infected. Mean helminth species richness was low and equaled or exceeded 2.0 in only 22 of 114 communities. No single group of helminths was identified as a dominant component of the fauna and species composition was variable among and within broader geographical areas. The richest enteric helminth assemblages were found in mochokid and clariid catfish with a mixed carnivorous diet, whereas algal feeders, herbivores and detritivores generally had species-poor gut helminth communities. Comparisons indicated that certain areas in the north temperate region had higher helminth species richness in fishes than areas in the tropics. Main conclusions Expectations of high species richness in helminth communities of tropical freshwater fishes are not fulfilled by the data. Direct comparisons of infracommunities and component communities in host species across widely separated phylogenetic and geographical lines are inappropriate. Examination of latitudinal differences in richness of monophyletic parasite groups or of compound communities may uncover patterns different from those found in this study. Richness of helminth communities may be ultimately determined not by the number of host species present but by the degree of divergence of host lineages and by their diversification modes. A phylogenetic framework for hosts and parasites will reveal if increased host species richness within host clades, when host speciation is accompanied by habitat or diet specialization, or both, leads to lower helminth diversity in host species by fragmentation of a core helminth fauna characteristic or specific of the larger host clade. This pattern may be analysed in the context of cospeciation and acquisition from other unrelated hosts (host-sharing or host-switching). [source]

Host,parasite interactions and vectors in the barn swallow in relation to climate change

GLOBAL CHANGE BIOLOGY, Issue 4 2010
A. P. MØLLER
Abstract Recent climate change has affected the phenology of numerous species, and such differential changes may affect host,parasite interactions. Using information on vectors (louseflies, mosquitoes, blackflies) and parasites (tropical fowl mite Ornithonyssus bursa, the lousefly Ornithomyia avicularia, a chewing louse Brueelia sp., two species of feather mites Trouessartia crucifera and Trouessartia appendiculata, and two species of blood parasites Leucozytozoon whitworthi and Haemoproteus prognei) of the barn swallow Hirundo rustica collected during 1971,2008, I analyzed temporal changes in emergence and abundance, relationships with climatic conditions, and changes in the fitness impact of parasites on their hosts. Temperature and rainfall during the summer breeding season of the host increased during the study. The intensity of infestation by mites decreased, but increased for the lousefly during 1982,2008. The prevalence of two species of blood parasites increased during 1988,2008. The timing of first mass emergence of mosquitoes and blackflies advanced. These temporal changes in phenology and abundance of parasites and vectors could be linked to changes in temperature, but less so to changes in precipitation. Parasites had fitness consequences for hosts because intensity of the mite and the chewing louse was significantly associated with delayed breeding of the host, while a greater abundance of feather mites was associated with earlier breeding. Reproductive success of the host decreased with increasing abundance of the chewing louse. The temporal decrease in mite abundance was associated with advanced breeding of the host, while the increase in abundance of the lousefly was associated with earlier breeding. Virulence by the tropical fowl mite decreased with increasing temperature, independent of confounding factors. These findings suggest that climate change affects parasite species differently, hence altering the composition of the parasite community, and that climate change causes changes in the virulence of parasites. Because the changing phenology of different species of parasites had both positive and negative effects on their hosts, and because the abundance of some parasites increased, while that of other decreased, there was no consistent temporal change in host fitness during 1971,2008. [source]