Parasite communities Community ► Heterotypic assemblage composed of individu different species which may actually interact i.e. communities of gill parasites in fish Hierarchical classification of parasite communities sisting of all parasites of different species individual ► Metacommunity or component community Assemblage consisting of all parasites of different species exploiting host population (in a given time and in a given space) ► Supracommunity or compoud community assemblage composed of all metacommunities in a given ecosystem Hierarchical classification of parasite communities in a given host species Parasitofauna of a given host species - 5 parasite species Host population 2 to 4 parasite species Host individual - 0 to 3 parasite species Hierarchical level of parasite communities (Guegan, Morand A Poulin, 2004) Infracommunity ► Number of parasite species ► Relative abundance (number of specimens of each parasite species) ► Dynamic system - mobility, natality, mortality ► Formation during ecological time, influence of infection and demographic processes Typically short-lived Infracommunity Number of parasite species Relative abundance (number of specimens of each parasite species) Dynamic system Formation during ecological time, influence of infection and demographic processes (mobility, natality, mortality) ► Typically short-lived Hostitel t1 Hostitel t2 Hostitel t3 Infracommunity ► Maximum number of species in IC = number of species in MC This upper limit is not realized. i.e. 31 intestinal helminth communities in birds 0 10 20 30 40 Component community richness 37 intestinal helminth communities in mammals Saturation of communities Saturation of parasite infracommunities? Kennedy & Guegan (1996) 64 metacommunities of intestinal helminths Can the saturation limit the number of species in helmintl infracommunities? maximum number of species in infracommunities = 3 number of species in metacommunities > 3 saturation of infracommunities - number of species in IC bellow the number of species in MC Infracommunities ► very rare saturation of infracommunities b; species - vacant niches parasite ► saturation by parasite biomass E.g. Helminth communities in 131 vertebrate species total biomass of intracommunitv increased with host bod' size, large hosts = high biomass of parasites Infracommunities ► Variability in the number of species in infracommunities of a given host population - infracommunities with low number of species, infracommunitiies with high number of species ► Number of species in infracommunities 1. random distribution of parasite species on/in host 2. affected by interactions (competitive exclusion) or colonization of one species is dependent on the other species Infracommunities ► Frequency distribution of parasite species in infracommunities (species prevalence) - observed vs. predicted distribution by null model (Janovy et al., 1995) I ■ I IH MhMHHMH ■ interactive community -competitive exclusion positive interactions - using host by other parasite species is facilitated heterogeneity among hosts in susceptibility to infection 4 metacommunities of gastrointestinal helminths in mammals Infracommunities Larval digeneans in intermediate hosts (snails) - very few infracommunities with more than 1 species —> temporal and spatial heteroqeneitv in infection rate -»• relative effect of antagonistic interactions on frequency of infections between two larval digenean speci Metacommunity Longer-lived assemblages than any of their infracommunities MC is formed over evolutionary time scales by invasion, speciation, extinction, colonization or host switches Maximum number of parasite species in MC = the number of species in the parasite fauna ► Often a saturation of the level of species below that of the P« ;ite fauna Saturation of metacommunity Ex. relationship between parasite species richness in MC and richness in the parasite fauna (helminth parasites of 32 freshwater fish species in UK published by Kennedy & égan, 1994) Decay in metacommunities similarity with increasing distances I I-1 I-1 *-* □ O O o o o o o o □ o o o o o o Geographical distances Climatic or environmental gradient Species-specific dispersion Similarity in parasite metacommunities ► Contacts of host populations and exchange of parasites Physically isolated host populations - different parasite MC ► Geographical distances - good predictor of similarity in species composition (but this is not universal phenomenon) Similarity in parasite metacommunities role of host ► Dispersal capacity and migration - homogeneity of metacommunities in region e.g. limited dispersal capacity of freshwater fish (fragmented freshwater habitats), no-limited dispersal capacity in open space in marine ► Different food availabilities and preferences in different continents Diversity of metacommunities: role of host ► Higher host diversity —► species-richer parasite metacommunities ► Positive relationship between number of host species of a given taxon in a habitat and number of parasite species using this taxon Diversity of metacommunities: role of host ► Time necessary for evolution ommunity ► Translocation of host populations ► e.g. introduction of host species - initial stage - species-poor metacommunties asing diversity in time - host switching between sympatric hosts, migration of new parasitized specimens of host Diversity of metacommunities: role of host Composition of metacommunities in relation to host specificity e.g. Anguilla rostrata - metacommunities with mainly specialists on the Atlantic coast, and mainly generalits in the continents in geographical space the number of species in parasitofauna increases, relative number of special creases Similarity in parasite metacommunities: role of parasite Colonization and dispersion of some parasites associated with life cycle (IH, DH, parathenic hosts) ► allogenic parasites - used birds as a DH - homogenous id predicted metacommunities ► autogenic parasites - used strictly water organisms, different metacommunities e.g. Coregonus lavaretus- helminth metacommunitie: - share allogeneic species - differ in autogenic species depending on the distanc between lakes fe- es Nested structure of parasite infracommunities ► Nonrandom distribution of species richness among infracommunities Type of hierarchical structure of communities in fragmented habitats (firstly described for mammal communities in islands) ► Host = fragmented habitat - nonrandom distribution ol parasite species among IC i.e. within Nested structure of parasite infracommunities Infracommunities Infracommunities CO CD "u CD Q. B C Nested structure Random structure Two hypothetical distributions of parasite species among the infracommunities Each parasite species of a species poorer infracommunity is the subset of species-richer infracommunity Nestedness in parasite metacommunities Each parasite species of a species-poorer locality (host population) is the subset of species-richer locality (host population) Nestedness in different hierarchical level of organization of parasite communities Hosts populations (■■■■■■i aimi Localities Parasites >opulations Localities ► from local to regional level Parasites ■■■■■ Hostfe ■■■■ ■■■ ■■ Nestedness of metacommunities and phylography Ex. Helminths in Apodemus sylvaticus Host populations (by rank) Mainland ^- Islands Parasite species (by rank) High probability of invasion Low probability of extinction Low probability of invasion High probability of extinction Habitats with low extinction rates Habitats with high exctinction rates Large area size Small area size High biodiversity Low biodiversity Which processes generate the nested pattern? ► Free living species - different extinction, colonization and dispersion ► Parasites - different transmission, host heterogeneity generates different extinction and colonization of parasites - heterogeneity in host size, small host —► big host - competition - different opinions (increase/descrease/no effect) - association to host specificity e.g. Gyrodactylus in freshwater cyprinids (high nestednesss in the communities with dominant position of specialists) Which processes generate nestedness? Nestedness - result of epidemiological processes (Morand et alv 2002) _ Link between nestedness and parasite prevalence -consequences of different parasite colonization and extinction linked with natality and mortality Nestedness vs. antinestedness Nested structure = one extreme case of hierarchical structure of parasite communities ► Alternative antinested structure - parasite species present in species-poor communities are never present in species rich communities (some parasite communities of fish) Biological interpretation unclear Nestedness vs. antinestedness Basics of data processing of parasitic communities Number of parasite species in communities of p Species 1 Species 2 Species 3 I sp« Community A ♦ ♦♦ ¥¥¥ Community B ♦ Analyses of diversity of parasite communities index of diversity - Shannon index diversity Brillouin index diverzity Shannon index diversity it assumes a random selection of individuals from a theoretically unlimited number and the presence of a species of community in the sample ► to analyze diversity of parasite metacommuni where S is the total number of species, pi is the proportion of individuals of the i-th species, N is the total number individuals, ni is the number of individuals of the i-th species ►variability in Shannon diverzity Shannon index diverzity The difference between the Shannon index values for the two communities can be compared using a t-test (VarHi+VarHiy (VarHi + VarHi)2 (VarHi)2 | (VarHif The maximum value of the Shannon index for a given community = In S = Shannon index at identical species frequency in the community Indexes of diversity Equitability = evenness - the relative value of the diversil depleted by a given community in relation to a communi with the same number of species ► Brillouin index of diverzity - in case it is not possible to ensure random sampling or the sample contains all members - describes only the sampled part of the community - for the study of parasite infracommunities n- number of specimens of /-th species N- total number of specimens Indexes of dominance ► the most important is the number of the most common species ► Simpson index of domin; - strongly dependent on the most numerous species in the community, less sensitive to rare species - with increasing value, dominance increases and finuitabilitv of mmmunitv dfinrfiasfis. often uses its inverse or subtraction from one n- number of specimens ofAth species N- total number of specimens Indexes of dominance ► Berger-Parker index - expresses the relative importance of the most numerous species - its inverse value is often used - is independent of the number of species but is affected by the sample size Nmax - number of specimens of the most numerous species N- total number of specimens Similarity of communities ► Association coefficients ► dependence coefficients (0 - no dependence) ► similarity coefficients (maximum value - identical communities, minimum value - completely different communities) ► distances coefficients (distances between communities increase with the value of coefficient) ► Types of data: binary data (presence - absenci quantitative data (abundance) indance Numerical Ecology Legend gendre (1998) Similarity of communities ► asymmetric coefficients - zero values are evaluated differently than other values ► symmetric coefficients - zero values for two objects are evaluated in the same wav as other values for pairs of communities ► problem of evaluation of double absence of species Qualitative similarity of communities ► Association matrix - binary data 1 0 l a b a+b Community A 0 c d c+d a+c b+d a - number of parasites present in two communities (in two localities) d- number of absences of parasites in two communities (in two localities) b - presence of parasites at the first locality, absence at the second locality c- absence of parasites at the first locality, presence at the second locality Qualitative similarity of communities Jaccard coefficient - asymmetric binary coefficiei a, b, c have the same weight ► Sorensen coefficient where the presence of the species is more informative than the absence Quantitative similarity of communities Symmetric coefficient Abundance of parasites Community a 9 3 7 3 4 9 5 4 0 6 Community b 2 3 2 12 9 3 2 0 6 congruence 0 1 0 0 0 10 0 1 1 S(a, b) = congruence/p = 4/10 = 0.4 Abundance of parasites aN bN jN Community a 7 3 0 5 0 1 16 Community b 2 4 7 6 0 3 22 Minimum 2 3 0 5 0 1 11 where aNand bN are the total numbers of individuals in the community „a" or „b" yTVthe sum is always the lowest of the abundances of the species found in one of the communities