Spatial heterogeneity in recruitment of larval trematodes to snail intermediate hosts

Smith, Nancy F.

doi:10.1007/s004420000560

Cited by 132 publications

(117 citation statements)

References 42 publications

(72 reference statements)

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“…We found a significant negative correlation between density of snails and the proportion of snails infected by trematode parasites, suggesting that parasites may determine, at least in part, the current population density in our study system. From other studies it is known that the prevalence of infection in snails is largely determined by the presence and movements of infected definitive hosts (mammals and birds; see , Sousa 1990;Jokela and Lively 1995;Esch et al 2001;Smith 2001), and is thus potentially subject to a high degree of spatial and temporal variation (Brown et al 1988;Sousa 1990;Esch et al 2001). Perhaps, then, variation in the prevalence of trematode infection causes fluctuations in population size, decreasing long-term effective size and increasing the amount of drift load.…”

Section: Discussionmentioning

confidence: 99%

Genetic Variability and Drift Load in Populations of an Aquatic Snail

et al. 2004

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Abstract. Population genetic theory predicts that in small populations, random genetic drift will fix and accumulate slightly deleterious mutations, resulting in reduced reproductive output. This genetic load due to random drift (i.e., drift load) can increase the extinction risk of small populations. We studied the relationship between genetic variability (indicator of past population size) and reproductive output in eight isolated, natural populations of the hermaphroditic snail Lymnaea stagnalis. In a common laboratory environment, snails from populations with the lowest genetic variability mature slower and have lower fecundity than snails from genetically more variable populations. This result suggests that past small population size has resulted in increased drift load, as predicted. The relationship between genetic variability and reproductive output is independent of the amount of nonrandom mating within populations. However, reproductive output and the current density of snails in the populations were not correlated. Instead, data from the natural populations suggest that trematode parasites may determine, at least in part, population densities of the snails.

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Section: Discussionmentioning

confidence: 99%

Genetic Variability and Drift Load in Populations of an Aquatic Snail

et al. 2004

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“…However, defining local diversity will depend on the home-range of different hosts and vectors and the spatial scale at which they interact (landscape epidemiology) (see Ostfeld et al, 2005). For example, the movement of short-lived trematode miracidia is often extremely local, frequently leading to significant spatial heterogeneity in snail infections, even within a single wetland ecosystem (Smith, 2001). In contrast, tick vectors are comparatively long lived and can travel widely with their vertebrate hosts, effectively increasing the spatial scale of transmission.…”

Section: How Does the Relationship Between Diversity And Disease Varymentioning

confidence: 99%

Diversity, decoys and the dilution effect: how ecological communities affect disease risk

Johnson

Thieltges

2010

Journal of Experimental Biology

289

264

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SUMMARY Growing interest in ecology has recently focused on the hypothesis that community diversity can mediate infection levels and disease (‘dilution effect’). In turn, biodiversity loss — a widespread consequence of environmental change — can indirectly promote increases in disease, including those of medical and veterinary importance. While this work has focused primarily on correlational studies involving vector-borne microparasite diseases (e.g. Lyme disease, West Nile virus), we argue that parasites with complex life cycles (e.g. helminths, protists, myxosporeans and many fungi) offer an excellent additional model in which to experimentally address mechanistic questions underlying the dilution effect. Here, we unite recent ecological research on the dilution effect in microparasites with decades of parasitological research on the decoy effect in macroparasites to explore key questions surrounding the relationship between community structure and disease. We find consistent evidence that community diversity significantly alters parasite transmission and pathology under laboratory as well as natural conditions. Empirical examples and simple transmission models highlight the diversity of mechanisms through which such changes occur, typically involving predators, parasite decoys, low competency hosts or other parasites. However, the degree of transmission reduction varies among diluting species, parasite stage, and across spatial scales, challenging efforts to make quantitative, taxon-specific predictions about disease. Taken together, this synthesis highlights the broad link between community structure and disease while underscoring the importance of mitigating ongoing changes in biological communities owing to species introductions and extirpations.

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“…Because the diversity and abundance of these additional hosts correlates with species richness and prevalence of trematodes infecting horn snails at small spatial scales (Smith 2001, Hechinger and Lafferty 2005, Hechinger et al 2007), these final and second intermediate hosts might drive some of the observed diversity patterns. However, both bird and second intermediate host richness are likely greater in the tropics, considering general diversity patterns in the ocean (Hillebrand 2004, Roy andWitman 2009).…”

Section: Possible Explanations For the Reversed Ldgsmentioning

confidence: 99%

Parasite species richness and intensity of interspecific interactions increase with latitude in two wide‐ranging hosts

Torchin

Miura

Hechinger

2015

Ecology

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Abstract. Although the latitudinal diversity gradient is a well-known and general pattern, the mechanisms structuring it remain elusive. Two key issues limit differentiating these. First, habitat type usually varies with latitude, precluding a standardized evaluation of species richness. Second, broad-scale and local factors hypothesized to shape diversity patterns covary with one another, making it difficult to tease apart independent effects. Examining communities of parasites in widely distributed hosts can eliminate some of these confounding factors. We quantified diversity and interspecific interactions for trematode parasites infecting two similar snail species across 27 degrees of latitude from 43 locations in tropical and temperate oceans. Counter to typical patterns, we found that species richness, levels of parasitism, and intensity of intraguild predation increased with latitude. Because speciation rates are precluded from driving diversity gradients in this particular system, the reversed gradients are likely due to local ecological factors, specifically, increased productivity and stability. We highlight how this system may serve as a useful tool to provide insight into what processes drive diversity gradients in general.

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Spatial heterogeneity in recruitment of larval trematodes to snail intermediate hosts

Cited by 132 publications

References 42 publications

Genetic Variability and Drift Load in Populations of an Aquatic Snail

Genetic Variability and Drift Load in Populations of an Aquatic Snail

Diversity, decoys and the dilution effect: how ecological communities affect disease risk

Parasite species richness and intensity of interspecific interactions increase with latitude in two wide‐ranging hosts

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