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

Abstract

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.

Latitudinal gradients of parasite richness: a review and new insights from helminths of cricetid rodents

“…Merino et al (2008) failed to find a significant relationship between latitude and richness of three genera of haematozoa (blood parasites) in 26 species of forest birds in Chile. Thieltges et al (2009) and Torchin et al (2015) each sampled two snail host species for parasitic trematodes. Schemske et al (2009) and Poulin (2014) suggested that investigations of the LDG of parasites within a single, widely-distributed host species may provide stronger tests of latitudinal patterns than studies combining host taxa, given that the taxonomic composition of host and parasite communities change between temperate and tropical areas and might therefore be incomparable (Poulin 2014).…”

“…Using small mammals from Brazil, Linardi and Krasnov (2013) found that flea species richness was not significantly related to latitude and mite species richness was significantly and positively correlated with latitude, with mite richness increasing with distance from the equator. Torchin et al (2015) examined trematodes along the east and west coasts of the southern United States to Panama and found that species richness increased with increasing latitude. However, few studies have explored the LDG within a host species, and even fewer have used a globally-distributed species, as recommended by Poulin (2014).…”

“…In another geographically restricted study, Blaylock et al (1998) found a significant and positive relationship between parasite species richness and latitude in one species of halibut at high latitudes (approximately 40-60 degrees north) along the western coasts of Canada and Alaska, with richness increasing with latitude. Thieltges et al (2009) and Torchin et al (2015) each sampled two snail host species for parasitic trematodes. Torchin et al (2015) examined trematodes along the east and west coasts of the southern United States to Panama and found that species richness increased with increasing latitude.…”

Drivers of symbiont diversity in freshwater snails: a comparative analysis of resource availability, community heterogeneity, and colonization opportunities

“…Aquatic snails offer an excellent system in which to investigate patterns of symbiont richness and their underlying drivers (e.g., Torchin et al 2015). They are the obligate first intermediate hosts for parasitic flatworms (trematodes), some of which affect the health of humans, domestic animals, or wildlife (Crompton 1999; Johnson et al 1999; King et al 2005; Gryseels et al 2006).…”

The Rise of Disease Ecology and Its Implications for Parasitology— A Review

“…Morand and Krasnov, 2008;Dunn et al, 2010;Kamiya et al, 2014;Poulin, 2014;Smith et al, 2014;Torchin et al, 2015 The interface between parasitology, community ecology, and ecosystem science How do parasites and pathogens affect communityand ecosystem-scale processes, including nutrient cycling, disturbance regimes, primary production, and community composition? Can this information be used to enhance our understanding of global parasite biodiversity and the identification of disease hotspots?…”