Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges

Abstract

Aim To use a comparative approach to understand parasite demographic patterns in native versus introduced populations, evaluating the potential roles of host invasion history and parasite life history.Location North American east and west coasts with a focus on San Francisco Bay (SFB).Methods Species richness and prevalence of trematode parasites were examined in the native and introduced ranges of two gastropod host species, Ilyanassa obsoleta and Littorina saxatilis. We divided the native range into the putative source area for introduction and areas to the north and south; we also sampled the overlapping introduced range in SFB. We dissected 14,781 snails from 103 populations and recorded the prevalence and identity of trematode parasites. We compared trematode species richness and prevalence across the hosts' introduced and native ranges, and evaluated the influence of host availability on observed patterns.Results Relative to the native range, both I. obsoleta and L. saxatilis have escaped (lost) parasites in SFB, and L. saxatilis demonstrated a greater reduction of trematode diversity and infection prevalence than I. obsoleta. This was not due to sampling inequalities between the hosts. Instead, rarefaction curves suggested complete capture of trematode species in native source and SFB subregions, except for L. saxatilis in SFB, where infection was extremely rare. For I. obsoleta, infection prevalence of trematodes using fish definitive hosts was significantly lower in SFB compared to the native range, unlike those using bird hosts. Host availability partly explained the presence of introduced trematodes in SFB.Main conclusions Differential losses of parasite richness and prevalence for the two gastropod host species in their introduced range is probably the result of several mechanistic factors: time since introduction, propagule pressure, vector of introduction, and host availability. Moreover, the recent occurrence of L. saxatilis' invasion and its active introduction vector suggest that its parasite diversity and distribution will probably increase over time. Our study suggests that host invasion history and parasite life history play key roles in the extent and diversity of trematodes transferred to introduced populations. Our results also provide vital information for understanding community-level influences of parasite introductions, as well as for disease ecology in general.

Patterns of host and flea communities along an elevational gradient in Colorado

“…Generally, taxa will occur where environmental conditions are suitable and available, and these will be limited by resources and dispersal (Peterson et al 2011). Parasites are then constrained to at least a subset of these conditions, but likely have additional resources, dispersal, and physiological limits (Poulin 1995(Poulin , 2004Combes 2001;Blakeslee et al 2012;Hoberg and Brooks 2008;Krasnov et al 2010a). Furthermore, the level of specialization of parasites may restrict distribution and abundance through resource availability (Combes 2001;Krasnov et al 2007), as well as interactions with other parasite species (Krasnov et al 2006a(Krasnov et al , 2006c.…”

Aquatic Introductions and Genetic Founder Effects: How do Parasites Compare to Hosts?

“…The snail is infected by fourteen trematode parasites in its native East Coast range but only three (from a single population) are found in SFB , again representing a significant reduction in parasite diversity and abundance in the introduced range. While genetic data exists for the snail's native and introduced populations (Brown, 2007;Brown, Geller, Blakeslee, unpublished), there is no available genetic data for its introduced parasites because of the extremely low abundance and richness of trematodes infecting L. saxatilis in SFB (<0.5% throughout the Bay; Blakeslee et al, 2011). However, because the snail is a prominent host to trematode parasites in its native range, and because extensive genetic data exists for the snail in both its native and introduced regions, we include L. saxatilis here to complement the data we have for the other two snails in order to provide a better understanding of genetic diversity patterns in general for native versus introduced first-intermediate gastropod hosts.…”

“…The snail inhabits soft sediment, estuarine, and marine environments and often reaches extremely high abundances in both native and introduced populations (Scheltema, 1961;Brown, 1969;Curtis & Hurd, 1981;Blakeslee et al, 2011;A.M.H.B., pers. obs.).…”

The invasive sun coral Tubastraea coccinea hosting a native Christmas tree worm at Curaçao, Dutch Caribbean

“…For example, the American slipper limpet Crepidula fornicata (Linnaeus, 1758) is an introduced host for the boring sponge Cliona celata Grant, 1826, and the digenean trematode Himasthla elongata (Mehlis, 1831) in the northeastern part of the Atlantic (Hoeksema 1983;Thieltges et al 2009), whereas both parasites also occur in their host's native range (Blakeslee et al 2011;Carroll et al 2015). Another example concerns ctenophores of the species Mnemiopsis leidyi Agassiz, 1865, which can become infested by parasitic larvae of the actiniarian genus Edwardsiella in the ctenophore's original native range along the North American east coast and also in its new, introduced range in northwestern Europe (Reitzel et al 2009;Selander et al 2010).…”

“…Only a few reports deal with marine host species that are recognized as invasives, and usually their parasites are co-introduced (e.g., Blakeslee et al 2011).…”