Introduced cryptic species of parasites exhibit different invasion pathways

Abstract

Sometimes infectious agents invade and become established in new geographic regions. Others may be introduced yet never become established because of the absence of suitable hosts in the new region. This phenomenon may be particularly true for the many parasites with complex life cycles, where various life stages require different host species. Homogenization of the world's biota through human-mediated invasions may reunite hosts and parasites, resulting in disease outbreaks in novel regions. Here we use molecular genetics to differentiate invasion pathways for two digenean trematode parasites and their exotic host, the Asian mud snail, Batillaria attramentaria. All of the snail haplotypes found in introduced populations in North America were identical to haplotypes common in the areas of Japan that provided oysters for cultivation in North America, supporting the hypothesis that the snails were introduced from Japan with seed oysters. Two cryptic trematode species were introduced to North American populations in high frequencies. We found a marked reduction of genetic variation in one of these species, suggesting it experienced a bottleneck or founder event comparable to that of the host snail. In contrast, no genetic variation was lost in the other parasite species. We hypothesize that this parasite was and is dispersed naturally by migratory shorebirds and was able to establish only after the host snail, B. attramentaria, was introduced to North America. Evaluation of the nature of invasion pathways and postinvasion consequences will aid mitigation of spreading diseases of humans, livestock, and wildlife in an increasingly globalized world. Batillaria attramentaria ͉ Trematode parasites

Genetic population structure of the invasive signal crayfish Pacifastacus leniusculus in Japan inferred from newly developed microsatellite markers

“…Anecdotal evidence suggests that juvenile crayfish have been introduced unintentionally together with aquaculture species such as the Japanese smelt (Hypomesus nipponensis McAllister) or transplanted macrophytes such as water chestnuts (Trapa). Such unintentional introductions have been reported in various aquaculture species including the Pacific oyster, Crassostrea gigas (Thunberg) (Miura et al 2006), Japanese clam, Ruditapes philippinarum (Adams & Reeve) (Okoshi 2007) and ayu, Plecoglossus altivelis (Temminck & Schlegel) (Takamura 2009). Identifying invasion pathways and dispersal methods of P. leniusculus is urgently required, probably through large-scale spatio-temporal crayfish sampling together with finer-scale population genetic analysis.…”

Molecular phylogenetics reveals differential divergence of coastal snails separated by the Isthmus of Panama

“…While the 28S gene is generally conservative and is not ideal for genetic resolution at the species level, given the absence of other more appropriate nuclear markers for these taxa, we included it to evaluate potential hybridizations between these snails. As primer pairs, we used COI-bf (Miura et al, 2006a) and COI-6 (Shimayama et al, 1990) for amplification of the COI gene, 16Sar and 16Sbr (Kessing et al, 1989) for the 16S gene, and DIE and D6 (Park and 6 Foighil, 2000) for the 28S gene. For the COI gene, PCR were run for 35 cycles under the following conditions: denaturing at 94 °C for 60 s, annealing at 45 °C for 60 s and extension at 72 °C for 90 s. The 35 cycles were preceded by an initial denaturing at 94 °C for 1 min.…”

Parasite co-structure: broad and local scale approaches

“…There was higher genetic subdivision between tick populations from the different host species in sympatry than between allopatric tick populations of the same host species. Miura et al (2006) examined colonization dynamics by comparing the genetic diversity of an introduced snail and its trematode parasites. Molecular data indicated a founder effect in the snail and one of its flukes.…”