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Hybridization between two cestode species and its consequences for intermediate host range.

Henrich T, Benesh DP, Kalbe M - Parasit Vectors (2013)

Bottom Line: We used an in vitro breeding system to hybridize Schistocephalus solidus and S. pungitii; hybridization rate was quantified using microsatellite markers.We show that the parasites can hybridize in the in vitro system, although the proportion of self-fertilized offspring was higher in the heterospecific breeding pairs than in the control pure parental species.Further studies are needed to find the reason for the maintenance of the species boundaries in wild populations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Ecology, Max Planck Institute for Evolutionary, Biology, August-Thienemann-Strasse 2, Plön 24306, Germany.

ABSTRACT

Background: Many parasites show an extraordinary degree of host specificity, even though a narrow range of host species reduces the likelihood of successful transmission. In this study, we evaluate the genetic basis of host specificity and transmission success of experimental F(1) hybrids from two closely related tapeworm species (Schistocephalus solidus and S. pungitii), both highly specific to their respective vertebrate second intermediate hosts (three- and nine-spined sticklebacks, respectively).

Methods: We used an in vitro breeding system to hybridize Schistocephalus solidus and S. pungitii; hybridization rate was quantified using microsatellite markers. We measured several fitness relevant traits in pure lines of the parental parasite species as well as in their hybrids: hatching rates, infection rates in the copepod first host, and infection rates and growth in the two species of stickleback second hosts.

Results: We show that the parasites can hybridize in the in vitro system, although the proportion of self-fertilized offspring was higher in the heterospecific breeding pairs than in the control pure parental species. Hybrids have a lower hatching rate, but do not show any disadvantages in infection of copepods. In fish, hybrids were able to infect both stickleback species with equal frequency, whereas the pure lines were only able to infect their normal host species.

Conclusions: Although not yet documented in nature, our study shows that hybridization in Schistocephalus spp. is in principle possible and that, in respect to their expanded host range, the hybrids are fitter. Further studies are needed to find the reason for the maintenance of the species boundaries in wild populations.

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Relationship between fish weight and worm weight. The figure shows the relationship of fish and worm weight in mg for the different treatment groups. (G. ac with S. solidus: n=12, G. ac with hybrids: n=11, P. pu with S. pungitii: n=4, P. pu with hybrids: n=14).
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Figure 5: Relationship between fish weight and worm weight. The figure shows the relationship of fish and worm weight in mg for the different treatment groups. (G. ac with S. solidus: n=12, G. ac with hybrids: n=11, P. pu with S. pungitii: n=4, P. pu with hybrids: n=14).

Mentions: There was a significant relationship between fish weight and worm weight (F1, 39 = 104.4, P < 0.001). Moreover, this relationship seemed to depend on the worm group (interaction between fish weight and worm group, F3, 33 = 8.68, P < 0.001) (Figure 5). Differences between groups were biggest in large fish, with pure S. solidus growing particularly large in G. aculeatus (Figure 5). Unfortunately, there were few data points in the largest fish, making these results tenuous. When we eliminated the data points from the largest fish (>0.7 g), there was no longer a significant interaction (F3, 29 = 0.09, P = 0.96) nor were there significant differences in the mean weight of hybrids and pure species worms (F3, 29 = 0.27, P = 0.84). Thus, these results suggest that hybrids and pure lines grow to quite comparable sizes in sticklebacks, although it remains possible that in larger fish worm sizes may diverge between groups.


Hybridization between two cestode species and its consequences for intermediate host range.

Henrich T, Benesh DP, Kalbe M - Parasit Vectors (2013)

Relationship between fish weight and worm weight. The figure shows the relationship of fish and worm weight in mg for the different treatment groups. (G. ac with S. solidus: n=12, G. ac with hybrids: n=11, P. pu with S. pungitii: n=4, P. pu with hybrids: n=14).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3584927&req=5

Figure 5: Relationship between fish weight and worm weight. The figure shows the relationship of fish and worm weight in mg for the different treatment groups. (G. ac with S. solidus: n=12, G. ac with hybrids: n=11, P. pu with S. pungitii: n=4, P. pu with hybrids: n=14).
Mentions: There was a significant relationship between fish weight and worm weight (F1, 39 = 104.4, P < 0.001). Moreover, this relationship seemed to depend on the worm group (interaction between fish weight and worm group, F3, 33 = 8.68, P < 0.001) (Figure 5). Differences between groups were biggest in large fish, with pure S. solidus growing particularly large in G. aculeatus (Figure 5). Unfortunately, there were few data points in the largest fish, making these results tenuous. When we eliminated the data points from the largest fish (>0.7 g), there was no longer a significant interaction (F3, 29 = 0.09, P = 0.96) nor were there significant differences in the mean weight of hybrids and pure species worms (F3, 29 = 0.27, P = 0.84). Thus, these results suggest that hybrids and pure lines grow to quite comparable sizes in sticklebacks, although it remains possible that in larger fish worm sizes may diverge between groups.

Bottom Line: We used an in vitro breeding system to hybridize Schistocephalus solidus and S. pungitii; hybridization rate was quantified using microsatellite markers.We show that the parasites can hybridize in the in vitro system, although the proportion of self-fertilized offspring was higher in the heterospecific breeding pairs than in the control pure parental species.Further studies are needed to find the reason for the maintenance of the species boundaries in wild populations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Ecology, Max Planck Institute for Evolutionary, Biology, August-Thienemann-Strasse 2, Plön 24306, Germany.

ABSTRACT

Background: Many parasites show an extraordinary degree of host specificity, even though a narrow range of host species reduces the likelihood of successful transmission. In this study, we evaluate the genetic basis of host specificity and transmission success of experimental F(1) hybrids from two closely related tapeworm species (Schistocephalus solidus and S. pungitii), both highly specific to their respective vertebrate second intermediate hosts (three- and nine-spined sticklebacks, respectively).

Methods: We used an in vitro breeding system to hybridize Schistocephalus solidus and S. pungitii; hybridization rate was quantified using microsatellite markers. We measured several fitness relevant traits in pure lines of the parental parasite species as well as in their hybrids: hatching rates, infection rates in the copepod first host, and infection rates and growth in the two species of stickleback second hosts.

Results: We show that the parasites can hybridize in the in vitro system, although the proportion of self-fertilized offspring was higher in the heterospecific breeding pairs than in the control pure parental species. Hybrids have a lower hatching rate, but do not show any disadvantages in infection of copepods. In fish, hybrids were able to infect both stickleback species with equal frequency, whereas the pure lines were only able to infect their normal host species.

Conclusions: Although not yet documented in nature, our study shows that hybridization in Schistocephalus spp. is in principle possible and that, in respect to their expanded host range, the hybrids are fitter. Further studies are needed to find the reason for the maintenance of the species boundaries in wild populations.

Show MeSH
Related in: MedlinePlus