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The dilution effect in a freshwater mutualism: impacts of introduced host species on native symbionts
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  • Robert Creed,
  • Gretchen L. Bailey,
  • James Skelton,
  • Bryan L. Brown
Robert Creed
Appalachian State University

Corresponding Author:[email protected]

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Gretchen L. Bailey
Appalachian State University
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James Skelton
William & Mary Department of Biology
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Bryan L. Brown
Department of Biological Sciences Virginia Tech Blacksburg VA 24061 USA
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The dilution effect was originally proposed to describe the negative effect of increased host diversity on parasite abundance; with greater host diversity, parasite levels per host are predicted to be lower due to a higher probability of dispersing parasites encountering non-competent hosts. Dilution effects could also occur in many mutualisms if dispersing symbionts encounter hosts that vary in their competency. The introduction of non-native hosts can change community competency of a local group of host species. Crayfish introductions are occurring world-wide and these introductions are likely disrupting native crayfish-symbiont systems. Branchiobdellidan symbionts declined on native Cambarus crayfish occurring in the presence and absence of non-native Faxonius crayfish in the New River, USA. We performed an experiment investigating the effect of host density (1 vs 2 native hosts) and host diversity (1 native host and 1 introduced host) on branchiobdellidan abundance. The introduced F. cristavarius is a non-competent host for these worms. Six C. ingens were stocked on a C. chasmodactylus in each treatment and worm numbers were followed over 34 days. Worm numbers decreased over time on C. chasmodactylus alone and in the treatment in which a C. chasmodactylus was paired with an F. cristavarius. Worm numbers remained highest in the 2 C. chasmodactylus treatment . There was no significant effect of host diversity on worm reproduction. Crayfish invasions may have negative effects on mutualistic symbionts depending on the competence of introduced hosts. Loss of native symbionts is one of the potential hidden, negative effects of invasions on native freshwater diversity.
09 Sep 2021Submitted to River Research and Applications
10 Sep 2021Submission Checks Completed
10 Sep 2021Assigned to Editor
13 Sep 2021Review(s) Completed, Editorial Evaluation Pending
13 Sep 2021Reviewer(s) Assigned
15 Oct 2021Editorial Decision: Revise Minor
12 Nov 20211st Revision Received
12 Nov 2021Assigned to Editor
12 Nov 2021Submission Checks Completed
12 Nov 2021Review(s) Completed, Editorial Evaluation Pending
14 Nov 2021Reviewer(s) Assigned
03 Dec 2021Editorial Decision: Revise Minor
22 Dec 20212nd Revision Received
22 Dec 2021Review(s) Completed, Editorial Evaluation Pending
22 Dec 2021Submission Checks Completed
22 Dec 2021Assigned to Editor
28 Dec 2021Editorial Decision: Revise Minor
31 Dec 20213rd Revision Received
04 Jan 2022Review(s) Completed, Editorial Evaluation Pending
04 Jan 2022Submission Checks Completed
04 Jan 2022Assigned to Editor
05 Jan 2022Editorial Decision: Accept
Oct 2022Published in River Research and Applications volume 38 issue 8 on pages 1460-1468. 10.1002/rra.3940