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Life history shifts in an exploited African fish following invasion by a castrating parasite
  • Nestory Gabagambi
Nestory Gabagambi
University of Bergen Faculty of Mathematics and Natural Sciences
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Abstract

Evolutionary theory predicts that infection by a parasite that reduces future host survival or fecundity should select for increased investment in current reproduction. In this study we use the cestode Ligula intestinalis and its intermediate fish host Engraulicypris sardella in Wissman Bay, Lake Nyasa (Tanzania) as a model system. Using data about infection of E. sardella fish hosts by L. intestinalis collected for a period of 10 years, we explored whether parasite infection affects the fecundity of the fish host E. sardella, and whether host reproductive investment has increased at the expense of somatic growth. We found that L. intestinalis had a strong negative effect on the fecundity of its intermediate fish host. For the non-infected fish we observed an increase in relative gonadal weight at maturity over the study period, while size at maturity decreased. These findings suggest that the life history of E. sardella has been shifting towards earlier reproduction. Further studies are warranted to assess whether these changes reflect plastic or evolutionary responses. We also discuss the interaction between parasite and fishery-mediated selection as a possible explanation for the decline of E. sardella stock in the lake. KEYWORDS Life history evolution; African Great Lakes; Lake Nyasa; Usipa; Lake Malawi sardine; Parasite invasion; Environmental change.

Peer review status:ACCEPTED

26 Aug 2020Submitted to Ecology and Evolution
28 Aug 2020Submission Checks Completed
28 Aug 2020Assigned to Editor
02 Sep 2020Reviewer(s) Assigned
15 Sep 2020Review(s) Completed, Editorial Evaluation Pending
16 Sep 2020Editorial Decision: Revise Minor
22 Sep 20201st Revision Received
23 Sep 2020Submission Checks Completed
23 Sep 2020Assigned to Editor
23 Sep 2020Review(s) Completed, Editorial Evaluation Pending
24 Sep 2020Editorial Decision: Accept