Life history shifts in an exploited African fish following invasion by a castrating parasite
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Date
2020-09-24
Journal Title
Journal ISSN
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Publisher
John Wiley & Sons Ltd.
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 noninfected 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 toward 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.
Description
Keywords
African Great Lakes, environmental change, Lake Malawi sardine, Lake Nyasa, life history evolution, parasite invasion, Usipa