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ADAPTIVE SEX ALLOCATION IN A SIMULTANEOUS HERMAPHRODITE.

Sandrine Trouvé1, Joseph Jourdane1, François Renaud2

  • 1Centre de Biologie et d'Ecologie Tropicale et Méditerranéenne, Laboratoire de Biologie Animale, UMR 5555 du CNRS, Université de Perpignan, Av. de Villeneuve, 66860, Perpignan Cedex, France.

Evolution; International Journal of Organic Evolution
|June 1, 2017
PubMed
Summary

Local mate competition in the hermaphroditic parasite Echinostoma caproni drives increased sperm allocation as mates increase. This shift reduces ovary size and fecundity, supporting evolutionary predictions.

Keywords:
Echinostomalocal mate competitionparasitephenotypic plasticitysex allocationsimultaneous hermaphrodite

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Area of Science:

  • Evolutionary Biology
  • Parasitology
  • Reproductive Biology

Background:

  • The local mate competition (LMC) hypothesis predicts altered reproductive investment in hermaphrodites with increased mate numbers.
  • Hermaphroditic organisms face unique reproductive challenges, including selfing and outcrossing dynamics.

Purpose of the Study:

  • To test the LMC hypothesis in the hermaphroditic trematode Echinostoma caproni.
  • To investigate how mating group size influences reproductive organ investment and fecundity.

Main Methods:

  • Echinostoma caproni were isolated individually, in pairs, or in groups of 20.
  • Investment in reproductive organs (testes, ovary) and egg size/fecundity were measured.
  • Adult body size was recorded as a covariate.

Main Results:

  • Increased mating group size led to significantly greater resource allocation to male reproductive functions.
  • Ovary size significantly decreased with increasing mating group size.
  • Reduced ovary size correlated with decreased fecundity but not egg size.

Conclusions:

  • Results support the LMC hypothesis, demonstrating increased male allocation with more potential mates in Echinostoma caproni.
  • Reproductive strategies in hermaphrodites are plastic and responsive to social mating environments.
  • Shifts in investment impact overall reproductive output (fecundity).