Reproductive interference alters species coexistence in nematodes due to
asymmetric sperm-induced harm
Abstract
Species coexistence is shaped by a range of biotic and abiotic factors.
Beyond predation, parasitism, and competition, one species may interfere
with another’s reproduction to induce sexual exclusion from a habitat.
Here, we test for reproductive interference from inter-species mating
between sympatric nematodes Caenorhabditis macrosperma and
C. nouraguensis. Higher intrinsic population growth of C.
nouraguensis arises from greater fecundity of both sexes, predicting it
to be superior in resource competition. Mate discrimination between
species is incomplete, however, with inter-species mating errors
reducing lifespan and reproductive fitness of female C.
nouraguensis only. These asymmetric costs arise within hours, due to
ectopic migration of C. macrosperma’s giant sperm cells. We
modelled the population dynamic impacts of reproductive interference,
then confirmed rapid sexual exclusion in mixed-species communities with
multi-generation experiments. These findings demonstrate the profound
ecological implications of reproductive interference for demographic
parameters and species coexistence through a cell-mediated mechanism of
inter-species harm.