Data from: Aging alters interspecific competition between two sympatric insect-parasitic nematode species

Interspecific competition can vary depending on the stage, age, or
physiological state of the competitors. Competitive ability often
increases with age or size; alternatively, senescence can lead to a loss
of viability and reduced competitive success. Differences between species
in their age-specific competitive abilities can promote coexistence in the
face of substantial niche overlap. We examined two sympatric species of
nematodes (genus Steinernema) to determine whether their competitive
relationship changes as a function of age. These obligately killing insect
parasites are known for their broad host ranges and are transmitted from
insect to insect via a juvenile stage propagule that is free-living in the
soil. Here, we tested whether the two species differed in the effects of
age by examining the mortality of insect hosts infected with young or old
transmission stage nematodes of each species. We also performed mixed
infections, where an equal ratio of both species was simultaneously
exposed to a host, to determine the effect of age on competitiveness. One
species showed reduced performance with age, as older propagules were
slower at inducing host mortality. In contrast, the other species
increased in killing speed with age. In competition, insect mortality rate
was predictive of competitive outcome, such that if one species induced
considerably faster host death in a single-species infection, it was
competitively dominant in the coinfection. Accordingly, we found a shift
in the competitive relationship between the two species with age. Our work
demonstrates that species differences in the effects of aging can lead to
dramatic shifts in reproductive success. As these effects are realized
solely in a competitive environment, both spatial patchiness and temporal
niche partitioning may be important for promoting coexistence.