Sexual morph specialisation in a trioecious nematode balances opposing selective forces

Area of Science:

• Evolutionary biology
• Reproductive strategies
• Nematology

Background:

• The coexistence of selfing and outcrossing mating strategies is evolutionarily puzzling.
• Theory suggests stable states are either pure selfing or pure outcrossing, with mixed systems being rare and transient.
• Opposing selective forces on mating strategies make stable mixed breeding systems theoretically unlikely.

Purpose of the Study:

• To investigate the hypothesis that distinct roles during a species' life history can balance opposing selective pressures for selfing and outcrossing.
• To determine if the selfing and outcrossing morphs of Auanema freiburgensis possess specialized adaptations for their respective roles.
• To understand the mechanisms allowing the stable coexistence of mixed mating systems.

Main Methods:

• Behavioral studies
• Physiological analyses
• Gene expression profiling
• Life cycle analysis of Auanema freiburgensis sexual morphs

Main Results:

• Selfing hermaphrodites, produced under stress, show metabolic and intestinal adaptations for dispersal and reproduction.
• Outcrossing females, produced in favorable conditions, reallocate resources from intestinal development to mate-finding for rapid population growth.
• Each sexual morph exhibits specialized adaptations supporting its distinct role in the A. freiburgensis life cycle.

Conclusions:

• Specialization of mating strategies for specific life history roles can balance opposing selective forces.
• This specialization allows for the stable maintenance of both selfing and outcrossing mating systems within Auanema freiburgensis.
• The findings provide a potential explanation for the persistence of mixed breeding systems in nature.