Rival male relatedness does not affect ejaculate allocation as predicted by sperm competition theory

Area of Science:

• Evolutionary biology
• Behavioral ecology
• Animal reproduction

Background:

• Sperm competition intensity influences male mating strategies.
• Male reproductive success can be affected by the relatedness of rival males.
• Theoretical models predict kin-biased sperm allocation.

Purpose of the Study:

• To empirically test if male Australian field crickets adjust ejaculates based on rival relatedness.
• To investigate kin recognition and biased mating investment in a natural population.
• To determine if males transfer sperm of different quality when competing against siblings versus non-siblings.

Main Methods:

• Exposing male Teleogryllus oceanicus to sperm competition from full siblings or non-siblings.
• Utilizing the presence of a rival male and its ejaculate as cues for competition.
• Analyzing ejaculate quality in response to different relatedness treatments.

Main Results:

• Male crickets did not adjust ejaculate quality in response to the relatedness of their rivals.
• Sperm quality allocated to females was similar whether the rival was a full sibling or a non-sibling.
• This lack of kin-biased behavior was observed irrespective of rearing conditions (full sibling or mixed relatedness groups).

Conclusions:

• The study found no evidence of kin-biased sperm allocation in Australian field crickets.
• Contrary to theoretical predictions, males did not alter their reproductive investment based on rival relatedness.
• These findings suggest that kin recognition or biased behavior may not play a significant role in sperm competition in this species.