Extreme sequential polyandry insures against nest failure in a frog

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Herpetology

Background:

• Sequential polyandry, where females mate with multiple males sequentially, may evolve as an adaptive strategy.
• Potential benefits include insurance against mate infertility, genetic quality, or incompatibility, and mitigating environmental unpredictability.
• In oviparous (egg-laying) species with variable nest site quality, polyandry could insure offspring success by distributing eggs.

Purpose of the Study:

• To test the hypothesis that polyandrous females insure offspring success against nest failure by distributing eggs across multiple nests.
• To investigate the extent of sequential polyandry in a wild population of Australian terrestrial toadlets.
• To determine if increased polyandry correlates with enhanced offspring survivorship.

Main Methods:

• Field observations of a wild population of Australian terrestrial toadlets, a known polyandrous species.
• Quantification of egg partitioning by females across multiple male-constructed nests.
• Analysis of the relationship between the degree of female polyandry and mean offspring survivorship.

Main Results:

• Females were observed partitioning their eggs across the nests of 2 to 8 males.
• A higher degree of polyandry in females led to a significant increase in mean offspring survivorship.
• This study documents the most extreme case of sequential polyandry observed to date in a vertebrate.

Conclusions:

• Nest failure insurance, achieved by distributing eggs across multiple nests, may be a significant factor favoring the evolution of sequential polyandry.
• The findings suggest that insurance against nest failure could be a widespread phenomenon in oviparous taxa.
• This provides a compelling explanation for the prevalence of sequential polyandry in the natural world.