Inbreeding avoidance and cost in a small, isolated trout population.

Area of Science:

• Population Genetics
• Conservation Biology
• Ecology

Background:

• Population persistence is threatened by inbreeding, influenced by mating avoidance strategies.
• Few studies have simultaneously assessed passive and active inbreeding avoidance and their consequences.

Purpose of the Study:

• To investigate inbreeding dynamics in a small, isolated westslope cutthroat trout population.
• To evaluate the extent of passive and active inbreeding avoidance.
• To assess inbreeding depression across the life cycle.

Main Methods:

• Utilized extensive genetic and demographic data from a westslope cutthroat trout population.
• Quantified passive inbreeding avoidance through predicted lifetime dispersal estimates.
• Assessed active inbreeding avoidance by analyzing spatial clustering and relatedness of mate pairs.

Main Results:

• Low passive inbreeding avoidance observed, with limited dispersal distances for females and males.
• Minimal evidence for active inbreeding avoidance during reproduction; relatives remained spatially clustered.
• Increased relatedness among mate pairs (0.09 higher than random) and evidence of inbreeding depression in fitness components (family size, juvenile survival, reproductive success).

Conclusions:

• Limited passive and active inbreeding avoidance in this trout population leads to higher inbreeding than expected.
• Observed inbreeding and inbreeding depression pose a significant risk to population persistence.
• Findings highlight the vulnerability of small, isolated populations to inbreeding and potential decline.