Inbreeding and inbreeding depression in endangered red wolves (Canis rufus)

Abstract

In natural populations, the expression and severity of inbreeding depression can vary widely across taxa. Describing processes that influence the extent of inbreeding and inbreeding depression aid in our understanding of the evolutionary history of mating systems such as cooperative breeding and nonrandom mate selection. Such findings also help shape wildlife conservation theory because inbreeding depression reduces the viability of small populations. We evaluated the extent of inbreeding and inbreeding depression in a small, re-introduced population of red wolves (Canis rufus) in North Carolina. Since red wolves were first re-introduced in 1987, pedigree inbreeding coefficients (f) increased considerably and almost every wild born wolf was inbred (average f = 0.154 and max f = 0.383). The large inbreeding coefficients were due to both background relatedness associated with few founders and numerous close relative matings. Inbreeding depression was most evident for adult body size and generally absent for direct fitness measures such as reproductive success and survival; no lethal equivalents (LE = 0.00) were detected in juvenile survival. The lack of strong inbreeding depression in direct measures of fitness could be due to a founder effect or because there were no outbred individuals for comparison. Our results highlight the variable expression of inbreeding depression across traits and the need to measure a number of different traits when evaluating inbreeding depression in a wild population.

Survival and population size estimates of the red wolf

“…This allowed them to identify territories and, during spring, locate dens and daybeds of radio‐collared females to count and process pups (Beck et al , Rabon et al ). From 2000 to 2013, after implementation of the RWAMP, biologists took blood samples of red wolf pups discovered during den checks to verify parentage and maintain a pedigree of the wild population (Miller et al , Brzeski et al , Gese et al ) and implanted passive integrated transponder (PIT) tags in each pup subcutaneously to identify non‐collared red wolves captured during annual trapping (Beck et al , Hinton and Chamberlain ). Collectively, annual trapping and den work allowed the Recovery Program to estimate population size, survival, and reproduction through a known count approach (USFWS , Rabon et al ).…”

“…Therefore, the standard error of the population estimate for each year was the same as the standard error of unknowns remaining because the number of living radio‐collared wolves was known without error (i.e., it had no variance). We reported standard errors only for 2000–2013 because more thorough attempts to find and investigate dens to construct a red wolf pedigree began in 2000 (Miller et al , Brzeski et al , Gese et al ). In other words, accurate estimates of recapture rates for non‐collared red wolves occurred after the implementation of the RWAMP when finding and marking red wolves and monitoring breeding pairs became essential to limiting hybridization.…”

Space Use and Habitat Selection by Resident and Transient Red Wolves (Canis rufus)

“…We identified resident pairs of red wolves as radio-collared individuals of breeding age (≥2 years old) that were temporally and spatially associated with one another and defending a territory for ≥4 months as a breeding pair [3,33]. Recovery Program biologists confirmed breeding pair status during spring den work by locating dens and daybeds of radio-marked females to verify and obtain pup counts for each radio-collared breeding pair [23,39–40,46–47]. We also classified non-dispersing juveniles fitted with radio-collars as residents.…”

No evidence of inbreeding depression in a Tasmanian devil insurance population despite significant variation in inbreeding

“…On average, slightly stronger HFCs are detected when using direct fitness measures 19 . Significant HFCs are still detected using indirect fitness correlates 23–25 , and these measures are often more easily attainable than direct measures, such as survival of long-lived species, or reproductive success in wild populations. In the presence of inbreeding depression, HFCs may not be detected unanimously across all measures of fitness (e.g.…”