Cryptic inbreeding depression in a growing population of a long‐lived species

Abstract

Genetic effects are often overlooked in endangered species monitoring, and populations showing positive growth are often assumed to be secure. However, the continued reproductive success of a few individuals may mask issues such as inbreeding depression, especially in long-lived species. Here, we test for inbreeding depression in little spotted kiwi (Apteryx owenii) by comparing a population founded with two birds to one founded with 40 birds, both from the same source population and both showing positive population growth. We used a combination of microsatellite genotypes, nest observations and modelling to examine the consequences of assessing population viability exclusively via population growth. We demonstrate (i) significantly lower hatching success despite significantly higher reproductive effort in the population with two founders; (ii) positive growth in the population with two founders is mainly driven by ongoing chick production of the founding pair; and (iii) a substantial genetic load in the population founded with two birds (10-15 diploid lethal equivalents). Our results illustrate that substantial, cryptic inbreeding depression may still be present when a population is growing, especially in long-lived species with overlapping generations.

Small fish, large river: Surprisingly minimal genetic structure in a dispersal‐limited, habitat specialist fish

“…perienced bottlenecks(Johnson et al, 2010;Noren, Godoy, Dalen, Meijer, & Angerbjorn, 2016;Taylor et al, 2017), E. lemniscatum showed no evidence of inbreeding and actually showed signatures of outbreeding in the area downstream of DJD Brown et al (2017). made a similar observation in highly endemic sulfide spring fishes, suggesting that inbreeding is not an inevitability of bottlenecked populations, especially in species, like E. lemniscatum, that have evolved in small geographic areas Eisenhour and Burr (2000).…”

Genetic and demographic vulnerability of adder populations: Results of a genetic study in mainland Britain

“…Small population size is an important factor in loss of genetic diversity, exacerbated by bottleneck events. This has led to the concept of a minimum viable population size [18,19], based on the inverse relationship between the effective population size (N e ) [20] and the rate of erosion of genetic variation by drift, which is supported by studies of wild populations [21,22]. N e estimates tend to be low in relation to census population size in natural populations [23,24], influenced by demographic fluctuation and life-history traits [25,26].…”

Inbreeding in an endangered killer whale population

“…This process likely involves population bottlenecks and inbreeding (Hoelzel et al ., ; Moura et al ., ). Low levels of gene flow from other populations may be an important source of genetic variation, particular as new populations may experience reduced population growth due to inbreeding after the original founders have died (cryptic inbreeding depression; Taylor et al ., ). The southern resident population is particularly isolated from other populations (Pilot et al ., ; Ford et al ., ; Parsons et al ., ), and it is possible that this isolation is contributing to inbreeding and relatively low population growth rate compared to other similar populations (Allen & Angliss, ).…”

“…These types of studies have revealed that inbreeding occurs frequently in wild populations (reviewed by Kardos et al ., ), contributing to variation in individual fitness even in populations that are already inbred (e.g. Weiser et al ., ) or growing (Taylor et al ., ). Characterizing patterns of inbreeding is therefore an important step in evaluating population viability and understanding the factors that may be limiting population recovery (O'Grady et al ., ; Frankham, ).…”