Inbreeding depression in sperm quality in a critically endangered amphibian

Abstract

Small, isolated populations often experience increased inbreeding and decreased heterozygosity, which increases the potential risk of inbreeding depression.The relationship between inbreeding and sperm health is well-documented in a variety of taxa, but has yet to be explored in amphibians. The dusky gopher frog, Lithobates sevosus, is a critically endangered species with years of documented inbreeding and low genetic variability as a consequence of isolation and population size reduction. This study investigated the effects of inbreeding on sperm quality in captive L. sevosus using an outbred, sister species (Lithobates pipiens) as a standard for comparison. We found L. sevosus to have severely reduced sperm quality in terms of total motility, forward progressive motility, concentration, and viability. Additionally, we observed a significant, negative relationship between total sperm motility and mean kinship within captive-bred individuals. These data serve to enhance our understanding of the role inbreeding plays in amphibians, and to provide valuable insight into new risk factors declining amphibian populations may face. K E Y W O R D S assisted reproductive technologies, captive breeding, dusky gopher frog, fertility, Lithobates sevosus

Genetic Consequences of Forest Fragmentation in a Widespread Forest Bat (Natalus mexicanus, Chiroptera: Natalidae)

“…Although genetic diversity in areas inhabited by the funnel-ear bat is currently moderate, contemporary gene flow is virtually zero among most groups and low between group 1 (Baja California) and group 4 (GM, PM, and PYUC individuals). This may be a consequence of habitat fragmentation, which should be interpreted as a warning signal, given that the loss of genetic variation and flow can reduce the ability of individuals to adapt to a changing environment, resulting in endogamic depression [121], lower reproduction [122,123], and a higher probability of extinction [124,125]. The information obtained for Natalus mexicanus in this study is also alarming because the current status of most of its populations is unknown [40], and during the development of our field work, we have been able to verify that some populations have either declined or completely disappeared due to human disturbances [126].…”

“…The following are available online at https://www.mdpi.com/1424-2 818/13/4/140/s1, Table S1: Sampling locations. Sample size (N, sequences/microsatellites); main type of vegetation: Sarcocaul shrubland (MSC), secondary shrub vegetation of low deciduous forest (VSA/SBC), Savannah-like (VSI), secondary shrub vegetation of medium subdeciduous forest (VSA/SMS), pine-oak forest (BPE), low deciduous forest (SBC), medium subdeciduous forest (SMS), submontane shrubland (Msm), Tamaulipecan thorny shrubland (MET), vegetation and soil use map, scale 1:250,000 [123]. Table S2: Genetic diversity indices by groups and localities.…”

Effects of age on sperm quality metrics in endangered Mississippi gopher frogs (Lithobates sevosus) from captive populations used for controlled propagation and reintroduction efforts

“…Moreover, across all age categories, the percentage of atypical sperm was found to be very high. A recent paper by Hinkson and Poo (2020) explored the effect of inbreeding on sperm quality in Mississippi gopher frogs and found sperm quality (forward progressive motility, total motility, concentration and viability) were significantly reduced compared to an outbred sister species, the northern leopard frog ( Lithobates pipiens ). The potential reproductive consequences of inbreeding depression found in this study may explain the overall high percentage of atypical sperm across all age categories.…”

“…Due to small population sizes and isolation, many imperilled species with captive breeding programs often exhibit reduced genetic variation as a consequence of inbreeding between close relatives (reviewed in Allentoft & O'Brien, 2010; Fitzpatrick & Evans, 2009). Consequently, inbreeding can lead to inbreeding depression and result in a reduction in reproductive capacity; a negative relationship between sperm quality metrics (including sperm motility and morphology) and inbreeding has often been observed across and within taxa in wild and in captive populations (Asa et al, 2007; Fitzpatrick & Evans, 2009; Gage et al, 2006; Hinkson & Poo, 2020; Opatová et al, 2016; Zajitschek & Brooks, 2010). Furthermore, natural breeding events in captivity may be hindered due to reproductive dysfunction—an impairment of an organism's reproductive system (Synder et al, 1996), which is thought to arise in captivity from a mismatch of environmental cues, behavioral incompatibility, or inbreeding (reviewed in Schulte‐Hostedde & Mastromonaco, 2015).…”

Sperm morphometry is affected by increased inbreeding in the Retinta cattle breed: A molecular approach

“…Inbreeding depression is defined as the reduction in the mean values of phenotypic traits from breeding‐related individuals (Leroy, 2014). This genetic effect is particularly important in endangered species (Hinkson & Poo, 2020) and local livestock breeds (Rodero Serrano & Molina Alcalá, 2008; Williams et al, 2016) due to the number of available male breeders is often reduced. Increased inbreeding values have also been detected in large livestock breeds as a result of the aggressive use of embryo transfer (Azcona et al, 2019; Perez et al, 2019) and selective breeding (Howard et al, 2017), which have decreased the number of reproductive individuals.…”