An assessment of genetic diversity in wild and captive populations of endangered Japanese bitterling Tanakia tanago (Cyprinidae) using amplified fragment length polymorphism (AFLP) markers

Abstract

The Japanese bitterling Tanakia tanago (Cyprinidae) is on the verge of extinction in the wild, placing great importance on captive breeding programs for current conservation of the species. However, the loss of genetic diversity during captive breeding is an ongoing matter of concern. Since some captive populations have been almost monomorphic in mitochondrial DNA (mtDNA), this hampers assessments of their genetic diversity during captive breeding. To more accurately assess their genetic diversity, one wild and three captive populations were examined using amplified fragment length polymorphism (AFLP) markers. Estimates of average heterozygosity and nucleotide diversity ranged 0.0479-0.1920 and 0.0023-0.0088, respectively, enabling comparison of genetic diversity among the wild and captive populations, and among year-classes of captive populations. Significant differences in numbers of amplified fragments and proportions of polymorphic fragments were observed among year-classes of all populations. The indices of genetic diversity calculated from AFLP seemed to be, however, less sensitive to weak bottlenecks. No continuous decrease in genetic diversity in nuclear DNA was detected in presently captive populations. This supports the possibility of re-introduction of the captive populations into the original habitats, although survival and reproductive ability in the wild must be taken into consideration.

Effects of parental number and duration of the breeding period on the effective population size and genetic diversity of a captive population of the endangered Tokyo bitterling Tanakia tanago (Teleostei: Cyprinidae)

“…The experimental breeding population of Tanakia tanago (2001 year‐class, one‐year‐old fish) had been bred in captivity since 1971 and maintained at the Tochigi Prefectural Fisheries Experimental Station. This population was derived from a mixture of three distinct populations, which resulted in high initial genetic variability [Kubota and Watanabe, ; Kubota et al, ]. Experimental breeding was conducted in 18 aquaria measuring 90 × 45 × 40 cm with external filtration.…”

“…With such dramatic habitat loss, captive breeding programs are considered to have a critical role in the conservation of this species [Maehata, ; Kubota et al, ]. However, a significant reduction in genetic diversity has been detected using mtDNA and AFLP analyses in some year‐classes of captive T. tanago populations [Kubota and Watanabe, ; Kubota et al, ]. Thus, there are increasing concerns over the loss of genetic diversity through inbreeding in this species, which may hamper future attempts for its reintroduction.…”

Migration patterns counteract seasonal isolation of Squalius torgalensis, a critically endangered freshwater fish inhabiting a typical Circum-Mediterranean small drainage

“…As recently suggested by Saura et al (2008) it is possible to avoid such problems for populations where pedigrees cannot be inferred, such as S. torgalensis, by conducting genetic studies before release to ensure that captive populations possess similar levels of genetic diversity as the ones observed in the wild populations (e.g. Kubota et al 2008). Intermittent systems, such as the Mira Basin are particularly vulnerable to environmental changes.…”

Genetic population structure and management units of the endangered Tokyo bitterling, Tanakia tanago (Cyprinidae)

“…Some captive populations have been reintroduced into the wild (original or new locations) with individuals propagated in captivity (Oda 2005). The captive populations include those with already reduced genetic variability in the wild and those derived from a limited number of founders (Kubota and Watanabe 2003;Kubota et al 2008). In most cases, captive populations have been managed and propagated separately by original locality, but there are also admixed populations founded from multiple populations (Nakamura 1998).…”

“…However, relatively little is known about the genetic variability and possible genetic bottlenecks experienced by most populations within this species. Understanding these genetic events is essential for proper genetic management of this species (Kubota and Watanabe 2003;Kubota et al 2008).…”