Mating of escaped domestic pigs with wild boar and possibility of their offspring migration after the Fukushima Daiichi Nuclear Power Plant accident

Abstract

The 2011 Tohoku earthquake drastically changed human activities in some regions of Fukushima Prefecture, Japan. The subsequent tsunami damage and radioactive pollution from the Fukushima Daiichi nuclear power plant resulted in the evacuation of humans, and abandonment of agricultural lands, allowing population expansion of wildlife into areas formally inhabited by domesticated livestock. Unintentional escape of domesticated pigs into wildlife inhabited environments also occurred. In this study, we tested the possibility of introgression between wild boar and domesticated pigs in Fukushima and neighboring prefectures. We analyzed mitochondrial DNA sequences of 338 wild boar collected from populations in the Tohoku region between 2006 and 2018. Although most boar exhibited Asian boar mitochondrial haplotypes, 18 boar, phenotypically identified as wild boar, had a European domesticated pig haplotype. Frequencies of this haplotype have remained stable since first detection in 2015. This result infers ongoing genetic pollution in wild boar populations from released domesticated pigs. In 2018, this haplotype was detected outside of evacuated areas, suggesting migration and successful adaptation. The natural and anthropocentric disasters at Fukushima gave us the rare opportunity to study introgression processes of domestic genes into populations of wild boar. The present findings suggest a need for additional genetic monitoring to document the dispersal of domestic genes within wild boar stock.

Robust microsatellite markers for hybrid analysis between domesticated pigs and wild boar

“…In this study, pig samples were from slaughterhouses and farms nearby the evacuated area to improve the likelihood of detecting newly introgressive pig alleles in the hybridized wild boar. One of the pigs sampled had the mtDNA haplotype that was the same as hybrid wild boar in Fukushima (Anderson et al, 2019), and the sampled pig population in this study had high genetic variation (mean N A = 5.1). Therefore, we were confident in the representation of the pig genetic composition involved in the hybridization for this study and were able to distinguish an appropriate set of markers for hybrid analysis.…”

“…The mtDNA analysis has shown that this population is the same haplotype (D42172) and has extremely high genetic similarity to the wild boar population in eastern Fukushima prefecture (Nagata et al, 2006). Pop3 samples were collected in 2015-2016, after the Fukushima disasters, from eight suggested hybridized wild boar that had a typical mtDNA haplotype of pig (suggested pig ancestor in maternal lineage; MK801664, see Anderson et al (2019)). All animals were legally culled by licensed hunters, and this entire study was approved by Fukushima University's Institutional Animal Care and Use Committee.…”

“…Genetic diversity and ancestry of wild boar have been well studied, including areas of South East Asia, and information from hybridization occurrences with domestic pigs is of increasing interest due to possible genetic alterations (Choi et al, 2014;Todesco et al, 2016). Wild boar populations inhabiting Fukushima prefecture, in Japan, are suggested to be threatened by hybridization following the uncontrolled release of domesticated pigs after mandated evacuations due to the Fukushima nuclear disasters in 2011 (Okuda et al, 2018;Anderson et al, 2019). Additionally, hybridization in this area has not altered the morphological characteristics of wild boar (Anderson et al, 2019) and possible hybrids can only be detected using DNA.…”

“…Wild boar populations inhabiting Fukushima prefecture, in Japan, are suggested to be threatened by hybridization following the uncontrolled release of domesticated pigs after mandated evacuations due to the Fukushima nuclear disasters in 2011 (Okuda et al, 2018;Anderson et al, 2019). Additionally, hybridization in this area has not altered the morphological characteristics of wild boar (Anderson et al, 2019) and possible hybrids can only be detected using DNA. Thus, estimating appropriate genotypes of wild boar from the period prior to 2011, after 2011, and from domestic pigs in this area, with microsatellite markers will provide an important source of information for better understanding hybridization effects with native species following such events.…”

Introgression dynamics from invasive pigs into wild boar following the March 2011 natural and anthropogenic disasters at Fukushima

“…All data used in this study, supplemental tables and figures are provided in the electronic supplementary material available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.qnk98sfgz [ 55 ].…”