Abstract
Natural disturbances often destroy local populations and can considerably affect the genetic properties of these populations. The 2011 Tohoku Earthquake Tsunami greatly damaged local populations of various coastal organisms, including the mud snail Batillaria attramentaria, which was an abundant macroinvertebrate on the tidal flats in the Tohoku region. To evaluate the impact of the tsunami on the ecology and population genetic properties of these snails, we monitored the density, shell size, and microsatellite DNA variation of B. attramentaria for more than ten years (2005–2015) throughout the disturbance event. We found that the density of snails declined immediately after the tsunami. Bayesian inference of the genetically effective population size (Ne) demonstrated that the Ne declined by 60–99% at the study sites exposed to the tsunami. However, we found that their genetic diversity was not significantly reduced after the tsunami. The maintenance of genetic diversity is essential for long-term survival of local populations, and thus, the observed genetic robustness could play a key role in the persistence of snail populations in this region which has been devastated by similar tsunamis every 500–800 years. Our findings have significant implications for understanding the sustainability of populations damaged by natural disturbances.
Highlights
Large scale natural disturbances, such as fire, hurricanes, floods, drought, high wind, and large waves, often change the abundance and structure of local populations or communities[1]
We demonstrated that the mud snail B. attramentaria was greatly declined due to the tsunami associated with the 2011 Great East Japan Earthquake
The estimates of temporal Ne demonstrated that several B. attramentaria populations in this study experienced a severe population decline, a loss of genetic diversity was not evident in any local populations at Sendai Bay
Summary
Large scale natural disturbances, such as fire, hurricanes, floods, drought, high wind, and large waves, often change the abundance and structure of local populations or communities[1]. No studies have evaluated the impact of the tsunami on the genetic components of local populations Among these coastal organisms, the case of the mud snail Batillaria attramentaria is of particular interest. But populations of B. attramentaria were severely diminished and were nearly extirpated at several sites around Sendai Bay in the Tohoku region after the tsunami[11] These severe population declines can cause a loss of genetic diversity, which potentially increases extinction risk[6]. We have expanded the ecological survey of Miura et al.[11], and we further estimated population genetic indices of local populations of B. attramentaria for more than ten years throughout the tsunami event to evaluate the ecological and genetic impact of the tsunami on B. attramentaria. This is the first study that simultaneously examined the ecological and genetic impact of a tsunami on marine organisms
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