Integrated Population Genomic Analysis and Numerical Simulation to Estimate Larval Dispersal of Acanthaster cf. solaris Between Ogasawara and Other Japanese Regions

Abstract

The estimation of larval dispersal on an ecological timescale is significant for conservation of marine species. In 2018, a semi-population outbreak of crown-of-thorns sea star, Acanthaster cf. solaris, was observed on a relatively isolated oceanic island, Ogasawara. The aim of this study was to assess whether this population outbreak was caused by large-scale larval recruitment (termed secondary outbreak) from the Kuroshio region. We estimated larval dispersal of the coral predator A. cf. solaris between the Kuroshio and Ogasawara regions using both population genomic analysis and simulation of oceanographic dispersal. Population genomic analysis revealed overall genetically homogenized patterns among Ogasawara and other Japanese populations, suggesting that the origin of the populations in the two regions is the same. In contrast, a simulation of 26-year oceanographic dispersal indicated that larvae are mostly self-seeded in Ogasawara populations and have difficulty reaching Ogasawara from the Kuroshio region within one generation. However, a connectivity matrix produced by the larval dispersal simulation assuming a Markov chain indicated gradual larval dispersal migration from the Kuroshio region to Ogasawara in a stepping-stone manner over multiple years. These results suggest that the 2018 outbreak was likely the result of self-seeding, including possible inbreeding (as evidenced by clonemate analysis), as large-scale larval dispersal from the Kurishio population to the Ogasawara population within one generation is unlikely. Instead, the population in Ogasawara is basically sustained by self-seedings, and the outbreak in 2018 was also most likely caused by successful self-seedings including possible inbreeding, as evidenced by clonemate analysis. This study also highlighted the importance of using both genomic and oceanographic methods to estimate larval dispersal, which provides significant insight into larval dispersal that occurs on ecological and evolutionary timescales.

Crown of thorns starfish life-history traits contribute to outbreaks, a continuing concern for coral reefs

“…COTS are one of the most extensively studied sea stars and remain an ongoing research priority in many tropical regions [ 22 , 25 , 81 , 119–121 ]. Identifying the key traits and highly adaptive biology of COTS across life stages such as their recently recognised phenotypic plasticity is crucial to understand the outbreak phenomenon.…”

Coastal ecological impacts from pumice rafts

“…Genetic studies have revealed the transport of larval corals 36 and crown-of-thorn starfish 37 between the Okinawa and Ogasawara Archipelagos, which are more than 1000 km apart, with no large islands in between. Given that corals can be transported long-distances on pumice 1 – 3 , 5 , 6 , integrating spatiotemporal information on the exact pumice movement on the sea surface with such genetic analyses may help to clarify the dispersal processes of marine organisms in greater detail.…”

Population admixtures in medaka inferred by multiple arbitrary amplicon sequencing

“…This indicates a potential ability of MAAS methods. MAAS methods have been usually conducted using the Illumina MiSeq platform, in which the read number ranges from 10 4 to 10 5 per sample 17,22,35 . However, our result suggests that there is a room for increasing the number of the genotyped sites if the sequencing throughput increases.…”