Citizen science reveals the present range and a potential native predator of the invasive slug Limax maximus Linnæus, 1758 in Hokkaido, Japan

Yuta Morii,Takafumi Nakano

doi:10.3391/bir.2017.6.3.01

Abstract

The giant garden slug Limax maximus Linnaeus, 1758 (Limacidae, Pulmonata) is considered one of the most widely spread terrestrial molluscs in the world and is a formidable pest of agricultural and horticultural crops. This slug was recently introduced to Japan, where its population is now rapidly increasing and spreading. A naturalised population of L. maximus was first discovered in Hokkaido, Japan, in 2012 in the isolated natural forest of Maruyama Forest Park in Sapporo City, and the species has become common in this area. In the present study, we investigated observations of L. maximus reported by ordinary citizens acting as citizen scientists to assess the recent expansion of this invasive slug. We posted an announcement in the local newspaper requesting reports of the occurrence of L. maximus via e-mail and analysed 38 observations provided by local citizens. As a result of these reports, 16 naturalised populations of L. maximus were detected in Hokkaido, several of which were quite far from the original population in Sapporo City. Moreover, a terrestrial macrophagous leech, Orobdella kawakatsuorum Richardson, 1975 (Arhynchobdellida, Orobdellidae), is reported as a potential native predator of L. maximus for the first time.

Highlights

Invasive terrestrial mollusc species have been recognized as some of the most significant and persistent threats to native ecosystems and agriculture (e.g., Lowe et al 2000; Barker 2002; Mito and Uesugi 2004)
This slug was recently introduced to Japan, and its population is increasing rapidly and spreading throughout the country; it has been observed on two main islands, Honshu Island (Ibaraki, Nagano and Fukushima prefectures; Hasegawa et al 2009; Iijima et al 2013) and Hokkaido Island (Iijima et al 2013; Morii et al 2016)
Our citizen science data for the L. maximus populations in Hokkaido demonstrated that this invasive slug has become well established in and around Sapporo City over the last six years

Summary

Introduction

Invasive terrestrial mollusc species have been recognized as some of the most significant and persistent threats to native ecosystems and agriculture (e.g., Lowe et al 2000; Barker 2002; Mito and Uesugi 2004). Observations of L. maximus in Hokkaido, contacted the owners of these web sites and identified another naturalised population in Hokkaido (Ebetsufuto, Ebetsu City; #5 in Table S1 and Figure 1), located 30 km from Maruyama Forest Park, Sapporo City (Morii et al 2016) This result suggests that data from citizen scientists (Bonney et al 2009; Silvertown et al 2011; Worthington et al 2012) may allow the distribution of this invasive slug to be tracked throughout Hokkaido. Our collaboration with the citizen scientists revealed a potential predator, indigenous to the island, of this novel invasive slug

Methods and findings

Discussion