Invasion genetics of the mummichog (Fundulus heteroclitus): recent anthropogenic introduction in Iberia.

Teófilo Morim,Regina L Cunha,Enric Gisbert,David D Duvernell,Rita Castilho,Grant R Bigg,Pedro M Madeira,Jorge Palma

doi:10.7717/peerj.6155

Abstract

Human activities such as trade and transport have increased considerably in the last decades, greatly facilitating the introduction and spread of non-native species at a global level. In the Iberian Peninsula, Fundulus heteroclitus, a small euryhaline coastal fish with short dispersal, was found for the first time in the mid-1970s. Since then, F. heteroclitus has undergone range expansions, colonizing the southern region of Portugal, southwestern coast of Spain and the Ebro Delta in the Mediterranean Sea. Cytochrome b sequences were used to elucidate the species invasion pathway in Iberia. Three Iberian locations (Faro, Cádiz and Ebro Delta) and 13 other locations along the native range of F. heteroclitus in North America were sampled. Results revealed a single haplotype, common to all invasive populations, which can be traced to the northern region of the species’ native range. We posit that the origin of the founder individuals is between New York and Nova Scotia. Additionally, the lack of genetic structure within Iberia is consistent with a recent invasion scenario and a strong founder effect. We suggest the most probable introduction vector is associated with the aquarium trade. We further discuss the hypothesis of a second human-mediated introduction responsible for the establishment of individuals in the Ebro Delta supported by the absence of adequate muddy habitats linking Cádiz and the Ebro Delta. Although the species has a high tolerance to salinity and temperature, ecological niche modelling indicates that benthic habitat constraints prevent along-shore colonisation suggesting that such expansions would need to be aided by human release.

Highlights

As a consequence of human activities involving large distance marine transportation and trade, worldwide marine biological invasion rates have increased dramatically in the last 30 years (e.g., Hulme, 2009)
Fundulus heteroclitus invasive Iberian populations revealed the presence of a single cyt b haplotype common to all individuals
This haplotype is predominant in the northern group of the native distribution, and we cannot determine which exact location was at the origin of the introduced individuals, one can identify the northern end of range as the source of the introduction

Summary

Introduction

As a consequence of human activities involving large distance marine transportation and trade, worldwide marine biological invasion rates have increased dramatically in the last 30 years (e.g., Hulme, 2009). Invasive species spread and occupy new marine and coastal ecosystems through several maritime introduction vectors such as ballast water, biofouling of vessels, aquaculture escape or ornamental species trade (see Williams et al, 2013 and references therein). Since it was first recorded in Iberian saltmarshes, several studies linked F. heteroclitus introduction to different vectors. Since there are countless vessels active around the world (e.g., Kaluza et al, 2010), ballast water-mediated transport allows the possibility of multiple introduction events, each with large groups of individuals (Hulme, 2009). Suggest that this was not the introduction vector responsible for the spread of the species; in contrast to the expectation of similar levels of genetic diversity between the native and invasive range, the Iberian locations display a strong founder effect, with all samples sharing a single haplotype

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