Abstract
The slipper limpet Crepipatella dilatata, native to Chile and Argentina, was introduced in Spain in 2005. The species was thought to inhabit the region of Rias Bajas, yet recently, putative C. dilatata populations have been documented on the coast of north-central Spain and in the Ebro Delta of the Spanish Mediterranean. Here we undertook a multidisciplinary approach to study the invasion biology of this species. Specifically, two geographically distant populations, one being a successfully established population from O Grove and the other a declining population from Gijon, were studied over the course of four years. Analyses of morphological and developmental traits as well as genetic information confirmed the presence of C. dilatata in these sites. The results revealed polymorphism in anatomical traits and shell shape. Shell shape polymorphism was unevenly distributed among sites and among sexes. Males were monomorphic, while females were polymorphic. Of the female morphotypes encountered, one was absent in the declining population from Gijón. Size at first female maturation and female size were greater in the declining population than in the established population. Reproductive success varied seasonally but not spatially among populations. In the established population, gregariousness was significantly greater; the size when sex changes was found to be plastic and socially controlled. The sex ratio of the declining population was female biased while in the established population the sex ratio changed during the study period from being balanced to being female biased. This change in sex ratio was probably due to higher male mortality. Molecular analyses pointed to the localities of Corral Bay in southern Chile and Puerto Madryn in southern Argentina as potential population sources. The intercontinental import of fresh mussels cultivated in Chilean farms is a likely source of this mussel in Spain. Comparison with available data of native populations of C. dilatata strongly indicate that ecophenotypic plasticity, socially controlled sex change, high gregariousness, increased nurse egg supply to viable larvae during the encapsulated developmental period, later maturation and larger female sizes altogether enhance establishment success of this non-indigenous species. Human-mediated factors like the intraregional mussel trade and transplantation are also likely secondary dispersal mechanisms favouring the spread of this organism.
Highlights
Non-indigenous species (NIS) transported across natural biogeographical barriers and released, whether unintentionally or deliberately, into new environments have the potential to become invasive species and profoundly alter native biodiversity [1,2,3,4]
The risk of overlooking a cryptic introduction is high and the use of complementary approaches for unambiguous taxonomic identification is necessary to monitor the introduction of NIS [7, 75]
We used morphological, reproductive and molecular data to confirm the presence of the non-indigenous South American slipper limpet C. dilatata in two geographically distant populations in the Iberian Peninsula, one located in El Arbeyal, (Gijon, Central Northern Spain) and another in O Grove (Arousa Estuary, NW Spain)
Summary
Non-indigenous species (NIS) transported across natural biogeographical barriers and released, whether unintentionally or deliberately, into new environments have the potential to become invasive species and profoundly alter native biodiversity [1,2,3,4]. In order for policies to be effective, conservation management must have an accurate record of the native biota and must be able to trace and manage potential introduction pathways and vectors [7, 8]. To understand invasions and to develop methods of invasion control it is necessary to identify the factors, and their interactions, that promote establishment success and the spread of NIS [9]. Potential invaders that are released to the receptor environment and initiate the invasion process are exposed to a series of filters that operate at different stages in the progression of the invasion: introduction, establishment and spread [10]. During the first stages of the invasion process, when population sizes are generally low, founder and Allee effects may impede NIS to establish successfully, grow demographically, and spread [9]. Many interacting factors, such as asexual reproduction [9, 11], plasticity in life history traits [12, 13, 14], hermaphroditism [9, 11] and gregariousness [11, 15], likely influence invasion success
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