Roman, J. and J. A. Darling. Paradox lost: genetic diversity and the success of aquatic invasions. Trends Ecol. Evol.

Gund Institute for Ecological Economics, University of Vermont, 617 Main Street, Burlington, VT 05443, USA.
Trends in Ecology & Evolution (Impact Factor: 16.2). 10/2007; 22(9):454-64. DOI: 10.1016/j.tree.2007.07.002
Source: PubMed


There is mounting evidence that reduced genetic diversity in invasive populations is not as commonplace as expected. Recent studies indicate that high propagule vectors, such as ballast water and shellfish transplantations, and multiple introductions contribute to the elimination of founder effects in the majority of successful aquatic invasions. Multiple introductions, in particular, can promote range expansion of introduced populations through both genetic and demographic mechanisms. Closely related to vectors and corridors of introduction, propagule pressure can play an important role in determining the genetic outcome of introduction events. Even low-diversity introductions have numerous means of avoiding the negative impact of diversity loss. The interaction of high propagule vectors and multiple introductions reveal important patterns associated with invasion success and deserve closer scrutiny.

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    • "Thulin and Tegelstrom, 2001; Golani et al., 2007; Tarnowska et al., 2013). Many recent studies working on aquatic invaders use molecular markers to trace the colonization history and to analyse the respective population structure (Roman and Darling, 2007; Tarnowska et al., 2013). Unfortunately, at this point no comparison can be done because no other previously published studies of COI haplotype data of T. navalis exists. "
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    ABSTRACT: The common shipworm Teredo navalis is one of the most widespread marine wood-boring bivalves of the world and probably one of the most wood destructive and cost-incurring marine invertebrates. First reports on T. navalis for Europe date back to 1731 for the North Sea (The Netherlands) and to 1835 for the Baltic Sea (Germany). It is still unclear, however, where this species originates from. Therefore, T. navalis is considered cryptogenic for European waters, including the Baltic Sea.In this study, 181 specimens of Teredinidae from six different sampling areas all over Europe and North America were molecular-taxonomically investigated using several molecular markers, two nuclear (18S/28S) as well as one mitochondrial marker (cytochrome c oxidase subunit I, hereafter COI). For the COI gene amplification, a new specific primer pair (Ter fw II/Ter rev I) for T. navalis was developed, which allowed sequencing of a 675 bp COI gene fragment for the first time. For amplifying the COI gene fragment of other examined teredinids than T. navalis, a third primer (Ter fw III) was designed. These three new primers are valuable tools to identify teredinid species with the DNA barcoding approach.Classification of T. navalis into the system of wood-boring bivalves using a combined 18S/28S dataset showed no differentiation between specimens from Europe and the North American East Coast. The results of the COI dataset analyses showed high haplotype diversity in combination with a low nucleotide diversity and a star-shaped network with a predominant haplotype occurring in all investigated regions. Moreover, no indications have been found on a sibling species in the Baltic Sea. The data indicate a recent population expansion for the examined sampling sites whereas the origin of the assumed worldwide distributed species T. navalis remains open.
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    • "Low genetic diversity caused by a founder effect or a bottleneck is not always the benchmark 61 for introduction events (Cornuet and Luikart 1996; Sakai et al. 2001; Dlugosch and Parker 2008). In 62 fact, recurrent introductions, a process commonly observed during marine invasion, typically increase 63 the gene pool available for successful allelic combinations when facing heterogeneous foreign habitats 64 ( Roman and Darling 2007; Suarez and Tsutsui 2008, 65 Rius and Darling 2014). Genetic diversity plays therefore a crucial role on the successful 66 establishment and posterior spread of an introduced species in a new area ( Grosberg 67 and Cunningham 2001; Sakai et al. 2001;). "
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    ABSTRACT: The analysis of temporal genetic variability is an essential yet largely neglected tool to unveil and predict the dynamics of introduced species. We here describe the temporal genetic structure and diversity over time of an introduced population of the ascidian Styela plicata (Lesueur, 1823) in Wilmington (North Carolina, USA, 34°08'24" N, 77°51'44" W). This population suffers important salinity and temperature changes, and in June every year we observed massive die-offs, leaving free substratum that was re-colonized within a month. We sampled 12-14 individuals of S. plicata every 2 months from 2007 to 2009 (N=196), and analyzed a mitochondrial marker (the gene Cytochrome Oxidase subunit I, COI) and seven nuclear microsatellites. Population genetic analyses showed similar results for both types of markers and revealed that most of the genetic variation was found within time periods. However, analyses conducted with microsatellite loci also showed weak but significant differences among time periods. Specifically, in the samplings after die-off episodes (August-November 2007 and 2008) the genetic diversity increased, the inbreeding coefficient showed prominent drops, and there was a net gain of alleles in the microsatellite loci. Taken together, our results suggest that recruits arriving from neighboring populations quickly occupied the newly available space, bringing new alleles with them. However, other shifts in genetic diversity and allele loss and gain episodes were observed in December-January and February-March 2008, respectively and were apparently independent of die-off events. Overall, our results indicate that the investigated population is stable over time and relies on a periodic arrival of larvae from other populations, maintaining high genetic diversity and a complex interplay of allele gains and losses.
    Full-text · Article · Feb 2016 · Marine Biology
    • "Evidence of rapid evolution in novel environments supports the idea that genetic diversity is important to the success of introduced populations because adaptations are more likely to be derived from existing genetic variation rather than mutation (Barrett and Schluter 2008 ). Some studies have demonstrated rapid evolution despite the presence of low genetic diversity (Dlugosch and Parker 2008 ), but more often the invasion success has been explained by high propagule pressure, multiple introductions, or genetic admixture, all of which are processes that maintain high genetic diversity and therefore enable adaptation (Allendorf and Lundquist 2003 ; Stepien et al. 2005 ; Roman and Darling 2007 ). However, due to the complexity of evolutionary processes, it would be imperative to genetically monitor the populations in order to recognize the underlying evolutionary patterns and manage them accordingly. "

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