Unexpected genetic structure of mussel populations in South Africa: indigenous Perna perna and invasive Mytilus galloprovincialis

Abstract

Genetic structure of sedentary marine organisms with planktonic larvae can be influenced by oceanographic transport, larval behaviour and local selection. We analysed the population genetic structure (based on mtDNA) of the invasive mussel Mytilus galloprovincialis and the indigenous mussel Perna perna along the southern African coastline. Low genetic divergence of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the genetic structure of P. perna revealed strong divergence on the south-east coast, forming a western and an eastern lineage. The distribution of the 2 lineages is extraordinary. They overlap for ca. 200 km on the southeast coast, and the western lineage includes animals occurring on either side of a 1000 km break in distribution across the Benguela upwelling system. In cluster analyses, animals on the south coast grouped with others 1000s of km to the west, rather than with those only 200 km to the east. This genetic disjunction may be caused by the south-flowing Agulhas Current preventing larval dispersal, or by different selective forces acting on local populations. M. galloprovincialis spread eastward along the south coast for 15 yr, but its range extension has virtually ceased in the region of genetic disjunction in P. perna, again indicating an oceanographic barrier to larval dispersal or selection driven by sharp gradients in environmental conditions. The results suggest that local selection can produce genetic structure opposite to that predicted by oceanographic data and that determining the population structure of indigenous species with similar larval dispersal can help us understand domain expansion of invading species. KEY WORDS: Mytilus galloprovincialis · Perna perna · Invasion · Biogeographic region · Currents · mtDNAResale or republication not permitted without written consent of the publisher

Scale-dependent patterns and processes of intertidal mussel recruitment around southern Africa

“…All these locations had regular annual recruitment events and strong synchrony among sites within locations. This accords with previous studies showing highly seasonal spawning and/or recruitment at or near these locations (Berry 1978, Lasiak 1986, Zardi et al 2007. Port Alfred lacked a seasonal pattern, supporting previous reports of irregular seasonal and annual recruitment and spawning around this location (Ndzipa 2002, McQuaid & Lawrie 2005, Porri et al 2006a.…”

Morphological and Molecular Differences Between the Invasive BivalveRuditapes philippinarum(Adams & Reeve, 1850) and the Native SpeciesRuditapes decussatus(Linnaeus, 1758) from the Northeastern Adriatic Sea

“…Based on the 16S rRNA sequence data, all Croatian R. philippinarum specimens share the same haplotype with no genetic variability, implying a recent entrance of the species, most probably from a unique recruitment stock. Low genetic variability has also been noticed in other aquatic invaders at the first stage of their invasions, as it was recorded for the invasive mussel Mytilus galloprovincialis (Lamarck, 1819) (Zardi et al 2007) and the European green crab Carcinus maenas (Linnaeus, 1758) (Darling et al 2008). Although it is impossible to verify the exact origin of the Croatian R. philippinarum population, there is a strong possibility that it may have originated from founding populations in the Italian part of the northern Adriatic Sea, as identical 16S rDNA haplotypes have been evidenced in R. philippinarum specimens from the Venice Lagoon as well as the Marano Lagoon (Passamonti et al 2003, Chiesa et al 2014.…”

Coastal topography drives genetic structure in marine mussels

“…Mitochondrial DNA sequences for Perna perna indicate a strong phylogeographic break on the southern coast of South Africa, north of East London (approximately 300 km east of our site at Kenton-on-Sea), leading to the formation of an eastern and western lineage (Zardi et al 2007). No significant isolation by distance was found within lineages.…”

“…They include a long stretch of sandy beach, with patches of sand-influenced granite rock (Bownes & McQuaid 2006). All populations belong to the same genetic lineage (Zardi et al 2007). Mussels were opened in the laboratory, and a piece of gonad tissue was examined under the microscope to determine the sex of the animal by the presence of eggs or sperm.…”