Exchange between populations of Adamussium colbecki (Mollusca: Bivalvia) in the Ross Sea

Abstract

The endemic Antarctic scallop Adamussium colbecki (Mollusca: Bivalvia) represents a key species in the Ross Sea littoral benthic ecosystem, locally reaching very high densities. This species has an annual gametogenic cycle, with a summer spawning event, and a pelagic larval behaviour. This paper aims at describing population structure and genetic polymorphism (using AFLP) of the large populations inhabiting the Ross Sea (Terra Nova Bay and McMurdo Sound) in order to investigate possible genetic exchange between A. colbecki in these areas. In Terra Nova Bay, size-frequency distributions show, generally, the dominance of large individuals, although site related differences are found in the abundance of smaller size classes (less than 40 mm), suggesting that recruitment is not a regular event. All McMurdo sites are characterized by large individuals and, at least during this sampling period, recruitment is completely absent. Nuclear DNA analyses show that the largest differences are found at the largest scale (between McMurdo Sound and Terra Nova Bay), but all populations sampled, even at a smaller spatial scale, have a well-settled genetic structure, notwithstanding the pelagic larval strategy. The panmixia hypothesis has therefore to be rejected for this species.

The spatial structure of Antarctic biodiversity

“…Over the longer term, genetic drift is, therefore, the prevailing evolutionary process (Held and Leese 2007). For example, Adamussium colbecki, which has a long, planktotrophic larval phase, shows demonstrable genetic isolation in populations both at relatively large (;450 km) and more local spatial scales (within ;50 km), although the latter differences are of an order of magnitude lower (Guidetti et al 2006). The genetic and biogeographic structure of this and other species may therefore reflect a complex pattern of isolation events and range expansions occurring at different spatial and temporal scales (further examples in Held and Wa¨gele 2005, Barnes and Hillenbrand 2010.…”

EarlyMioceneMollusca fromMcMurdoSound,Antarctica (ANDRILL2Adrill core), with a review ofAntarcticOligocene andNeogenePectinidae (Bivalvia)

“…Guidetti et al . () also showed that genetic exchange between quite closely spaced populations of A. colbecki is very limited.…”

Peer Review #2 of "Oceanographic moorings as year-round laboratories for investigating growth performance and settlement dynamics in the Antarctic scallop Adamussium colbecki (E. A. Smith, 1902) (v0.2)"

“…Manuscript to be reviewed A. colbecki has been the subject of research within the Italian PNRA since the first Italian expeditions, resulting in an unusual in depth knowledge for an Antarctic species, testified by a large number of published studies (e.g. Cerrano et al 2000;2001;Chiantore et al, 1998;2001;Guidetti et al, 2006;Schiaparelli and Linse, 2006;Dell'Acqua et al 2017, Moro et al, in press). This species was also proposed as a candidate for a 'Southern Ocean mussel-watch program' (Berkman and Nigro, 1992;Nigro et al, 1997;Dalla Riva et al, 2004).…”