Genetic diversity of the NE Atlantic sea urchin Strongylocentrotus droebachiensis unveils chaotic genetic patchiness possibly linked to local selective pressure

Abstract

We compared the genetic differentiation in the green sea urchin Strongylocentrotus droebachiensis from discrete populations on the NE Atlantic coast. By using eight recently developed microsatellite markers, genetic structure was compared between populations from the Danish Strait in the south to the Barents Sea in the north (56–79°N). Urchins are spread by pelagic larvae and may be transported long distances by northwards-going ocean currents. Two main superimposed patterns were identified. The first showed a subtle but significant genetic differentiation from the southernmost to the northernmost of the studied populations and could be explained by an isolation by distance model. The second pattern included two coastal populations in mid-Norway (65°N), NH and NS, as well as the northernmost population of continental Norway (71°N) FV. They showed a high degree of differentiation from all other populations. The explanation to the second pattern is most likely chaotic genetic patchiness caused by introgression from another species, S. pallidus, into S. droebachiensis resulting from selective pressure. Ongoing sea urchin collapse and kelp forests recovery are observed in the area of NH, NS and FV populations. High gene flow between populations spanning more than 22° in latitude suggests a high risk of new grazing events to occur rapidly in the future if conditions for sea urchins are favourable. On the other hand, the possibility of hybridization in association with collapsing populations may be used as an early warning indicator for monitoring purposes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-015-2801-y) contains supplementary material, which is available to authorized users.

Oceanographic features and limited dispersal shape the population genetic structure of the vase sponge Ircinia campana in the Greater Caribbean

“…Asynchronicity in reproduction within populations could be a further component of temporal variability in recruitment dynamics (Eldon et al 2016 ). Another possible cause is differential post-settlement selection (Norderhaug et al 2016 ); in I. campana , this could result from high selection pressure exerted by cyanobacterial blooms (Butler et al 1995 ) or disease (Maldonado et al 2010 ). Indeed, we found evidence of a genetic bottleneck at Bamboo Key following a known mass mortality caused by a cyanobacterial bloom (see section below).…”

Cryptic species diversity and reproductive isolation among sympatric lineages ofStrongylocentrotussea urchins in the northwest Atlantic

“…Sea urchins have long been a model organism for the studies of developmental biology, and species in the genus Strongylocentrotus are becoming an increasingly popular in the study of population genetics and evolution (Addison and Hart 2004;Addison and Hart 2005;Addison and Pogson 2009;Pujolar and Pogson 2011;Kober and Bernardi 2013;Norderhaug et al 2016). Genetic studies of Strongylocentrotus droebachiensis (Müller, 1776) detected local panmixis but significant population substructure between the east and west coasts of the north Atlantic, where the eastern populations had low genetic diversity at both microsatellite loci and mtDNA sequences Hart 2004, 2005;Harper et al 2007).…”

Research agendas for profitable invasive species

“…These results suggest that applying a high fishing mortality for the purposes of controlling the population of the invasion may no longer be the preferred policy. In addition, some recent research attributes ecosystem benefits to the introduction of the crab; a prime example is the crab's predation upon sea urchins, which helps protect the kelp forests (Norderhaug et al, 2016). Such positive effects are not yet considered certain and remain disputed among experts (Sivertsen, 2006) (Knut Sivertsen, UiT, personal communication).…”