Correlation between pelagic larval duration and realised dispersal: long-distance genetic connectivity between northern New Zealand and the Kermadec Islands archipelago

The extent to which marine populations are “open” (panmixia) or “closed” (self- recruitment) remains a matter of much debate, with recent reports of high levels of genetic differentiation and self-recruitment among populations of numerous species separated by short geographic. However, the interpretation of patterns of gene flow (connectivity) is often based on a stepping stone model of dispersal that can genetically homogenise even distant populations and blur genetic patterns that may better reflect realised dispersal. One way in which realised long-distance dispersal can be accurately determined is by examination of gene flow of taxa between isolated archipelagos and a mainland where there is no possible stepping stone dispersal across the open ocean. We investigated the genetic structuring of populations of the intertidal gastropod Nerita melanotragus from the subtropical Kermadec Islands and temperate New Zealand’s North Island (the mainland), separated by 750 km of open ocean and characterised by contrasting environmental conditions. Analyses of seven microsatellite markers revealed an absence of genetic structuring with low F ST and Jost’s D values (from 0.000 to 0.007 and from 0.000 to 0.015, respectively) over large geographic distances and no evidence of isolation by distance among all populations. These results indicate that the realised dispersal of N. melanotragus is of at least 750 km, this species exhibits a very “open” form of connectivity and its larvae exhibit sufficient phenotypic plasticity to settle successfully in different environmental conditions, ranging from subtropical to cool temperate

COI-16S Phylogenetic alignment

Complete phylogenetic alignment of COI and 16S concatenated fragments. Base pair 1-425:COI; base pair 426-852:16S

ATPS Phylogeography alignment

Complete alignment used for the nuclear haplotype network

COI-16S Phylogeography alignment

Complete alignment used for the haplotype network. Base pair 1-425:COI, base pair 426-891:16S

RAPD primers

File containing the primer names for the RPD study, as well as their loci and the size of the product scored in the analysis

Data from: Connectivity, small islands and large distances: the Cellana strigilis limpet complex in the Southern Ocean.

The Southern Ocean contains some of the most isolated islands on Earth and fundamental questions remain regarding their colonisation and the connectivity of their coastal biotas. Here we conduct a genetic investigation of the Cellana strigilis (limpet) complex that was originally classified based on morphological characters into six subspecies, five of which are endemic to the New Zealand (NZ) subantarctic and Chatham islands (44° to 52° S). Previous genetic analyses of C. strigilis from six of the seven island groups revealed two lineages with little or no within-lineage variation. We analysed C. strigilis samples from all seven island groups using two mitochondrial (COI and 16S), one nuclear (ATPase ) and randomly amplified polymorphic DNA markers (RAPDs), and confirmed the existence of two distinct lineages. We also detected pronounced genetic structuring within each lineage, with limpets from each island having their own genetic identity. These results are strikingly congruent with those recently reported for the southern bull kelp Durvillea antarctica, in which the NZ subantarctic and Chatham islands were proposed as refugia during the Last Glacial Maximum. Given the likely absence of larval dispersal among the islands, limpet rafting on kelp most probably explains the observed phylogeographic structure. Island-specific genetic identities and the paucity of shared haplotypes suggest that a small number of isolated colonisation events have occurred within each lineage are characterised by little or no genetic connectivity and therefore very high (southwest group) or total (northeast group) self-recruitment

ATPS Phylogeography alignment

Complete alignment used for the nuclear haplotype network

RAPD dataset

RAPD datase