Phylogeography of New Zealand's coastal benthos

Abstract

During the past 30 years, 42 molecular studies have been undertaken in New Zealand to examine the phylogeography of coastal benthic invertebrates and plants. Here, we identify generalities and/or patterns that have emerged from this research and consider the processes implicated in generating genetic structure within populations. Studies have used various molecular markers and examined taxonomic groups with a range of life histories and dispersal strategies. Genetic disjunctions have been identified at multiple locations, with the most frequently observed division occurring between northern and southern populations at the top of the South Island. Although upwelling has been implicated as a cause of this disjunction, oceanographic evidence is lacking and alternative hypotheses exist. A significant negative correlation between larval duration and genetic differentiation (r 2 = 0.39, P < 0.001, n = 29) across all studies suggests that larval duration might be used as a proxy for dispersal potential. However, among taxa with short larval durations (<10 days) there was greater variability in genetic differentiation than among taxa with longer pelagic periods. This variability implies that when larval duration is short, other factors may determine dispersal and connectivity among populations. Although there has been little congruence between the phylogeographic data and recognised biogeographic regions, recent research has resolved population subdivision at finer spatial scales corresponding more closely with existing biogeographic classifications. The use of fast-evolving and ecologically significant molecular markers in hypothesis-driven research could further improve our ability to detect population subdivision and identify the processes structuring marine ecosystems.

Widespread Dispersal of the Crown-of-Thorns Sea Star,Acanthaster planci, across the Hawaiian Archipelago and Johnston Atoll

“…Females release up to 10 8 eggs during one spawning season and can spawn for up to 4 years of their approximated 8-year lifespan [26,54]. The use of PLD as a reliable proxy for dispersal potential has been questioned in several recent meta-analyses of the existing literature [55][56][57][58]. In this case, however, the data support the expectations based on life-history traits.…”

The genetic architecture of hybridisation between two lineages of greenshell mussels

“…In addition, we do not have information about sex-linked markers and nor do we have even a rudimentary genetic linkage map for the greenshell mussel. We do, however, have evidence of the existence of two lineages that interact at a geographic location that is coincident with the existence of contact zones for several other marine coastal taxa (Ross et al, 2009;Gardner et al, 2010). Despite the existence of the challenges noted above, the combined analyses provided a consistent set of results, which has permitted us to develop new insights into the origin and maintenance of this multitaxon hybrid zone.…”

“…The origin and structure of the hybrid zone The region just south of Cook Strait is an area of genetic discontinuities for many continuously distributed coastal marine taxa (Ross et al, 2009;Gardner et al, 2010). Mussels of the genus Perna are subtropical in origin and the fossil record suggests that they arrived in NZ~25 M ybp (Fleming, 1979;Wood et al, 2007).…”

“…This mussel is widely distributed with population sizes into the millions, has external fertilisation, produces larvae with a pelagic duration of~4 weeks and has the potential to produce millions of offspring per female with considerable dispersal potential (Wei et al, 2013a,b). A pronounced genetic discontinuity between northern and southern lineages occurs in central NZ (Figure 1) where genetic discontinuities exist for many coastal taxa (Ross et al, 2009;Gardner et al, 2010;Wei et al, 2013a). Dating places the time of the genetic divergence at~0.3 to 1.3 million years before present (M ybp) in the greenshell mussel, P. canaliculus, and to~0.2 to 0.3 M ybp in limpets, Cellana spp.…”

“…Thus, interpreting the present situation requires an understanding of the historical events that led to the creation of genetically differentiated lineages within taxa, and contemporary events that may now be eroding or maintaining such genetic differences. Recent investigations have focussed on the population genetics, phylogeography and seascape genetics of multiple taxa (Ross et al, 2009;Gardner et al, 2010;Wei et al, 2013a,b), but no previous study has looked at the genetic architecture of the hybrid zone of any taxon in this region. In this study, we use a variety of different analytical approaches to examine the structure of the greenshell mussel hybrid zone to better understand its architecture and how it is maintained in the face of extensive potential gene flow.…”