Connectivity within and among a Network of Temperate Marine Reserves

Abstract

Networks of marine reserves are increasingly being promoted as a means of conserving marine biodiversity. One consideration in designing systems of marine reserves is the maintenance of connectivity to ensure the long-term persistence and resilience of populations. Knowledge of connectivity, however, is frequently lacking during marine reserve design and establishment. We characterise patterns of genetic connectivity of 3 key species of habitat-forming macroalgae across an established network of temperate marine reserves on the east coast of Australia and the implications for adaptive management and marine reserve design. Connectivity varied greatly among species. Connectivity was high for the subtidal macroalgae Ecklonia radiata and Phyllospora comosa and neither species showed any clear patterns of genetic structuring with geographic distance within or among marine parks. In contrast, connectivity was low for the intertidal, Hormosira banksii, and there was a strong pattern of isolation by distance. Coastal topography and latitude influenced small scale patterns of genetic structure. These results suggest that some species are well served by the current system of marine reserves in place along this temperate coast but it may be warranted to revisit protection of intertidal habitats to ensure the long-term persistence of important habitat-forming macroalgae. Adaptively managing marine reserve design to maintain connectivity may ensure the long-term persistence and resilience of marine habitats and the biodiversity they support.

Management and conservation of the kelp speciesLaminaria digitata: using genetic tools to explore the potential exporting role of the MPA “Parc naturel marin d’Iroise”

“…In agreement with the lack of available substrate, and therefore conspecific populations on the adjacent coastline (Billot et al 2003;Valero et al 2011), these two groups exhibited low genetic diversity and strong differentiation. Indeed, the influence of habitat discontinuity on population connectivity has been also evoked for other kelp species (Alberto et al 2010;Fraser et al 2010;Coleman et al 2011). The two remaining groups revealed a clear differentiation between Northwestern and Southern Brittany.…”

“…However, they are also subject to growing anthropogenic pressures and a worldwide decline has been recently reported (Airoldi and Beck 2007). Ensuring that marine reserves adequately protect these habitats, including their connectivity, is therefore a key issue in conservation of temperate marine regions (Coleman et al 2011).…”

Seed dispersal in the seagrass Zostera marina is mostly within the parent bed in a protected bay

“…Their seed-dispersal distance depends on the residence time of seeds rafting on the water surface, on the current speed (Harwell & Orth 2002, Boedeltje et al 2004, Erftemeijer et al 2008, Källström et al 2008, Coleman et al 2011a, and on the activity of seed consumers (Sumoski & Orth 2012). These mech-anisms can disperse seeds to a range of hundreds of kilometers and genetically connect separate populations (Kendrick et al 2012).…”

Genetic and morphological diversity in sympatric kelps with contrasting reproductive strategies

“…Given that genetic diversity often confers adaptive capacity through change (Reusch et al 2005, Hughes et al 2008, Wernberg et al 2018, this lower diversity may have implications for the vulnerability of this unique morph to local climatic and environmental stressors, relative to co-occurring haplodiplontic morphs. Indeed, we recently documented the potential role of reduced genetic diversity in mediating vulnerability of E. radiata forests to climate stress at lower latitudes along this same coast (Wernberg et al 2018 Despite genetic diversity (number of alleles) being lower in the vegetative morph than in nearby haplodiplontic morphs in Hamelin Bay, diversity estimates were similar to many other populations of haplodiplontic E. radiata throughout Australia (Coleman et al 2011a,b, Coleman 2013. This raises the possibility that vegetative reproduction may be more prevalent than previously known, although we find this unlikely given the distinct morphology of vegetative morphs and their absence from extensive surveys elsewhere throughout Australia (Wernberg et al 2003).…”

“…In addition, we tested for Hardy-Weinberg equilibrium at each locus and across all loci using FSTAT 1.2 (Goudet 1995). There was no evidence of linkage disequilibrium in any locus for E. radiata , 2011a,b, Coleman 2013. Inbreeding and the extent of asexuality were estimated by testing F IS estimates using permutation tests (1000 permutations, FSTAT 1.2, Goudet 1995).…”