Contrasting patterns of population connectivity between regions in a commercially important mollusc Haliotis rubra: integrating population genetics, genomics and marine LiDAR data

Estimating contemporary genetic structure and population connectivity in marine species is challenging, often compromised by genetic markers that lack adequate sensitivity, and unstructured sampling regimes. We show how these limitations can be overcome via the integration of modern genotyping methods and sampling designs guided by LIDAR and SONAR datasets. Here we explore patterns of gene flow and local genetic structure in a commercially harvested abalone species (Haliotis rubra) from South Eastern Australia, where the viability of fishing stocks is believed to be dictated by recruitment from local sources. Using a panel of microsatellite and genome-wide SNP markers we compare allele frequencies across a replicated hierarchical sampling area guided by bathymetric LIDAR imagery. Results indicate high levels of gene flow and no significant genetic structure within or between benthic reef habitats across 1400 km of coastline. These findings differ to those reported for other regions of the fishery indicating that larval supply is likely to be spatially variable, with implications for management and long-term recovery from stock depletion. The study highlights the utility of suitably designed genetic markers and spatially informed sampling strategies for gaining insights into recruitment patterns in benthic marine species, assisting in conservation planning and sustainable management of fisheries.

Digital suburbs? Some policy implications of greater domestic connectivity

Since the mid-1990s there has occurred a communications revolution. With the development and widespread dissemination of Information Communications Technologies (ICTs), the capacity of virtually everyone in the developed world to send, receive and manipulate masses amounts of information has been transformed. In the light of high levels of internet uptake across Australian cities and the looming rollout of the National Broadband Network, it is timely to investigate just what the impacts may be on house design, service access, socialisation and connections to localities. The answer to these questions will potentially have profound implications for the future planning of Australian cities and suburbs. So, has the proliferation of domestic broadband led to more people working from home rather than commuting, on line socialising, and on line service access? Or has greater connectivity meant that the form and range of information flow has altered but the physicality of service provision, job access and socialisation is just, if not more, important? This paper will locate these questions within research on the economic, social and political impacts of ICTs before discussing how the digital revolution is having limited economic effects but profound social and political impacts on Melbourne’s western suburbs.

Species- and sex-specific connectivity effects of habitat fragmentation in a suite of woodland birds

Loss of functional connectivity following habitat loss and fragmentation could drive species declines. A comprehensive understanding of fragmentation effects on functional connectivity of an ecological assemblage requires investigation of multiple species with different mobilities, at different spatial scales, for each sex, and in different landscapes. Based on published data on mobility and ecological responses to fragmentation of 10 woodland-dependent birds, and using simulation studies, we predicted that (1) fragmentation would impede dispersal and gene flow of eight "decliners" (species that disappear from suitable patches when landscape-level tree cover falls below species-specific thresholds), but not of two "tolerant" species (whose occurrence in suitable habitat patches is independent of landscape tree cover); and that fragmentation effects would be stronger (2) in the least mobile species, (3) in the more philopatric sex, and (4) in the more fragmented region. We tested these predictions by evaluating spatially explicit isolation-by-landscape-resistance models of gene flow in fragmented landscapes across a 50 x 170 km study area in central Victoria, Australia, using individual and population genetic distances. To account for sex-biased dispersal and potential scale- and configuration-specific effects, we fitted models specific to sex and geographic zones. As predicted, four of the least mobile decliners showed evidence of reduced genetic connectivity. The responses were strongly sex specific, but in opposite directions in the two most sedentary species. Both tolerant species and (unexpectedly) four of the more mobile decliners showed no reduction in gene flow. This is unlikely to be due to time lags because more mobile species develop genetic signatures of fragmentation faster than do less mobile ones. Weaker genetic effects were observed in the geographic zone with more aggregated vegetation, consistent with gene flow being unimpeded by landscape structure. Our results indicate that for all but the most sedentary species in our system, the movement of the more dispersive sex (females in most cases) maintains overall genetic connectivity across fragmented landscapes in the study area, despite some small-scale effects on the more philopatric sex for some species. Nevertheless, to improve population viability for the less mobile bird species, structural landscape connectivity must be increased.

Roadside connectivity does not increase reptile abundance or richness in a fragmented mallee landscape

The effect of isolation and the importance of dispersal in establishing and maintaining populations in fragments of remnant habitat remain poorly understood. Nevertheless, environmental connectivity is likely to be important for ensuring the long-term preservation of biodiversity in extensively cleared landscapes. In this study, we compared reptile communities in large conservation parks with those in small woodland remnants 6.5-12km from the parks, on the Eyre Peninsula, South Australia, Australia. We assessed the impact of fragmentation on the abundance, richness and habitat preferences of reptiles, and examined whether connection to linear roadside vegetation altered reptile communities in small woodland remnants. Of the 31 reptile species, 12 were restricted to conservation parks and six to habitat fragments in farmland. There was a substantial reduction in reptile species richness and abundance in farmland fragments. Direct connection of remnant vegetation to roadside corridors did not affect abundance of common species in the farmland fragments, although species richness was lower in isolated remnants in one of our two study regions. The habitat preference of the scincid lizard Menetia greyii differed between farmland fragments, where they were regularly found on dunes and roadsides, and conservation parks, where they were rare and not detected on dunes. We suggest that habitat fragmentation may have altered interspecific interactions, enabling an expansion of habitat use in the farming landscape. Significantly lower abundance of four common species in farmland settings compared with reserves indicated that existing corridors and small fragments provide inadequate connectivity over larger distances. To counter this effect, large reserves may need to be less than 10km apart.