Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Marine Biodiversity
11.3.4. Progress on Science Objective 4. Marine genetic
biodiversity
Genetic biodiversity can be measured directly by measurement made at the genes and chromosomes
scale or indirectly by measuring physical features at the organism scale (assuming they have a genetic
basis).
Genetic diversity is fundamental to the long-term survival, stability and success of a species. Central
to this is the “metapopulation” concept where populations are sufficiently genetically distinct from
each other to be identifiable as individual units. A low level of recruitment between populations
counters the effects of random genetic drift and inbreeding depression of genetic diversity.
Human activities can profoundly affect genetic diversity both within populations and between
populations. For example, shipping activity (movement across the globe) and aquaculture practices
(transfer of organisms to different areas) can increase population connectivity such that genetic
biodiversity may decrease between populations. In extreme cases, populations can become the same
genetically (homogeneous) although considerable within population diversity may remain. In the
event of increased genetic connectivity, a species may become more susceptible to extinction through
biological or catastrophic stochasticity. That is, in the absence of between population diversity there is
insufficient genetic variance to adapt to the effects of climate change, disease epidemics and so on.
In contrast, under the much more common scenario of habitat fragmentation caused by human
activities (fishing, pollution), decreased connectivity between populations will result in greater
between-population diversity, but a reduction of within-population diversity. This also results in a
decrease in a species survival (fitness) because fragmented or isolated populations may become
extinct through environmental and genetic stochasticity or localised depletion. Periodic fluctuations in
annual temperature for example can lead to small scale population extinction, which in the absence of
recruitment between populations will result, over time, in the demise of all populations.
To reduce the risk of species loss information about the genetic diversity both within populations
(population isolation) and between populations (population connectivity) is needed. Without such
information, the effects of perturbation on a species persistence and survival cannot be predicted.
Furthermore, the links between genetic diversity, the dispersal capacity (mode of reproduction and life
history development) of a species and the minimum viable population (MVP) size required in the
marine environment to ensure population persistence, are little understood. For example, the MVP
size for a species with a large dispersal capacity is likely to be quite different from that of a species
with a relatively restricted dispersal capacity. Examining the connectivity between populations in the
marine environment is fundamental to resolving some of the central challenges in ecology and has
almost been ignored in the management of New Zealand fisheries or protection of biodiversity.
Projects
ZBD2002-12 Molecular identification of cryptogenic/invasive marine species – gobies.
Project complete. (Lavery et al. 2006.)
ZBD2009/10 Multi-species analysis of coastal marine connectivity.
An extensive literature review of published and unpublished information about connectivity
of New Zealand coastal biota has been completed. Reviews were made of 58 studies of 42
taxa to identify the taxon or taxa studied, the habitat where each study took place, and
geographic location of sampling sites used by each study. From these data, gaps in knowledge
about taxa, habitats and spatial coverage of sampling were identified. Recommendations
about four species to be studied, habitats that they should be collected from, and location of
sampling sites were made. Recommendations included a standardised collecting protocol and
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