1 Genomics in the Discovery and Monitoring
23
are the current focus of intense research activity, partly because of the threat to the
goods and services that ecosystems provide to society. Much of the research to date
has been controversial, with disagreement over the role of diversity as opposed to
the roles of individual species or functional groups. Marine environments are more
diverse at higher taxonomic levels than terrestrial systems and have higher levels
of functional diversity. There are several hypotheses proposed, ranging from diversity having no effect on ecosystem function, through diversity driving ecosystem
functioning and must be redundant to cope with the magnitude of changes, and the
direction of change with diversity loss may or may not be predicatable. The question of how biodiversity affects ecosystem functioning is to search for communities
differing in one aspect of biodiversity.
Few data are available to assess the potential ecosystem level importance of
genetic diversity within species known to play a major functional role. However,
Hughes and Stachowicz (2004) have shown that increasing genotypic diversity in
a habitat-forming seagrass, Zostera marina, enhanced the community resistance
to disturbance by grazing geese. In addition, the time required for the community to recovery to near predisturbance densities also decreased with increasing
eelgrass genotypic diversity. A study on the population structure of the microalga
Phaeocystis antarctica from all of the major continental gyres around Antarctica
using microsatellites has shown that each continental gyre is highly genetically
diverse with reduced gene flow between the gyres (Gaebler and Medlin, unpubl.).
However, isolates from each gyre are physiologically distinct. For example, in those
gryes with annual ice cover, isolates can survive a range of salinities from 18 to
70‰ with only a delay in maximum growth over time, whereas isolates from icefree gyres can only survive at full strength sea water (33‰). Thus there appears to
be an integrated phenotypic response to the environment such that should climate
change occur, local extinctions would be expected and repopulation of an area would
depend on gene flow and dispersal from other others. The high diversity within each
gyre suggests that P. antarctica has exploited the niche available in each gyre to
cover different possible combinations of environmental conditions that occur in that
gyre and to make a more stable population.
1.4 Concluding Remarks
Documented shifts in the distribution and abundance of organisms in response to
climate change (Umina et al. 2005, Bradshaw and Holzapfel, 2006) indicate that
environments are changing rapidly. The ability of biota to persist is determined by
their genetic constitution and ability to adapt physiologically. In extreme changes,
an organism may respond in four ways: it migrates to a more favourable area, a
physiological response increases the metabolic range for survival and reproduction, selective mortality results in local adaptation, or populations become locally
extinct. Crucially, genetic markers can assist in monitoring the impact of environmental change at the level of DNA sequences, proteins or metabolites, as well as
23
are the current focus of intense research activity, partly because of the threat to the
goods and services that ecosystems provide to society. Much of the research to date
has been controversial, with disagreement over the role of diversity as opposed to
the roles of individual species or functional groups. Marine environments are more
diverse at higher taxonomic levels than terrestrial systems and have higher levels
of functional diversity. There are several hypotheses proposed, ranging from diversity having no effect on ecosystem function, through diversity driving ecosystem
functioning and must be redundant to cope with the magnitude of changes, and the
direction of change with diversity loss may or may not be predicatable. The question of how biodiversity affects ecosystem functioning is to search for communities
differing in one aspect of biodiversity.
Few data are available to assess the potential ecosystem level importance of
genetic diversity within species known to play a major functional role. However,
Hughes and Stachowicz (2004) have shown that increasing genotypic diversity in
a habitat-forming seagrass, Zostera marina, enhanced the community resistance
to disturbance by grazing geese. In addition, the time required for the community to recovery to near predisturbance densities also decreased with increasing
eelgrass genotypic diversity. A study on the population structure of the microalga
Phaeocystis antarctica from all of the major continental gyres around Antarctica
using microsatellites has shown that each continental gyre is highly genetically
diverse with reduced gene flow between the gyres (Gaebler and Medlin, unpubl.).
However, isolates from each gyre are physiologically distinct. For example, in those
gryes with annual ice cover, isolates can survive a range of salinities from 18 to
70‰ with only a delay in maximum growth over time, whereas isolates from icefree gyres can only survive at full strength sea water (33‰). Thus there appears to
be an integrated phenotypic response to the environment such that should climate
change occur, local extinctions would be expected and repopulation of an area would
depend on gene flow and dispersal from other others. The high diversity within each
gyre suggests that P. antarctica has exploited the niche available in each gyre to
cover different possible combinations of environmental conditions that occur in that
gyre and to make a more stable population.
1.4 Concluding Remarks
Documented shifts in the distribution and abundance of organisms in response to
climate change (Umina et al. 2005, Bradshaw and Holzapfel, 2006) indicate that
environments are changing rapidly. The ability of biota to persist is determined by
their genetic constitution and ability to adapt physiologically. In extreme changes,
an organism may respond in four ways: it migrates to a more favourable area, a
physiological response increases the metabolic range for survival and reproduction, selective mortality results in local adaptation, or populations become locally
extinct. Crucially, genetic markers can assist in monitoring the impact of environmental change at the level of DNA sequences, proteins or metabolites, as well as