MacDonald, C. Murray
Description
Electrophoretic and heat stability data have been
obtained from 22 enzymatic proteins to assess the amount
and distribution of genetic variation in fishes of the
temperate percoid genera Arripis and Chrysophrys.
Available biological and life history data have been
reviewed, and indicate that Arripis species are mobile,
migratory, pelagic fishes, with planktonic larvae and a
comparatively short life span (up to 9 years), while
Chrysophrys species are comparatively sedentary...[Show more] and
demersal, have benthic larvae, and are long-lived (up to
60 years). The electrophoretic and heat stability data
have been used to test the hypothesis that species with
different life history characteristics exhibit
different distribution patterns of genetic variation,
and that these differences are the result of different
adaptive strategies adopted by the organisms to cope with
contrasting environmental regimes. The results generally
agreed with predictions, although some alternative
explanations for observed gene distributions could not be
eliminated.
Electrophoretic data were also analysed using kinship
and genetic distance techniques to provide information on the structure of snapper (C. Auratus) and western salmon (Arripis sp) populations in
Australian waters. The results indicate that western
salmon consist of a single breeding population extending
across the southern Australian coastline, while at least
five geographically distinct snapper populations were
detected. Enzyme kinetic studies were carried out on snapper
isocitrate dehydrogenase (IDH) and salmon malic enzyme
(ME) allozymes to determine whether or not functional differences existed in response to temperature fluctuation.
It was found that differences did exist between IDH allozymes, but that the functional variation was correlated
with heat stability variants rather than electrophoretic
variants. The geographical distribution of snapper IDH variation was re-examined in the light of this result, and the relative contributions of random and selective
processes to observed patterns were discussed. No
functional differences in response to temperature fluctuations were detected for salmon ME electrophoretic or heat stability allozymes. The observed functional characteristics of snapper
IDH and salmon ME allozymes over known biological
temperature ranges of the species were compared as
indicators of biochemical adaptive strategies in
organisms with different ecological requirements. The
observed results agree with expectations based on the
known biology of snapper and salmon, but further enzymes
need to be assayed to confirm this pattern.
Taxonomy and evolutionary relationships within the
genera Arripis and Chrysophrys have been examined using genetic distance and time-since-divergence estimates based
on the electrophoretic data. Attempts have been made to
reconstruct the evolutionary history of each genus on the
basis of the genetic data, the current distribution of
taxa, and information about past geomorphological events
in key areas, such as Bass Strait.
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