Physiological ecology of the clonal corallimorpharian <Emphasis Type="Italic">Corynactis californica</Emphasis> |
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Authors: | Peter J Edmunds |
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Institution: | (1) Department of Biology, California State University, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA |
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Abstract: | For clonal taxa, the reduced genetic variability associated with clonal proliferation is hypothesized to reduce the ability
to respond to variable conditions, unless a general-purpose genotype (GPG) confers success in multiple environments. In this
study, Corynactis californica (Carlgren 1936) from the subtidal of California was used as a model system to test the hypothesis that clones dampen fluctuations
in fitness through a GPG that facilitates phenotypic plasticity. To achieve this goal, tissue composition, respiration, excretion,
and growth were compared among clones of C.
californica at one site, and a reciprocal transplant experiment was used to test the response of clones to differing conditions at two
sites. All experiments were completed at Santa Catalina Island (N 33°25′, W 118°30′) between April and September 1991. Clones
at a single site differed significantly in multiple traits, varying as much as 1.6-fold in protein content, 3.4-fold in respiration,
and 3.5-fold in excretion. Interestingly, while tissue growth was the most labile trait (differing up to 35.4-fold among clones),
polyp fission rates were not significantly different among clones, in part because fission continued even though tissue growth
was unable to restore polyp size in between divisions. Partial energy budgets revealed that the majority (47–90%) of the daily
energy expenditure was accounted for by respiration, 13–47% by growth, and 0.3–14% by excretion. In the transplant experiment,
reaction norms revealed strong effects of the environment on some traits but not others, notably with growth differing between
sites in a pattern that differed among clones, and excretion differing between sites; neither respiration nor fission were
affected by transplantation. Partial energy budgets revealed that the energy allocation to respiration varied between sites
in a pattern that differed among clones, and a similar trend was evident for tissue growth. Together, these results demonstrate
that clones of C. californica have markedly different phenotypes and exploit phenotypic plasticity to maintain relatively constant fission rates, even
though tissue growth varies greatly among clones and between environments. While these findings support the GPG hypothesis
for clones of C. californica—at least based on relative fitness achieved through asexual proliferation—this conclusion depends on the extent to which
polyps are successful when they have low rates of tissue growth. |
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