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We simulated these stressors in the laboratory and recorded their effects on sex allocation in clonally propagated colonies.To interpret any effect of stress on sex allocation successfully, it is necessary also to consider the implications of sperm competition.
Sonia Scowcroft, the adoption centre’s manager, said she was "pretty stunned" as the condition is "so unusual".were established from larvae settled on acetate in April 1996 and propagated by taking cuttings (ramets) to generate a corresponding set of clones (36).Each clone was isolated from sources of allosperm and, consequently, no ramets produced larvae before experimentation (24).A relative measure of sex allocation, therefore, can be gained simply by counting the number of male or female zooids per autozooid in a colony (25). Frontal males, like females, are produced by frontal (upper surface) budding of the basal layer of autozooids, whereas basal males are produced by lateral budding of autozooids in the peripheral meristem or, occasionally, by conversion of established autozooids remote from the meristem (26).In the laboratory, extensive basal male production has been recorded among colonies of include physical impediment to growth (11), reduced food supply (28, 29), temperature shock or desiccation during tidal emersion (30), and destruction of zooids by predators (31).Colonial invertebrates are a globally dominant life form on sublittoral hard substrata (11).
Their sessile habit, modularity, and external dissemination of male gametes are features shared with higher plants; these features generate selection pressures common to the reproductive biology of the two types of organism (12).
Parallel trends appear consequently in many aspects of life history, including dispersal of propagules (13), mating strategies (14, 15), resource allocation to sexual and somatic functions (16, 17), and the frequent occurrence of hermaphroditism (18-20).
Accordingly, we used the bryozoan , however, can be extended indefinitely in the laboratory by artificial propagation with colonies showing no symptoms of senescence (23).
There is a strong tendency of such plants to increase the ratio of pollen to seed production when growing under environmentally stressful conditions, such as drought (2), nutrient deficiency (3), herbivory (4), or pathogenic infection (5). Despite subsequent experimental demonstrations of stress-induced maleness in plants, quantitative Darwinian treatment remained lacking until Freeman (7) used a newly emergent theory on environmental sex determination (8, 9) to present an evolutionarily stable strategy model predicting stress-induced maleness in plants occupying patchily stressful environments.
Stress-induced maleness in plants was first given theoretical consideration, albeit in Lamarckian spirit, by Henslow: “there seems to be a tolerably uniform consensus of opinion that the female sex in plants is correlated with a relatively stronger vital vigour than the male; and this is just what an assumption would look for, as the duration of existence and the work to be done in making fruit require a greater expenditure of energy than the temporary function of the stamens” (ref. Freeman (7) considered the example of patch dryness, but stress could mean any condition induced by the physical or biological environment that reduces scope for resource allocation or survivorship and, hence, reduces fitness (10).
The demonstrated similarity to plants transcends specific physiological pathways and suggests that stress-induced bias toward male function is a general response of hermaphroditic modular organisms to impaired prospects for parental productivity or survival.