A condition-dependent handicap is an ornament that is only developed in males with high viability because its development depends on the general condition of its possessor. Andersson presents the first detailed analysis of condition-dependent handicaps, using analytical and simulation studies of a three-locus model of sexual selection preference, sex-trait, viability loci.
Kumagai, R. IntechOpen: Are there any significant research developments currently being explored which are aimed at generating new insights for the field of bioenergetics? Griffin, J. Hawkridge and T. Tarasevich and V. Every e ort is tming m that this d:as;; not happen again.
In the first generation, the approximate condition for the spread of female preference is that the increase in survival attributable to heritable variation in viability e must be greater than half the reduction in survival caused by the ornament p , i. This is a lax condition which is likely to be easily met in nature. It is especially lax when compared to the condition required for the spread of female preference for a rigid, conditionindependent ornament i.
Zahavi handicap -that t must be very much greater than p Ref. A similar pattern emerges from simulations of subsequent generations.
This is an important result. It shows that female choice for markers of male genetic quality can by itself without the help of the Fisher process easily lead to exaggeration of male ornamentation and female preference when the expression of the marker is condition-dependent. The next stage for theoreticians is to establish what type of handicap, whether Zahavi, revealing or condition-dependent, is most likely to cause the evolution of extravagant ornamentation.
Andersson has begun to unravel this question; he has shown in monogamous mating systems that female preference for condition-dependent male ornaments is more likely to evolve than preference for Zahavi handicaps, that is, for ornaments produced irrespective of male viability.
References 1 Majerus, M. E vol.
Townsend Organisms can be viewed as resource transformers that partition a finite input of resource between the metabolic compartments of storage, growth, repair, reproduction, defence and foraging to obtain further resources. The way in which resources are allocated is critical to the fitness of the individual.
The optimum pattern of allocation is the one that, in the prevailing environmental circumstances, most effectively transforms resource input to reproductive output and thus transmits more genes to future generations. Fitness is properly measured as the proportionate contribution of genes to future generations and clearly the ideal would be to calibrate each energy transaction in terms of its effects on reproductive success.
But they have largely ignored the metabolic details of resource processing and the biochemical aspects of allocation. He argues that although selection can act on power and efficiency independently, these will often covary positively since they are both promoted by the same kinetic adjustments. This contrasts with earlier claims that efficiency could only be increased at the expense of power6.
Watt argues that previous analyses were based on an inappropriate equilibrium premise and points out that organisms are far from equilibrium in nature. He shows algebraically that an increase in either power or efficiency of processing can lead to an increase in production of successful offspring; therefore, metabolic character states that differ in their power or efficiency should be distinguishable by natural selection.
The way to probe these ideas is to study the consequences of genetic variation in metabolic systems, especially natural polymorphisms. The a allele is fixed in Florida while the b allele is almost fixed at the colder end of the cline in northern New England Fig. At low temperatures, bb homozygotes have a significantly higher catalytic capacity for pyruvate reduction Fig.
Evidently, in this case selection favours metabolic processing power, though efficiency may be promoted as well. In environments with greater temperature fluctuation there may be a net heterozygote advantage in kinetic function. Thus, for example, the coot clam Mulinia lateralis grows faster and its net growth efficiency ratio of energy available for growth to total energy absorbed increases with greater individual heterozygosity at six polymorphic enzyme locig. A reduction in routine metabolic costs, measured as respiratory and excretory losses, accounts for well over half of the increased growth observed.
The manner in which heterozygosity at loci coding for proteins is translated into greater metabolic efficiency is, as yet, unknown. When you place your order through Biblio, the seller will ship it directly to you. This reflects the percentage of orders the seller has received and filled. Stars are assigned as follows:.
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