THE EVOLUTION OF SELECTIVE AGGRESSION CONDITIONED ON ALLORECOGNITION SPECIFICITY.

Area of Science:

• Evolutionary Biology
• Animal Behavior
• Genetics

Background:

• Sessile cnidarians compete for space, often exhibiting aggression modulated by relatedness.
• Aggression is typically passive between clonemates/kin and aggressive towards non-kin.
• This selective aggression necessitates an allorecognition system for cell-surface determinant discrimination and a polymorphic genetic system for relatedness labeling (haplotypes/allotypes).

Purpose of the Study:

• To analyze evolutionary models of aggression and allorecognition specificity in sessile cnidarians.
• To determine the evolutionary stability of discriminating phenotypes based on haplotypic distinctness.
• To investigate potential mechanisms for the maintenance of allotypic specificity beyond direct aggressive behavior.

Main Methods:

• Analysis of evolutionary models simulating interactions between different phenotypes (discriminating, unconditionally aggressive, unconditionally nonaggressive).
• Modeling the establishment of rare recognition alleles necessary for allotypic specificity.
• Exploration of alternative selective mechanisms, including kin selection and pleiotropic effects.

Main Results:

• Populations with discriminating phenotypes are evolutionarily unstable against unconditionally aggressive or nonaggressive phenotypes.
• Rare recognition alleles for allotypic specificity are unlikely to be established via natural selection acting on aggressive behavior alone.
• Individual selection directly through aggressive behavior is unlikely to maintain allotypic specificity.

Conclusions:

• Allotypic specificity in cnidarian aggression is unlikely to be maintained by individual selection via aggressive behavior.
• Alternative mechanisms like kin selection or pleiotropic effects (gametic incompatibility, pathogen resistance, somatic fusion) may maintain allotypic polymorphism.
• Further theoretical and empirical research is needed to understand the costs/benefits of aggression and its role in maintaining allorecognition specificity.