Sexo, mentiras e handicaps: Reflexões sobre os mecanismos de selecção sexual (*)

 

Rui Filipe Oliveira (**)

 

RESUMO

No presente artigo o autor revê os diferentes modelos de selecção sexual, nomeadamente a teoria dos descendentes atractivos, a teoria dos bons genes e a teoria do enviezamento sensorial. É analisado o caso particular da possível acção dos mecanismos de selecção sexual nos sistemas de reprodução em arenas, nas quais os machos se agregam para cortejar, uma vez que estes sistemas potenciam a competição entre os machos e as situações de escolha de parceiros sexuais por parte das fêmeas. Neste contexto é dada especial atenção a dois fenómenos: (a) a possível existência de mecanismos de escolha passivos por parte das fêmeas que gerem padrões consitentes de preferências, como é o caso conhecido das preferências por machos com territórios centrais nas arenas em relação a machos com territórios periféricos; (b) a possibilidade de existirem benefícios não-genéticos para as fêmeas em sistemas de arenas que expliquem os padrões de preferências detectados. Finalmente é discutido o modelo do handicap da imunocompetência e apresentam-se evidências que apontam para um papel dos androgénios como mediadores fisiológicos de qualidades fenotípicas dos machos.

Palavras-chave: Selecção Sexual, Escolha de Parceiros, Competição intra-sexual, Androgénios, Arenas reprodutoras.

 

ABSTRACT

In the present paper the author reviews the different models of sexual selection, namely the sexy sons theory, the good genes theory and the sensory bias theory. The particular case of the possible action of sexual selection mechanisms in arena breeding systems, on which males gather to display to females, is analysed as these systems promote the occurrence of male-male competition and female mate choice mechanisms. In this context special attention is paid to two phenomena: (a) the possible existence of passive mechanisms of female mate choice which generate consistent patterns of preferences, such as the known case of the female preference for males with more central territories in leks; (b) the possibility that there are non-genetic benefits for females in lek-breeding systems, which may account for the patterns of female mate choice found. Finally, the immunocompetence handicap model is discussed and evidences are presented which point to a role for androgens as physiological mediators of male phenotypic qualities.

Key words: Sexual selection, Mate choice, intra-sexual competition, Androgens, Leks.

 

 

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(*) O presente texto em muito beneficiou de prolongadas discussões com o Prof. Vitor Almada. Gostaría também de agradecer à Prof. Teresa Avelar pela revisão crítica do manuscrito que em muito beneficipou a versão final do texto. Este artigo foi escrito no contexto de uma dissertação de doutoramento submetida à Faculdade de Ciências da Universidade de Lisboa, sendo na altura o autor bolseiro de doutoramento do Programa Ciência da Junta Nacional de Investigação Científica e Tecnológica (JNICT-BD/1032/90-IG).

(**) Instituto Superior de Psicologia Aplicada. Unidade de Investigação em Eco-Etologia, ISPA. E-mail: ruiol@ispa.pt