Mating strategies and resulting patterns in mate guarding crustaceans: an empirical and theoretical approach

Defended on the 13th December 2012

Funding: ministry of research

Supervisors: Loïc Bollache and F.-X. Dechaume-Moncharmont

Started in October 2009

Abstract

In several species, reproductive partners associate for a long time before or after reproduction. Pairs are therefore easily observable in natural population which provides useful information about pairing strategies used by individuals. However, several constraints induced by competition for access to mates for example may affect pairing strategies. Consequently, it is generally not sufficient to infer paring strategies from pairing patterns only. In species with precopulatory mate guarding strategies, males grab females several days before copulation. Males and females have often been reported to be assorted by size. During this PhD, we first focused our investigations on the causes of such size assortment between mates. Using a theoretical approach, we showed that size-assortative pairing could result from a male mate choice strategy based on female maturity. This emphasizes the possibility for a given pairing pattern to come from several pairing strategies and highlights the importance of considering the whole pairing process in mate choice studies. We then studied male mate choice strategies in Gammarus pulex, a precopulatory mate guarding amphipod crustacean. Previous studies on the subject showed that males were capable of discriminating females before entering in precopulatory mate guarding, after which they were considered to be resolute in their choice, remaining with the chosen female until reproduction. However, we showed that males sometimes switched partners while guarding a female. This switching behaviour yet seemed not always optimal, as males did not always switch when a female of better quality than there current female was available for pairing. This reveals possible constraints on the evolution of decision making in mate choice in such mating systems.

Female mating strategies may also have an important effect on pairing patterns. Precopulatory mate guarding is often considered to be beneficial for males and costly for females. Consequently, a sexual conflict is supposed to exist over the duration of precopulatory mate guarding, males preferring long lasting guarding whereas females preferring short lasting guarding. However, only few studies have examined potential benefits associated with precopulatory mate guarding for females, therefore potentially over-estimating the strength of a sexual conflict over guarding duration. We showed that G. pulex females potentially benefited from being pairing for a long time because they had higher mating rates. This result call into question the existence of a strong sexual conflict over precopulatory mate guarding in this species.

Jury

Loïc Bollache, Professeur, Université de Bourgogne, directeur
Frank Cézilly, Professeur, Université de Bourgogne, examinateur
François-Xavier Dechaume-Moncharmont, Maître de conférences, Université de Bourgogne, directeur
Tim W. Fawcett, Research associate, University of Bristol, examinateur
Jacques Labonne, Chargé de recherche, INRA, Saint-Pée sur Nivelle, examinateur
François Rousset, Directeur de recherche, CNRS, Université Montpellier II, rapporteur
Michael Taborsky, Professor, University of BERN, rapporteur

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Mating strategies and resulting patterns in mate guarding crustaceans: an empirical and theoretical approach

Defended on the 13th December 2012

Funding: ministry of research

Supervisors: Loïc Bollache and F.-X. Dechaume-Moncharmont

Started in October 2009

 

Abstract

In several species, reproductive partners associate for a long time before or after reproduction. Pairs are therefore easily observable in natural population which provides useful information about pairing strategies used by individuals. However, several constraints induced by competition for access to mates for example may affect pairing strategies. Consequently, it is generally not sufficient to infer paring strategies from pairing patterns only. In species with precopulatory mate guarding strategies, males grab females several days before copulation. Males and females have often been reported to be assorted by size. During this PhD, we first focused our investigations on the causes of such size assortment between mates. Using a theoretical approach, we showed that size-assortative pairing could result from a male mate choice strategy based on female maturity. This emphasizes the possibility for a given pairing pattern to come from several pairing strategies and highlights the importance of considering the whole pairing process in mate choice studies. We then studied male mate choice strategies in Gammarus pulex, a precopulatory mate guarding amphipod crustacean. Previous studies on the subject showed that males were capable of discriminating females before entering in precopulatory mate guarding, after which they were considered to be resolute in their choice, remaining with the chosen female until reproduction. However, we showed that males sometimes switched partners while guarding a female. This switching behaviour yet seemed not always optimal, as males did not always switch when a female of better quality than there current female was available for pairing. This reveals possible constraints on the evolution of decision making in mate choice in such mating systems.

Female mating strategies may also have an important effect on pairing patterns. Precopulatory mate guarding is often considered to be beneficial for males and costly for females. Consequently, a sexual conflict is supposed to exist over the duration of precopulatory mate guarding, males preferring long lasting guarding whereas females preferring short lasting guarding. However, only few studies have examined potential benefits associated with precopulatory mate guarding for females, therefore potentially over-estimating the strength of a sexual conflict over guarding duration. We showed that G. pulex females potentially benefited from being pairing for a long time because they had higher mating rates. This result call into question the existence of a strong sexual conflict over precopulatory mate guarding in this species.

 

Jury

Loïc Bollache, Professeur, Université de Bourgogne, directeur
Frank Cézilly, Professeur, Université de Bourgogne, examinateur
François-Xavier Dechaume-Moncharmont, Maître de conférences, Université de Bourgogne, directeur
Tim W. Fawcett, Research associate, University of Bristol, examinateur
Jacques Labonne, Chargé de recherche, INRA, Saint-Pée sur Nivelle, examinateur
François Rousset, Directeur de recherche, CNRS, Université Montpellier II, rapporteur
Michael Taborsky, Professor, University of BERN, rapporteur