Spawning behaviour of the Salmoninae subfamily members. A phylogenetic study.

Resumen

Long-term data from underwater video recordings in the wild and in semi-natural channels are used to describe and compare the reproductive behaviour of fishes in the Salmoninae subfamily. The thesis is divided into five chapters. In the first, a new division of male alternative strategies and tactics based on relative age at maturation (strategy) and on behaviour in the spawning grounds (tactic) is proposed. A variation to the evolutionarily stable strategies (ESS) model based on a growth velocity-dependent maturation threshold is suggested. In the second chapter, methods of video recording and analyzing behaviour during spawning are introduced. The reproductive behaviour in the Salmoninae is described dividing it into different phases related to female nest selection, construction, and completion. In the third chapter, the role of instincts during spawning, as well as the mechanisms by which they are released, are explained based on internal motivation and external stimuli. Data are used to propose "false spawnings" in females should be regarded as low intensity behaviour and that "male digging" represents two different types of displacement reaction with threatening and courting functions as ultimate causes. In the fourth chapter, observations on different species are used to open a theoretical discussion about the role of female choice in salmonines. Particularly, the importance of Zahavis principle among the different breeding patterns is contrasted with Fisherian runaway selection. A combination of both mechanisms is suggested. Special attention is given to male "quivering" behaviour. Different hypotheses are proposed to explain its origin and function. Chapter 5 uses data from underwater video recordings to construct the phylogeny of "Oncorhynchus" and "Salvelinus" based only on behavioural traits during spawning. A maximum parsimony analysis using "Thymallus, Hucho" and Salmo" as outgroups is conducted (PAUP* 4.0 b10). The results agree with some minor differences our current understanding of these two genera based on morphological and molecular data. The possible evolution of several characters is discussed in detail. RESUMEN: Se estudió el comportamiento de 12 especies de salmoninos: "Salmo salar" y "S. trutta; Salvelinus malma, S. fontinalis" y "S. confluentus;Oncorhynchus clarkii, O. mykiss, O. tshawytscha, O. kisutch, O. nerka, O. keta" y "O. gorbuscha"; y "Thymallus arcticus". Los datos y filmaciones se realizaron a lo largo de 10 años y corresponden a un total de 309 horas de grabación subacuática, en diversos ríos de España, Gran Bretaña, Estados Unidos y Canadá. Se realizó una revisión sobre el origen, historia evolutiva, y análisis teórico sobre el sistema reproductivo de los Salmoninae. Se explican los métodos utilizados para la grabación acuática. Se describe de forma comparativa el comportamiento de los salmoninos durante la puesta. Se registraron los siguientes comportamientos: temblores del macho ("quiverings"), excavaciones de la hembra, comprobaciones del nido ("probings"), demostraciones ("displays"), ataques, falsos desoves y desoves. Se analiza la importancia y mecanismo de los instintos en la freza. Se propuso la freza de los salmoninos como una cadena interrelacionada de reacciones instintivas. Se utilizaron dos modelos artificiales imitando a hembras de salmón. Se discute el papel que juega la elección de la hembra en la reproducción de salmoninos. Se propuso que el sistema reproductivo de los salmoninos debe ser entendido como una combinación de los procesos Fisheriano (Fisher, 1930) y Zahaviano (Zahavi, 1975). Se realizó un análisis filogenético de los géneros "Salvelinus" y "Oncorhynchus" basado únicamente en su comportamiento durante la freza. Se realizó un estudio filogenético vía máxima parsimonia utilizando el programa PAUP* beta 10 (Swofford 2003). El análisis de los caracteres resultó en un único árbol, coincidiendo con otras filogenias de esta subfamilia basadas en datos moleculares y morfológicos, y validando el uso del comportamiento como herramienta filogenética.