Long-term dynamics of dimorphism in salmonid fishes in changing environment

1.在实验条件下，研究了影响马苏鲑（Oncorhynchus masou）雄性早熟伴侣生殖行为和成功的因素。与其他鲑科鱼类不同，马苏鲑很少受到优势洄游雄性的攻击。为了接近巢穴，企鹅们相互之间进行互动。结果，距离巢穴的远近不同导致了平均潜入成功率的不同。多变量回归分析表明，选择倾向于较大的体型，以获得更接近巢的位置。一种可能的考虑是，通过配偶内部以及配偶与迁徙雄性之间的自然和性选择，存在着配偶的最佳体型。其他形态性状未见选择。由于迁徙的雄性具有较长的鼻峰和较大的驼峰可以获得较高的繁殖成功率，因此对配偶的进化要求可能与迁徙的雄性不同。用指纹DNA技术测定了成熟雄性的受精成功率。成熟雄虫数量越多，总受精成功率越高，但个体受精成功率降低。这表明产卵地周围的避难所的存在对成年雄性伴侣终生的繁殖成功起着重要的作用。

1.The factors that affect reproductive behavior and success of precocious male parr in masu salmon, Oncorhynchus masou, were examinsd under experimental conditions.2.Unlike other salmonid fishes, masu salmon parr were rarely attacked by dominant migratory males. Parr engaged in interactions among themselves to get close to the nest. As a result, the difference in the proximity to the nest resulted in the difference in average sneaking success at a nest.3.The multivariate regression analyzes revealed selection favoring larger body size for gaining more proximate positions to the nest. A possible consideration is that an optimal body size exists for parr through natural and sexual selection within parr and between parr and migratory males.No selection on the other morphological characters was detected. Since migratory males having longer snout and larger hump can acquire higher reproductive success, the evolutionary demands on parr might be different from that on migratory males.4.In miyabe charr, fertilization success of mature male parr was measured by using finger printing DNA.The more numerous the number of mature male parrs, the higher the total fertilization success, but fertilization success per individual decrease. This suggest that existence of refuge around spawning ground plays an important role for life time reproductive success of mature male parr.