Bensch Staffan, Hasselquist Dennis, Nielsen Bo, Hansson Bengt
Department of Animal Ecology, Ecology Building, Lund University, S-223 62, Lund, Sweden.
Evolution. 1998 Jun;52(3):877-883. doi: 10.1111/j.1558-5646.1998.tb03712.x.
To compare the fitness of philopatric and immigrant individuals we examined the lifetime reproductive success of 116 male and 137 female great reed warblers. The study was carried out in a semi-isolated population in Sweden and covered breeding adults hatched between 1985 and 1993. Lifetime fitness, measured as life time number of fledglings and offspring recruits, was lower for immigrant than for philopatric males. We found no such relationships for females. The difference in reproductive success could not be explained by immigrant males having lower phenotypic quality because they had similar life span, spring arrival date, and territory quality as philopatric males. The lower lifetime fitness among immigrant than philopatric males appeared to result from reduced mating success. This suggests that females are reluctant to mate with immigrant males despite their apparently similar phenotypic quality. Though it is not known whether females gain in fitness by avoiding matings with immigrant males, it is notable that immigrant males have smaller song repertoires than philopatric males. Large repertoires, previously shown to sexually arouse great reed warbler females, correlate with the occurrence of extrapair paternity and postfledging survival of offspring in our population.
为了比较留居型和迁入型个体的适合度，我们研究了116只雄性大苇莺和137只雌性大苇莺的终生繁殖成功率。该研究在瑞典的一个半隔离种群中进行，涵盖了1985年至1993年间孵化的繁殖期成年个体。以雏鸟和后代新加入种群个体的终生数量来衡量，迁入型雄性的终生适合度低于留居型雄性。对于雌性，我们未发现此类关系。繁殖成功率的差异无法用迁入型雄性具有较低的表型质量来解释，因为它们与留居型雄性具有相似的寿命、春季到达日期和领地质量。迁入型雄性比留居型雄性终生适合度较低似乎是由于交配成功率降低所致。这表明雌性尽管迁入型雄性的表型质量明显相似，但仍不愿与它们交配。虽然尚不清楚雌性通过避免与迁入型雄性交配是否能提高适合度，但值得注意的是，迁入型雄性的鸣唱曲目比留居型雄性少。此前已表明，丰富的曲目能在性方面唤起大苇莺雌性的兴趣，在我们的种群中，这与婚外父权的发生以及后代离巢后的存活情况相关。
