Alatalo Rauno V, Lundberg Arne
Department of Zoology, Uppsala University, Box 561, S-751 22, Uppsala, Sweden.
Evolution. 1986 May;40(3):574-583. doi: 10.1111/j.1558-5646.1986.tb00508.x.
The heritability estimate (±SE) for tarsus length in the pied flycatcher is 0.53 ± 0.10, based on mother-offspring regressions. The heritability is almost the same (0.50 ± 0.22) for offspring transferred to other nests and reared by foster parents, whereas there is no resemblance (0.04 ± 0.23) between the offspring and their foster mothers. Hence, the nest environment does not affect parent-offspring resemblance. However, a full-sib correlation yields an estimate of the heritability twice as high as the parent-offspring regression did, indicating that shared environment effects, which are not correlated with the tarsus length of parents, must be important. An environmental deviation due to food factors affecting tarsus length is demonstrated. The most important food factors are probably associated with 1) polygyny, which leads to reduced paternal feeding at secondary nests, 2) high breeding density, and 3) progress of the breeding season. All three are associated with reductions in offspring mean tarsus length. We estimate selection on tarsus length for the major components of lifetime reproductive success. Offspring with the shortest tarsi have reduced survival from fledging until breeding, and males with tarsus length close to the mean are most successful in attracting mates. Clutch size increases with female tarsus length, except for individuals with very long tarsi. In general, directional selection is weak, but stabilizing selection is rather strong for survival and male mating success.
根据亲代与子代的回归分析，白斑姬鹟跗骨长度的遗传力估计值（±标准误）为0.53±0.10。对于转移到其他巢穴并由养父母抚养的子代，其遗传力几乎相同（0.50±0.22），而子代与其养母之间不存在相似性（0.04±0.23）。因此，巢穴环境不会影响亲子相似性。然而，全同胞相关性得出的遗传力估计值是亲子回归分析的两倍，这表明与亲代跗骨长度无关的共享环境效应一定很重要。研究表明，食物因素会导致影响跗骨长度的环境偏差。最重要的食物因素可能与以下几点有关：1）一雄多雌制，这会导致次级巢穴中父本的喂食减少；2）高繁殖密度；3）繁殖季节的进程。这三点都与子代平均跗骨长度的减少有关。我们估计了跗骨长度对终生繁殖成功主要组成部分的选择作用。跗骨最短的子代从 fledging 到繁殖的存活率降低，跗骨长度接近平均值的雄性在吸引配偶方面最成功。窝卵数随雌性跗骨长度增加，但跗骨非常长的个体除外。一般来说，定向选择较弱，但对于生存和雄性交配成功，稳定选择相当强烈。
