Cichlids do not adjust reproductive skew to the availability of independent breeding options
Cichlids do not adjust reproductive skew to the availability of independent breeding options
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DOI：
10.1093/beheco/arj056
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发表时间：
2006-05-01
影响因子：
2.4
通讯作者：
Taborsky, M
中科院分区：
文献类型：
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作者：
Heg, D;Bergm端ller, R;Taborsky, M
合作繁殖物种的助手留在家中并协助繁殖者抚养后代时，会放弃全部或部分繁殖。不同的生殖偏差模型会根据生态约束的程度，对不相关的下属将获得的生殖份额产生不同的预测。特许模型预测，当独立育种选择良好时，比例会更大，而限制和拔河模型则预测对繁殖偏差没有影响。我们通过确定坦噶尼喀湖慈鲷 Neolamprologus pulcher 中不相关的雄性和雌性帮手的繁殖份额来测试这些预测，具体取决于实验操纵的帮手分散和独立繁殖的可能性以及取决于帮手的大小和性别。我们在实验室中创建了 32 个繁殖组，每个组由两名饲养员和两名助手组成，其中只有助手才能进入附近有（处理）或没有（对照）繁殖基质的扩散室，采用重复测量设计。我们使用 5 到 9 个 DNA 微卫星位点确定了 47 个群体的 1185 个后代的父系和母系，结果发现：(1) 助工者在各个处理中平等地参与繁殖，(2) 体型较大的雄性助工者比小型助工者更有可能进行繁殖，(3) 男性助工者的繁殖明显多于女性助工者。有趣的是，在四个巢中，群体外的辅助雄性使部分巢受精。没有观察到助手繁殖后助手被逐出群体。我们的结果表明，基于群体内繁殖竞争的拔河模型最能描述我们研究系统中观察到的繁殖偏差。当大型帮手是雄性时，与对照情况相比，雌性饲养员在处理中产生了更大的窝。这表明，雄性饲养者与雄性帮手的繁殖冲突可能会因雌性在帮手周围产下更大的窝而得到缓解。
Helpers in cooperatively breeding species forego all or part of their reproduction when remaining at home and assisting breeders to raise offspring. Different models of reproductive skew generate alternative predictions about the share of reproduction unrelated subordinates will get depending on the degree of ecological constraints. Concession models predict a larger share when independent breeding options are good, whereas restraint and tug-of-war models predict no effects on reproductive skew. We tested these predictions by determining the share of reproduction by unrelated male and female helpers in the Lake Tanganyika cichlid Neolamprologus pulcher depending on experimentally manipulated possibilities for helper dispersal and independent breeding and depending on helper size and sex. We created 32 breeding groups in the laboratory, consisting of two breeders and two helpers each, where only the helpers had access to a nearby dispersal compartment with (treatment) or without (control) breeding substrate, using a repeated measures design. We determined the paternity and maternity of 1185 offspring from 47 broods using five to nine DNA microsatellite loci and found that: (1) helpers participated in reproduction equally across the treatments, (2) large male helpers were significantly more likely to reproduce than small helpers, and (3) male helpers engaged in significantly more reproduction than female helpers. Interestingly, in four broods, extragroup helper males had fertilized part of the brood. No helper evictions from the group after helper reproduction were observed. Our results suggest that tug-of-war models based on competition over reproduction within groups describe best the reproductive skew observed in our study system. Female breeders produced larger clutches in the treatment compared to the control situation when the large helpers were males. This suggests that male breeder-male helper reproductive conflicts may be alleviated by females producing larger clutches with helpers around.