Female-female competition leads to female‐biased sex allocation and dimorphism in brood sex composition in a gall‐forming aphid.
Female-female competition leads to female‐biased sex allocation and dimorphism in brood sex composition in a gall‐forming aphid.
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雌性竞争导致雌性偏向的性别分配和胆形成蚜虫的巢性别组成的二态性。
DOI：
10.1111/1365-2435.13248
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发表时间：
2019
影响因子：
5.2
通讯作者：
Tong X and Akimoto S
中科院分区：
文献类型：
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作者：
Kobayashi S;Yamada K;Yoshino K;Henmi Y;﨑村豪太郎・逸見泰久・吉野健児・山田勝雅;Tong X and Akimoto S
如果每单位母亲投资，儿子和女儿产生不同的边际适应性回报，那么动物的性别分配预计会偏离 1:1 的比例。我们使用形成瘿的蚜虫 Tetraneura sorini 测试了这一预测，其中雌性之间致命的战斗很常见，而雄性之间的竞争是温和的。母亲（秋翅雌性）在腹部孤雌生殖地产生雌性和雄性，并可以控制它们的大小和数量。雌性和雄性在出生后不进食。交配后，雌性产下单卵，只有雌性（母龟）孵化，在受咬过程中，彼此之间会发生激烈的战斗。体型较大的母龟在战斗中具有压倒性的优势。如果母亲对雌性个体投入更多，她们就能生出更大的女创始人（孙女），从而产生更大的健康回报。这种情况与最初的特里弗斯-威拉德假设相反。因此，我们预测该物种中多产的母亲会在雌性身上投入更多。研究发现，生产一只雌性的成本是生产一只雄性成本的 3.0-3.2 倍。人口性别比例以男性为主（54.8%–58.2%为男性），但人口性别分配以女性为主（68%–72%为女性）。较大的母亲使后代的性别比例更偏向雌性，并产生更大的雌性，从而支持我们的预测。母亲产生两种类型的后代：全雌性后代和混合性别的后代。拥有全雌性巢的母亲比拥有混合性别巢的母亲产下更大的雌性，从而为它们的孙女（女创始人）提供了战斗优势。局部交配竞争被认为可以解释形成瘿的蚜虫中雌性偏向的种群性别分配。然而，我们得出的结论是，创始人之间的竞争导致了种群水平上偏向女性的性别分配的演变以及巢穴性别构成的二态性。
Sex allocation in animals is predicted to be skewed from a 1:1 ratio if sons and daughters yield different marginal fitness returns per unit maternal investment.We tested this prediction using the gall‐forming aphidTetraneura sorini, in which lethal fighting is common among females, whereas male–male competition is moderate. Mothers (autumnal winged females) parthenogenetically produce females and males in their abdomen and can control their sizes and numbers. The females and males do not feed after birth. After mating, females produce single eggs, from which only females (foundresses) hatch and fight intensely with one another during the galling process.Larger‐sized foundresses have overwhelming advantages in fighting. If mothers invest more in individual females, they can produce larger foundresses (granddaughters), which yields greater fitness returns. This situation is contrary to the original Trivers–Willard hypothesis. Thus, we predicted that more fecund mothers in this species would invest more in females.The cost of producing one female was found to be 3.0–3.2 times the cost of producing one male. Population sex ratios were male‐biased (54.8%–58.2% male), but population sex allocation was highly female biased (68%–72% females). Larger mothers biased their progeny sex ratios more towards females and produced larger females, thus supporting our prediction.Mothers produced two types of brood: all‐female broods and mixed‐sex broods. Mothers with an all‐female brood produced larger females than those with a mixed‐sex brood, thereby offering their granddaughters (foundresses) an advantage in fighting.Local mate competition has been postulated to explain female‐biased population sex allocation in gall‐forming aphids. However, we concluded that competition among foundresses has led to the evolution of female‐biased sex allocation at the population level and dimorphism in brood sex composition.