Large part of the morphological diversity observed across taxa is attributed to the effect of sexual selection; and the static allometry of these structures vary largely from highly positive to negative, depending on their function, and position on the animal's body. In arthropods, information of how sexually selected contact and reaching male structures use during courtship scale on body size is scarce. We tested two complementary hypotheses: the reaching structure hypothesis and the contact‐function hypothesis, in the spider Kukulcania hibernalis. We used the length of the proximal segments of the male pedipalp to test the reaching structure hypothesis, and claw features to test the contact‐function hypothesis. Our results support both hypotheses. Small males have disproportionally longer pedipalps (highly negative allometry) than large males, increasing the probability of small‐bodied males to inseminate even large females. We also found that both distal contact and noncontact homologous structures scaled shallow (slope < 1) on body size, but allometry was significantly shallower for contact than for noncontact distal structures, providing support to the contact‐function hypothesis, and allowing teasing apart the effect of sexual selection on distal contact structures with dual functions.

中文翻译：

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冬青Kukulcania（Araneae：Filistatidae）的触角和接触结构的异构。

整个分类单元观察到的大部分形态多样性归因于性选择的影响。这些结构的静态异构关系从高度正向到负向变化很大，这取决于它们的功能以及在动物体内的位置。在节肢动物中，缺乏关于求偶时按性别选择性接触和如何达到男性结构的信息。我们在蜘蛛Kukulcania hibernalis中测试了两个互补的假设：到达结构假设和接触功能假设。我们使用雄性pedipalp近端节段的长度来检验到达结构的假设，并使用爪状特征来检验接触功能的假设。我们的结果支持两种假设。小型雄性比大型雄性有更长的pedipalps（高度消极异体症），增加了小型雄性授精甚至大雌性授精的可能性。我们还发现，远端接触和非接触同源结构的体形均变浅（斜率<1），但接触接触的异速测量显着浅于非接触远端结构，从而为接触功能假说提供了支持，并允许将效果分开性选择对具有双重功能的远端接触结构的影响。