Mate competition and relatedness among males mediate the evolution of lethal fights in bulb mites

Aggression can enhance direct fitness by aiding the aggressor’s in securing reproductive resources, but it negatively impacts inclusive fitness when directed toward kin. We investigated the trade-off between the indirect fitness costs of aggression among kin and the direct benefits of increased success in mate competition using the bulb mite Rhizoglyphus echinopus, a male dimorphic species in which male fighters kill rivals with their modified third legs, while unmodified male scramblers seek unguarded females to mate. Our experiments showed that fighter aggression was never directed toward females, suggesting that fighter aggression evolved as a tactic to monopolize mates. Fighters grab other males before killing them, and grabbing behavior increased in the presence of a female, regardless of the presence of kin. Scrambler mortality increased with fighters’ grabbing activity, but whereas the presence of mate competition increased lethal aggression, kinship decreased it, as higher morta..., , ## Description of data and files

### MITES Aggression Analysis.R

This script conducts all multi-model analyses and data visualizations included in the manuscript.

### Data\_Main\_Analyses.csv

This dataset includes three explanatory variables — relatedness, female presence, and fighter presence — and three response variables — number of kills, number of grabs by fighters, and number of grabs between scramblers.

Description of columns (variables):

* Relatedness: Relatedness between the focal fighter and scramblers (\"Related\" = full-siblings; \"Unrelated\" = non-siblings).
* Female: Presence of a female (\"Present\" or \"Absent\"); the female was unrelated to both the fighter and the scramblers.
* Fighter: Presence of a focal fighter (\"Absent\" = fighter-absent control groups).
* Fighter_family: Family ID of the focal fighters. Initially planned for use as a random effect, but it was not included in the final model analyses for the response variables below, as models without this random eff...,

攻击行为可通过帮助攻击者获取繁殖资源以提升其直接适合度，但当攻击对象为亲属时，会对广义适合度（inclusive fitness）产生负面影响。我们以棘刺根嗜螨（Rhizoglyphus echinopus）为研究对象，探究了亲属间攻击行为带来的间接适合度代价，与配偶竞争成功率提升带来的直接收益之间的权衡关系。该物种为雄性二态性物种：具有特化第三足的格斗型雄虫会通过该足击杀竞争对手，而未特化的漫游型雄虫则会寻找未被守护的雌虫进行交配。我们的实验结果显示，格斗型雄虫的攻击行为从未针对雌虫，这表明其攻击行为演化出的目的是独占交配机会。格斗型雄虫会在击杀其他雄虫前先将其抓住，且当存在雌虫时，抓取行为的频次会升高，无论该场景中是否存在亲属。漫游型雄虫的死亡率会随格斗型雄虫的抓取活动增强而升高；不过，尽管配偶竞争的存在会提升致死性攻击的发生概率，但亲属关系却会降低该概率，因为更高的死亡率……

## 数据与文件说明
### MITES Aggression Analysis.R
该脚本可复现论文中包含的所有多模型分析与数据可视化流程。

### Data_Main_Analyses.csv
本数据集包含三类解释变量——亲缘关系、雌虫存在状态与格斗型雄虫存在状态，以及三类响应变量——击杀次数、格斗型雄虫抓取次数、漫游型雄虫间的抓取次数。

各列（变量）说明如下：
* 亲缘关系（Relatedness）：目标格斗型雄虫与漫游型雄虫间的亲缘关系，"Related"表示全同胞个体，"Unrelated"表示非亲缘个体。
* 雌虫状态（Female）：雌虫是否存在，取值为"Present"（存在）或"Absent"（不存在）；该雌虫与格斗型雄虫及漫游型雄虫均无亲缘关系。
* 格斗型雄虫状态（Fighter）：目标格斗型雄虫是否存在，"Absent"代表无格斗型雄虫的对照组。
* 格斗型雄虫家系ID（Fighter_family）：目标格斗型雄虫的家系编号。该变量最初计划作为随机效应纳入模型，但最终未被加入下述响应变量的最终模型分析，原因是未纳入该随机效应的模型……