Prezygotic reproductive barriers in precopulatory behavior of tidepool copepod species

Complexity in prezygotic mating behavior can contribute to the emergence of sexual incompatibility and reproductive isolation. In this study, we performed behavioral tests with two tidepool copepod species of the genus Tigriopus to explore the possibility of precopulatory behavioral isolation. We found that interspecific mating attempts failed prior to genital contact and that this failure occurred at different behavioral steps between reciprocal pairings. Our results suggest that prezygotic barriers may exist at multiple points of the behavioral process on both male and female sides, possibly due to interspecific differences in mate-recognition cues used at those “checkpoints”. While many copepod species are known to show unique precopulatory mate-guarding behavior, the potential contribution of prezygotic behavioral factors to their isolation is not widely recognized. The pattern of sequential mate-guarding behaviors may have allowed diversification of precopulatory communication and ..., The data were obtained by video and microscopic observations of interspecific and intraspecific mating behavior of tidepool copepods, Tigriopus californicus and Tigriopus japonicus. For detailed methods, see the published manuscript as well as Tsuboko-Ishii S, Burton RS. Individual Culturing of Tigriopus Copepods and Quantitative Analysis of Their Mate-guarding Behavior. J Vis Exp. 2018 Sep 26;(139):58378 (doi: 10.3791/58378).

Figure 4. Difference in frequency of approaches by males between conspecific and interspecific pairs. Each datapoint was obtained from one tested pair. One approach is defined as a swift (<0.5 s) chase or pounce by a male.
Figure 5. Difference in mean velocity of captured females between conspecific and interspecific pairs. Each datapoint was obtained from one observed attempt. 
Figure 6. Difference in paring duration between conspecific and interspecific pairs. Each datapoint was obtained from one tested pair.
Figure 7. Duration of each step of prezygotic beh..., This .xlsx file was created with Microsoft Excel for Mac (version 16.75).

Figure 4. Difference in frequency of approaches by males between conspecific and interspecific pairs. Each datapoint was obtained from one tested pair. One approach is defined as a swift (<0.5 s) chase or pounce by a male.

Fig 4A. Frequency of approaches by T. californicus males toward conspecific (T. californicus) and heterospecific (T. japonicus) females. The unit is times/min (number of approaches per free time).
Fig 4B. Frequency of approaches by T. japonicus males toward conspecific (T. japonicus) and heterospecific (T. californicus) females. The unit is times/min (number of approaches per free time).

Figure 5. Difference in mean velocity of captured females between conspecific and interspecific pairs. Each datapoint was obtained from one observed attempt. 

Fig 5A. Mean velocity of T. californicus females against conspecific (T. californicus) and heterospecific (T. japonicus) males. The unit is mm/s.
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前合子交配行为（prezygotic mating behavior）的复杂性可促成性不亲和与生殖隔离（reproductive isolation）的产生。本研究选取潮间带猛水蚤属（Tigriopus）的两个物种开展行为学测试，以探究交配前行为隔离（precopulatory behavioral isolation）的可能性。研究发现，种间交配尝试在接触生殖器官前即告失败，且正反交配对的失败环节存在差异。结果表明，前合子障碍可能存在于雌雄双方行为过程的多个节点，这或许源于各“检查点”所使用的配偶识别线索（mate-recognition cues）存在种间差异。尽管已知多种桡足类物种具备独特的交配前守卫行为（mate-guarding behavior），但前合子行为因素对其生殖隔离的潜在贡献尚未得到广泛认可。序列性交配守卫行为的模式或可促进交配前通讯的多样化及……

本数据集通过视频与显微观察获取，观测对象为潮间带猛水蚤属加州猛水蚤（Tigriopus californicus）和日本猛水蚤（Tigriopus japonicus）的种内与种间交配行为。详细实验方法可参见已发表论文及Tsuboko-Ishii S、Burton RS的《虎甲水蚤的单个体培养与交配守卫行为定量分析》，刊载于《Journal of Visualized Experiments》，2018年9月26日，第139期，文章编号58378，DOI: 10.3791/58378。

本.xlsx文件使用Mac版Microsoft Excel（版本16.75）制作。

### 图表说明
图4：同种配对与种间配对中雄性趋近行为频率的差异。每个数据点对应一组受试配对。单次趋近定义为雄性发起的、时长小于0.5秒的快速追逐或扑击。
- 图4A：加州猛水蚤雄性对同种（加州猛水蚤）与异种（日本猛水蚤）雌性的趋近频率，单位为次/分钟（单位自由活动时间内的趋近次数）。
- 图4B：日本猛水蚤雄性对同种（日本猛水蚤）与异种（加州猛水蚤）雌性的趋近频率，单位为次/分钟（单位自由活动时间内的趋近次数）。

图5：同种配对与种间配对中被捕获雌性的平均移动速度差异。每个数据点对应一次观测到的交配尝试。
- 图5A：加州猛水蚤雌性面对同种（加州猛水蚤）与异种（日本猛水蚤）雄性时的平均移动速度，单位为mm/s。
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图7：前合子行为各步骤的时长……