Data_Sheet_1_Behavioral Variation in the Pygmy Halfbeak Dermogenys collettei: Comparing Shoals With Contrasting Ecologies.CSV

Variation in biotic and abiotic factors among populations affects individual behaviors by transforming the social landscape and shaping mating systems. Consequently, describing behaviors in natural populations requires consideration of the biological and physical factors that different individuals face. Here, we examined variation in socio-sexual and locomotor behaviors in a small, livebearing, freshwater fish, the pygmy halfbeak Dermogenys collettei, across natural populations in Singapore. The pygmy halfbeak is a surface feeding fish that spends most of the time near the water surface, making it ideal for non-invasive behavioral observations. We compared behaviors between sexes among 26 shoals while simultaneously accounting for environmental variation. We demonstrated that sexual interactions and locomotor behaviors differed among shoals with varying levels of canopy cover and water flow. Specifically, in areas with greater canopy cover, sexual interactions decreased, whereas time spent in a stationary position increased. Sexual interactions were more numerous in still water, where fish spent less time swimming. Variation in the expression of socio-sexual and locomotor behaviors were not associated with differences in the amount of aquatic vegetation, water depth or halfbeak shoal size. Agonistic interactions were robust to environmental effects, showing little variation among environments. However, there were strong sex effects, with males performing more agonistic behaviors and spending less time in a stationary position compared to females, regardless of the environment. Moreover, sexual interactions, measured as actively performed by males and passively received by females, were on average more frequent in males than in females. Our findings help us explore the proximal causes of intraspecific behavioral variation and suggest that fundamental information on socio-sexual behaviors from wild populations can lead to a better understanding of how sexual selection operates when the strength of natural selection varies across environments.

种群间生物与非生物因子（biotic and abiotic factors）的变异，可通过重塑社会环境与婚配制度，对个体行为产生影响。因此，对自然种群的行为开展描述性研究时，需充分考量不同个体所面临的生物与物理环境因子。
本研究以新加坡境内自然种群中的小型卵胎生（livebearing）淡水鱼类——侏形下鱵（pygmy halfbeak，学名Dermogenys collettei）为研究对象，探究其社会性行为（socio-sexual behaviors）与运动行为（locomotor behaviors）的变异模式。该鱼种为表层摄食性鱼类，多数时间栖息于水体表层附近，非常适合开展非侵入式行为观察。
研究团队对26个鱼群的雌雄个体行为进行了比较，同时纳入环境变异的影响。
研究结果显示，冠层覆盖度与水流速度存在差异的鱼群间，性互动行为与运动行为存在显著分化。具体而言，冠层覆盖度越高的区域，鱼类的性互动行为频次越低，而静止停留的时间则越长；静水环境中的性互动行为更为频繁，此时鱼类的游泳时长相对更短。
社会性行为与运动行为的表达变异，与水生植被丰度、水深或侏形下鱵鱼群规模均无显著关联。
攻击性行为不受环境因子的显著影响，在不同环境中均未表现出明显变异。不过，性别效应十分显著：无论所处环境如何，雄性个体的攻击性行为频次均高于雌性，且静止停留的时间也短于雌性。
此外，以雄性主动发起、雌性被动接受的方式统计的性互动行为，其平均发生频次在雄性个体中显著高于雌性。
本研究结果有助于探究种内行为变异的近因，同时表明，获取野生种群社会性行为的基础数据，能够帮助我们更好地理解：当自然选择强度在不同环境中存在差异时，性选择是如何发挥调控作用的。