Cross-context behavioral correlations and signals of aggression in females of a livebearing fish

Behaviors may be adaptively correlated with each other and with other
aspects of phenotype. We investigated behavior across foraging, mating,
and risk contexts in females of the poeciliid fish, Girardinus metallicus.
We quantified relationships between these behaviors and aggression
signals, body size, and reproductive output. Behaviors describing
aggression and boldness, some of which were repeatable, were correlated in
females. Aggression was signaled by the darkening of a black spot on the
extended dorsal fin or by fin flaring. Spot darkening occurred during
intra- and intersexual interactions and was positively correlated with
inter-female aggression and negatively correlated with time females spent
following males, suggesting that it honestly indicates motivational state.
In contrast, fin flaring was only directed at females and occurred more
frequently in the foraging context. Larger females had fewer offspring and
received fewer courtship displays, possibly because they were more
aggressive to males. In contrast to studies of males, we found a negative
relationship between rank order of boldness and aggression, consistent
with either a tradeoff or with selection favoring the negative
relationship. Our results highlight the importance of studying females in
model systems to uncover novel patterns and potentially meaningful
departures from what is typically seen in males.

行为可与其他行为及表型的其他方面形成适应性关联。本研究以花鳉科（Poeciliidae）金属吉拉德鳉（Girardinus metallicus）的雌性个体为研究对象，考察了其在觅食、交配与风险三类情境下的多种行为，并量化了这些行为与攻击信号、体型及繁殖产出之间的关联。雌性个体中，表征攻击行为与大胆程度的行为（部分具有行为可重复性）存在显著关联。该物种的攻击行为可通过两种方式传递信号：一是展开背鳍时其上黑斑的变暗，二是鳍部张开。黑斑变暗现象出现于同性及异性互动过程中，且与雌间攻击行为呈正相关，与雌性追随雄性的时长呈负相关，这表明该黑斑变暗可真实反映个体的动机状态。与之相反，鳍部张开仅针对雌性个体，且在觅食情境中的出现频率更高。体型更大的雌性个体产下的后代更少，获得的雄性求偶展示次数也更少，这可能是因为它们对雄性的攻击性更强。与针对雄性的相关研究不同，本研究发现雌性的大胆程度等级与攻击行为之间呈负相关，这一结果与两者间存在权衡取舍，或是自然选择青睐该负相关关系的假说相符。本研究结果凸显了在模式生物系统中开展雌性研究的重要性，这有助于发现全新的行为模式，以及与雄性典型行为模式存在潜在实质性差异的生物学现象。