Abstract The non-native, aggressive, convict cichlid Amatitlania nigrofasciata is often regarded as a cause for the decline of native Mexican mojarra Cichlasoma istlanum in Mexican rivers. Convict cichlids are assumed dominant in areas they invade. Cooperative territorial defense has been observed in convict cichlids, suggesting that they can dominate Mexican mojarras by coalition. Behavioral observations were recorded and analyzed to experimentally test hierarchical dominance establishment (ES) and maintenance (MN) between uneven numbers of both species. Counts of aggressive interactions (bites, chases, and confrontations) between species were used to measure dominance in ES and MN interactions. More chases and bites were made by Mexican mojarra than convict cichlids in both ES and MN tests. Mexican mojarra attained and maintained dominance against two convict cichlids when competing for food resources via increased antagonistic interactions. Intraspecific confrontations were more common than interspecific confrontations for convict cichlids. Our results offer insight into competition mechanisms potentially occurring in natural settings, suggesting that while convict cichlids may be exploitative and interference competitors to Mexican mojarra, behavioral interactions between these species may not be the sole cause of observed Mexican mojarra population declines in freshwater ecosystems throughout western and southern Mexico. Significance statement Successfully established non-native freshwater fishes are often regarded as better competitors than native fishes. Populations of the native fish Mexican mojarra, Cichlasoma istlanum , have been hypothesized to be negatively affected by the introduction of the non-native convict cichlid, Amatitlania nigrofasciata . Behavioral observations were analyzed to demonstrate that a native fish can outcompete and establish and maintain hierarchical dominance over non-native fish, even when at numerical disadvantage. We expected to find a cooperative territorial defense strategy as a mechanism to obtain dominance and hypothesized that hierarchies among these species would be determined by the number of individuals of each species present in contests. Mexican mojarra consistently attained and maintained dominance over convict cichlids via increased antagonistic interactions despite being outnumbered. Our results suggest that behavioral interactions between these species may not be the sole cause of observed Mexican mojarra population declines.

中文翻译：

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墨西哥莫哈拉即使寡不敌众，也能主宰非本地罪犯慈鲷

摘要 非本地的、侵略性的、被定罪的慈鲷 Amatitlania nigrofasciata 通常被认为是墨西哥河流中墨西哥本土 mojarra Cichlasoma istlanum 衰落的原因。被定罪的慈鲷在它们入侵的地区被认为占主导地位。已在被判刑的慈鲷中观察到合作领土防御，这表明它们可以通过联盟统治墨西哥的莫哈拉。记录和分析行为观察以通过实验测试两个物种的奇数之间的等级优势建立（ES）和维持（MN）。物种之间侵略性相互作用（咬、追逐和对抗）的计数被用来衡量 ES 和 MN 相互作用中的优势。在 ES 和 MN 测试中，墨西哥 mojarra 比定罪的慈鲷进行了更多的追逐和咬伤。墨西哥莫哈拉在通过增加对抗性相互作用来争夺食物资源时，获得并保持了对两只被定罪的慈鲷的统治地位。对于被定罪的慈鲷来说，种内对抗比种间对抗更常见。我们的研究结果提供了对自然环境中可能发生的竞争机制的深入了解，这表明虽然被定罪的慈鲷可能会剥削并干扰墨西哥 mojarra 的竞争者，但这些物种之间的行为相互作用可能不是观察到的整个西部淡水生态系统中墨西哥 mojarra 种群下降的唯一原因和墨西哥南部。意义声明 成功建立的非本地淡水鱼类通常被认为是比本地鱼类更好的竞争者。当地鱼类墨西哥 mojarra，Cichlasoma istlanum 的种群，已被假设受到引入非本地罪犯慈鲷 Amatitlania nigrofasciata 的负面影响。对行为观察进行了分析，以证明本地鱼可以胜过并建立和保持对非本地鱼的等级优势，即使在数量上处于劣势时也是如此。我们期望找到一种合作的领土防御策略作为获得支配地位的机制，并假设这些物种之间的等级将由竞赛中每个物种的个体数量决定。墨西哥的 mojarra 一直通过增加对抗性互动获得并保持对被定罪的慈鲷的统治地位，尽管数量超过了。