Climate change is promoting fast poleward expansion in many tropical marine fish species. With projected increases in sea surface temperatures, there is significant scope for increased range expansions in the future. However, the strength and consequences of density‐driven competitive interactions between vagrant and resident fishes are largely unknown. Here, we investigate how the density effects resulting from the addition of tropical fishes to temperate assemblages may alter patterns of habitat and behaviour usage by both tropical vagrant and temperate resident species. We explore these impacts for two ecologically similar (diet, habitat and behaviour) pairs of vagrant and resident species (the territorial species Stegastes gascoynei and Parma microlepis, and the shoaling species Abudefduf vaigiensis and Atypichthys strigatus, respectively). We compare situations where the other member of each of these ecological pairs was present or absent. There was a shift in the type and structural complexity of habitat occupied, with all species displaying some characteristics of occupying seemingly less‐preferred habitats in the presence of their pair species than without them. Behavioural effects were only apparent for the territorial species, which had altered feeding and vigilance patterns in the presence of their pair. These data indicate that the increased density of ecologically similar fish which results from the annual arrival of vagrant fishes is likely driving shifts away from optimal habitat usage and alterations in activity of both residents and vagrants, suggesting resource competition. The degree to which this competition was evident depended on the life history of the species, being stronger for the more territorial species. While similar research on additional species would be required to determine to what degree these results could be generalised to other territorial or shoaling species, this work suggests to highlight the important role that competition will play in determining both the ability of the vagrant species to become established within temperate communities, as well as the impact they may have once they have done so.

中文翻译：

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评估竞争过程在介导热带流浪鱼的范围扩展中的作用

气候变化正在促进许多热带海洋鱼类物种的极速扩张。随着预计海平面温度的升高，将来会有很大的范围扩大范围。但是，很大程度上未知的是流浪鱼和常驻鱼类之间由密度驱动的竞争相互作用的强度和后果。在这里，我们研究了将热带鱼添加到温带组合中所引起的密度效应如何可能改变热带无性游and和温带常驻物种的栖息地模式和行为习惯。我们针对流浪和常驻物种（领土物种Stegastes gascoynei和Parma microlepis）和浅滩物种的两个生态相似（饮食，栖息地和行为）对探讨了这些影响Abudefduf vaigiensis和Atypichthys strigatus，分别）。我们比较了这些生态对中每个对的其他成员存在或不存在的情况。所栖息生境的类型和结构复杂性发生了变化，所有物种都显示出在存在成对物种的情况下似乎比没有栖息地的情况下似乎更不受欢迎的栖息地的某些特征。行为影响仅对于该领土物种而言是显而易见的，该物种在存在该物种的情况下改变了喂养和警觉模式。这些数据表明，由于流浪鱼类的年度到来而造成的生态相似鱼类的密度增加，可能促使人们偏离最佳栖息地的使用方式，居民和流浪者的活动发生变化，这说明了资源竞争。这种竞争的明显程度取决于该物种的生活史，对于更多的领土物种来说更强大。尽管将需要对其他物种进行类似的研究，以确定这些结果可以推广到其他领土或浅滩物种的程度，但这项工作表明，竞争将在确定无业游民物种的确立能力方面发挥重要作用。在温带社区中，以及这样做后可能产生的影响。