The influence of the invasive process on behaviours in an intentionally introduced hybrid, Xiphophorus helleri-maculatus

Both intentionally and unintentionally introduced populations vary greatly in their ability to succeed as invasive species. What causes this extreme variability in success largely remains controversial. Understanding the extent to which these differences are due to aspects of the invasive process could lead to better mitigation of invasive species. We investigated the effect of the invasive process in selecting for individual behaviours and behavioural syndromes in the Xiphophorus helleri-maculatus hybrid, an intentionally introduced fish species. We measured three behaviours (boldness, aggression and exploration) known to play a role in invasive success across three populations representing different stages of invasion: fish from commercial breeding pools, from pet stores and from an established invasive population in Hawaii. We detected significant differences in boldness across populations, with a significant decrease from the breeding pool to the pet store and a significant increase from the pet store to the established invasive population. In addition, we detected behavioural syndromes between either two or all three behaviours that were significantly different across populations. Overall variation in behaviours was similar between breeding pool and pet store fish but appeared to decrease in the invasive population when compared to the pet store population, potentially leading to a more defined behavioural syndrome between exploration and aggression. Our results suggest that while aspects of the invasive process influenced boldness and behavioural syndromes, the increased variation, produced either through hybridization or relaxed selection in the pet trade, is at least partly responsible for the success of X. helleri-maculatus as an invasive species. Additional studies are needed to examine the source of the variation in the pet trade and its influence on the formation of behavioural syndromes in invasive populations. (C) 2019 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Both intentionally and unintentionally introduced populations vary greatly in their ability to succeed as invasive species. What causes this extreme variability in success largely remains controversial. Understanding the extent to which these differences are due to aspects of the invasive process could lead to better mitigation of invasive species. We investigated the effect of the invasive process in selecting for individual behaviours and behavioural syndromes in the Xiphophorus helleri-maculatus hybrid, an intentionally introduced fish species. We measured three behaviours (boldness, aggression and exploration) known to play a role in invasive success across three populations representing different stages of invasion: fish from commercial breeding pools, from pet stores and from an established invasive population in Hawaii. We detected significant differences in boldness across populations, with a significant decrease from the breeding pool to the pet store and a significant increase from the pet store to the established invasive population. In addition, we detected behavioural syndromes between either two or all three behaviours that were significantly different across populations. Overall variation in behaviours was similar between breeding pool and pet store fish but appeared to decrease in the invasive population when compared to the pet store population, potentially leading to a more defined behavioural syndrome between exploration and aggression. Our results suggest that while aspects of the invasive process influenced boldness and behavioural syndromes, the increased variation, produced either through hybridization or relaxed selection in the pet trade, is at least partly responsible for the success of X. helleri-maculatus as an invasive species. Additional studies are needed to examine the source of the variation in the pet trade and its influence on the formation of behavioural syndromes in invasive populations. (C) 2019 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.