Consistent Behavioral Syndrome Across Seasons in an Invasive Freshwater Fish

Abstract

Understanding the linkage between behavioral types and dispersal tendency has become a pressing issue in light of global change and biological invasions. Here, we explore whether dispersing individuals exhibit behavioral types that differ from those remaining in the source population. We investigated a feral population of guppies (Poecilia reticulata) that undergoes a yearly range shift cycle. Guppies are among the most widespread invasive species in the world, but in temperate regions these tropical fish can only survive in winter-warm freshwaters. Established in a thermally-altered stream in Germany, guppies are confined to a warm-water influx in winter, but can spread to peripheral parts as these become thermally accessible. We sampled fish from the source population and a winter-abandoned site in March, June and August. Fish were tested for boldness, sociability and activity involving open-field tests including interactions with a robotic social partner. Guppies differed consistently among each other in all three traits within each sample. Average trait expression in the source population differed across seasons, however, we could not detect differences between source and downstream population. Instead, all populations exhibited a remarkably stable behavioral syndrome between boldness and activity despite strong seasonal changes in water temperature and associated environmental factors. We conclude that random drift (opposed to personality-biased dispersal) is a more likely dispersal mode for guppies, at least in the investigated stream. In the face of fluctuating environments, guppies seem to be extremely effective in keeping behavioral expressions constant, which could help explain their successful invasion and adaptation to new and disturbed habitats.

Male Sexual Preference for Female Swimming Activity in the Guppy (Poecilia reticulata)

“…Levels of individual swimming activity in an open field arena were found to be consistently different among individuals (i.e., there was considerable and significant repeatability) when males and females were tested both alone and together (=significant among-individual correlation). These results are consistent with previous studies showing significant repeatability in activity levels in the guppy [38,[56][57][58] even when interacting with (artificial) conspecifics (see [40,59,60]). Those individual differences in swimming patterns can be maintained even in larger groups as shown for mosquitofish (Gambusia holbrooki, [46]) and sticklebacks, Gasterosteus aculeatus [61].…”

“…We decided to use the live-bearing Trinidadian guppy (Poecilia reticulata) as a model organism as both males and females are known to exercise mate choice [37] and individuals often differ consistently in their activity levels (with males being on average more active than females [38,39]). In this species, higher activity levels in females correlate positively with risk-taking behaviours [40], and negatively with gestation period [34] and body size [40].…”

“…In a second step, activity levels of females alone and in the dyads were used as the dependent variables with Female ID as a random factor. We allowed within-individual as well as among-individual variances to differ between treatments as well as to correlate within treatments (see [40,47] for similar approaches). As for repeatability, LRT tests were employed to assess whether the inclusion of within-and among-individual correlations significantly improved the model.…”

Increased water temperature and turbidity act independently to alter social behavior in guppies (Poecilia reticulata)

“…As independent effects, the stressors affected different characteristics of guppy behavior. In warmer waters, guppies reduced refuge use, demonstrating an increase in boldness (Biro et al, 2010 ; Forsatkar et al, 2016 ; Gomez‐Maldonado & Camacho‐Cervantes, 2022 ; Lukas et al, 2021 ). We observed an increase in shoaling at the higher temperature as measured by the local‐scale NND and one of the global scale measures (the index of dispersion), although no effect on the other global measure of cohesion, the mean inter‐individual distance, was found.…”

Effect of a temperature gradient on the behaviour of an endangered Mexican topminnow and an invasive freshwater fish

“…This could be explained since invasive species tend to be more resilient to environmental changes than natives 7 – 9 . An example is that of invasive guppies in Germany, where they were also found to be very resilient to temperature changes and their boldness behaviour was not affected by them 41 . In contrast, both male and female invasive Australian guppies were found swimming less and engaging less in mating behaviour at 18 °C 42 .…”