Consistent behavioral syndrome across seasons in an invasive freshwater fish

Abstract

12The linkage between behavioural types and dispersal tendency has been suggested to be a 13 widespread phenomenon and understanding its mechanisms has become a pressing issue in light 14 of global change and biological invasions. Here, we investigate whether individuals who colonize 15 new habitats exhibit a certain set of behavioural types that differs from those remaining in the 16 source population. We focussed on a feral population of guppies (Poecilia reticulata) that is 17 assumed to undergo a yearly (re)colonization process. Guppies are among the most widespread 18 invasive species in the world, but in temperate regions these fish can only survive in thermally 19 altered freshwaters due to their tropical origin. The investigated population has sustained in a 20 thermally-altered stream in Germany for over 50 years, where they find year-round suitable water 21 temperatures around a warm-water influx. However, in warm seasons, peripheral parts of the 22 warm-water flume become thermally accessible and may be colonized. We sampled fish from the 23 source population and from a winter-abandoned downstream site in March, June and August. Fish 24 were tested for boldness, sociability and activity involving open field tests as well as interactions 25 with a biomimetic robot as social partner. Guppies differed consistently among each other in all 26 three traits. Behavioural trait expression in the source population differed across seasons, 27 however, we could not detect differences between source and downstream populations. Instead, 28 all sampled populations showed a remarkably stable behavioural syndrome between boldness and 29 activity despite strong changes in water temperatures across seasons. We conclude that random 30 drift (as opposed to a personality-biased dispersal) is a more likely dispersal mode for guppies, at 31 least in the investigated stream system. In the face of highly fluctuating environments, guppies 32 seem to be extremely effective in keeping their behavioural expressions constant, which could help 33 explain their successful invasion and adaptation to disturbed habitats. 34

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 ].…”

“…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.…”

“…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 ].…”

Consistent Behavioral Syndrome Across Seasons in an Invasive Freshwater Fish

“…Finally, we thank the editor as well as two reviewers for their valuable comments and effort to improve this manuscript. A previous version of this manuscript has been released as a pre-print (Lukas et al, 2020).…”

Captivity-induced behaviour and spatial learning abilities in an enigmatic, aquifer-dwelling blind eel,Rakthamichthys digressus

“…Active R. digressus , spending more time in ‘vertical wall following’ could either be due to the inability to recognize the presence of wall [23], or searching for biologically significant resources similar to its function in natural habitats. Although boldness - propensity to take a risky decision is positively correlated with activity in many epigean fishes [28,29], ‘startle response’, duration of the ‘inactivity after the startle’, and ‘reaction’, which are potential indirect measures of boldness [30,31] failed to show any association with activity in R. digressus . Furthermore, life in captivity for 45 days neither changed any existing behavioural syndromes, nor generated new associations between behaviour traits in this species.…”