Cross-population responses to conspecific chemical alarm cues in wild Trinidadian guppies, Poecilia reticulata: evidence for local conservation of cue production Grant E. Brown, Chris K. Elvidge, Camille J. Macnaughton, Indar Ramnarine, and Jean-Guy J. Godin Abstract: Within freshwater fishes, closely related species produce alarm cues that are chemically similar, leading to con- served antipredator responses. Similar conservation trends are predicted for species with geographically isolated popula- tions. Here, we tested this hypothesis with the guppy (Poecilia reticulata Peters, 1859) from two populations within the Aripo River, Trinidad. Free-ranging guppies in the Lower Aripo (high-predation population) exhibited more risk-aversive inspection behaviour towards a fish predator model paired with the alarm cues of guppies collected from the same popula- tion versus a river water control. In comparison, when paired with the alarm cues of guppies from the Upper Aripo (low- predation population), the response was intermediate. In the laboratory, we tested Upper and Lower Aripo guppies to the alarm cues of the same or different Aripo River donors, Quare ´ River guppies (a high-predation population from a different drainage), or a water control. Both Upper and Lower Aripo River guppies exhibited the highest intensity response to do- nors from the same population and the lowest intensity response to Quare ´ River donors, with the response to different Aripo donors being intermediate. Collectively, these results demonstrate a trend of intraspecific conservation of chemical alarm cue production, leading to population-specific responses to conspecific cues. Re ´sume ´: Chez les poissons d’eau douce, les espe `ces fortement apparente ´es produisent des signaux d’alarme qui se res- semblent chimiquement, ce qui re ´sulte en une conservation des re ´actions vis-a `-vis les pre ´dateurs. Nous pre ´disons l’exis- tence de tendances conservatrices semblables chez les populations isole ´es ge ´ographiquement. Nous testons ici cette hypothe `se chez des guppys (Poecilia reticulata Peters, 1859) de deux populations habitant la rivie `re Aripo, Trinidad. Les guppys libres dans le cours infe ´rieur de l’Aripo (population a ` forte pre ´dation) montrent un comportement d’inspection ac- compagne ´ d’une plus forte aversion au risque en pre ´sence d’un mode `le de poisson pre ´dateur assorti des signaux d’alarme de guppys provenant de la me ˆme population, par comparaison a ` un te ´moin d’eau de rivie `re. En contraste, lorsque le mo- de `le est assorti des signaux d’alarme des guppys du cours supe ´rieur de l’Aripo (population a ` faible pre ´dation), la re ´action est interme ´diaire. En laboratoire, nous avons teste ´ des guppys des cours supe ´rieur et infe ´rieur de l’Aripo en re ´action a ` des signaux d’alarme de donneurs de la me ˆme ou de l’autre population de l’Aripo, de guppys de la rivie `re Quare ´ (une popula- tion a ` forte pre ´dation d’un autre bassin hydrographique) et d’un te ´moin d’eau. Les guppys, tant du cours supe ´rieur que du cours infe ´rieur de l’Aripo, re ´agissent de la fac ¸on la plus intense aux donneurs de leur propre population; la re ´action aux donneurs de la Quare ´ sont les plus faibles et la re ´action aux donneurs de l’autre population de l’Aripo sont interme ´diaires. Dans leur ensemble, ces re ´sultats de ´montrent une tendance a ` la conservation intraspe ´cifique de la production de signaux d’alarmes chimiques, ce qui me `ne a ` des re ´actions aux signaux conspe ´cifiques qui sont particulie `res a ` chaque population. [Traduit par la Re ´daction] Introduction Population specificity of behavioural phenotypes is often attributed to adaptations to local biotic and (or) abiotic con- ditions (Endler 1995; Foster 1999; Blumstein 2006). Given the intense selection gradients exerted by predators, it is not surprising that a wide range of prey organisms exhibit popu- lation-specific responses in predator avoidance strategies (Endler 1995; Lima and Steury 2005; Blumstein 2006; Herc- zeg et al. 2009). Population specificity is known to extend to sensitivity towards predation threats (Endler 1995; Owings et al. 2001; Brown et al. 2007; Botham et al. 2008). Such local adaptations, presumably, allow prey organisms to bal- ance the conflicting demands of predator detection and avoidance and a suite of fitness-related activities such as Received 27 July 2009. Accepted 27 October 2009. Published on the NRC Research Press Web site at cjz.nrc.ca on 15 January 2010. G.E. Brown, 1 C.K. Elvidge, and C.J. Macnaughton. Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montre ´al, QC H4B 1R6, Canada. I. Ramnarine. Department of Life Sciences, University of the West Indies, St. Augustine, Trinidad and Tobago. J.-G.J. Godin. Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. 1 Corresponding author (e-mail: gbrown@alcor.concordia.ca). 139 Can. J. Zool. 88: 139–147 (2010) doi:10.1139/Z09-127 Published by NRC Research Press