The effects of familiarity on escape responses in the Trinidadian guppy (Poecilia reticulata)

This study was funded by a Postdoctoral fellowship to Miguel Barbosa (SFRH/BPD/82259/2011). The raw data supporting this publication can be accessed at http://dx.doi.org/10.17630/92831d81-38f0-4573-b2e5-e1d11adf9322.Predation is the main cause of mortality during early life stages. The ability to avoid and evade potential threats is, therefore, favoured to evolve during the early stages of life. It is also during these early stages that the process of familiarization occurs. It has long been recognized that associating with familiar individuals confers antipredator benefits. Yet gaps in our knowledge remain about how predator evasion is affected by social experience during early stages. In this study, we test the hypothesis that familiarization acquired during early life stages improves escape responses. Using the guppy Poecilia reticulata, we examine the effect of different recent social conditions in the three main components of predator evasion. Using high-speed motion analysis, we compared the number of individuals in each test group that responded to a visual stimulus, their reactive distance and magnitude of their response (maximum speed, maximum acceleration and distance) in groups composed either of familiar or non-familiar individuals. Contrary to the prediction, groups composed of familiar individuals were less responsive than groups of unfamiliar individuals. Reactive distance and magnitude of response were more dependent on individual size rather than on familiarity. Larger individuals reached higher maximum speeds and total distances in their escape response. Our result indicates that familiarity is likely to affect behaviour earlier in a predator-prey interaction, which then affects the behavioural component of the response. Taken together, our study contributes to previous ones by distinguishing which components of an escape response are modulated by familiarity.Publisher PDFPeer reviewe

The effects of familiarity on escape responses in the Trinidadian guppy ([i]Poecilia reticulata[i])

Predation is the main driver of mortality during early life stages. The ability to avoid and evade potential threats is, therefore, favoured to evolve during the early stages of life. It is also during these early stages that the process of familiarization occurs. It has long been recognized that associating with familiar individuals confers anti predator benefits. Less, however, is known about how predator evasion is affected by social experience during early stages. In this study we test the hypothesis that familiarization acquired during early life stages improves anti predator escape responses. Using the Trinidadian guppy we examine the effect of different early social conditions in the three main components of predator evasion. Using high-speed motion analysis we compared the responsiveness, reactive distance and magnitude of the response (maximum speed, maximum acceleration and distance) of the response to a visual stimulus in groups composed either of familiar or non-familiar individuals. Surprisingly, groups composed by familiar individuals were less responsive than groups of unfamiliar individuals. It is plausible that familiarity equips individuals with better skills to accurately assess the threat avoiding false alarms. Reactive distance and magnitude of response were more dependent on individual size than on familiarity. Larger individuals reached higher maximum speeds and total distances in their escape response. Our approach allowed us to tease apart which aspects of an escape response are more likely to be influenced by early social conditions. 19 Predation is the main driver of mortality during early life stages. The ability to avoid and evade 20 potential threats is, therefore, favoured to evolve during the early stages of life. It is also during 21 these early stages that the process of familiarization occurs. It has long been recognized that 22 associating with familiar individuals confers antipredator benefits. Less, however, is known 23 about how predator evasion is affected by social experience during early stages. In this 24 study we test the hypothesis that familiarization acquired during early life stages improves 25 antipredator escape responses. Using the Trinidadian guppy we examine the effect of different 26 early social conditions in the three main components of predator evasion. Using high-speed 27 motion analysis we compared the responsiveness, reactive distance and magnitude of the 28 response (maximum speed, maximum acceleration and distance) of the response to a visual 29 stimulus in groups composed either of familiar or non-familiar individuals. Surprisingly, groups 30 composed by familiar individuals were less responsive than groups of unfamiliar individuals. It 31 is plausible that familiarity equips individuals with better skills to accurately assess the threat 32 avoiding false alarms. Reactive distance and magnitude of response were more dependent on 33 individual size than on familiarity. Larger individuals reached higher maximum speeds and total 34 distances in their escape response. Our approach allowed us to tease apart which aspects of an 35 escape response are more likely to be influenced by early social conditions

Sociability between invasive guppies and native topminnows

This investigation was funded by the European Research Council though a grant (project BioTIME 250189) awarded to AEM and the Concejo Estatal de Ciencia y Tecnología del Estado de Michoacán through a grant awarded to MCC.The role of interspecific social interactions during species invasions may be more decisive than previously thought. Research has revealed that invasive fish improve their foraging success by shoaling with native Mexican species, and potentially increase the chances of invasion success. However, do native individuals tend to associate with invaders as well? We tested the hypothesis that the twoline skiffia (Neotoca bilineata) and the Lerma livebearer (Poeciliopsis infans), both native endemic Mexican topminnows, will associate with guppies, a notorious invasive species present in Mexico. Our investigation shows that guppies, twoline skiffias and Lerma livebearers have a mutual tendency to associate with each other. Although there is a marked tendency to shoal with heterospecifics in this system, shoaling partners do not necessarily benefit equally from the association. Further research on invasive-native social interactions is needed to promote our understanding of potential facilitation by natives.Publisher PDFPeer reviewe

How pre- and postcopulatory sexual selection influence male mating decisions in a promiscuous species

This work was supported by Portuguese National Funds through FCT (Fundação para a Ciência e a Tecnologia), within the cE3c Unit FCT funding (grant number UID/BIA/00329/2013), IO PhD grant (grant number SFRH/BD/90686/2012) and SAMV and MB Post-Doctoral research grants (grant numbers SFRH/BPD/66042/2009 and SFRH/BPD/82259/2011, respectively). This work was also supported by ERC (European Research Council) BioTIME (grant number 250189).When females mate multiply, male reproductive success depends on both pre- and postcopulatory processes, including female choice and sperm competition. However, these processes can favour different mating tactics in males. Here we used the Trinidadian guppy, Poecilia reticulata, system to understand how this conflict is resolved. We asked whether knowledge of recent female mating history leads males to adjust their mating effort with respect to the time devoted to mating activity, and the frequency and the sequence of mating tactics employed. To do this we quantified male mating behaviour in three competitive scenarios: (1) Single, when a focal male arrives near a single female and remains alone with her; (2) First, when a focal male is joined by a rival male; and (3) Second, when a focal male arrives after a rival male. We hypothesized that males adjust their behaviour based on arrival order. If female sequential mate choice is the main process shaping male mating behaviours (favouring First males in guppies), males should avoid competition and invest most when Single. Alternatively, if last- male sperm precedence is the major driver of decision making, males should invest more in mating attempts in the Second scenario. Greatest investment when First implies an intermediate strategy. We found that order of arrival influenced mating decisions with most mating activity during the First rather than the Single and Second scenarios. This result suggests that both pre- and postcopulatory processes influence mating investment, and that individual males make contingent decisions to maximize both mating and fertilization success.PostprintPeer reviewe

The effect of water temperature on routine swimming behaviour of new born guppies (Poecilia reticulata)

Funding for this research came from The Buckland Foundation, The Scottish Fisheries Museum Trust Ltd. Additional costs and supplies were provided by the School of Biology of The University of St Andrews.Guppies have successfully established populations in places with thermal regimes very different from the Tropical conditions in their native range. This indicates a remarkable capacity for thermal adaptation. Given their vulnerability to predation as juveniles, acute changes in temperature, which can alter predator-prey relationships, can impact juvenile survival and have amplified consequences at the population level. To understand how temperature may impact juvenile survival and gain insight into their success as an invasive species, we researched the effect of acute temperature changes on the routine swimming behaviour of juvenile guppies. Using a novel 3-dimensional tracking technique, we calculated 4 routine swimming parameters, speed, depth, and variation in speed or depth, at 6 different test temperatures (17, 20, 23, 26, 29, or 32°C). These temperatures cover their natural thermal range and also extended past it in order to include upper and lower thermal limits. Using model selection, we found that body length and temperature had a significant positive relationship with speed. Variation in speed decreased with rising temperatures and fish swam slightly closer to the bottom at higher temperatures. All juveniles increased variation in depth at higher temperatures, though larger individuals maintained slightly more consistent depths. Our results indicate that guppies have a large thermal range and show substantial plasticity in routine swimming behaviours, which may account for their success as an invasive species.Publisher PDFPeer reviewe

Effects of size and morphology on swimming performance in juvenile brown trout (<i>Salmo trutta</i> L.)

Our study assesses swimming capacity (speed and stamina) and possible morphometric determinants of locomotor performance of juvenile brown trout (Salmo trutta L.). We addressed these issues at the individual level to have an approach of the functional significance of intraspecific variation in morphological design. Both swimming speed and endurance time showed significant positive relationships with fish length. Size-corrected values of speed and endurance time were negatively correlated suggesting a phenotypic trade-off between burst and prolonged swimming. Size was also highly correlated with all the morphological variables measured. Therefore, we used the residuals of the regressions of those variables on fish length to remove the effect of body size. A principal components analysis (PCA) summarised the 12 morphological variables into two factors, which accounted for 44.3% of the variance. PC1 combined several measures of body depth and width, whereas PC2 represented mainly postanal length relative to abdomen length. Relationships between the scores of the two factors and size-corrected values of maximum swimming speed and endurance time were weak. PC2 showed a significant positive relationship with endurance time; that is, individuals with longer caudal regions were able to swim against water flow for longer periods of time. Stoutness (PC1) showed a marginally significant negative correlation with endurance time. The lack of stronger relationships could be because of the low morphometric variability among the test individuals, all proceeding from the same population, reared in a common environment, and measured at the same ontogenetic stage.</p

Thermal dependence of embryonic growth and development in brown trout

Fertilized eggs from a brown trout Salmo trutta population in northern Spain were incubated in the laboratory at 4, 6, 8, 10, 12, 14, 16 and 18degrees C. Developmental stage and embryo size were monitored by taking samples at regular intervals. Survival was maximal at 8 and 10degrees C and decreased at higher and lower temperatures. Despite starting development, no embryo hatched at 16 and 18degrees C, which suggests an upper thermal limit for development between 14 and 16degrees C. Time required to reach a given ontogenetic stage decreased with increasing temperature. Embryos incubated at lower temperatures were larger at 50% hatching, and these differences.. persisted throughout the subsequent embryonic period until the start of exogenous feeding. A comparison with previously published data indicates low interpopulation variability in thermal sensitivity of embryonic development, even in consideration of the great latitudinal range of the studies. (C) 2003 The Fisheries Society of the British Isles.</p

Seasonal variability in antipredator performance of red drum larvae

Variability in environmental conditions during early life-history stages can have important consequences for recruitment and population success. The red drum Sciaenops ocellatus spawns between September and November, a period of seasonal temperature decline overlain by quick and rather unpredictable change brought by frequent meteorological fronts. During 3 consecutive spawning seasons (2005 to 2007), we assessed behavioral performance of wild-caught red drum larvae in response to simulated predator attacks. Responsiveness and reactive distance of postsettlement red drum larvae decreased towards the end of the season. Several factors could explain the observed seasonal trends in escape performance, including variability in egg quality, changes in the intensity of predation, and declining temperatures (which may act on performance through a developmental mechanism). Our data suggest that long-term thermal experience (10 to 14 d) is more important than short-term thermal acclimation in determining escape performance. These results imply that late season larvae are less likely to survive to the juvenile stage and recruit to the fishery.</p