Peer- reviewed (journal articles)
Palacios, M.M., S.S. Killen, L.E. Nadler., J.R. White & M.I. McCormick 2016. Top- predators negate the effect of mesopredators on prey physiology. Journal of Animal Ecology 85: 1078-1086
Palacios, M.M., D.T. Warren & M.I. McCormick 2016. Sensory cues of a top‐predator indirectly control a reef fish mesopredator. Oikos 125: 201 -209
Palacios, M.M., C.G. Muñoz & F.A. Zapata. 2014. Fish corallivory on a pocilloporid reef and experimental coral responses to predation. Coral Reefs 33: 625 -636
Palacios, M.M. & F.A. Zapata. 2014. Fish community structure on coral habitats with contrasting architecture in the Tropical Eastern Pacific. International Journal of Tropical Biology and Conservation 62(1): 343-357
Palacios, M.M., & F.A. Zapata. 2011. Biases associated with visual surveys of reef fish in the Eastern Tropical Pacific: Implications of using single or mixed size transects, of the experience of the divers, and of fish size estimations. Bulletin of Marine and Coastal Research 40: 111-132
MM Palacios, SS Killen, SE Nadler, JR White, MI McCormick
1. Predation theory and empirical evidence suggest that top-predators benefit the survival of resource prey through the suppression of mesopredators. However, whether such behavioural suppression can also affect the physiology of resource prey has yet to be examined.
2. Using a three-tier reef fish food-web and intermittent-flow respirometry, our study examined changes in the metabolic rate of resource prey exposed to combinations of mesopredator and top-predator cues.
3. Under experimental conditions, the mesopredator (dottyback, Pseudochromis fuscus) continuously foraged and attacked resource prey (juveniles of the damselfish Pomacentrus amboinensis) triggering an increase in prey O2 uptake by 38 ± 12.9 % (mean ± SE). The visual stimulus of a top-predator (coral trout, Plectropomus leopardus) restricted the foraging activity of the mesopredator, indirectly allowing resource prey to minimise stress and maintain routine O2 uptake. Although not as strong as the effect of the top-predator, the sight of a large non-predator species (thicklip wrasse, Hemigymnus melapterus) also reduced the impact of the mesopredator on prey metabolic rate.
4. We conclude that lower trophic-level species can benefit physiologically from the presence of top-predators through the behavioural suppression that top-predators impose on mesopredators. By minimising the energy spent on mesopredator avoidance and the associated stress response to mesopredator attacks, prey may be able to invest more energy in foraging and growth, highlighting the importance of the indirect, non-consumptive effects of top-predators in marine food-webs.
MM Palacios, DT Warren, MI McCormick Abstract: Behavioural trophic cascades highlight the importance of indirect/risk effects in the maintenance of healthy trophic-level links in complex ecosystems. However, there is limited understanding on how the loss of indirect top-down control can cascade through the food-web to modify lower level predator-prey interactions. Using a reef fish food-web, our study examines behavioural interactions among predators to assess how fear elicited by top-predator cues (visual and chemical stimuli) can alter mesopredator behaviour and modify their interaction with resource prey. Under experimental conditions, the presence of any cue (visual, chemical, or both) from the top-predator (coral trout, Plectropomus leopardus) strongly restricted the distance swum, area explored and foraging activity of the mesopredator (dottyback, Pseudochromis fuscus), while indirectly triggering a behavioural release of the resource prey (recruits of the damselfish Pomacentrus chrysurus). Interestingly, the presence of a large non-predator species (thicklip wrasse, Hemigymnus melapterus) also mediated the impact of the mesopredator on prey, as it provoked mesopredators to engage in an “inspection” behaviour, while significantly reducing their feeding activity. Our study describes for the first time a three-level behavioural cascade of coral reef fish and stresses the importance of indirect interactions in marine food-webs.
MM Palacios, CG Munoz, FA Zapata Abstract: This study examined the pressure and effects of the Guineafowl pufferfish (Arothron meleagris), a major corallivore in the Eastern Pacific, on a pocilloporid reef at Gorgona Island, Colombia. Here, pufferfish occur at a density of 171.2 ind ha-1 and feed at a rate of 1.8 bites min-1 exerting a standing pressure between 215 and 608 bites m-2, depending on the reef zone. In terms of the predation effect, coral nubbins exposed to pufferfish corallivory increased less in length but gained similar weight compared to those protected from predators. Nubbins exposed to corallivory were thicker and shorter, suggesting that corallivory influences coral morphology. Colonies with simulated predation injuries on up to 75 % of branch tips recovered successfully and had a growth rate similar to that of uninjured colonies. We estimate that the pufferfish population removes 15.6 % of the pocilloporid carbonate production. Despite the high corallivore pressure exerted by the pufferfish, we conclude that they have a low destructive impact on the reef because Pocillopora colonies can withstand and tolerate partial predation by recovering well from injuries and by maintaining their carbonate production rate. Pufferfish predation, however, may increase environmentally-induced morphological variability in Pocillopora.
Fish community structure on coral habitats with contrasting architecture in the Tropical Eastern Pacific
MM Palacios, FA Zapata Abstract: Reefscape architecture, shaped by dominant coral morphologies, can play a major role in determining the structure and composition of fish assemblages by affecting niche and resource availability and mediating interspecific interactions. To explore the role of dominant coral morphologies on reef fish communities, we car- ried out a comparative study of the fish community associated with a Massive Coral Community (MCC) and a Branching Coral Community (BCC) at Gorgona island, Tropical Eastern Pacific (TEP). On each community, the benthic substrate was assessed through the “chain transect method” while the fish assemblage was evalu- ated through visual surveys on belt transects. We found differences between both fish assemblages in terms of the abundance, diversity (H’), and evenness (J’). The BCC, despite being formed by morphologically complex pocilloporid colonies, had a simple and relatively flat architecture that attracted principally small and territorial fishes. Significant higher abundances of Chromis atrilobata and Thalassoma lucasanum at the BCC boosted the total fish abundance but caused low fish evenness and diversity. Conversely the MCC, composed of massive coral species with considerable sizes and diversity of shapes, held a complex and high-relief reefscape capable of sustaining a more diverse and even fish community, although with the same species richness as the BCC. Fishes with large sizes, roving behavior and piscivore-feeding preferences were especially attracted to the MCC. Although, massive coral species are important in determining a diverse and complex reefscape architecture, both dominant coral morphologies (massive and branching) attract and provide resources to different types of fish according to their size, mobility and trophic group. Our results suggest that a loss of massive coral species and a community shift towards stress-resistant taxa (such as Pocillopora spp.), could alter the structure and function of fish assemblages in the TEP due to the habitat loss for large, mobile and piscivore species.
Biases associated with visual censuses of reef fishes in the Eastern Tropical Pacific: implications of using single vs mixed-size transects, observer experience, and fish size estimation.
MM Palacios, FA Zapata Abtrasct: Visual censuses on belt transects implemented to assess reef fish populations in the Eastern Tropical Pacific (ETP) vary greatly in the size of sampling units and census protocols. To examine the effects of such variation on estimates of species richness and density, and to help identify an appropriate (accurate, precise and efficient) protocol, we compared two belt transect methods: a single-size transect (one 30 x 2 m band) and a mixed-size transect (two bands, a 50 x 5 m band for large, mobile fishes, and a 50 x 1 m band for small or cryptic fishes). Three observers with different experience conducted 72 visual censuses on three fixed transects at El Arrecife coral formation in Malpelo Island, Colombia, following a factorial design to evaluate the effect of methods, observers and fish size estimation on the accuracy and precision of species richness and density estimates. Additionally, we examined the efficiency (cost in time in relation to the accuracy and precision) of each method. The Mixed Transect (MT) yielded more precise estimates of population and community parameters and more accurate estimates of species richness. However, it had a high implementation cost (25 min/census) and consistently underestimated total density and the density of species recorded in the 50 x 5 m transect (probably due to its greater band width and associated decrease in species detectability). The Single Transect (ST) was more cost-efficient (14 min/census) and produced more accurate estimates of total and specific density for most species (except cryptic or small ones). Both methods were biased by the estimation of fish size during the censuses and by observer inexperience, so they should be implemented under oceanographic conditions that facilitate carrying out visual censuses and by divers with prior training. Alternatively, random sampling can be performed independently of visual censuses to estimate size frequency distributions without affecting estimates of abundance and species richness. Given the generally poor visibility in the ETP and insufficient funding for research and monitoring projects, the ST protocol is more suitable for conducting surveys of multiple species. In addition to producing more accurate estimates of total and specific density for most species, the greater cost-efficiency of STs allows to increase the number of replicates and thus to improve the estimate of total species richness and the precision of all population and community estimates. However, due to the greater accuracy of the MT to assess total species richness and density of small and cryptic species, an alternative would be to use a MT of at least 30 m length, with a maximum width of 2 m for censusing large and mobile species, and of 1 m for small and cryptic species.