Browsing by Author "Manzur, Tatiana"

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    Geographic variation in diversity of wave exposed rocky intertidal communities along central Chile
    (2011) Broitman, Bernardo R.; Veliz, Fredy; Manzur, Tatiana; Wieters, Evie A.; Randall Finke, G.; Fornes, Paulina A.; Valdivia, Nelson; Navarrete, Sergio A.
    Along the coast of central Chile, geographic trends of diversity have been inferred from literature compilations and museum collections based on species range limits for some taxonomic groups. However, spatially-intensive field-based assessments of macrobenthic species richness are largely missing. Over the course of a multiyear study (1998-2005), we characterized latitudinal patterns of rocky intertidal diversity at 18 sites along the coast of central Chile (29-36 degrees S). At each site, the number of sessile and mobile macrobenthic species was quantified in 0.25 m(2) quadrats. Two estimators of local (alpha) diversity were used: observed local species richness, calculated from the asymptote of a species-rarefaction curve, and the Chao2 index, which takes into account the effect of rare species on estimates of local richness. We identified a total of 71 species belonging to 66 genera for a total of 86 taxa. The most diverse groups were herbivorous mollusks (27 taxa) and macroalgae (43 taxa). Diversity showed a complex spatial pattern with areas of high species richness interspersed with areas of low richness. In accordance with previous work, we found no trend in the number of herbivorous mollusks and an inverse and significant latitudinal gradient in the number of algal species. Our results highlight the need for taxonomically diverse assessments of biodiversity of the dominant taxa that conform intertidal communities.
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    Ontogenetic changes in habitat use and diet of the sea-star Heliaster helianthus on the coast of central Chile
    (2010) Manzur, Tatiana; Barahona, Mario; Navarrete, Sergio A.
    Ontogenetic shifts in habitat use and diet are ubiquitous in nature and usually have profound consequences for the ecology and evolution of the species. In the case of species with strong interactions within their communities, such as keystone predators, understanding this kind of size-related change is critical to understand variation and connectivity among spatially distinct habitats of coastal communities. Yet the ecology of early life stages of marine benthic invertebrates, particularly asteroids, is poorly understood. Here we describe the results of surveys to characterize the habitat and quantify the abundance and diet of recruits of the sun star Heliaster helianthus, a keystone predator at rocky intertidal sites in central Chile. Our results support the existence of size-related, ontogenetic changes in habitat use and diet of this species. Recruits occupy boulders and crevices in the high or mid-high intertidal zones of wave-protected habitats and as they grow they move down towards lower tidal levels. Adults are characteristically found in the low intertidal zone of wave exposed and semi-exposed habitats. These changes in habitat use are accompanied by changes in diet composition and particularly by a broadening of the prey species incorporated in the diet. Since early stages of Heliaster appear to be most sensitive to predation and abiotic stress and since adults are such important predators in wave exposed rocky shores, knowledge of the basic ecology of early stages of this species is critical to fully understand the dynamics of intertidal communities.
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    Scales of detection and escape of the sea urchin Tetrapygus niger in interactions with the predatory sun star Heliaster helianthus
    (2011) Manzur, Tatiana; Navarrete, Sergio A.
    Predators can simultaneously have lethal (consumption) and non-lethal (modification of traits) effects on their prey. Prey escape or fleeing from potential predators is a common form of a non-lethal predator effect. The efficiency of this response depends on the prey's ability to detect and correctly identify its predator far enough to increase the probability of successful escape, yet short enough to allow it to allocate time to other activities (e.g. foraging). In this study, we characterized the non-lethal effect of the sun star Heliaster helianthus on the black sea urchin Tetrapygus niger by assessing the nature of predator detection and the spatial scale involved both in predator detection and in the escape response. Through field and laboratory experiments we demonstrate that T. niger detects chemical cues released by H. helianthus. In the laboratory, these chemical signals can be detected at distances of up to about 50 cm. In the field, the distance traveled by urchins when escaping, after recognition of the predation risk, was also restricted to about 40 cm. Thus, considering the sizes of the predator and prey, the spatial scale of both detection and escape is comparatively small suggesting that non-lethal effects of H. helianthus (e.g. how it modifies the behavior of T. niger) should be important at local spatial scales and highly variable at the landscape scale. (C) 2011 Elsevier B.V. All rights reserved.