January 14, 2021
EcoEvoPub Seminar Series
Department of Ecology and Evolutionary Biology, UCLA
" Graduate Student Presentations "
Erick Zerecero Marin
Department of Ecology and Evolutionary Biology, UCLA, Barber Lab
“Toxin producing dinoflagellates and their relationship with Turbinaria ornata, a dominant macroalga on human-impacted reefs in French Polynesia”
Worldwide, tropical reefs are being transformed from coral-dominated to macroalgal-dominated communities, transitions that are often driven by anthropogenic stressors. In the South Pacific, the macroalga Turbinaria ornata has recently expanded its range and habitat usage, forming dense algal stands in reefs of Moorea, French Polynesia, negatively impacting local corals. Recent studies show that the epiphytes on T. ornata serve as a novel food source for juvenile herbivorous fishes. This observation is concerning because among these epiphytes are dinoflagellates that cause illnesses in humans, such as ciguatera and diarrhetic shellfish poisoning. This study examines the impacts of increased T. ornata density on toxin producing dinoflagellates. Results showed that T. ornata had significantly higher abundances of toxin producing dinoflagellates (Gambierdiscus spp., Ostreopsis spp., and Prorocentrum spp.) than other macroalgae, including Padina sp., Sargassumm sp. and Dictyota sp. Combined, these results suggest that transitions from coral to algal dominated ecosystems not only have negative impacts on the health and function of local reef communities, but these transitions may also negatively impact human health. Increased grazing on T. ornata epiphytes by juvenile fish provides a pathway introduction of dinoflagellate toxins into the food chain, potentially increasing the incidence of ciguatera, particularly on reefs impacted by anthropogenic stressors.
Department of Ecology and Evolutionary Biology, UCLA, Alfaro Lab
“Evolutionary and functional consequences of sexually dimorphic color pattern diversity in labrid fishes”
Sexual color dimorphism is largely attributed to sexual selection, where different sexes will broadcast distinct displays to conspecifics to convey information such as mating availability and fitness for reproduction. This is balanced by the effects of natural selection, where colors that allow an organism to mitigate conspicuousness to potential predators may also contribute to fitness. Colors themselves contribute to conspicuousness, but so can overall pattern through the juxtaposition of adjacent or other co-occurring colors. Among species that exhibit sexual color dimorphism, disparity in color pattern geometry contributes to differences in relative conspicuousness towards both predators and conspecifics among sexes. We quantify color pattern geometry and complexity across males and females of dichromatic and non-dichromatic species of wrasses (Labridae) using sashimi and charisma, novel high-throughput image processing and color classification methods, to automatically crop fish from image backgrounds and detect the number and proportions of color classes on each individual to best capture overall pattern diversity. While previous work has examined the evolution of color dimorphism in terms of the presence or absence of discrete colors across labrids, the evolution of the relative proportion and distribution of colors that comprise patterns among sexually dichromatic species has not been previously evaluated. We also use visual models and phylogenetic comparative methods to test how males and females diverge from one another in terms of statistics that capture color pattern geometry. We demonstrate that not only color composition, but also relative proportion and orientation of colors in patterns have important implications for different life histories among sexes of wrasses on a macroevolutionary scale.
Thursday, January 14th, 2021 @ 5 PM