Meneses
Michael J.
Meneses
Michael J.
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ThesisVertical distributions of megafauna on inactive vent sulfide features correspond to their feeding modes(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2024-09) Meneses, Michael J. ; Mullineaux, Lauren S.The discovery of inactive hydrothermal vent sulfide features located off the ridge axis in the 9°50'N region of the East Pacific Rise provides an opportunity to investigate knowledge gaps in the distribution and feeding ecology of communities inhabiting this type of deep-sea habitat. Previous seafloor imaging studies indicate that megafaunal taxa on inactive sulfides are not endemic to these features, but their assemblages differ from other deep-sea habitats. I investigated the influence of environmental conditions on megafaunal distributions using highresolution imagery of two inactive sulfide features, Lucky's Mound and Sentry Spire, to determine how taxonomic composition and feeding traits vary with vertical position on the features. A total of 51 morphotypes, each categorized to feeding mode, was identified from three levels of the features (spire, apron, and base) and a section of the surrounding flat oceanic rise. Quantitative image analysis showed that passive suspension feeders were more abundant on the spires of the sulfide features than the base or surrounding rise. Deposit feeders were more abundant on the base of Lucky’s mound and the oceanic rise, than on the spire or apron, but were unexpectedly abundant on the spire of Sentry Spire. These distributions correspond generally to the expected availability of suspended organic particles and detritus on the seafloor that serve, respectively, as food for these two feeding modes, and indicate a potential role for physical attributes of the sulfide feature to influence their faunal assemblages. Distinct differences in community composition between the two inactive sulfide features, however, suggest that other, feature-specific processes, perhaps including local chemoautotrophic production, may also play a role.
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ArticleThermal plasticity has higher fitness costs among thermally tolerant genotypes of Tigriopus californicus(British Ecological Society, 2024-05-02) Bogan, Samuel N. ; Porat, Olivia I. ; Meneses, Michael J. ; Hofmann, Gretchen E.Under climate change, ectotherms will likely face pressure to adapt to novel thermal environments by increasing their upper thermal tolerance and its plasticity, a measure of thermal acclimation. Ectotherm populations with high thermal tolerance are often less thermally plastic, a trade-off hypothesized to result from (i) a phenotypic limit on thermal tolerance above which plasticity cannot further increase the trait, (ii) negative genetic correlation or (iii) fitness trade-offs between the two traits. Whether each hypothesis causes negative associations between thermal tolerance and plasticity has implications for the evolution of each trait. We empirically tested the limit and trade-off hypotheses by leveraging the experimental tractability and thermal biology of the intertidal copepod Tigriopus californicus. Using populations from four latitudinally distributed sites in coastal California, six lines per population were reared under a laboratory common garden for two generations. Ninety-six full sibling replicates (n = 4–5 per line) from a third generation were developmentally conditioned to 21.5 and 16.5°C until adulthood. We then measured the upper thermal tolerance and fecundity of sibships at each temperature. We detected a significant trade-off in fecundity, a fitness corollary, between baseline thermal tolerance and its plasticity. Tigriopus californicus populations and genotypes with higher thermal tolerance were less thermally plastic. We detected negative directional selection on thermal plasticity under ambient temperature evidenced by reduced fecundity. These fitness costs of plasticity were significantly higher among thermally tolerant genotypes, consistent with the trade-off hypothesis. This trade-off was evident under ambient conditions, but not high temperature. Observed thermal plasticity and fecundity were best explained by a model incorporating both the limit and trade-off hypotheses rather than models with parameters associated with one hypothesis. Effects of population and family on tolerance and plasticity negatively covaried, suggesting that a negative genetic correlation could not be ruled as contributing to negative associations between the traits. Our study provides a novel empirical test of the fitness trade-off hypothesis that leverages a strong inference approach. We discuss our results' insights into how thermal adaptation may be constrained by physiological limits, genetic correlations, and fitness trade-offs between thermal tolerance and its plasticity.
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ArticleVertical distributions of megafauna on inactive vent sulfide features(Elsevier, 2024-07-16) Meneses, Michael J. ; Beaulieu, Stace E. ; Best, Ayinde C. ; Dykman, Lauren N. ; Mills, Susan Wier ; Wu, Jyun-Nai ; Mullineaux, Lauren S.The discovery of inactive hydrothermal vent sulfide features near 9°50′N on the East Pacific Rise provides an opportunity to investigate the distribution and feeding ecology of communities inhabiting this type of habitat. We quantify megafaunal distributions on two features, Lucky's Mound and Sentry Spire, to determine how taxonomic composition and feeding traits vary with vertical elevation. Fifty-one morphotypes, categorized by feeding mode, were identified from three levels of the features (spire, apron, and base) and the surrounding flat oceanic rise. About half of the morphotypes (26 of 51) were only observed at the sulfide features. Passive suspension feeders were more abundant on the spires, where horizontal particulate flux is expected to be elevated, than the base or rise. Deposit feeders tended to be more abundant on the base and rise, where deposition is expected to be enhanced, but were unexpectedly abundant higher up on Sentry Spire. Community differences between the two sulfide features suggest that other processes, such as feature-specific chemoautotrophic production, may also influence distributions.