Seagrass can mitigate negative ocean acidification effects on calcifying algae

The ultimate effect that ocean acidification (OA) and warming will have on the physiology of calcifying algae is still largely uncertain. Responses depend on the complex interactions between seawater chemistry, global/local stressors and species-specific physiologies. There is a significant gap regarding the effect that metabolic interactions between coexisting species may have on local seawater chemistry and the concurrent effect of OA. Here, we manipulated CO2 and temperature to evaluate the physiological responses of two common photoautotrophs from shallow tropical marine coastal ecosystems in Brazil: the calcifying alga Halimeda cuneata, and the seagrass Halodule wrightii. We tested whether or not seagrass presence can influence the calcification rate of a widespread and abundant species of Halimeda under OA and warming. Our results demonstrate that under elevated CO2, the high photosynthetic rates of H. wrightii contribute to raise H. cuneata calcification more than two-fold and thus we suggest that H. cuneata populations coexisting with H. wrightii may have a higher resilience to OA conditions. This conclusion supports the more general hypothesis that, in coastal and shallow reef environments, the metabolic interactions between calcifying and non-calcifying organisms are instrumental in providing refuge against OA effects and increasing the resilience of the more OA-susceptible species.E.B. would like to thank the Coordenação de Aperfeiçoamento de Pessoas de Nível Superior (CAPES) for Masters funding. Funding for this project came from the Synergism grant (CNPq 407365/2013-3). We extend our thanks to the Brazil-based Projeto Coral Vivo and its sponsor PetroBras Ambiental for providing the Marine Mesocosm structure and experimental assistance.info:eu-repo/semantics/publishedVersio

Population genetics of Cedrela fissilis (Meliaceae) from an ecotone in central Brazil

Cedrela fissilis is an endangered timber species associated with seasonal forests throughout South America. We investigated a population of C. fissilis (PAN) located toward central Brazil to uncover insights on how an ecotone may have shaped the evolutionary history of this species at the local scale. PAN consisted of 18 mother trees and their 283 offspring (18 families), which were genotyped with ten microsatellite loci. We supplemented our dataset with equivalent microsatellite data from 175 specimens representing the east and west lineages of C. fissilis. An array of complementary methods assessed PAN for genetic diversity, population structure, and mating system. In PAN, the gene pool of the east lineage combined with a third (previously unidentified) lineage to form an admixture population. PAN is under inbreeding (Ho = 0.80 and 0.74, uHe = 0.85 and 0.82, Ap = 1.1 and 7.1, F = 0.06 and 0.10, for mother trees and offspring, respectively). Mother trees were predominantly outcrossing (tm = 0.95), with some selfing (1 − tm = 0.05), and crossing between related individuals (tm–ts = 0.07); they received pollen from few donors (Nep = 9). Restricted gene flow within PAN gave rise to a strong population structure, which split the 18 families into six groups. Some mother trees were reproductively isolated. Conservation perspectives are discussed