Meeting Abstract
Selection should favor individuals that choose to occupy habitats that confer highest fitness. In heterogeneous environments, this often equates to individuals actively navigating alternative habitat types and dispersing to areas that offer higher potential for survival and reproduction. When habitat preferences exhibited in the lab do not align with the conditions under which individuals are found in natural environs, it suggests that: i) some other element precludes optimal habitat choice in the wild, and ii) the potential for measurable fitness consequences experienced by individuals occupying subpar habitats. Mangrove rivulus fish inhabit salinities ranging from 0 to 65 ppt but are most often collected at ~25 ppt. However, recent experiments showed that rivulus prefer to occupy lower salinities (5-15 ppt). To evaluate the fitness consequences of living in various salinities across ontogeny, fish from three life stages (hatchling, juvenile, adult) were randomly assigned to one of 7 salinities between 5 – 65 ppt for two weeks. Growth rate and mortality were quantified as fitness proxies. Hatchling survival decreased by ~10% between 5 and 25 ppt but, mortality increased precipitously as habitats became more saline. Hatchlings also showed significantly greater mass gain at 5 and 15 than at 25 ppt, and considerably less as salinity increased further. Juveniles did not experience significant mortality until 55 ppt and gained more mass at 5, 15 and 25 ppt than at higher salinities. Adults appeared unaffected by salinity, with no difference among salinities in mass gained and a slight increase in mortality at 65 ppt. For species inhabiting variable environments with multiple microhabitats, fitness might be maximized in habitats that are quite different from those in which the animals are commonly found in the wild.
