DOES THE AUTECOLOGY OF THE MANGROVE RIVULUS FISH (RIVULUS-MARMORATUS)REFLECT A PARADIGM FOR MANGROVE ECOSYSTEM SENSITIVITY

The killifish Rivulus marmoratus, mangrove rivulus, represents the one of the two potentially truly ''mangrove dependent'' fish species in w estern Atlantic mangrove ecosystems. The distribution of this species closely parallels the range of red mangroves. These plants and fish ex hibit parallel ecological and physiological tolerances to the wide ran ges of tropical temperatures and salinities, as well as substrate and hydrological conditions of mangrove habitats. The mangrove rivulus, R. marmoratus, is, as well, the only truly marine representative of a sp eciose genus of otherwise freshwater fish species. Many of the biologi cal specializations of this species characterize the specific challeng es to survival in mangrove forest conditions. As recent studies report , this fish species, once considered ''rare,'' has been shown to be ve ry abundant in specific substrate microhabitats of the mangal. Among t he unique specializations of this fish are amphibious emersion from wa ter, survival in moist detrital substrate during periods of low water or drought, and reproduction through internal self-fertilization produ cing homozygous clones. The autecology of this species provides fascin ating insights and generates a wealth of questions regarding evolution of specific adaptations for distribution, dispersal, colonization, po pulation genetics and the interrelationships between adaptation and sp ecialization. The Indian River Lagoon (IRL) represents both the site o f rediscovery of the fish as well as the northern frontier of the spec ies distribution range, habitat, and ecosystem. This suggests close in terrelationships and parallels in the parameters to which the species has adapted, perhaps representing a commonage, of ecological associati on. These aspects are discussed with respect to details and insight ne eded to develop strategies for the management of unique communities an d ecosystems, especially along their natural distributional borders. T he topic raises such questions as: Are some ''exotic species'' actuall y examples of newly arrived colonizers, representing dynamic biotic re sponses to climate change and/or anthropogenic habitat modification?