Marine Ecology. ISSN 0173-9565 ORIGINAL ARTICLE Adaptation of reef and mangrove sponges to stress: evidence for ecological speciation exemplified by Chondrilla caribensis new species (Demospongiae, Chondrosida) Klaus Ru¨ tzler1, Sandra Duran2 & Carla Piantoni1 1 Department of Invertebrate Zoology, Smithsonian Institution, Washington, DC, USA 2 Smithsonian Marine Station at Fort Pierce, Fort Pierce, FL, USA Keywords Abstract Caribbean Sea; Chondrilla caribensis new species; Chondrilla nucula; morphological and Sponges (Porifera) in mangroves have adapted to a wide range of environmen- molecular characteristics; Porifera ecology; tal parameters except for extended periods of exposure to freshwater or air. salinity; sedimentation; temperature. Many marine mangrove islands are located in the shallow backwaters of coral reefs in Belize and elsewhere in the Caribbean and have a mean tidal range of Correspondence only 15 cm. They are densely populated by sponges, mostly attached to subtid- Klaus Ru¨ tzler, al red-mangrove stilt roots and peat banks lining tidal channels. Some species Department of Invertebrate Zoology, Smithsonian Institution, MRC 163, are endemic to mangroves, others are immigrants from nearby reefs. Mangrove Washington, DC 20013-7012, USA. endemics endure environmental hardships, such as occasional exposure to air E-mail:
[email protected] during spring tides, temperature and salinity extremes, fine sediments, even burial in detritus. Reef immigrants into mangroves enjoy protection from spongivores that do not stray into the swamp but they eventually succumb to environmental stress. There is evidence exemplified by the common demo- sponge Chondrilla aff. nucula, that sponges flourishing in both mangrove and reef habitats may develop separate ecologically specialized and reproductively isolated populations. Such processes can lead to genetic modifications and thus serve as mechanisms for ecological speciation.