title: Symbiotic state influences life-history strategy of a clonal cnidarian.
abstract: Along the North American Pacific coast, the common intertidal sea anemone Anthopleura elegantissima engages in facultative, flexible symbioses with Symbiodinium muscatinei (a dinoflagellate) and Elliptochloris marina (a chlorophyte). Determining how symbiotic state affects host fitness is essential to understanding the ecological significance of engaging in such flexible relationships with diverse symbionts. Fitness consequences of hosting S. muscatinei, E. marina or negligible numbers of either symbiont (aposymbiosis) were investigated by measuring growth, cloning by fission and gonad development after 8.5-11 months of sustained exposure to high, moderate or low irradiance under seasonal environmental conditions. Both symbiotic state and irradiance affected host fitness, leading to divergent life-history strategies. Moderate and high irradiances led to a greater level of gonad development in individuals hosting E. marina, while high irradiance and high summer temperature promoted cloning in individuals hosting S. muscatinei and reduced fitness of aposymbiotic anemones. Associating with S. muscatinei may contribute to the success of A. elegantissima as a spatial competitor on the high shore: (i) by offsetting the costs of living under high temperature and irradiance conditions, and (ii) by promoting a high fission rate and clonal expansion. Our results suggest that basic life-history characteristics of a clonal cnidarian can be affected by the identity of the endosymbionts it hosts.
authors.affiliation: Department of Environmental Sciences, Western Washington University, 516 High Street, Bellingham, WA 98225, USA brian.bingham@wwu.edu.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Bingham
authors.affiliation: Shannon Point Marine Center, Western Washington University, 1900 Shannon Point Road, Anacortes, WA 98221, USA.
authors.forename: James L
authors.initials: JL
authors.lastname: Dimond
authors.affiliation: Division of Graduate Education, National Science Foundation, Arlington, VA 22230, USA.
authors.forename: Gisèle
authors.initials: G
authors.lastname: Muller-Parker
mesh_terms: D000818:Animals; D001835:Body Weight; D000460:Chlorophyta / Q000502:physiology; D004141:Dinoflagellida / Q000502:physiology*; D005260:Female; D005854:Germ Cells; D006066:Gonads; D008018:Life Cycle Stages; D008297:Male; D010140:Pacific Ocean; D012098:Reproduction; D012615:Sea Anemones / Q000254:growth & development / Q000502:physiology*; D012621:Seasons; D013559:Symbiosis; D013696:Temperature; D014861:Washington
keywords: Anthopleura elegantissima; Symbiodinium; fitness; life history; reproduction; symbiosis