AN EXPERIMENTAL ASSESSMENT OF THE TEMPERATURE RESPONSES OF 2 SYMPATRIC SEAGRASSES, AMPHIBOLIS-ANTARCTICA AND AMPHIBOLIS-GRIFFITHII, IN RELATION TO THEIR BIOGEOGRAPHY

Walker, D. I. and Cambridge, M. L. 1994. An experimental assessment of the temperature responses of two sympatric seagrasses, Amphibolis ant arctica and Amphibolis griffithii, in relation to their biogeography. Seedlings of the viviparous seagrasses, Amphibolis antarctica (Labill. ) Sonder & Aschers. and Amphibolis griffithii (Black) den Hartog, were grown in seawater cultures at temperatures of 10-30-degrees-C. This t emperature range exceeded the range of temperatures occurring in habit ats where Amphibolis grows. All seedlings of both species survived at 15-degrees-C, and all A. antarctica at 10 and 20-degrees-C. There was some mortality at 25-degrees-C, but more in A. griffithii than in A. a ntarctica. All seedlings showed marked senescence at 30-degrees-C with in 2 weeks, and all seedlings of both species were dead at this temper ature in 6 weeks. Leaf production rates were different at different te mperatures for each species, but were high across the 15-25-degrees-C temperature range for both species. Given the time of release of seedl ings from parent plants (winter), these results are consistent with th e observed distribution of adult plants, and so the more restricted ra nge of A. griffithii can be explained partially by its' response to te mperature in culture. These results do not explain the absence of both Amphibolis species from the east coast of Australia, which may be a c onsequence of habitat availability.