Effects of temperature on success of (self and non-self) fertilization and embryogenesis in Diploria strigosa (Cnidaria, Scleractinia)

The effects of seawater temperature on the degree of success of self-fertilization versus cross-fertilization and on embryogenesis were investigated in the scleractinian coral Diploria strigosa (Dana 1846). Gametes from nine colonies were collected from the Flower Garden Banks reefs, a set of coral reefs in the northern Gulf of Mexico, ~110 nm offshore from Texas, United States. Gametes from the coral colonies were combined in all possible combinations and placed in 30 degree , 31 degree , and 32 degree C water baths on successive nights, respectively. Each cross, whether selfed or out-crossed, and each temperature treatment, was replicated twice. A high frequency of successful self- and cross-fertilization was observed at all temperature treatments and in both blocks. Higher temperatures, however, commonly produced numerous developmental aberrations during embryogenesis of the larvae. Thus, although fertilization rates can remain high under high temperature conditions, if temperatures remain high for several days, embryonic development and larval viability may be expected to decrease dramatically. We propose that the success of coral larval development may be diminished in areas where abnormally high sea surface temperatures occur during the spawning season. We also propose that highly successful selfing may enhance the abundance of locally adapted genotypes, which in turn may be advantageous where reefs, such as the Flower Garden Banks, are relatively geographically isolated.