COMPARATIVE MORPHOLOGY, CROSSABILITY, AND TAXONOMY WITHIN THE CALOGLOSSA-CONTINUA (DELESSERIACEAE, RHODOPHYTA) COMPLEX FROM THE WESTERN PACIFIC

Systematic studies were undertaken on the Caloglossa continua (Okamura ) King et Puttock complex from Japan, Singapore, and Australia, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodal axial cell, at the margin o pposite the branch, whereas those from Australia possessed only a sing le cell row. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at feast one single cell row on any one thallus. These differences were maintained in cultured materi als over a range of temperatures or salinities. Type material of C. co ntinua had the same morphology as the Japanese specimens in this study . Carpospores discharged from the Japanese isolate germinated at 10 de grees C, whereas those from Singapore and Australia died at this tempe rature. In hybridization experiments, the Japanese entity was complete ly nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the male from A ustralia and the female from Singapore, although the reciprocal combin ation did not produce any such structures. On the basis of the discont inuous morphology coupled with the complete reproductive isolation, th e entities from Singapore and Australia are described here as C. monos ticha sp. nov. The entities with multiple cell rows likely expanded th eir geographic range from tropical regions, where the majority of Calo glossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquiring low-temperature toler ance.