ECOTYPIC VARIATION IN PHYLLOPHORA PSEUDOCERANOIDES (RHODOPHYTA) ENSURES WINTER REPRODUCTION THROUGHOUT ITS GEOGRAPHIC RANGE

Responses to temperature and daylength were determined in laboratory c ulture for isolates of the red alga Phyllophora pseudoceranoides (Gmel in) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (Franc e), and Helgoland (Germany). All isolates grew from 3 degrees to 25 de grees C and survived from -2 degrees or 0 degrees C to 27 degrees C bu t not 30 degrees C. Reproductive requirements differed between life hi story phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3 degrees-20 degrees C, tetraspores at 3 degrees-12 degrees C, and procarps at 10 degrees-20 degrees C, irrespective of d aylength. Spermatangia developed at 10 degrees-23 degrees C but only i n long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3 degrees-12 degrees C, but it had an additio nal requirement for short days. The Nova Scotian isolate formed sori a t 10 degrees-20 degrees C and sporulated at 10 degrees-18 degrees C. W hen grown plants were transferred from noninductive to inductive condi tions, sori were formed after 4 months and tetraspores developed and w ere shed (1-)3 months later. Procarps formed 1(-3) months after transf er. The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were pe rennial,forming new blades from October to June, which degenerated bet ween August and February. In June, reproductive structures (sori, sper matangia, and procarps) started to appear on the new blades. From Octo ber to April, mature cystocarps were found. Mature tetrasporangia were observed only in February. The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the d ifferent life history phases all serve to confine the production of sp ores (both carpospores and tetraspores) to the winter season. Differen ces in response between isolates from different geographic regions bri ng about the same effect: spores are only shed in winter. The nature o f the geographic boundaries of p. pseudoceranoides is discussed.