Intraspecific reproductive variation in Gelidium pusillum (Stackh.) Le Jol. (Gelidiales, Rhodophyta) from Europe

Interfertility has been demonstrated in vitro between isolates of G. pusillum from Norway, France and the British Isles, but anomalies in reproductive behaviour were observed in the two Norwegian isolates. In one of the latter (Fedje), female gametophytes were sterile. Carpogonia and nutritive filaments were differentiated, but further development was always disrupted and carposporangia never formed. On one occasion, bilocular ‘pseudo-cystocarps’ were formed in a self-cross, but no carpospores were produced. Male reproductive structures were functional and used in crossability tests. In the other Norwegian isolate (Solund), only a small percentage of the released tetraspores survived, and most of these had an aberrant dwarfed growth habit. Only a few of several thousand spores produced functional male and female gametophytes of normal appearance. In quantitative experiments, significantly higher sporeling survival was found in one of the French isolates (Cancale) than in the Solund isolate. Stages of the first meiotic division were observed and a haploid chromosome number of approximately n =15 − 20 was counted for the Solund isolate. During the second meiotic division, failure was frequently observed in that cytokinesis took place without completion of nuclear divison. In the French isolates of the same species (Cancale and Wimereux isolates), a haploid chromosome number of n = 20 or 21 was determined during meiosis in tetrasporocytes. This revised version was published online in June 2006 with corrections to the Cover Date.