LIFE HISTORIES IN THE PHYLLOPHORACEAE (RHODOPHYTA: GIGARTINALES) FROM THE PACIFIC COAST OF NORTH AMERICA. I.GYMNOGONGRUS LINEARISANDG. LEPTOPHYLLUS¹

Abstract

Carpospores of Gymnogongrus linearis (C. Ag.) J. Ag. collected from Sonoma Co., California were cultured and gave rise to crustose plants. Tetrasporogenesis could not be induced. However, tetraspores from field‐collected crustose tetrasporophytes found near G. linearis from San Mateo Co., California were cultured. These field crusts superficially resemble Petrocelis middendorffii (Ruprecht) Kjellman, but differ in size, color, number of tetrasporangia per filament, and distal dichotomous branching of the perithallial filaments. Tetraspores gave rise to upright plants identical to G. linearis. Gymnogongrus leptophyllus J. Ag. collected from California and Baja California, Mexico were found as narrow and wide forms. Narrow form isolates recycled directly without producing a crustose tetrasporophyte. These are interpreted as apogamous. Carpospores of the wide form grew into crusts resembling Petrocelis (=Erythrodermis) haematis Hollenberg. Tetrasporogenesis was induced in culture by abrasion or dehydration. Tetraspores from field‐collected crusts and laboratory cultured tetrasporophytes grew into plants identical to G. leptophyllus, completing a sexual life history with an alternation of heteromorphic generations.

Taxonomy of phyllophoroid algae: the implications of life history

“…This is exemplified by the position of Besa, which was originally placed in the Gigartinaceae on the basis of its elongated medullary cells . This attribution was supported on morphological grounds by DeCew in DeCew & West (1981) but McCandless et al (1982 considered that as the type species, B . papillaeformis Setchell, contained iota-carrageenan the genus should be referred to the Phyllophoraceae .…”

“…devoniensis (Greville) Schotter, appears to be derived from the heteromorphic type . Carpospores released by internal cystocarps do not develop into crustose tetrasporophytes but instead recycle the female gametophytes (DeCew & West, 1981 ;Maggs, 1988) . No isomorphic life histories are known in the genus.…”

“…The obvious differences between these phyllophoracean algae and A . plicata led DeCew & West (1981), Masuda (1982), McCandless et al (1982) andDeCew (1983) to propose that several species should be segregated into a new genus, provisionally named Ahnfeltiopsis . Unfortunately, however, the description of this genus (Silva & DeCew, unpubl .)…”

“…griffithsiae differs considerably from that in other tetrasporoblastic species. One point of possible interest is to determine whether there is homology between the cortical breaks that allow the tetrasporoblast to emerge and the specialized carpostomes through which carpospores are released (see DeCew & West, 1981) . The evolution of the tetrasporoblastic type of life history from a heteromorphic one might not require a great deal of genetic alteration .…”

“…In addition, Dixon (1982a) recognized the possibility that apomictic life histories might occur in the Rhodophyta, although they were not well documented . Apomixis has been discussed in relation to several phyllophoracean species (Newroth & Markham, 1972 ;DeCew & West, 1981) .…”