A Mediterranean population of Spongites fruticulosus (Rhodophyta, Corallinales), the type species of Spongites, and the taxonomic status of S. stalactitica and S. racemosa

Tetrasporangial male and female/carposporangial plants of a Mediterranean population of Spongites fruticulosus are described and compared with the type material of S. fruticulosus, Spongites racemosa and Spongites stalactitica. The three species were established by Kutzing on the basis of Mediterranean collections. The type material of S. fruticulosus is a rhodolith composed of a tetrasporangial plant possessing uniporate conceptacles, multistratose noncoaxial hypothallium and ovoid epithallial cells, growing on another unidentified sterile coralline with different vegetative characters. Spongites fruticulosus is lectotypified here with the tetrasporangial plant. The original material of S. racemosa represents a male plant of Neogoniolithon, here identified as Neogoniolithon racemosum (Kutzing) comb. nov. The type material of S. stalactitica is a rhodolith composed of a mixture of two species belonging to different genera: one, here selected as lectotype of S. stalactitica, is a female plant regarded as conspecific with S. fruticulosus. The second is the tetrasporophyte of a Neogoniolithon species. Detailed morphological-anatomical accounts of the species are presented, and their features are documented and discussed. The comparison between the Mediterranean types and new collections and the Australian population of S. fruticulosus revealed that Mediterranean plants have smaller sexual and asexual conceptacles and lack trichocytes. However, overlap in conceptacle dimensions and the rarity of trichocytes in the Australian specimens do not allow us to separate the Mediterranean and the Indo-Pacific populations into different species at this time.