The red algal genus Liagora (Liagoraceae, Rhodophyta) from the Canary Islands

Abstract

Eight species of the genus Liagora (Liagoraceae, Rhodophyta) are reported from the Canary Islands. Six of these (L. viscida (Forsskål) C. Agardh, L. distenta (Mertens) Lamouroux, L. gymnarthron Børgesen, L. canariensis Børgesen, L. maderensis Kützing and L. tetrasporifera Børgesen) are endemic to the NE Atlantic and Mediterranean and two (L. valida Harvey and L. ceranoides Lamouroux) have a wide distribution. L. maderensis, known only from the type collection and often cited as a synonym for L. ceranoides or L. valida, has a reproductive and vegetative morphology that supports its recognition as an independent species. Evidence suggests that L. gymnarthron has often been erroneously identified as L. distenta (Mertens) Lamouroux and that the latter species has thus been characterized by a combination of features from two different taxonomic entities. Although closely related, the two species show distinctive differences in the morphology of their cystocarps: in L. distenta sterile filaments persist under the gonimoblast and do not surround the mature carposporophyte, while in L. gymnarthron mature carposporophytes are surrounded by a conspicuous involucre. Habit, vegetative and reproductive development have been examined in the eight species. The previously controversial reproductive development in L. viscida, the lectotype species of the genus, has been clarified. Gametophytes of L. viscida are monoecious and, after presumed fertilization, cells adjacent to the supporting cell form sterile colourless filaments that grow and branch towards the thallus surface; simultaneously gonimoblast initials produce outwardly radiating lax gonimoblast filaments that form terminal carposporangia, resulting in a mature carposporophyte with sterile filaments intermingled with the gonimoblast filaments. The features used at present to delineate the genus Liagora in the Liagoraceae are analysed and the potential use of post-fertilization characters to subdivide the genus is discussed.