Amphiroa

Abstract: STUDIES of the algal collections from Pacific Mexico currently being assembled at the Allan Hancock Foundation Herbarium continue to give data permitting an expanson of our knowledge of the marine flora of this region. Some of these data are herein reported. STRUVEA DE LICATULA Kutzing.-Material which appears to be typical of this species, first described from New Caledonia, was found in the innermost, protected area of Bahia de Acapulco, Guerrero, Mexico in February, 1947, Dawson 3898. The plants occurred among small Amphiroa colonies on rocks slightly submerged at low tide. Though the species is known to occur widely in tropical seas, it has not hitherto been reported from the Pacific American coast. The plant is well illustrated by Okamura (1908) and by Murray and Boodle (1888). DICTYOPTERIS MEMBRANACEA (Stackh.) Batters. -Several northwest Mexican specimens are now at hand which seem indistinguishable from examples of this species both from the Mediterranean region and from the northeastern Atlantic. The broad, uniformly and sparsely dichotomously branched membranous blades which are often eroded in the lower parts leaving the slender, wiry midrib, are distinctive of the plant. The following collections represent the first records of this species from the northeast Pacific: Hubbs 46-145, Isla Guadalupe, Baja Calif., Dec., 1946; Williams, April 27, 1946, Isla Conche, and May 5, 1946, Laguna de Scammon, Bahia Viscaino, Baja California. GYMNOGONGRUS HANCOCKII Dawson, 1944, p. 300. Gymnogongrus divaricatus Holmes, as interpreted by Dawson, 1944, p. 301. (fig. 1).-Recent collections of this species from twenty stations in the Gulf of California and from central Sinaloa have demonstrated clearly its abundance, wide range, and exceeding variability in size and degree of proliferation. The type specimens, though fertile, prove to be among the smallest of any of the collections made to date, some of the more ample specimens now at hand being fully ten times as great in stature. The availability of the entire series of specimens (numbering more than 200) also shows that the examples interpreted by Dawson (1944) as G. divaricatus actually represent the larger, broader form of G. Hancockii such as has been found at Puerto Libertad and at Isla Alcatraz. The occurrence of reproductive structures in the

Abstract: A population of the association between the haplosclerid sponge Haliclona caerulea and the red algae Jania adherens was studied in the Bay of Mazatlan (east tropical Pacific Ocean, Mex- ico), along a spatial gradient (from 1 to 5 m depth) and over time (from February 2001 to September 2003). No clear seasonality was found in the abundance (from 0.5 to 17 ind. 25 m -2 ), volume (from 741 to 7241 cm 3 25 m -2 ), recruitment (up to 9 new ind. 25 m 2 mo -1 ) and mortality (50% loss mo -1 average). The population was capable of recovering after 50% of the specimens were lost; abundance and volume recovered after 7 and 17 mo, respectively. Recruitment was determined in part by asexual propagation through fragmentation, and the relationship with abundance suggested that the popula- tion was self-sustaining. Seasonality was only evident in the sexual reproduction of the sponge, which occurred when water temperature increased: from May to September in 2001, from March to July in 2002, and from April to October in 2003. An important feature was that axial conceptacles of J. adherens living in association with the sponge were never found. The association was permanent over time and the interaction affected the abundance, survival and distribution of the 2 partners in the association. J. adherens was found growing independently in the intertidal zone, which is out of the range of distribution for the association, but we did not find any evidence of sponge living in iso- lation, although in association it is one of the dominant members of the shallow rocky ecosystem in the Bay of Mazatlan. The association was very highly specific; other coralline algae such as Amphi- roa spp. were found in the same habitat, but H. caerulea only associated with Amphiroa spp. in less than 3% of the samples studied. The advantages for J. adherens can be deduced from the fact that it spreads and persists below 1 m thanks to its association with the sponge. The sponge benefits from the fact that it can persist and colonize shallower zones by living in association with the alga. Thus, we conclude that this association is mutualistic.

Abstract: Nuclear small subunit ribosomal RNA (18S rRNA) gene sequences were determined for six species representing three genera classified within the Mastophoroideae, and also for two species of Amphiroa (Lithophylloideae). These data were combined with previously published 18S rRNA sequences for 38 other coralline species and analysed (1) to determine the phylogenetic position of the Mastophoroideae within the Corallinaceae and (2) to examine relationships among Hydrolithon, Metamastophora, Neogoniolithon and Spongites. Trees derived from parsimony and maximum likelihood analyses of these data indicate that the Mastophoroideae is not monophyletic. Instead, our data suggest that the group is polyphyletic and includes species belonging to four distinct evolutionary lineages. For example, Neogoniolithon spp. were associated with geniculate members of the Corallinoideae, and Hydrolithon was resolved as sister to the geniculate genus Metagoniolithon. We demonstrate that each of the four ‘mastophoroid’ lineag...