Phylogeny and systematics of Demospongiae in light of new small-subunit ribosomal DNA (18S) sequences
Redmond, N.E. ; Morrow, C. ; Thacker, R.W. ; Diaz, M.C. ; Boury-Esnaul, N. ; Cardenas, P.D. ; Hajdu, E. ; Lobo-Hajdu, G. ; Picton, B.E. ; Pomponi, S.A. ; Kayal, E. ; Collins, A.G. - \ 2013
Integrative and Comparative Biology 53 (2013)3. - ISSN 1540-7063 - p. 388 - 415.
glass sponges porifera - phylum porifera - molecular phylogeny - animal phylogeny - gene-sequences - fossil record - evolution - hexactinellida - classification - verongida
The most diverse and species-rich class of the phylum Porifera is Demospongiae. In recent years, the systematics of this clade, which contains more than 7000 species, has developed rapidly in light of new studies combining molecular and morphological observations. We add more than 500 new, nearly complete 18S sequences (an increase of more than 200%) in an attempt to further enhance understanding of the phylogeny of Demospongiae. Our study specifically targets representation of type species and genera that have never been sampled for any molecular data in an effort to accelerate progress in classifying this diverse lineage. Our analyses recover four highly supported subclasses of Demospongiae: Keratosa, Myxospongiae, Haploscleromorpha, and Heteroscleromorpha. Within Keratosa, neither Dendroceratida, nor its two families, Darwinellidae and Dictyodendrillidae, are monophyletic and Dictyoceratida is divided into two lineages, one predominantly composed of Dysideidae and the second containing the remaining families (Irciniidae, Spongiidae, Thorectidae, and Verticillitidae). Within Myxospongiae, we find Chondrosida to be paraphyletic with respect to the Verongida. We amend the latter to include species of the genus Chondrosia and erect a new order Chondrillida to contain remaining taxa from Chondrosida, which we now discard. Even with increased taxon sampling of Haploscleromorpha, our analyses are consistent with previous studies; however, Haliclona species are interspersed in even more clades. Haploscleromorpha contains five highly supported clades, each more diverse than previously recognized, and current families are mostly polyphyletic. In addition, we reassign Janulum spinispiculum to Haploscleromorpha and resurrect Reniera filholi as Janulum filholi comb. nov. Within the large clade Heteroscleromorpha, we confirmed 12 recently identified clades based on alternative data, as well as a sister-group relationship between the freshwater Spongillida and the family Vetulinidae. We transfer Stylissa flabelliformis to the genus Scopalina within the family Scopalinidae, which is of uncertain position. Our analyses uncover a large, strongly supported clade containing all heteroscleromorphs other than Spongillida, Vetulinidae, and Scopalinidae. Within this clade, there is a major division separating Axinellidae, Biemnida, Tetractinellida, Bubaridae, Stelligeridae, Raspailiidae, and some species of Petromica, Topsentia, and Axinyssa from Agelasida, Polymastiidae, Placospongiidae, Clionaidae, Spirastrellidae, Tethyidae, Poecilosclerida, Halichondriidae, Suberitidae, and Trachycladus. Among numerous results: (1) Spirophorina and its family Tetillidae are paraphyletic with respect to a strongly supported Astrophorina within Tetractinellida; (2) Agelasida is the earliest diverging lineage within the second clade listed above; and (3) Merlia and Desmacella appear to be the earliest diverging lineages of Poecilosclerida.
Long-term effects of elevated atmospheric CO2 on species composition and productivity of a southern African C4 dominated grassland in the vicinity of a CO2 exhalation.
Stock, W.D. ; Ludwig, F. ; Morrow, C. ; Midgley, G.F. ; Wand, S.J.E. ; Allsopp, N. ; Bell, T.L. - \ 2005
Plant Ecology 178 (2005)2. - ISSN 1385-0237 - p. 211 - 224.
tallgrass prairie ecosystem - soil carbon - biomass production - plant-communities - water relations - gas-exchange - growth - enrichment - responses - dynamics
We describe the long-term effects of a CO2 exhalation, created more than 70 years ago, on a natural C4 dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO2 enrichment changes the competitive balance between plants with C3 and C4 photosynthetic pathways and how CO2 enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO2 on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO2 alone. Species compositional data and soil ¿13C isotopic evidence suggest no detectable effect of CO2 enrichment on C3:C4 plant mixtures and individual species dominance. Contrary to many general predictions C3 grasses did not become more abundant and C3 shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO2 concentrations averaging 610 ¿mol mol-1. Leaf properties such as total N decreased in the C 3 but not C4 grass under elevated CO2 while total non-structural carbohydrate accumulation was not affected. Elevated CO2 possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO2 enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO2 source. The conservative response of this grassland suggests that many of the reported effects of elevated CO2 on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO2 conditions