Giribet, G., and S. Carranza. 1999. “What can 18S rDNA do for bivalve phylogeny?.” J Mol Evol 48: 256-61.
Palacin, C., G. Giribet, S Carner, L Dantart, and X Turon. 1998. “Low densities of sea urchins influence the structure of algal assemblages in the western Mediterranean..” Journal of Sea Research 39: 281-290.
Giribet, G. 1998. “'Molluscs as evolving constructions' and phylogenetic deconstructivism..” Iberus 16: 123-128.
Giribet, G., and A. Penas. 1998. “A new Epilepton species (Bivalvia, Montacutidae) from the western Mediterranean..” Iberus 16: 117-121.
Palacin, C., X Turon, M Ballesteros, G Giribet, and S Lopez. 1998. “Stock evaluation of three littoral echinoid species on the Catalan coast (nrth-western Mediterranean).” P.S.Z.N.: Marine Ecology 19: 163-177.
1998. “Terrestrial planarians (Platyhelminthes, Tricladida, Terricola) from the Iberian Peninsula: first records on the family Rhynchodemidae with the description of a new Microplana species..” Contributions to Zoology 67: 267-276.
Giribet, G., and C. Ribera. 1998. “The position of arthropods in the animal kingdom: a search for a reliable outgroup for internal arthropod phylogeny.” Mol Phylogenet Evol 9: 481-8.Abstract

Morphological evidence for the phylogeny of the animal kingdom has been discussed by numerous authors. DNA sequencing and phylogenetic methods for analyzing these data are alternative approaches to animal phylogeny, but the phenomenon of long branch attraction and poor taxonomic sampling have caused misinterpretations of metazoan relationships. Here we report a cladistic approach to metazoan evolution including 133 18S rDNA sequences of 31 animal phyla. Despite the difficulties associated with analyzing large data sets, our data suggest that the Bilateria and Protostomia are monophyletic. The internal phylogeny of the protostomes is divided into two main clades. One clade includes the classical protostome worms (annelids, sipunculans, echiurans, pogonophorans, and vestimentiferans), mollusks, nemerteans, "lophophorates," platyhelminths, rotiferans, and acanthocephalans, although the internal resolution of the clade is very low. The second clade includes arthropods and other molting animals: tardigrades, onychophorans, nematodes, nematomorphans, kinorhynchs, and priapulans. The arthropods and related phyla lack a ciliated larvae, lack a multiciliate (locomotory) epithelium, and share many features, notably, a reduced coelomic cavity and the presence of a cuticle which molts. The use of these outgroups within the molting clade to root arthropod phylogenies is recommended instead of using annelids or other spiralians. The data are quite conclusive in those phyla with a good taxonomic sampling (i.e., platyhelminths and arthropods).

Giribet, G., and A. Penas. 1997. “Malacological marine fauna from Garraf coast (NE Iberian Peninsula).” Iberus 15: 41-93.
Palacin, C., G. Giribet, and X. Turon. 1997. “Patch recolonization through migration by the sea urchin Paracentrotus lividus (Lamarck) in communities with high algal cover and low sea urchin densities..” Cahiers de Biologie Marine 38: 267-271.
Carranza, S., G. Giribet, C. Ribera, Baguna, and M. Riutort. 1996. “Evidence that two types of 18S rDNA coexist in the genome of Dugesia (Schmidtea) mediterranea (Platyhelminthes, Turbellaria, Tricladida).” Mol Biol Evol 13: 824-32.Abstract

Sequences of 18S ribosomal DNA (rDNA) are increasingly being used to infer phylogenetic relationships among living taxa. Although the 18S rDNA belongs to a multigene family, all its copies are kept homogeneous by concerted evolution (Dover 1982; Hillis and Dixon 1991). To date, there is only one well-characterized exception to this rule, the protozoan Plasmodium (Gunderson et al. 1987; Waters, Syin, and McCutchan 1989; Qari et al. 1994). Here we report the 1st case of 18S rDNA polymorphism within a metazoan species. Two types (I and II) of 18S rDNA have been found and sequenced in the platyhelminth Dugesia (Schmidtea) mediterranea (Turbellaria, Seriata, Tricladida). Southern blot analysis suggested that both types of rDNA are present in the genome of this flatworm. This was confirmed through sequence comparisons and phylogenetic analysis using the neighbor-joining method and bootstrap test. Although secondary structure analysis suggests that both types are functional, only type I seems to be transcribed to RNA, as demonstrated by Northern blot analysis. The finding of different types of 18S rDNAs in a single genome stresses the need for analyzing a large number of clones whenever 18S sequences obtained by PCR amplification and cloning are being used in phylogenetic reconstruction.

Giribet, G., S. Carranza, J. Baguna, M. Riutort, and C. Ribera. 1996. “First molecular evidence for the existence of a Tardigrada + Arthropoda clade.” Mol Biol Evol 13: 76-84.Abstract

The complete 18S rDNA gene sequence of Macrobiotus group hufelandi (Tardigrada) was obtained and aligned with 18S rDNA and rRNA gene sequences of 24 metazoans (mainly protostomes). Discrete character (maximum-parsimony) and distance (neighbor-joining) methods were used to infer their phylogeny. The evolution of bootstrap proportions with sequence length (pattern of resolved nodes, PRN) was studied to test the resolution of the nodes in neighbor-joining trees. The results show that arthropods are monophyletic. Tardigrades represent the sister group of arthropods (in parsimony analyses) or they are related with crustaceans (distance analysis and PRN). Arthropoda are divided into two main evolutionary lines, the Hexapoda + Crustacea line (weakly supported), and the Myriapoda + Chelicerata line. The Hexapoda + Crustacea line includes Pentastomida, but the internal resolution is far from clear. The Insecta (Ectognatha) are monophyletic, but no evidence for the monophyly of Hexapoda is found. The Chelicerata are a monophyletic group and the Myriapoda cluster close to Arachnida. Overall, the results obtained represent the first molecular evidence for a Tardigrada + Arthropoda clade. In addition, the congruence between molecular phylogenies of the Arthropoda from other authors and this obtained here indicates the need to review those obtained solely on morphological characters.

Turon, X, G. Giribet, S. Lopez, and C. Palacin. 1995. “Growth and population structure of Paracentrotus lividus (Echinodermata: Echinoidea) in two contrasting habitats. .” Marine Ecology Progress Series 122: 193-204.
Giribet de Sebastian, G, and Carranza Gil Dolz S del Castellar. 1994. “Dos neuvas localidades para un nemertino de agua dulce del genero Prostoma Duges, 1828 (Hoplonemertini: Tetrastemmatidae) en la Penisula Iberica.” Graellsia 50: 170-172.