Diplostomum commutatum (Diesing, 1850) Dubois, 1937 (Trematoda: Diplostomatidae) cercaria

The cercaria of D. commutatum from the mollusk Radix ovata is described. Data on the biology and development of the cercaria up to the metacercarial stage are given. Cercariae of D. commutatum differ from all known species of the genus Diplostomum by a characteristic cuticular armament.     

Paraphyly, Outgroups, and Transformations

Book review in this article:
Cladistics: The Theory and Practice of Parsimony Analysis. By I. J. Kitching, P. L. Forey, C. J. Humphries, and D. M. Williams.     

Paraphyly and budding speciation in the hairy snail (Pulmonata,Hygromiidae)

Delimitation of species is often complicated by discordance of morphological and genetic data. This may be caused by the existence of cryptic or polymorphic species. The latter case is particularly true for certain snail species showing an exceptionally high intraspecific genetic diversity. The present investigation deals with the Trochulus hispidus complex, which has a complicated taxonomy. Our analyses of the COI sequence revealed that individuals showing a T. hispidus phenotype are distributed in nine highly differentiated mitochondrial clades (showing p‐distances up to 19%). The results of a parallel morphometric investigation did not reveal any differentiation between these clades, although the overall variability is quite high. The phylogenetic analyses based on 12S, 16S and COI sequences show that the T. hispidus complex is paraphyletic with respect to several other morphologically well‐defined Trochulus species (T. clandestinus, T. villosus, T. villosulus and T. striolatus) which form well‐supported monophyletic groups. The nc marker sequence (5.8S–ITS2–28S) shows only a clear separation of T. o. oreinos and T. o. scheerpeltzi, and a weakly supported separation of T. clandestinus, whereas all other species and the clades of the T. hispidus complex appear within one homogeneous group. The paraphyly of the T. hispidus complex reflects its complicated history, which was probably driven by geographic isolation in different glacial refugia and budding speciation. At our present state of knowledge, it cannot be excluded that several cryptic species are embedded within the T. hispidus complex. However, the lack of morphological differentiation of the T. hispidus mitochondrial clades does not provide any hints in this direction. Thus, we currently do not recommend any taxonomic changes. The results of the current investigation exemplify the limitations of barcoding attempts in highly diverse species such as T. hispidus.     

Paraphyly,ancestors, and the goals of taxonomy: A botanical defense of cladism

Cronquist (1987) criticizes cladism for its rejection of paraphyletic groups, which he would retain if he feels they are “conceptually useful.” We argue that paraphyletic higher taxa are artificial classes created by taxonomists who wish to emphasize particular characters or phenetic “gaps,” and that formal recognition of such taxa conveys a misleading picture of common ancestry and character evolution. In our view, classifications should accurately reflect the nested hierarchy of monophyletic groups that is the natural outcome of the evolutionary process. Such systems facilitate the study of evolution and provide an efficient summary of character distributions. Paraphyletic groups, such as “prokaryotes,” “green algae,” “bryophytes,” and “gymnosperms,” should be abandoned, as continued recognition of such groups will only serve to retard progress in understanding evolution. Contrary to Cronquist’s (1987) assertions, cladistic theory is not at odds with standard views on speciation and the existence of ancestors. Groups of interbreeding organisms can continue to exist after giving rise to descendant species, and there are several ways in which such groups, whether extant or extinct, can be incorporated into cladistic classification. In contrast, paraphyletic higher taxa are neither cohesive (integrated by gene flow) nor whole, do not serve as ancestors, and are unacceptable in the phylogenetic system. Fossils may be of great value in assessing phylogenetic relationships and are readily accommodated in cladistic classification. Cladistic studies are helping to answer major questions about plant evolution, and we anticipate increased efforts to develop a truly phylogenetic system.     

Suresh Dinker Jayakar, 1937–1988

This is an English version of the obituary that appeared inBoll. Zool., 56: 109-110, by permission of the Editors.     

Petrosal and Bony Labyrinth Morphology Supports Paraphyly of Elephantulus Within Macroscelididae (Mammalia,Afrotheria)

Interest in the phylogeny of Macroscelididae (sengis or elephant shrews) has been prompted by molecular studies indicating that Elephantulus rozeti is best placed as the sister group of Petrodromus tetradactylus (this clade being in turn the sister taxon to Macroscelides proboscideus) than among other species of the genus Elephantulus. Until now, no discrete morphological characters have been proposed to support the grouping of E. rozeti, Petrodromus, and Macroscelides into this single so-called ‘Panelephantulus’ clade. Here, we employed μCT scanning in order to investigate the petrosal and bony labyrinth (bony capsule of the inner ear) morphology of most species of extant Macroscelididae. We performed a cladistic analysis on ear traits and found that despite some convergences (e.g., concerning the bony arterial canals in Macroscelides and Rhynchocyon) the middle and inner ear morphology furnishes significant support for the ‘Panelephantulus’ clade. In our analysis, this clade is unambigously supported by the presence of a fully ossified stapediofacial tube. Two additional characters (the presence of a bony septum at the mouth of the fenestra cochleae dividing the D3 sinus into two distinct cavities and the absence of an accessory lateral pneumatic fossa) could also support ‘Panelephantulus.’ These newly discovered morphological characters support the molecular phylogenies published and highlight the importance of coding hitherto difficult to sample morphologies within cladistic analyses using micro-CT techniques. Taxonomic implications are briefly discussed.     

Paraphyly of Homoptera and Auchenorrhyncha inferred from 18S rDNA nucleotide sequences

Evolutionary affiliations of eighteen families of Hemiptera (s.l.) are inferred using molecular phylogenetic analysis of nucleotide (nt) sequences of 18S rDNAs. Exemplar taxa include: Archaeorrhyncha (=Fulgoromorpha): flatid, issid, dictyopharid, cixiid and delphacid; Prosorrhyncha (=Heteropterodea): Peloridiomorpha (=Coleorhyncha) -peloridiid, Heteroptera gerrid, lygaeid and mirid; Clypeorrhyncha [=extant (monophyletic) cicadomorphs]: cicadid, cercopoids (cercopid, aphrophorid), membracid and cicadellids (deltocephaline and cicadelline); and Sternorrhyncha: psyllid, aleyrodid, diaspidid and aphid. Analysed sequences encompass a region beginning ?550 nucleotides (nts) from the 5'-end to ?200 nts upstream from the 3'-end of the gene [?1150 base pairs (bp) in euhemipteran to >1400 bp in sternorrhynchan taxa]. Maximum parsimony and bootstrap analyses (PAUP) identify four principal hemipteran clades, Stenorrhyncha, Clypeorrhyncha, Archaeorrhyncha and Prosorrhyncha. These lineages are identified by synapomorphies distributed throughout the gene. Sternorrhyncha is a sister group to all other Hemiptera (i.e. Euhemiptera sensu Zrzavy), rendering Homoptera paraphyletic. Within Euhemiptera, clades Clypeorrhyncha, Archaeorrhyncha, Prosorrhyncha and Heteroptera are supported by one, three, two and three synapomorphic sites, respectively. There is equitable parsimonious inference for Archaeorrhyncha as the sister group to Prosorrhyncha (Neoherriiptera sensu Sorensen et al.) or Clypeorrhyncha, in either case rendering Auchenorrhyncha paraphyletic. Neohemiptera is supported by one synapomorphy. Within Clypeorrhyncha, clade cicada + cercopoids is the sister group of the clade cicadellids + membracid (Membracoidea sensu Dietrich & Deitz). Among archaeorrhynchans, clade delphacid + cixiid is the sister group of the clade dictyopharid + flatid + issid. Within Prosorrhyncha, the peloridiid is sister to the Heteroptera. Within Heteroptera, gerrid is the sister group of the clade mirid + lygaeid (Panheteroptera sensu Schuh). Based on secondary structure of synonymous 18S rRNA, two synapomorphies each of Sternorrhyncha, Prosorrhyncha and Heteroptera are compensatory substitutions on stem substructures. All other synapomorphies identifying major lineages of Hemiptera are noncompensatory substitutions on either bulges or stems. Short basal internodal distances suggest radiation of hemipteran lineages at the suborder level occurred rapidly. Morphological, palaeoentomological and eco-evolutionary factors supporting the 18S rDNA-based phylogenetic tree are discussed.     

Mitochondrial Genes Collectively Suggest the Paraphyly of Crustacea with Respect to Insecta

Complete sequences of seven protein coding genes from Penaeus notialis mitochondrial DNA were compared in base composition and codon usage with homologous genes from Artemia franciscana and four insects. The crustacean genes are significantly less A + T-rich than their counterpart in insects and the pattern of codon usage (ratio of G + C-rich versus A + T-rich codon) is less biased. A phylogenetic analysis using amino acid sequences of the seven corresponding polypeptides supports a sister-taxon status for mollusks–annelid and arthropods. Furthermore, a distance matrix-based tree and two most-parsimonious trees both suggest that crustaceans are paraphyletic with respect to insects. This is also supported by the inclusion of Panulirus argus COII (complete) and COI and COIII (partial) sequence data. From analysis of single and combined genes to infer phylogenies, it is observed that obtained from single genes are not well supported in most topologies cases and notably differ from that of the tree based on all seven genes. Received: 25 August 1998 / Accepted: 8 March 1999