The phylogeny of the Histeroidea (Coleoptera: Staphyliniformia)

For its size (ca. 4000 species) the Histeridae is one of the most ecologically and morphologically diverse families of beetles. Its mostly predaceous members occupy a wide variety of habitats for which their morphologies may be highly modified. Previous attempts to resolve the phylogeny of the family based on morphological data have left many difficult issues unresolved. This study is the first to utilize either larval or molecular (18S rDNA) data in combination with adult morphology in an attempt to resolve these issues. We compare the performance of optimization alignment with a fixed positional homology approach, over a range of parameter space. Optimizing alignment parameters for combined analyses of 18S and morphology for both approaches resulted in very similar topologies. Contrary to previous hypotheses which held the cylindrical, subcortical forms of the family (e.g., Niponius , Trypanaeus , Trypeticus ) to be the most primitive, our analyses find these to be highly specialized forms derived from within other more generalized taxa. Basal lineages within the family instead include Onthophilus , Anapleus , and Dendrophilus , all of which are ovoid, mainly generalist forms.     

A phylogenetic hypothesis for Asilidae based on a total evidence analysis of morphological and DNA sequence data (Insecta: Diptera: Brachycera: Asiloidea)

An hypothesis of phylogenetic relationships of Asilidae and its constituent taxa is presented, combining morphological and DNA sequence data in a total evidence framework. It is based on 77 robber fly species, 11 Asiloidea outgroup species, 211 morphological characters of the adult fly, and approximately 7300 bp of nuclear DNA from five genes (18S and 28S rDNA, AATS, CAD, and EF-1α protein-encoding DNA). The equally weighted, simultaneous parsimony analysis under dynamic homology in POY resulted in a single most parsimonious cladogram with a cost of 27,582 (iterative pass optimization; 27,703 under regular direct optimization). Six of the 12 included subfamily taxa are recovered as monophyletic. Trigonomiminae, previously always considered as monophyletic based on morphology, is shown to be non-monophyletic. Two of the three Trigonomiminae genera, Holcocephala Jaennicke, 1867 and Rhipidocephala Hermann, 1926, group unexpectedly as the sister taxon to all other Asilidae. Laphriinae, previously seen in the latter position, is the sister group of the remaining Asilidae. Five other subfamily taxa, i.e. Brachyrhopalinae, Dasypogoninae, Stenopogoninae, Tillobromatinae, and Willistonininae, are also shown to be non-monophyletic. The phylogenetic relationships among the higher-level taxa are partly at odds with findings of a recently published morphological study based on more extensive taxon sampling. The total evidence hypothesis is considered as the most informative one, but the respective topologies from the total-evidence, morphology-only, and molecular-only analyses are compared and contrasted in order to discuss the signals from morphological versus molecular data, and to analyze whether the molecular data outcompete the fewer morphological characters. A clade Apioceridae+Mydidae is corroborated as the sister taxon to Asilidae.     

Towards a phylogeny of chitons (Mollusca, Polyplacophora) based on combined analysis of five molecular loci

This study represents the first phylogenetic analysis of the molluscan class Polyplacophora using DNA sequence data. We employed DNA from a nuclear protein-coding gene (histone H3), two nuclear ribosomal genes (18S rRNA and the D3 expansion fragment of 28S rRNA), one mitochondrial protein-coding gene (cytochrome c oxidase subunit I), and one mitochondrial ribosomal gene (16S rRNA). A series of analyses were performed on independent and combined data sets. All these analyses were executed using direct optimization with parsimony as the optimality criterion, and analyses were repeated for nine combinations of parameters affecting indel and transversion/transition cost ratios. Maximum likelihood was also explored for the combined molecular data set, also using the direct optimization method, with a model equivalent to GTR + I + Γ that accommodates gaps. The results of all nine parameter sets for the combined parsimony analysis of all molecular data (as well as ribosomal data) and the maximum-likelihood analysis of all molecular data support monophyly of Polyplacophora. The resulting topologies mostly agree with a division of Polyplacophora into two major lineages: Lepidopleuridae and Chitonida (sensu Sirenko 1993). In our analyses the genus Callochiton is positioned as the sister group to Lepidopleuridae, and not as sister group to the remaining Chitonida (sensu Buckland-Nicks & Hodgson 2000), nor as the sister group to the remaining Chitonina (sensu Buckland-Nicks 1995). Chitonida (excluding Callochiton) is monophyletic, but conventional subgroupings of Chitonida are not supported. Acanthochitonina (sensu Sirenko 1993) is paraphyletic, or alternatively monophyletic, and is split into two clades, both with abanal gills only and cupules in the egg hull, but one has simple cupules whereas the other has more strongly hexagonal cupules. Sister to the Acanthochitonina clades is Chitonina, including taxa with adanal gills and a spiny egg hull. Schizochiton, the only genus with adanal gills that has an egg hull with cupules, is the sister-taxon to one of the Acanthochitonina clades plus Chitonina, or alternatively basal to Chitonina. Support values for either position are low, leaving this relationship unsettled. Our results refute several aspects of conventional classifications of chitons that are based primarily on shell characters, reinforcing the idea that chiton classification should be revised using additional characters.     

Towards the phylogeny of the Curculionoidea (Coleoptera): Reconstructions from mitochondrial and nuclear ribosomal DNA sequences

With about 60,000 described species, Curculionoidea represent the most species-rich superfamily in the animal kingdom. The immense diversity apparently creates difficulties in the reconstruction of the phylogenetic relationships. Independent morphological studies have led to very different classifications. This study is based on molecular data from two independent molecular sources, the 16S and 18S rDNA. Sensitivity analyses were conducted for the sequence alignment (gap costs were varied) as well as the phylogenetic reconstruction algorithms and some of their parameters. The higher-level relationships reconstructed within Curculionoidea are sensitive to alignment and reconstruction method. Nemonychidae or Oxycorynidae+Belidae were found to be sister to all remaining Curculionoidea in many analyses. The 16S rDNA sequence data (obtained from 157 species) corroborate many tribes and genera as monophyletic. It is observed that the phylogenetic reconstruction of genera with specific genetic features such as polyploidy and parthenogenetic reproduction is difficult in weevils. The curculionid subfamily Lixinae appears monophyletic. A new monophylum consisting of Entiminae, Hyperinae, Cyclominae, Myllorhinus plus possibly the Cossoninae is distinguished and we call it Entiminae s.l. For most other subfamilies and families homoplasy concealed the phylogenetic signal (due to saturation of the 16S sequences), or the species sampling was insufficient, although our sampling scheme was rather broad. We observed that although data from one source can easily be misleading (16S) or hardly informative (18S), the combination of the two independent data sets can result in useful information for such a speciose group of organisms. Our study represents the most thorough analysis of molecular sequence data of the Curculionoidea to date and although the phylogenetic results appear less stable than expected, they reflect the information content of these sequence data realistically and thus contribute to the total knowledge about the phylogeny of the Curculionoidea.     

Convergent evolution of chemical defence in Galerucine larvae

Selection pressure by natural enemies on phytophagous insect larvae is intense and has frequently triggered the evolution of chemical defence as an effective counterstrategy. In the chrysomelid subfamily Galerucinae, glandular structures and defensive fluids have been described for the tribe Sermylini Wilcox, 1965. Previous morphological and ultrastructural studies raised doubts that these defensive devices in Sermylini can be traced back to a common origin. The taxonomy of the Galerucinae cannot clear these doubts because the phylogeny of this taxon is a matter of current debate. We therefore investigated the phylogeny of the Galerucinae based on approximately 1740 bp of the mitochondrial 12S and 16S rRNA and the nuclear elongation factor 1 alpha genes. Our data support the hypothesized close relationship between the subfamilies Galerucinae and Alticinae, yet, by contrast to other recent analyses, the two groups are mostly resolved as monophyletic sister groups or, in some analyses, with the Galerucinae nested paraphyletically within the Alticinae. Within the subfamily Galerucinae, only the tribe Galerucini formed a monophyletic taxon, except for one species, Cerochroa brachialis Stal, 1858. In none of our analyses were the Sermylini recovered as a monophyletic tribe. However, our data support monophyly of each of the three groups within the Sermylini that have morphologically distinguishable larval defensive openings. We conclude that the defensive structures in larvae of Sermylini have no common origin, but evolved independently. Our data suggest that the tremendous selection pressure by natural enemies led to the recurrent evolution of similar chemical defensive devices in Sermylini larvae.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 165–175.