Cladistics

Prendini, Lorenzo

doi: 10.1111/j.1096-0031.2000.tb00348.xpmid: 34902920

S. A. Stockwell (1989, “Revision of the Phylogeny and Higher Classification of Scorpions (Chelicerata).” Univ. of California, Berkeley) proposed a cladogram and revised classification for the superfamily Scorpionoidea Latreille 1802 (comprising the families Bothriuridae, Diplocentridae, Heteroscorpionidae, Ischnuridae, and Scorpionidae), based on 47 morphological characters and 35 supraspecific terminal taxa, representing genera whose monophyly was implicitly assumed. Given the widespread practice of defining scorpion genera on the basis of plesiomorphic character states, the assumption of monophyly implicit in supraspecific terminal taxa reduces confidence in Stockwell's cladistic findings and, consequently, his revised suprageneric classification. A re‐investigation of scorpionoid phylogeny is presented here, based on 115 morphological characters (including the characters used by Stockwell) and 71 exemplar species. The criterion of “maximal morphological diversity” was employed for exemplar selection. This approach provides a stronger test of monophyly than random exemplar selection. Sixteen cladistic analyses were performed on the scorpionoid data matrix, which varied in the use of equal, successive, or implied weights and in the additive or nonadditive treatment of multistate characters. The preferred hypothesis, a single most parsimonious tree obtained by analysis with equal weights and 13 ordered multistate characters, yielded the scheme of relationships: (Bothriuridae ((Heteroscorpionidae Urodacinae) ((Hemiscorpiinae Ischnuridae) (Diplocentridae Scorpioninae)))). On the basis of these results, revisions are proposed to the existing suprageneric classification of the Scorpionoidea, including new diagnoses, new descriptions, and an illustrated key to the families and subfamilies. Familial status is provided for the scorpionid subfamilies Hemiscorpiinae and Urodacinae.

Klompen, J.S.H.; Black, William C.; Keirans, James E.; Norris, Douglas E.

doi: 10.1111/j.1096-0031.2000.tb00349.xpmid: 34902921

Systematic relationships among the basal Ixodidae are examined using one morphological and three molecular data sets, 18S and 28S nuclear and 16S mitochondrial rDNA. Although different combinations of partitions are incompatible in a partition homogeneity test, combining them produces similar or better support for most major lineages through both additive and complementary effects. The different data sets are not complete for all taxa, but inclusion or exclusion of taxa with missing data for one or more data sets (8 of 29 ingroup taxa) does not influence overall tree topology and only weakly affects support levels. The only notable effect was based on gap treatment in the 28S data set. Gap treatment completely changes the arrangement and support levels for one basal node. The combined analyses show strong support for the Metastriata, a lineage including most endemic Australian Ixodes, and a lineage including the remaining Ixodes, but not for the Prostriata (=Ixodes s.l.). The distribution pattern of endemic Australian taxa (nearly all included in three exclusively Australian basal lineages) suggests that these lineages, and by extension the Ixodidae, originated after the isolation of Australia in the late Cretaceous, much more recently than previously indicated.

Beutel, Rolf G.; Haas, Fabian

doi: 10.1111/j.1096-0031.2000.tb00350.xpmid: 34902922

One hundred seven external and internal characters of larval and adult representatives of 28 genera of the coleopteran suborders were analyzed cladistically. Four groups of Neuropterida were introduced as outgroup. The analysis yielded 18 trees with a minimum of 194 steps (CI 0.691). All trees support the monophyly of all four suborders and a branching pattern (Archostemata + (Adephaga + (Myxophaga + Polyphaga))). The presence of elytra with meso‐ and metathoracic locking devices, the specific hind‐wing folding, the close connection of exposed sclerites, the absence of the mera, the absence of eight thoracic muscles, the reduced abdominal sternite I, and the invagination of terminal segments are autapomorphies of Coleoptera. The monophyly of Coleoptera excl. Archostemata is supported by further transformations of the thoracic sclerites such as absence of the mesothoracic discriminal line and katepisternal joint, by an internalized or absent metathoracic trochantin, by the presence of a bending zone in the hind‐wing, and by eight further muscle losses. Fusion of tibia and tarsus and presence of a single claw are larval synapomorphies of Myxophaga and Polyphaga. Adults are characterized by fusion of protrochantin and propleura and by the rigid connection of the meso‐ and metathoracic ventrites. The eucinetoid lineage of Polyphaga is characterized by the secondary absence of the bending zone of the alae. This results in a distinctly simplified wing folding mechanism. The monophyly of Cucujiformia (+ Bostrichoidea) is supported by the presence of cryptonephric Malpighian tubules. Transformations of fore‐and hind‐wings, reinforcement and simplification of the thoracic exoskeleton, and an efficient use of a distinctly reduced set of thoracic muscles play an important role in the early evolution of Coleoptera. Many different larval character transformations take place in the earlier Mesozoic within the suborders.

Brower, Andrew V.Z.

doi: 10.1111/j.1096-0031.2000.tb00351.xpmid: 34902923

Although the point has already been emphasized by various authors that the assumption of descent with modification is not required to justify cladistics, recent debate suggests that there is still confusion surrounding the necessary and sufficient background knowledge underlying the method. Three general axioms necessary to justify cladistics—the discoverability of characters, hierarchy, and parsimony—are reviewed. Although the assumption of evolution is sufficient to justify cladistics, it is also sufficient to justify competing approaches like maximum likelihood, which suggests that the philosophical support for the cladistic approach is strengthened by purging reference to descent with modification altogether.