Recently, two phylogenetic studies using molecular characters confirmed that the associations between species-groups based on morphological similarities are similar to those based on molecular characters [14], [15].
Some authorities considered them subspecies based on morphological similarities and suspected cases of hybridization.
Based on morphological similarities, Jack Garrick in 1982 grouped this species with the bignose shark (C. altimus) and the sandbar shark (C. plumbeus), while Leonard Compagno in 1988 placed it as the sister species of the grey reef shark (C. amblyrhynchos).
Based on morphological similarities, Nebrius is believed to be the sister genus of Ginglymostoma, with both being placed in a clade that also contains the short-tail nurse shark (Pseudoginglymostoma brevicaudatum), the whale shark (Rhincodon typus), and the zebra shark (Stegostoma fasciatum).
Based on morphological similarities, Tyler [23] recognized the four major clades of tetraodontids that were found in the present study, and Holcroft [24] and Alfaro et al. [25] also produced phylogenetic structures that are largely congruent with our resulting topology, in that all four lineages are reproduced.
A close relationship between P. haroldii and P. zephyrus was suggested by Krogen [ 53], based on morphological similarities.
In evolutionary taxonomy, the prevailing form of taxonomy during much of the 20th century and still used in non-specialist textbooks, taxa based on morphological similarity are often drawn as "bubbles" or "spindles" branching off from each other, forming evolutionary trees.
In this study, multivariate morphometric analyses were performed for testing relationships based on morphological similarity of Aphis, especially comprising the four species groups, namely the gossypii group, the craccivora group, the fabae group, and the spiraecola group.
Examples include karyotyping by G-banding techniques based on morphological similarity (Drets and Shaw 1971); fluorescence in situ hybridization (FISH) (Bauman et al. 1980), such as M-FISH based on DNA sequence homology (Speicher et al. 1996); and array-based methods, such as array comparative genomic hybridization (array-CGH) (Solinas-Toldo et al. 1997).
