Phylogenetic and morphometric studies of major internal organ systems of the scarabaeoidea (Coleoptera)

Abstract

Section 1: Detailed descriptions of the alimentary canal, nervous system, male and female reproductive organs and ovipositor morphology of all 13 scarabaeoid families and most subfamilies are presented. Because no organ systems or ovipositor ground plan exists, one was constructed from literature (pertaining to all lnsecta, with special reference to Coleoptera and Scarabaeoidea) as well as personal observation of the changes in morphology of the characters. Character states from these systems are not stable, sometimes varying considerably between species of the same genus. Because of this variability, only 18 stable characters were identified. A branch-and-bound cladistic analysis (using PAUP/Mac version 3.1.2d5) was performed, followed by a strict consensus, and a 50% majority rule consensus (on all 18 characters). It was, however, decided to choose only the parsimony-informative characters (totaling 10) and again to perform a branch-and-bound search. This yielded 54 trees and 12 steps. A 50% majority rule consensus was then performed, and this tree chosen as representing the phylogeny of the organ systems and ovipositor. Although only 10 characters identified proved to be parsimony-informative, the 50% majority consensus tree is not totally different to that of the tree proposed by Browne and Scholtz (in press). Section 2: Geometric morphometric analyses of 12 families belonging to the Scarabaeoidea, using landmarks from three two-dimensional views (frontal, dorsal and lateral) of the metendosternite were done. The metendosternite is one of the internally situated anatomical structures that has largely been neglected in past studies. It, however, proved to be very useful in geometric morphometric studies, because of its rigidness. Procrustes distance matrices were obtained to produce phenograms, relative warp analyses were performed and the results of the first two relative warps (for each of the data sets) plotted against one another. The most landmarks (totaling 19) were identified on the lateral view, and this phenogram also corresponds best with the cladogram of Browne and Scholtz (in press). Geometric morphometrics is a powerful tool that can be used successfully to identify phenetic relationships between higher level taxa, and the metendosternite a new "tool" in the tool box of beetle systematists.