MALE REPRODUCTIVE SYSTEM
To make inferences about the phylogeny of Hymenoptera, I use morphological characters from all regions of the adults and larvae -- external and internal. My main interest is the male reproductive system, which contains a wealth of information.
Morphology and Functional Morphology
My first publication contains a detailed description of the internal and external morphology of the male genitalia of a tenthredinid (Tenthredo campestris) (Schulmeister 2001). It also included an account of the inferred function of each sclerite and muscle of the external male genitalia during copulation. For example, here are views of the medio-sagittal plane of two specimens of Aglaostigma lichtwardti, demonstrating how four muscles work together to rotate the penisvalva (red):
More recently, I examined the male reproductive system of 59 hymenopteran species, covering all 14 sawfly families and selected apocritans. This comparative morphological study yielded 87 characters (Schulmeister 2003d). The external genitalia from at least one member of each sawfly family are depicted in this publication. One example, Dolerus sp., is shown here:
The 87 characters were included in my most recent simultaneous analysis (Schulmeister 2003c). The results of this analysis were, in turn, used to make inferences about the evolution of the male reproductive organs, discussed in Schulmeister (2003d).
For the future, I am planning to extend my study of the male reproductive system to the Apocrita, particularly the Aculeata.
Terminology and Ontology
I reviewed 180 years of terminology used to describe the morphology of the male terminalia. The gist of this can be found in Schulmeister (2001) and I am planning to publish the complete terminological review later. I also compiled a thesaurus of the terms used for male genitalia, which I want to publish some time in the future.
I am now part of an effort to establish a "Hymenoptera Ontology", a controlled vocabulary of morphological terms for Hymenoptera. For more information, follow the link to the Hymenoptera Ontology homepage.
Evolution of strophandry and mating positions of Hymenoptera
In this first publication, I also discussed the evolution of orthandry, facultative strophandry, and obligate strophandry. Orthandry is the normal condition of the male genitalia, whereas strophandry is the condition in which the male external genitalia are rotated by 180 degrees during the last stages of development, so that the male external genitalia are carried upside down throughout adulthood. This is found in Xyelinae (Xyela and Pleroneura) and Tenthredinoidea s.str. and allows them to copulate standing on the substrate, end-to-end with the female. All other hymenopterans are orthandrous; for most of them this means that the male is on top of the female during copulation and bends his abdomen around to bring the upside down (known about Siricidae, Xiphydriidae, and many apocritans). However, Macroxyelinae and Pamphiliidae, in spite of being orthandrous, have been observed to copulate in strophandrous manner, end-to-end, which they achieve by rotating their genitalia shortly before or during copulation. I termed this facultative strophandry, as opposed to obligate strophandry as in Xyelinae and Tenthredinoidea s.str. In the paper, I optimized the three states on the hymenopteran tree and concluded that the state of the most recent common ancestor of all Hymenoptera is ambiguous. However, I know think that I must have made an error. The cladogram below shows the correct most parsimonious scenario. The color yellow represents orthandry, green stands for faculative strophandry, and blue for obligate strophandry. Grey stands for lineages which have unrotated genitalia, but it is not known whether they are obligately orthandrous or facultatively strophandrous. The most recent common ancestor of all hymenopterans is assumed to have been facultatively strophandrous.
However, the optimization of this character stands and falls with the unknown states. Even though the copulation posture of many outgroup taxa is known, I have coded them as unknown here, because I don't have enough information to infer the condition at the base of the Coleopterida and of the Mecopterida. Apart from that, I am not sure how to compare the copulation postures of hymenopterans and other holometabolans. Knowing the copulation posture of the Blasticotomidae could change the conclusion. (Since there are so many factors of uncertainty in this, I decided no to publish this as an erratum in Acta Zoologica, but rather here on my website. If you have information on the copulation posture of any holometabolan taxon, please let me know.)
Schulmeister, S., 2003d: Genitalia and terminal abdominal segments of male basal Hymenoptera (Insecta): morphology and evolution. Organisms, Diversity and Evolution 3: 253-279.