FIGURE 1. (A) Schematic line drawing of the secondary structure of the 5'-half of LSU 28S rRNA from the beetle Tenebrio sp. (redrawn from Gillespie et al. 2004). The shaded region shows the expansion segment D2 that was analyzed in this study. (B) Secondary structure model of the expansion segment D2 of the nuclear large subunit (28S) rRNA gene from Caenocholax fenyesi texensis (Texas locale). Bolded nucleotides depict variable characters in C. f. waloffi (Vera Cruz locale) with alternative states coloured red (and green where variation across individuals was detected). Blue helices depict structures strongly expanded in Strepsiptera. Helices in dark-lined boxes depict conserved helices across all arthropods. Helices in shaded boxes depict basepairs that are supported by both comparative evidence and thermodynamics. Basepairs within dash boxes illustrate support for one model (thermodynamics) that is not supported by comparative evidence across all sequences. Base-pairing is indicated as follows: standard canonical pairs by lines (C-G, G-C, A-U, U-A); wobble pairs by dots (G·U, U·G.); A-G pairs by open circles (A°G, G°A); other non-canonical pairs by filled circles (e.g. C•A). Gaps (-) represent insertions or deletions. Diagram was generated manually in Adobe Illustrator.