Tribe Acalyptaini (Hemiptera: Tingidae: Tinginae) Revisited: Can Apomorphies in Secondary and Tertiary Structures of 18S rRNA Length-Variable Regions (LVRs) Support Tribe Validity?

SIMPLE SUMMARY: The small subunit (SSU) of the nuclear ribosomal DNA that codes 18S rRNA is one of the most frequently sequenced genes in phylogenetic analyses of true bugs (Hemiptera: Heteroptera). However, no studies have been identified that use this method with lace bugs (Tingidae). Furthermore, the secondary and tertiary structures of the 18S rRNA have not been described nor used to interpret relationships among lace bug taxa. The number of nucleotides and shapes of the 18S rRNA length-variable regions (LVRs) have been confirmed to be phylogenetically informative; therefore, we verified their usefulness in resolving the validity issues within the Acalyptaini tribe. ABSTRACT: The lace bug tribe Acalyptaini (Tingidae: Tinginae) includes five genera, Acalypta, Derephysia, Dictyonota, Kalama, and Recaredus, and it was recently resurrected based on morphological and karyological characters. We aimed to validate the distinctiveness of this tribe using 18S rDNA sequences, which have not been used in previous Tingidae phylogenomic studies. Our results confirmed the monophyly of the tribe. Moreover, the monophyly of the subfamily Cantacaderinae and its basal position within the family Tingidae were indicated, as well as the position of the tribe Litadeini as sister to all other Tinginae. In addition, we attempted to determine the apomorphic morpho-molecular characters in the secondary and tertiary structures of length-variable regions of the 18S rRNA sequences of the analysed species. The results showed that two LVRs (LVR X and LVR L) of the hypervariable region V4 exhibited significant variability in the number of nucleotides and could be considered for apomorphic recognition.