The results provide first insights into the phylogeny of the family Lentulidae. The clear split between the two main clades was highly supported. However, this split does not reflect the current subdivision into the two subfamilies Lentulinae and Shelforditinae. Even though the two Shelforditinae genera Leatettix and Uvarovidium clustered as a monophylum, they showed a clear sister group relationship to the genus Devylderia (Lentulinae). This could mean that either Devylderia belongs to Shelforditinae as well or that the current taxonomy within the complete family needs to be revised. A broader taxon sampling across all described lentulid genera would provide more precise information on the systematic relationships of the genera and clarify the assignments to the respective subfamilies. The East African Usambilla group is likely to represent a sister clade to Lentula and Eremidium, confirming their systematic position within the subfamily Lentulinae. This also suggests that the Lentulidae as a whole originated in South Africa and started to diversify here, before one group (the ancestor of the Usambilla group) spread to the north to radiate within the East African Mountain systems.
Although our sampling only covers a small fraction of the Lentulidae genera, a strong genetic differentiation between and within genera becomes already evident. In some cases, our phylogeny does not reflect the current taxonomy. This is the case for the genus Leatettix, which does not represent a monophylum, but a paraphyletic group. Otte [11] mentioned in his revision of Leatettix that further division of Leatettix species into different genera might be necessary. As Leatettix emota from Cederberg are closer related to U. peninsulare than to Leatettix moraki from Swartberg and Baviaanskloof, his suggestion seems to be supported by our findings. Further morphological and genetic research is required to clarify these findings.
Recent revisions of several lentulid genera from South Africa showed that the number of Lentulidae species is much higher than currently known. In total, 44 new species and even three new genera have recently been described (Armstrongium, Tanquata, Tsautettix, [13]). The center of species richness of Lentulidae is in South Africa with 103 of the 146 described species occurring in the Cape Floristic Region [7]. Recent studies show that insect species diversity in the Cape Floristic Region is generally much higher than current taxonomy suggests [10, 14]. This seems to be particularly true for the genus Betiscoides (Matenaar et al. unpubl.), which is also confirmed in our study. Although this genus represents a monophylum, specimens from different localities showed a high genetic differentiation. All specimens used in our study would morphologically be assigned to Betiscoides meridionalis. However, the results indicate four clades of this species with high genetic differentiation, suggesting the existence of cryptic species (which is confirmed by first morphological inspection).
The reasons for the unique diversity in the Cape Floristic Region and potential drivers of differentiation and speciation have been discussed before [2, 3, 15]. Concerning insect diversity, there is a consensus about the long-term isolation of populations starting in the early Miocene [16–18]. The Cape Floristic Region experienced climatic changes during late Mio- and Pliocene and repeated orographic changes through the uplift of the Cape Fold Belt as well as oceanic regression. These changing environmental conditions probably triggered and influenced dispersal as well as survival of insect taxa in refugia. Coastal regions and mountains of the Cape Floristic Region probably functioned as refugia during unfavorable periods, whereas ocean regression repeatedly enabled taxa to disperse into lowland habitats and the interior of the Cape Floristic Region [19]. Climatic stability in mountain ranges throughout the Pleistocene is believed to have had positive effects on diversity as it supported the origin of new species while keeping extinction rates low [15, 18]. As a result, species were able to persist in montane or coastal refugia. The lack of gene flow caused by low dispersal capabilities led to high genetic differentiation within genera. As all Lentulidae are flightless, they are likely to have limited dispersal capabilities, as has been shown in the genus Betiscoides [9]. Consequently, this might also explain diversity patterns within the Lentulidae in general, even though the initial splits into several main clades or genera probably occurred much earlier. Several palaeorelictual insects of the Cape Floristic Region are known [5], suggesting that parts of the Cape Floristic Region may have served as refugia for quite a long time. Some represent ancient Gondwanan lineages. Some Lentulidae genera (Betisocoides, Devylderia) seem to be adapted to plants of typical fynbos plants, which radiated 70 my ago. The phylogeny of Orthoptera indicates that Lentulidae started radiating during that period as well [20]. It is thus unlikely that Lentulidae include ancient Gondwanan genera despite their high endemicity.