Systematics of the ant genus Proceratium Roger (Hymenoptera, Formicidae, Proceratiinae) in China – with descriptions of three new species based on micro-CT enhanced next-generation-morphology

Abstract

The genus Proceratium Roger, 1863 contains cryptic, subterranean ants that are seldom sampled and rare in natural history collections. Furthermore, most Proceratium specimens are extremely hairy and, due to their enlarged and curved gaster, often mounted suboptimally. As a consequence, the poorly observable physical characteristics of the material and its scarcity result in a rather challenging alpha taxonomy of this group. In this study, the taxonomy of the Chinese Proceratium fauna is reviewed and updated by combining examinations of traditional light microscopy with x-ray microtomography (micro-CT). Based on micro-CT scans of seven out of eight species, virtual 3D surface models were generated that permit in-depth comparative analyses of specimen morphology in order to overcome the difficulties to examine physical material of Proceratium. Eight Chinese species are recognized, of which three are newly described: Proceratium bruelheidei Staab, Xu & Hita Garcia, sp. n. and P. kepingmai sp. n. belong to the P. itoi clade and have been collected in the subtropical forests of southeast China, whereas P. shohei sp. n. belongs to the P. stictum clade and it is only known from a tropical forest of Yunnan Province. Proceratium nujiangense Xu, 2006 syn. n. is proposed as a junior synonym of P. zhaoi Xu, 2000. These taxonomic acts raise the number of known Chinese Proceratium species to eight. In order to integrate the new species into the existing taxonomic system and to facilitate identifications, an illustrated key to the worker caste of all Chinese species is provided, supplemented by species accounts with high-resolution montage images and still images of volume renderings of 3D models based on micro-CT. Moreover, cybertype datasets are provided for the new species, as well as digital datasets for the remaining species that include the raw micro-CT scan data, 3D surface models, 3D rotation videos, and all light photography and micro-CT still images. These datasets are available online (Dryad, Staab et al. 2018, http://dx.doi.org/10.5061/dryad.h6j0g4p).

A tale of scale: Plot but not neighbourhood tree diversity increases leaf litter ant diversity

“…These species are often rarely collected (e.g. cryptic species) and characterized by specialized life histories (Staab et al, ). However, plot tree diversity also seems to be beneficial for these ants, because abundance‐weighted and presence‐/absence‐based FD and PD results were congruent.…”

“…The diameter at breast height (DBH) of the target tree was recorded as a measure of tree size. Ant specimens were identified to species or morphospecies (referred to as species) with taxonomic literature and comparison with reference material (Staab, Blüthgen, & Klein, ; Staab, Hita Garcia, Liu, Xu, & Economo, ; Staab et al, ). As ant abundance, we use the sum of individuals per samples.…”

Odontomachus davidsoni sp. nov. (Hymenoptera, Formicidae), a new conspicuous trap-jaw ant from Ecuador

“…This offers morphological details of the new species to the reader and the ability to take exact trait measurements. 3D imaging techniques, and in particular micro-computed X-ray tomography (µCT), are becoming more frequently used in taxonomy and functional morphology, including studies on ants (Faulwetter et al 2013;Akkari et al 2015;Garcia et al 2017;Sarnat et al 2017;Staab et al 2018). Garcia et al (2017) provided a comprehensive overview of the benefits and caveats of µCT scans for such purposes.…”

Ants of the Hengduan Mountains: a new altitudinal survey and updated checklist for Yunnan Province highlight an understudied insect biodiversity hotspot

“…Globally, about 15,600 ant species and subspecies have been described (Bolton 2020), making them the most diverse group of social insects and one of the most diverse families of insects. Despite the fact that ant diversity is mainly concentrated within tropical regions (Dunn et al 2009;Economo et al 2018), the ant fauna of many other regions is still poorly known, especially in Asia (Guénard et al 2010). Compiling and curating comprehensive and accurate ant species checklists for these regions is essential not only for insights into ant taxonomy and systematics, but also for long-term monitoring and conservation of these ecosystems (Guénard et al 2017).…”

“…Since then, new ant inventories have been conducted (e.g. Liu et al 2015a ), as well as new species descriptions (e.g., Guénard et al 2013 ; Xu et al 2014a , b ; Liu et al 2015b ; Staab et al 2018 ), and the identification of previously dubious records have sensibly modified our understanding of Yunnan’s ant diversity and species composition. Therefore, in this study, we also provide an update to the ant species checklist of Yunnan province and discuss future trends.…”