Corresponding author: Francisco Hita Garcia (
Academic editor: B. Fisher
New technologies for imaging and analysis of morphological characters offer opportunities to enhance revisionary taxonomy and better integrate it with the rest of biology. In this study, we revise the Afrotropical fauna of the ant genus
Hita Garcia F, Fischer G, Liu C, Audisio TL, Economo EP (2017) Next-generation morphological character discovery and evaluation: an X-ray
The primary goal of taxonomic science is to organize life by developing hypotheses delimiting species and higher groups (
Micro-CT is a powerful imaging technology that enables the generation of high-resolution, virtual, and interactive 3D reconstructions of whole specimens or parts thereof. Such reconstructions can be virtually rotated, sectioned, measured, and dissected, thus allowing a comprehensive 3D analysis of the anatomy and morphology of the studied organisms (e.g.
Compared to traditional methods like histology, the use of
Compared to other insect groups, ant taxonomy is thoroughly founded on the morphology of the very simplified worker caste. Despite that several authors also examine reproductive castes (e.g.
The ant genus
A taxonomic problem commonly encountered in doryline ants is the existence of two or even three parallel taxonomic systems: a female-based one, which often splits into worker-based and queen-based, and a male-based one (e.g.
In this study, we provide a taxonomic revision of the genus for the Afrotropical region on the basis of the worker caste. All three species treated herein are newly described. The taxonomic decision-making was founded on the examination of all physical specimens, as well as on 3D volume reconstructions of high-resolution
Institutional museum collection abbreviations follow
The general terminology for ant morphology predominantly follows
All raw images were taken with a Leica DFC450 camera attached to a Leica M205C microscope and Leica Application Suite (version 4.1). The raw photo stacks were then processed to single montage images with Helicon Focus (version 6). All montage images used in this publication are available online and can be seen on AntWeb. Vector illustrations were created with Adobe Illustrator (version CS 5) by tracing specimen photographs.
We measured 17 physical workers with a Leica M125 equipped with an orthogonal pair of micrometers under magnifications of 80 to 100 ×. Measurements and indices are presented as minimum and maximum values with arithmetic means in parentheses. In addition, measurements are expressed in mm to two decimal places. Since the workers of all three species treated herein are eyeless we omit any eye measurements and do not generate an ocular (or eye) index. We refrain from using total length since it is difficult to measure in already dry-mounted specimens that are not orientated in a straight line. The standard measurements
Schematic line drawings illustrating the measurements used in this study.
Micro-CT scans were performed using a ZEISS Xradia 510 Versa 3D X-ray microscope and the ZEISS Scout and Scan Control System software (version 10.7.2936). The scanned specimens were left attached to their paper point, which was clamped to a holding stage. Scan settings were selected according to yield optimum scan quality: optical magnification of 4 ×, exposure times of 1–3 s, binning of two by two pixels, source filter “air”, voltage of 35–85 keV, power of 3–7.5 W, current of 71–88 μA, and field mode “normal”. The combination of voltage, power and exposure time was set to yield intensity levels of between 10,000 and 15,000 across the whole specimen. Scanning duration varied from 1.2 to 2.2 h, depending on exposure time. Full 360 degree rotations were done with a number of 1601 projections. The resulting scans have resolutions of 1013 × 1013 pixels and voxel sizes are in range of 0.94–4.6 μm. The original file size was 3113.577 MB for all scans. We scanned a varying number of specimens per species, depending on specimen availability and character suitability. An overview of the specimens used and scanning settings is provided in Table
Data summary for
Species | Body part scanned | Specimen identifier | voxel size (μm) | exposure time (s) | Power (W) | Voltage (kV) | Amperage (μA) |
---|---|---|---|---|---|---|---|
|
full body |
|
3.003 | 2 | 3 | 40 | 75 |
|
head |
|
0.945 | 3 | 6 | 70 | 85 |
|
mesosoma |
|
1.604 | 2 | 5 | 55 | 82 |
|
metasoma |
|
1.952 | 2 | 4 | 50 | 80 |
|
full body |
|
4.606 | 1.8 | 4 | 50 | 81 |
|
mouthparts |
|
0.945 | 3 | 6 | 65 | 84 |
|
full body |
|
3.861 | 2 | 3 | 40 | 76 |
|
head |
|
1.267 | 3 | 5 | 60 | 83 |
|
mesosoma |
|
1.931 | 2 | 4 | 50 | 80 |
|
metasoma |
|
2.834 | 1 | 4 | 45 | 78 |
|
full body | MCZ-ENT-00512764 | 3.137 | 2.5 | 3 | 35 | 71 |
|
head | MCZ-ENT-00512764 | 0.965 | 3 | 6 | 70 | 86 |
|
mesosoma | MCZ-ENT-00512764 | 1.292 | 2.7 | 5 | 55 | 82 |
|
metasoma | MCZ-ENT-00512764 | 2.312 | 2 | 4 | 45 | 78 |
3D reconstructions of the resulting scans were done with XMReconstructor (version 10.7.2936) and saved in DICOM file format (default settings; USHORT 16 bit output data type). Post-processing of DICOM raw data was performed with Amira software (version 6.1.1). Virtual examinations of 3D surface models were performed by using either the “volren” or “volume rendering” functions. The desired volume renderings were generated by adjusting colour space range to a minimum so that the exterior surface of specimens remained visible at the highest available quality. The 3D models were rotated and manipulated to allow a complete virtual examination of the scanned specimens. Images of shaded surface display volume renderings were made with the “snapshot” function at the highest achievable resolution (usually at around 1500 by 893 pixels). Volumetric surface rendering rotational videos of head, mesosoma, metasoma, and full body scans were created with the “camera path” object (5–10 keyframes, constant velocity for constant rotation speed) and “movie maker” function (parameters: MPEG format, AntiAlias2, total of 1200 frames at 60 frames per second, and resolution of 1920 × 1080 pixels).
In addition to the traditional morphological examination of the physical specimens under a light microscope with magnifications up to 100 ×, we virtually examined the full external morphology of the treated species in Amira. For this we compared more than 50 morphological characters potentially significant for dorylines (
List of all important characters examined in this study with assessment of diagnostic potential and information on usage in this study (characters marked with * were used for species delimitations).
Characters examined | Diagnostic assessment and usage |
---|---|
|
|
Shape of head in full-face view | none, no significant interspecific variation observed, not used in this study |
Shape of head in profile * | high, used in this study |
Shape of mandibles | none, no significant interspecific variation observed, not used in this study |
Mandibular dentition | none, no significant interspecific variation observed, not used in this study |
Shape of clypeus | low, no significant interspecific variation observed, not used in this study |
Presence of median clypeal tooth * | high, used in this study |
Cuticular apron of clypeus | none, no significant interspecific variation observed, not used in this study |
Torulo-posttorular complex * | high, used in this study |
Antennal bulbus | none, no significant interspecific variation observed, not used in this study |
Antennal scapes * | high, used in this study |
Antennal pedicel and funiculus | none, no significant interspecific variation observed, not used in this study |
Anterior tentorial pits | none, no significant interspecific variation observed, not used in this study |
Parafrontal ridges * | high, used in this study |
Eyes | none, absent in the worker caste |
Vertex * | high, used in this study |
Occipital margin in posterodorsal view * | high, used in this study |
Occiput in posterior view * | high, used in this study |
Occipital margin in posteroventral view * | high, used in this study |
Hypostoma * | high, used in this study |
Mouthparts (maxillae, labium, labrum) | unclear, none in closed in condition; described in open condition for |
Tentorium (internal) | unclear, tentatively examined in this study and appears species-specific, but needs further investigation with better preserved alcohol material for μCT scanning |
|
|
Mesosoma in profile * | high, used in this study |
Endosternum (internal) | unclear, tentatively examined in this study and appears species-specific, but needs further investigation with better preserved alcohol material for μCT scanning |
Transverse mesopleural groove | moderately variable among species, not used in this study |
Propleuron | none, no significant interspecific variation observed, not used in this study |
Pleural endophragmal pit * | high, used in this study |
Mesopleuron | moderately variable among species, not used in this study |
Metapleuron | low, no significant interspecific variation observed, not used in this study |
Mesosoma dorsal * | high, used in this study |
Probasitarsus | low, no significant interspecific variation observed, not used in this study |
Calcar of strigil | low, no significant interspecific variation observed, not used in this study |
|
|
Levator of petiole | unclear, not examined in this study, very difficult to virtually dissect |
Petiolar tergum in profile * | high, used in this study |
Laterotergites | low, no significant interspecific variation observed, not used in this study |
Subpetiolar process of petiolar sternum in profile * | high, used in this study |
Petiolar tergum in dorsal view * | high, used in this study |
Disc of petiole | none, no significant interspecific variation observed, not used in this study |
Subpetiolar process in ventral view * | high, used in this study |
Helcium | unclear, not examined in this study |
Abdominal segment III in dorsal view * | high, used in this study |
Abdominal segment III in ventral view * | high, used in this study |
Posterior end of abdominal segment III in ventral view * | high, used in this study |
Prora in anteroventral view * | high, used in this study |
Abdominal segment IV in dorsal view | moderate, relatively variable within species, not used in this study |
Abdominal segment IV in ventral view | moderate, relatively variable within species, not used in this study |
Abdominal segment V in dorsal view | low, no significant interspecific variation observed, not used in this study |
Abdominal segment V in ventral view | low, no significant interspecific variation observed, not used in this study |
Abdominal segment VI in dorsal view * | high, used in this study |
Abdominal segment VI in ventral view | high, not used in this study |
Girdling constrictions abdominal segments IV, V, VI * | high, used in this study |
Pygidium | low, no significant interspecific variation observed, not used in this study |
Hypopygium | low, no significant interspecific variation observed, not used in this study |
Spiracles abdominal segments II-VII | none, no significant interspecific variation observed, not used in this study |
General surface sculpture * | high, used in this study |
Cuticle thickness (internal) | unclear, examined in this study but needs further investigation with more specimens |
In addition to the taxonomic standard measurements of external morphology given above, we also measured the thickness of the exoskeleton cuticle of the cephalic capsule, the pronotum, and abdominal segments II (petiole) and III. Measuring was performed with Amira by using the 2D measuring tool on slices representing sagittal sections along the median axis of the chosen body parts. For each body part, we measured five times over a defined area (Fig.
Cephalic capsule cuticle thickness (
Dorsal pronotum cuticle thickness (
Dorsal abdominal segment II (petiole) cuticle thickness (
Dorsal abdominal segment III cuticle thickness (
Cephalic capsule cuticle thickness index (
Dorsal pronotum cuticle thickness index (
Dorsal abdominal segment II (petiole) cuticle thickness index (
Dorsal abdominal segment III cuticle thickness index (
Microtomographic slides showing cuticle thickness measurements (with measuring lines in white).
The first step to creating unicoloured 3D PDFs was to make 3D renderings of ant specimens in Amira using the Isosurface function (deselect compactify) for exporting surface meshes in the STL file format. These were imported into Meshlab (version 1.3.3) where the number of vertices per specimen was reduced in three steps to decrease total file size and before importing into Adobe Acrobat. First, the scan files were cleaned from isolated vertices (Filters > Cleaning and Repairing > Remove isolated pieces (wrt diameter) [set max diameter: 0.05–1%]) and the paper tips on which the ants are mounted were digitally removed as much as possible. The next step removed all internal vertices so that only the exoskeleton remained (1. Filters > Color Creation and Processing > Ambient Occlusion Per Vertex; 2. Filters > Selection > Select Faces By Vertex Quality (min = 0, max = 0.001); 3. Remove Selected Faces). In the last step, the number of total vertices was reduced to the final number of <750,000 (Filters > Remeshing, Simplification and Reconstruction > Quadratic Edge Collapse Decimation) in order to get a manageable resolution resulting in 3D PDF files of approximately 20 MB in size for supplementary files (the final step was omitted for files uploaded to Dryad). The processed STL files were annotated and exported as 3D PDFs in Adobe Acrobat Pro DC (version 2015.006.30119) using the Tetra4D Converter plug-in (version 5.1.2). When viewing the 3D PDFs with Adobe Acrobat Reader (version 8 or higher), trusting the document by clicking on the image will activate the interactive 3D-mode and allows rotating, moving and zooming into the 3D model.
To generate the coloured 3D PDF of the mouthparts, we first segmented each mouthpart (maxillae, labium, labrum) independently and labelled each with a different colour. A surface mesh of the combined segmentation data was then generated using Generate Surface function in Amira with Unconstrained Smoothing (Smoothing Extent set to 1.5). We exported the surface data into Open Inventor Format, where it was converted to U3D format using IvTuneViewer plugged in Amira. Finally, the 3D PDF was generated by importing the U3D file to Adobe Acrobat Pro DC (version 2015.006.30119) with Tetra4D plugged in (version 5.1.2).
All specimens used in this study have been databased and the data is freely accessible on AntWeb (
At the beginning of our study we encountered a situation in which the only two valid species from the region were described from males from West Africa (
These discrepancies led us to describe the three worker-based species independently from the already known male-based species and create a comprehensive worker-based taxonomic system for the genus in the Afrotropical region. With this approach, we follow
The following diagnosis is based on
HEAD: Antennae with 12 segments and relatively short (
MESOSOMA: Mesosoma in profile relatively low and elongate to moderately high and stocky (
LEGS: Mesotibia with single pectinate spur. Metatibia with single pectinate spur. Metabasitarsus not widening distally, circular in cross-section. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland an oval patch of whitish cuticle. Metabasitarsal gland absent. Pretarsal claws of metatibia simple. Metafemur short to moderately long (MFI 75–100).
METASOMA: Abdominal segment II (petiole) sessile without peduncle and petiolar node well developed. In profile petiolar tergum between 1.0 to 1.2 times longer than high (
SETATION: Most of body with numerous short to moderately long, appressed to suberect (very rarely erect) setae. Pygidium armed with modified, thick, and often peg-like setae. Hypopygium armed with modified setae.
COLOURATION: All known species predominantly dark brown to black with often lighter appendages.
* Only known from males and not treated in this study.
Based on a thorough examination of external morphology and character evaluation, we provide the following character matrix (Table
Character matrix showing all diagnostic characters used for worker-based species delimitation system of Afrotropical
Species |
|
|
|
---|---|---|---|
|
appearing longer and thinner (Fig. |
appearing shorter and thicker (Fig. |
appearing longer and thinner (Fig. |
|
without conspicuous median tooth (Fig. |
with conspicuous median tooth (Fig. |
without conspicuous median tooth (Fig. |
|
dorsal outline irregularly convex and conspicuously thickened (Fig. |
dorsal outline regularly convex and not conspicuously thickened (Fig. |
dorsal outline mostly regularly convex and conspicuously thickened (Fig. |
|
comparatively thicker and shorter (Fig. |
comparatively thinner and longer (Fig. |
comparatively thicker and shorter (Fig. |
|
scape thicker: 2.2 to 2.4 times longer than broad at apex (SI2 215–242) (Fig. |
scape moderately thick: 2.4 to 2.6 times longer than broad at apex (SI2 238–261) (Fig. |
scape thinner: 2.7 times longer than broad at apex (SI2 267) (Fig. |
|
vertexal margin and posterior face of head strongly developed (Fig. |
vertexal margin and posterior face of head weakly developed (Fig. |
vertexal margin and posterior face of head strongly developed (Fig. |
|
outline sharp and irregularly defined (Fig. |
outline sharp and very regularly defined (Fig. |
outline weakly and irregularly defined (Fig. |
|
posterior and ventral margins similarly broad; ventral margin medially protruding (Fig. |
more ellipsoid; posterior and ventral margins similarly broad; ventral margin not medially protruding (Fig. |
posterior clearly broader than ventral margin; ventral margin weakly medially protruding (Fig. |
|
outline sharp and irregularly defined (Fig. |
outline sharp and very regularly defined (Fig. |
outline moderately sharp and irregularly defined (Fig. |
|
less diverging with relatively thin and mostly rounded lateral arms (Fig. |
strongly diverging with very thick and strongly rounded lateral arms (Fig. |
strongly diverging with moderately thick and strongly angulate lateral arms (Fig. |
|
relatively lower and elongate ( |
moderately higher and compact ( |
relatively lower and elongate ( |
|
weakly developed and shallow but visible (Fig. |
strongly developed and deep (Fig. |
very weakly developed and inconspicuous (Fig. |
|
appearing thinner ( |
appearing thicker ( |
appearing intermediate ( |
|
relatively lower: 1.2 times longer than high ( |
relatively higher: 1.0 to 1.1 times longer than high ( |
relatively higher: 1.1 times longer than high ( |
|
with thickened anterior and ventral margins and well developed concavity with differentiated fenestra (Fig. |
with thickened anterior and ventral margins and well developed concavity with differentiated fenestra (Fig. |
with thickened anterior and ventral margins and weak concavity without differentiated fenestra (Fig. |
|
relatively thinner: around 1.2 times longer than broad ( |
relatively thicker: around 1.0 to 1.1. times broader than long ( |
relatively thinner: around 1.1 times longer than broad ( |
|
forklike, ventral margin very thick and short (Fig. |
forklike, ventral margin moderately thick and short (Fig. |
forklike, ventral margin thin and long (Fig. |
|
appearing more trapezoidal with anterior margin more angulate (Fig. |
appearing more rounded with anterior margin usually more rounded (Fig. |
appearing more trapezoidal with anterior margin more angulate (Fig. |
|
comparatively thinner, longer, and only gently narrowing towards prora (Fig. |
comparatively broad, short and strongly narrowing towards prora (Fig. |
comparatively broad, short and moderately narrowing towards prora (Fig. |
|
with thick, deep, sharply and irregularly outlined transverse groove (Fig. |
with thinner, deep, sharply and relatively regularly outlined transverse groove (Fig. |
transverse groove absent, instead with irregular grooves and rugosity (Fig. |
|
well-developed with thick, irregularly shaped and rounded lateroventral margins (Fig. |
well-developed with sharply and very regularly shaped lateroventral margins (Fig. |
very weak to almost absent lateroventral margins (Fig. |
|
distinctly longer: 1.7 times broader than long ( |
distinctly shorter: around 1.9 to 2 times broader than long ( |
distinctly longer: 1.6 times broader than long ( |
|
unsculptured (Fig. |
cross-ribbed, much weaker on IV than V & VI (Fig. |
unsculptured (Fig. |
|
mostly smooth and shining with abundant, relatively deep piliferous punctures, except for reticulate-punctate anteromedian area of cephalic dorsum, anterior pronotum, mesopleuron, lateral propodeum, most of lateral petiole, and hypopygium | almost completely smooth and very shining with scattered, relatively deep piliferous punctures; sometimes with punctate sculpture on metapleuron | cephalic dorsum mostly reticulate-rugose, mesosoma and petiole laterally mostly reticulate-punctate, hypopygium reticulate-rugose, remainder of body predominanly smooth and shining with abundant piliferous punctures |
1 | With head in full-face view median clypeal area with conspicuous tooth (Fig. |
|
– | With head in full-face view median clypeal area without any tooth (Fig. |
2 |
2 | With head in full-face view parafrontal ridges with irregularly shaped dorsal outline (Fig. |
|
– | With head in full-face view parafrontal ridges with regularly shaped dorsal outline (Fig. |
|
Map of sub-Saharan Africa showing the known distribution of the
3D rotation video of
See Table
See Table
Morphometric data of the three species treated in this study.
Min | Max | Mean | Min | Max | Mean | ||
---|---|---|---|---|---|---|---|
|
0.55 | 0.59 | 0.56 | 0.78 | 0.90 | 0.86 | 0.60 |
|
0.44 | 0.47 | 0.45 | 0.64 | 0.77 | 0.73 | 0.49 |
|
0.26 | 0.31 | 0.28 | 0.41 | 0.50 | 0.48 | 0.32 |
|
0.12 | 0.14 | 0.13 | 0.17 | 0.21 | 0.19 | 0.12 |
|
0.26 | 0.29 | 0.27 | 0.44 | 0.52 | 0.49 | 0.32 |
|
0.28 | 0.33 | 0.30 | 0.47 | 0.55 | 0.52 | 0.35 |
|
0.53 | 0.65 | 0.59 | 0.85 | 0.99 | 0.95 | 0.66 |
|
0.73 | 0.81 | 0.77 | 1.08 | 1.30 | 1.22 | 0.87 |
|
0.33 | 0.37 | 0.35 | 0.58 | 0.69 | 0.64 | 0.49 |
|
0.27 | 0.29 | 0.28 | 0.40 | 0.47 | 0.44 | 0.29 |
|
0.22 | 0.24 | 0.23 | 0.39 | 0.45 | 0.42 | 0.26 |
|
0.23 | 0.26 | 0.24 | 0.41 | 0.50 | 0.47 | 0.27 |
|
0.33 | 0.39 | 0.36 | 0.50 | 0.59 | 0.55 | 0.48 |
|
0.38 | 0.43 | 0.41 | 0.56 | 0.67 | 0.63 | 0.43 |
|
0.26 | 0.29 | 0.28 | 0.41 | 0.56 | 0.50 | 0.31 |
|
0.46 | 0.52 | 0.49 | 0.71 | 0.83 | 0.79 | 0.54 |
|
0.25 | 0.29 | 0.27 | 0.40 | 0.49 | 0.45 | 0.32 |
|
0.47 | 0.52 | 0.49 | 0.71 | 0.85 | 0.80 | 0.55 |
|
0.26 | 0.30 | 0.28 | 0.36 | 0.41 | 0.39 | 0.32 |
|
0.45 | 0.49 | 0.47 | 0.67 | 0.78 | 0.73 | 0.51 |
|
78 | 80 | 80 | 82 | 86 | 84 | 82 |
|
47 | 53 | 50 | 53 | 57 | 55 | 53 |
|
215 | 242 | 228 | 238 | 261 | 247 | 267 |
|
38 | 40 | 39 | 41 | 44 | 42 | 40 |
|
49 | 53 | 51 | 53 | 58 | 55 | 53 |
|
34 | 36 | 36 | 40 | 41 | 40 | 37 |
|
75 | 79 | 77 | 88 | 91 | 89 | 100 |
|
117 | 123 | 120 | 102 | 112 | 105 | 112 |
|
82 | 93 | 88 | 101 | 111 | 105 | 93 |
|
108 | 115 | 112 | 112 | 117 | 114 | 90 |
|
170 | 181 | 176 | 145 | 173 | 159 | 174 |
|
174 | 188 | 180 | 167 | 181 | 177 | 172 |
|
163 | 173 | 169 | 186 | 197 | 189 | 159 |
This species is named in honour of Barack Hussein
Illustrated diagnostic character matrix based on
Illustrated diagnostic character matrix based on
Illustrated diagnostic character matrix based on
Shaded surface display volume renderings of 3D models of
DEMOCRATIC REPUBLIC OF CONGO: Epulu,
See Table
See Table
The name of the new species is a patronym in honour of the famous Nigerian writer, environmentalist, and human rights activist Kenule Beeson “Ken” Saro-Wiwa. By naming a species from threatened rainforest habitats after him, we want to acknowledge his environmental legacy and draw attention to the often-problematic conservation situation in most Afrotropical rainforests.
The new species has a comparatively wide distribution ranging from Ivory Coast to Uganda, even though it is not known from all countries in-between. However, this is likely based on a sampling artefact considering the rarity of
Shaded surface display volume renderings of 3D models of
3D rotation video of
See Table
See Table
This new species is dedicated to the renowned scientist, author, and conservationist Edward O. Wilson from Harvard University in honour of his more than six decades of accomplishments to the fields of myrmecology, sociobiology, biodiversity, and conservation.
Currently,
Shaded surface display volume renderings of 3D models of
3D rotation video of
The small number and the preservation conditions of the specimens available for this study provided some limitations for the examination of mouthparts. It was not possible to dissect in vivo or
Shaded surface display volume renderings of 3D models of mouthparts (excluding mandibles) in closed configuration (green=maxillae; yellow=labrum; orange=labium).
Volumetric 3D model of segmented surface reconstructions of the mouthparts of
3D rotation video of segmented surface reconstructions of the mouthparts of
The results of our cuticle thickness data are provided in Table
Morphometric data generated from 3D measuring cuticle thickness. For each species the five raw measurements with corresponding calculations into indices are given, as well as mean values and standard deviations (
Species |
|
|
|
|||
---|---|---|---|---|---|---|
in mm |
|
in mm |
|
in mm |
|
|
0.019 | 41 | 0.022 | 30 | 0.014 | 29 | |
0.018 | 41 | 0.023 | 32 | 0.014 | 29 | |
0.019 | 41 | 0.022 | 29 | 0.016 | 32 | |
0.021 | 47 | 0.024 | 33 | 0.017 | 34 | |
0.022 | 49 | 0.023 | 31 | 0.015 | 30 | |
MEAN | 0.019 |
|
0.023 |
|
0.015 |
|
|
0.001 | 3 | 0.001 | 1 | 0.001 | 2 |
in mm |
|
in mm |
|
in mm |
|
|
0.017 | 37 | 0.027 | 36 | 0.018 | 38 | |
0.017 | 38 | 0.027 | 36 | 0.020 | 40 | |
0.016 | 36 | 0.025 | 34 | 0.019 | 39 | |
0.016 | 35 | 0.029 | 39 | 0.020 | 41 | |
0.015 | 34 | 0.030 | 40 | 0.021 | 42 | |
MEAN | 0.016 |
|
0.027 |
|
0.020 |
|
|
0.001 | 1 | 0.002 | 2 | 0.001 | 1 |
in mm |
|
in mm |
|
in mm |
|
|
0.013 | 29 | 0.025 | 33 | 0.017 | 34 | |
0.014 | 31 | 0.026 | 35 | 0.019 | 39 | |
0.016 | 35 | 0.027 | 37 | 0.020 | 41 | |
0.013 | 29 | 0.026 | 35 | 0.020 | 42 | |
0.014 | 31 | 0.030 | 40 | 0.020 | 40 | |
MEAN | 0.014 |
|
0.027 |
|
0.019 |
|
|
0.001 | 2 | 0.002 | 2 | 0.001 | 3 |
in mm |
|
in mm |
|
in mm |
|
|
0.013 | 29 | 0.022 | 30 | 0.018 | 37 | |
0.015 | 33 | 0.029 | 39 | 0.018 | 37 | |
0.013 | 29 | 0.021 | 29 | 0.017 | 34 | |
0.016 | 36 | 0.022 | 30 | 0.017 | 35 | |
0.013 | 30 | 0.020 | 28 | 0.019 | 38 | |
MEAN | 0.014 |
|
0.021 |
|
0.018 |
|
|
0.001 | 3 | 0.003 | 4 | 0.001 | 1 |
Based on our virtually reconstructed and segmented data, we can show that the mesosoma and metasoma both contain high degrees of musculature (Fig.
Still images of 3D model of full body of
Almost all previous studies that used
Comparison of full body scan versus single body part scans based on
3D rotation video of full body of
The visualised reconstruction of the mouthparts provides a comparatively adequate and detailed 3D model of the maxillae, labium, and labrum, but also presents some important limitations. The general morphology of maxillae, labium and labrum are well recovered, and they are very similar to the mouthparts of
Nevertheless, there are some problems with our 3D reconstructed model. The most problematic structure is the glossa. As already pointed out by
Another important limitation is that not all structures could be satisfactorily outlined during the segmentation process. This was especially difficult for the delineation of some components, such as the cardo, the lacinial comb, the regions where labium and maxillae meet, and generally everywhere where membranous and chitinous tissues are in contact. These problems are caused by scanning a dry mounted specimen, in which most internal structures have undergone desiccation, shrinkage, and deformation. In such specimens, the dissimilarities in density and contrast between different tissues or components are minimal to zero, thus causing significant problems for the proper recognition and subsequent outlining of borders between structures. In general, our 3D reconstructed model provides fewer details compared to histological dissections. However, these problems might be solvable in future studies if specimens are preserved and prepared in a way more suitable for
The application of
As pointed out in previous studies, a crucial advantage of using 3D models based on
One aim of this study was to evaluate new taxonomic characters for species level taxonomy on the basis of traditional morphological analysis and virtual examination of 3D reconstructions. Unfortunately, only dry mounted material was available for this study. As pointed out in
Initially, our intention was to omit a species identification key, which may appear counterintuitive and substandard. However, there are several problems with dichotomous identification keys that lead us to take a different approach in this study. Identification keys for well-studied regions, such as Japan and Central Europe, generally work well and are very stable since new species are rarely encountered and nomenclatorial benchmarking is rare. This is certainly not the case for most tropical and subtropical regions because our knowledge of the local and regional diversity is fragmentary to non-existent. One major limitation of keys for such regions is that they usually only work for the known species at the time of publication. Later discoveries of new species render keys less useful and often less reliable for identification purposes. To avoid this, it is necessary to update older keys in additional publications after new species are discovered, as done by Hita Garcia and Fischer (2014) to update
In the case of
Furthermore, the characters chosen are suited for diverse audiences with different interests and resources. For users with limited microscopy resources or little taxonomic training, we have included many easy-to-examine characters that are visible at lower magnifications, such as the shapes of head, mesosoma, or abdominal segment II in profile (e.g. Figs
As outlined above, compared to the taxonomy of most insect groups, the character sets used in the field of ant worker taxonomy are very often rather limited and rely heavily on setation, sculpture, body size, and colour. These are often problematic since they can be highly variable within species and prone to geographic variability, such as shown for the Neotropical
For the revision of Afrotropical
Furthermore, the use of virtually reconstructed 3D models permits a quick and effective use of time and resources. Dissections and manipulations of physical specimens are usually very time-consuming, especially if histology and SEM are involved. By contrast, the application of
As already discussed in previous studies employing
As outlined above, there is no knowledge of the natural history of Afrotropical
As mentioned above, all three Afrotropical
In
Our study highlights the potential of in-depth comparative morphology analyses for taxonomy founded on a combined investigation of physical specimens under light microscopy and virtual 3D models generated from
Furthermore, considering the lack of material and apparent rarity of Afrotropical
In general, even though it often appears as if the modern era of molecular systematics has dwarfed the importance of morphology-based systematics, we strongly concur with previous authors that by embracing and employing new technologies, such as
First, we want to thank Eli M. Sarnat for his suggestion at the initial stage of this study to present taxonomic data in a different way, which strongly influenced the direction of this study, and for providing very helpful comments and points of critique to a previous version of this manuscript. We thank Kenneth Dudley for the generation of the map used in this study. We are very thankful to Peter G. Hawkes from Pretoria, South Africa, Suzanne Ryder from
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