Corresponding author: Nicole Rasoamanana (
Academic editor: M. Borowiec
The ant genus
Rasoamanana N, Csősz S, Fisher BL (2017) Taxonomic revision of imitating carpenter ants,
Malagasy
We have attempted to overcome the problem of morphological variation in the Malagasy-endemic
In terms of overcoming the challenges of historical names, our work builds on 15 years of tracking down type material of all Malagasy taxa from across European collections to assess the identity of previous descriptions in relation to more recently collected material. Although we are still missing a small percentage of
Lastly, this work does not address the issue of the unnatural subgeneric classification for the genus which is better addressed with molecular phylogenetic methods and global sampling. Instead, for this revision, we retain the historic subgenus
All species are described here based on the worker caste, and the key provided combines qualitative characters and morphometric ratios that will help resolve the most problematic cases. Distribution maps are also provided.
The morphometric analysis was based on 130 workers principally collected by B.L. Fisher and the Madagascar Biodiversity Center team in 74 collecting events across Madagascar. Specimen data and images for material examined in this study is available on AntWeb (
Digital color montage images were created using a JVC KY-F75 digital camera and Syncroscopy Auto-Montage software (version 5.0), or a Leica DFC 425 camera in combination with the Leica Application Suite software (version 3.8).
Distribution maps for all species were generated by importing specimen distribution records into the Diva-GIS program (
Measurements were taken with a Leica MZ 9.5 stereomicroscope equipped with a cross-scaled ocular micrometer. Each worker was evaluated using 19 continuous morphometric traits, measured as in
Definitions and abbreviations for the measured characters are as follows (see Figure
Illustrations of measurements used to distinguish members of
Altogether 130 worker individuals (96 minor and 34 major workers) were measured and analyzed using multivariate statistics based on the protocol described by
Thanks to the higher number of minor workers (96 were minors out of 130 total) this subcaste was selected for the purpose of morphometric data analyses. Morphometric data and descriptions for major workers are also provided, but their morphometric data were not included in statistical processing.
Generation of species hypotheses by combined application of NC-PART clustering and confirmatory Linear Discriminant Analysis (
We evaluated the morphometric data recorded from 96 minor workers belonging to 66 samples. All samples represent nest series or individuals from one collecting event. We used a combined application of NC-clustering (
The optimal number of clusters and the partitioning of samples done by Partitioning Based on Recursive Thresholding (PART) were accepted as improved species hypothesis worth testing if the two clustering methods, ‘hclust’ and ‘kmeans’ via PART arrived at the same conclusion (see
Confirmatory Linear Discriminant Analysis with leave-one-out cross-validation (
The NC-PART clustering found three clusters (see numbered bars 1 (black), 2 (red) and 3 (blue) in Figure
Dendrogram solution for the Malagasy
The confirmatory Linear Discriminant Analysis with leave-one-out cross-validation (
Ratios of morphometric data for minors and majors of the four species. The means of the ratios and the standard deviations are written in bold; minimum and maximum values are shown in parentheses.
Species | Worker castes |
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PrOC/ |
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Minors (n=25) |
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[1.34, 2.18] | [0.71, 0.85] | [0.68, 0.78] | [0.22, 0.29] | [0.51, 0.57] | [0.23, 0.29] | [0.21, 0.28] | [0.16, 0.25] | [0.42, 0.51] | [1.21, 1.73] | ||
Majors (n=22) |
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[2.32, 3.94] | [0.84, 1.03] | [0.76, 0.84] | [0.24, 0.32] | [0.42, 0.56] | [0.27, 0.32] | [0.25, 0.28] | [0.21, 0.24] | [0.37, 0.42] | [0.71, 1.16] | ||
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Minors (n=2) |
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[1.80, 1.88] | [0.52, 0.54] | [0.55, 0.57] | [0.40, 0.42] | [0.40, 0.41] | [0.21, 0.23] | [0.22, 0.23] | [0.17, 0.19] | [0.40, 0.40] | [1.85, 1.88] | ||
Majors unknown | – | – | – | – | – | – | – | – | – | – | |
|
Minors (n=47) |
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[1.35, 1.92] | [0.49, 0.60] | [0.56, 0.61] | [0.40, 0.47] | [0.35, 0.43] | [0.18, 0.24] | [0.21, 0.26] | [0.17, 0.22] | [0.37, 0.46] | [1.65, 2.05] | ||
Majors (n=9) |
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[1.92, 2.28] | [1.39, 1.55] | [1.42, 1.55] | [0.36, 0.39] | [0.41, 0.45] | [0.24, 0.28] | [0.25, 0.29] | [0.20, 0.22] | [0.38, 0.42] | [1.22, 1.41] | ||
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Minors (n=22) |
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[1.74, 2.26] | [0.52, 0.59] | [0.54, 0.58] | [0.36, 0.47] | [0.38, 0.43] | [0.21, 0.26] | [0.19, 0.22] | [0.16, 0.20] | [0.39, 0.44] | [1.43, 1.68] | ||
Majors (n=3) |
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[2.41, 2.44] | [1.46, 1.60] | [1.54, 1.63] | [0.39, 0.40] | [0.43, 0.45] | [0.25, 0.27] | [0.24, 0.25] | [0.18, 0.21] | [0.39, 0.41] | [1.26, 1.34] | ||
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Minors (n=25) |
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[0.57, 0.63] | [0.16, 0.26] | [1.67, 2.15] | [0.95, 1.40] | [0.18, 0.27] | [1.71, 2.39] | [0.33, 0.51] | [0.20, 0.27] | [0.46, 0.53] | [3.64, 4.63] | ||
Majors (n=22) |
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[0.52, 0.56] | [0.20, 0.25] | [1.17, 1.66] | [0.69, 1.10] | [0.11, 0.22] | [1.01, 1.64] | [0.40, 0.45] | [0.16, 0.21] | [0.37, 0.47] | [2.84, 3.88] | ||
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Minors (n=2) |
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[0.50, 0.53] | [0.14, 0.15] | [2.25, 2.33] | [1.42, 1.42] | [0.23, 0.27] | [2.17, 2.24] | [0.42, 0.44] | [0.21, 0.22] | [0.40, 0.42] | [5.30, 5.83] | ||
Majors unknown | – | – | – | – | – | – | – | – | – | – | |
|
Minors (n=47) |
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[0.46, 0.55] | [0.16, 0.24] | [1.98, 2.40] | [1.19, 1.59] | [0.16, 0.27] | [1.93, 2.55] | [0.36, 0.45] | [0.20, 0.24] | [0.33, 0.50] | [4.50, 6.66] | ||
Majors (n=9) |
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[0.46, 0.56] | [0.21, 0.25] | [1.80, 2.00] | [1.10, 1.37] | [0.16, 0.19] | [1.64, 1.93] | [0.40, 0.44] | [0.20, 0.23] | [0.32, 0.45] | [4.08, 6.13] | ||
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Minors (n=22) |
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[0.54, 0.61] | [0.17, 0.23] | [2.10, 2.28] | [1.34, 1.58] | [0.09, 0.18] | [1.82, 2.14] | [0.37, 0.46] | [0.19, 0.23] | [0.41, 0.53] | [4.04, 5.40] | ||
Majors (n=3) |
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[0.58, 0.64] | [0.19, 0.21] | [1.85, 1.99] | [1.27, 1.37] | [0.13, 0.15] | [1.54, 1.68] | [0.38, 0.40] | [0.19, 0.20] | [0.42, 0.46] | [4.14, 4.69] |
Minor workers of this subgenus can be recognized by the combination of the following characters: maxillary palps particularly long with respect to head length, extending past a point on line with posterior margin of eye; mesosoma slender, mesonotum elongated and constricted at midlength, propodeum a protruding rounded hump; mesothoracic spiracles prominent, pointing upward; propodeum protuberant. The major worker can be recognized by the distinct form of the mesosoma. The propodeum is dome-like or subrectangular in lateral view and the metanotum is elongate and impressed, and the upper mesopleuron is laterally pinched (see Figures
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Illustration of the neck (posterior region of the head) and the anterior clypeal margin of
Head of major worker in full-face view.
Petiole in lateral view of
Head in lateral view showing the dorsal margin of the clypeus (similar in minor and major workers).
Lateral view of propodeum and petiole in minor workers of
Head suboval, posterior region of head only slightly and broadly extended with margins weakly convex. (
Pronotum weakly undulant. Suberect pronotal setae numerous (more than 12). Mesonotum straight,
Color: head and mesosoma red to reddish brown, gaster dark brown to black. Erect setae light brown. Sparse appressed pubescence present.
In full-face view, head truncated posteriorly, evenly tapering to base of mandibles, posterior margin of head weakly concave. Absolute cephalic size (
Dorsal outline of mesosoma complex. Promesonotum forms a regular convexity with a shallow impression at the promesonotal suture and is stepped to the propodeal dorsum. Suberect promesonotal setae inclined anteriorly,
Petiole higher than broad, node summit flat; brown standing setae present on entire dorsum.
Color: head, mesosoma, petiole, and base of first gastral segment reddish brown, remainder of gaster dark brown to black. Scattered appressed pubescence generally present. Setae light brown.
The minor worker of
We propose that
Province
Holotype worker: MADAGASCAR, Province Toamasina, Parc National de Zahamena, Onibe River,
Paratype worker: MADAGASCAR, Prov. Toamasina, Parc National de Zahamena, Sahavorondrano River,
Head longer than wide, rear portion of head extended into a long neck, sides of head narrowed in front of eyes.
Pronotum evenly curved over its length. Mesonotum straight and elongate,
Petiole nodiform. Dorsum of petiole strongly concave, tapering apically to a blunt spine,
Entire body including antennae dark brown. Coxae, femora, and tibiae brown. Head, pronotum, fore-coxae and petiole microreticulate, mesonotum and propodeum reticulate-costate.
Unknown.
Unknown.
Unknown.
This species is named for the shape of its petiole in profile; the Malagasy word “
Holotype worker: MADAGASCAR, Province Antsiranana, Parc National de Marojejy, Manantenina River, 27.6 km 35° NE Andapa, 9.6 km 327° NNW Manantenina, -14.435 49.76, 16.xi.2003, 775 m, rainforest, ex rotten log. (B.L. Fisher et al.). Collection code: BLF08983 Unique specimen identifier:
Paratype workers: Six workers with the same data as holotype, Collection code: BLF08983, Unique specimen identifiers:
Workers of
Head longer than wide, anterior region of head elongated, caudate, sides of the head narrowed in front of eyes,
Pronotum weakly undulant. Mesonotum straight and elongate, distinctly compressed laterally anterior to mesothoracic spiracles,
Petiole conical, petiolar apex with an obtuse angle, posterior face of petiole flat to slightly convex, sides always distinct.
Entire body generally black, pronotum may vary to brown, coxae a lighter color than mesosoma, basitarsus and up to 5 basal funiculi whitish. Mesonotum and propodeum smooth and glabrous to microsculptured with sparse appressed to subdecumbent setae.
Head subrectangular in full face view, occipital portion broad, sides of the head mostly parallel and weakly convex,
Pronotum weakly undulant. Anterior region of mesonotum (immediately posterior to the pro-mesonotal suture) in profile rising above pronotum. Dorsal outline of mesonotum and propodeum form a continuous straight line interrupted by a shallow metanotal groove. Erect setae present, appressed pubescence sparsely distributed. Mesothoracic spiracle feebly produced laterally.
In profile, petiole conical, node summit acute.
Entire body black; femora and tibia dark brown, basitarsus of second and third legs light brown, funicular segments light brown, becoming dark apically. Pronotum and mesonotum microreticulate, sides of propodeum finely punctate, standing filiform setae present in all surfaces.
The Malagasy word “
Workers of
Province
Holotype worker: MADAGASCAR, Province Antsiranana, Galoko chain, Mont Kalabenono,
Paratype workers: Two workers with the same data as holotype but collection code: BLF32133, Unique specimen identifier:
The following character combination distinguishes
Distribution maps of the three new species.
Head longer than wide, posterior region of head extended into an elongate neck, sides of the head narrowed anteriorly, absolute cephalic size: 2.035 mm [1.74, 2.26] (n = 22). Erect, short, filiform setae present on head. Eyes located posterior to the midlength of head capsule in full-face view, postocular distance vs. cephalic length.
Pronotum weakly undulant. Anterior region of mesonotum (immediately posterior of the promesonotal suture) in profile rising above pronotum. Mesonotum straight and elongate, distinctly compressed laterally anterior to mesothoracic spiracles.
Petiole low and nodiform. Posterior face of petiole meets its dorsum at a rounded angle.
Entire body dark brown to black; femora and tibiae dark brown, basitarsus of second and third legs light brown, funicular segments light brown becoming dark brown apically. Head and pronotum microreticulate, mesonotum smooth and shiny, propodeum and fore-coxae moderately reticulate-punctate.
Head suboval, posterolateral sides of head tapering to rear, absolute cephalic size: 2.427 mm [2.418, 2.444] (n=3). Erect, short, filiform setae present on head. Eyes located close to the cephalic midlength.
Similar appearance as minor worker. Anterior region of mesonotum (immediately posterior to the pro-mesonotal suture) in profile rising above pronotum. Mesonotum straight and elongate, distinctly compressed laterally anterior to mesothoracic spiracles. Suberect filiform setae present, propodeum covered with dense pubescence, pubescence generally sparse elsewhere. Mesothoracic spiracles feebly produced laterally; propodeal dorsum convex, mesonotum and propodeum dorsum meet at a right angle.
Petiole low and nodiform. Posterior face of petiole meeting its dorsum at rounded to acute angle.
Overall color black; basal funicular segments yellowish brown and becoming dark apically; basitarsus of second and third legs light brown. Color of filiform setae whitish. Head and pronotum finely reticulate, mesonotum smooth and shiny, clypeus, gena, propodeum and fore-coxae moderately reticulate punctate.
Unknown.
Unknown.
This species name is based on the Latin terms for long, “longi”, and collis, “neck”.
Province
We are especially grateful to our friends and colleagues at the Madagascar Biodiversity Center, who have contributed to this study by collecting large numbers of samples in the field and processing them in the lab. Thanks to the Madagascar Ministry of Environment, Ecology and Forests for permit issuance. We are also thankful to Michele Esposito for help with database management and imaging. Michele Esposito and Bob Zuparko provided helpful comments on earlier drafts. We are grateful to Rodrigo Feitosa and Lech Borowiec who provided suggestions to improve this manuscript. This research was supported in part by the Norvig Family Foundation and Lakeside Foundation.
Ratios of morphometric data for all specimens
species morphometric data