Biodiversity Data Journal : Taxonomic paper
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Corresponding author: Flavia A. Esteves (flaviaesteves@gmail.com)
Academic editor: Marek Borowiec
Received: 04 Feb 2016 | Accepted: 01 Jun 2016 | Published: 13 Jun 2016
© 2016 Flavia A. Esteves, Brian L. Fisher.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Esteves FA, Fisher BL (2016) Taxonomic revision of Stigmatomma Roger (Hymenoptera: Formicidae) in the Malagasy region. Biodiversity Data Journal 4: e8032. doi: 10.3897/BDJ.4.e8032
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In this study we present the first taxonomic revision of the ant genus Stigmatomma in the Malagasy biogeographic region, redescribe the previously known S. besucheti Baroni-Urbani, and describe seven new species to science (S. bolabola sp. n., S. irayhady sp. n., S. janovitsika sp. n., S. liebe sp. n., S. roahady sp. n., S. sakalava sp. n., and S. tsyhady sp. n.). The revision is based on the worker caste, but we provide brief descriptions of gynes and males for some species. Species descriptions, diagnosis, character discussion, identification key, and glossary are illustrated with 360 high-quality montage and SEM images. The distribution of Stigmatomma species in Madagascar are mapped and discussed within the context of the island’s biomes and ecoregions. We also discuss how some morphometric variables describe the differences among the species in the bioregion. Open science is supported by providing access to R scripts, raw measurement data, and all specimen data used. All specimens used in this study were given unique identifies, and holotypes were imaged. Specimens and images are made accessible on AntWeb.org.
Malagasy bioregion; taxonomy; ants; Amblyoponinae; Madagascar; Seychelles
Stigmatomma
Stigmatomma is distributed globally, but very little is known about the genus in the Malagasy region, apart from the description of S. besucheti (
Madagascar and its surrounding islands are extremely biodiverse, have a high rate of animal and plant endemism, and possess exceptional rates of habitat loss due to human activity (
Ants play a large role in a terrestrial ecosystem (
This study presents the first taxonomic revision for the genus Stigmatomma in the Malagasy region and recognizes eight species, of which seven are newly described. It focuses on the worker caste, but images and a brief description of gynes and males are provided when possible.
Our understanding of the biology of the species assigned to Stigmatomma is far from comprehensive as it is based on generalizations from limited observations of a few species. One of the major culprits for our lack of observations is the cryptobiotic lifestyle of these ants, which hampers access to their colonies and studies on their behavior (
Predominantly, Stigmatomma species nests in the soil or in rotten logs of humid forest habitats (
Larvae feed directly on prey when positioned on this food source (
The majority of the species produces winged gynes. However, some members of the Stigmatomma reclinatum species-group does not present a morphologicaclly distinct queen, and reproduction is performed by gamergates (
The biological species concept guides species delimitation in this study, implying that species represent reproductively isolated entities, enclosing one or many populations connected by gene flow (
In this study, new species names formed from a personal name are nouns in apposition and thus invariant. All other new species names presented are not latinized words, and thus also indeclinable (ICZN article 31.2.3,
Every specimen we examined bears a specimen code label (e.g., CASENT0797614, ANTWEB1008502). Each code is a registered unique identifier, which aggregates several information regarding a given specimen on AntWeb (e.g., collection record, images, identification). Specimen data can be accessed on AntWeb through the persistent URL of its specimen code: www.antweb.org/specimen/“specimen code" (e.g., www.antweb.org/specimen/CASENT0797614).
Morphological terminology used follows
llustrated glossary of terminology; plate I: male genitalia morphology.
llustrated glossary of terminology; plate II: mesosoma of Stigmatomma worker, lateral view.
Illustrated glossary of terminology; plate III: legs morphology.
IIllustrated glossary of terminology; plate IV: worker morphology.
Illustrated glossary of terminology; plate V: mesosoma morphology of alates.
Illustrated glossary of terminology; plate VI: worker morphology
Sculpture terminology follows
We describe setae and cuticular projections with the following terminology:
Illustrated glossary of terminology; plate VII: setae and cuticular projections.
Illustrated glossary of terminology; plate VIII: setae and cuticular projections.
The terminology used to describe pilosity inclination, in regards to cuticle surface, follows
Wing venation (
Diagram of the Stigmatomma generalized wing venation: A, forewing; B, hindwing. Abbreviations: C, costa; Sc, subcosta; R, radius; Rs, radial sector; M, media; C, cubitus; A, anal. The position of vein's free abscissas are indicated by the letter f followed by a cardinal number. Images by Masashi Yoshimura, available at AntWeb.org (specimen CASENT0083104). llustration by F. A. Esteves.
We used indices and measurements to quantify size, and as means of comparison among Stigmatomma species. Measurements were taken on a Leica MZ APO stereomicroscope, rounded to the nearest 0.01 mm. They are expressed in mm, and presented as minimum and maximum values with holotype measurements within parentheses. Indices are rounded to the nearest integer value, and expressed as minimum and maximum values with holotype index within parentheses. The raw data are presented in
Measurements taken from Stigmatomma worker caste. A: fullface view; B: lateral view of head and mesosoma; C: dorsal view of mesosoma and anterior abdominal tergites. Abbreviations: HL, head length; HW, head width; HW2, head width 2; ML, mandibular length; PPW, propodeal posterior width; PtL, petiolar length; PtW, petiolar width; SL, scape length; WL, Weber's length of mesosoma. Illustrations by F. A. Esteves.
We employed a UPGMA hierarchical cluster analysis to visualize how specimens are grouped based on the differences in their linear morphometry. We also compared the clustering result with our species hypothesis to see how well they reflect each other.
In the UPGMA analysis, specimens clustered together are morphometrically more similar than specimens grouped into different clusters (
Cluster analysis uses a dissimilarity matrix as input. As a measure of dissimilarity, we used Euclidean distances, defined as the squared differences of measurement values between each pair of specimens (function dist, method “euclidean”; stats package,
\(d_{x,y} = { \sqrt{ \displaystyle\sum_{j=1}^{J}(x_{j}-y_{j})^2}}\)
where d is the distance between specimens x and y, J is the total number of measurements taken from each specimen, and j is a given measurement.
Data normalization is imperative for unbiased Euclidean distances. It balances the contribution of each measurement to the distance matrix, neutralizing the weight of the absolute differences of larger variables (see more about data normalization in
\(d_{A,B} = { \sqrt{ (A_{WL}-B_{WL})^2+(A_{PtL}-B_{PtL})^2+(A_{PtW}-B_{PtW})^2}}\)
\(d_{A,B} = { \sqrt{ (1.508-1.396)^2+(0.692-0.674)^2+(0.758-0.704)^2}}\)
\(d_{A,B} = { \sqrt{ 0.0125+0.0003+0.0029}}\)
\(d_{A,B} =0.125\)
If the same measurement values were normalized to the log scale, the Euclidean distance between specimens A and B would be only 0.0022. Thus, before data normalization, the absolute difference between Weber’s length values dominates the equation’s result. To counteract this effect, we normalize original measurement values to the natural-log scale using function log (base package,
UPGMA starts by combining the couple of most similar specimens into a group, then, it adds other specimens, or combines groups to groups, until all specimens are united by a common root. We used the method "average" as clustering strategy. It combines similar clusters together using the distance among cluster centroids as a dissimilarity measurement. For clustering, we used function hclust (stats package).
We use the cophenetic correlation coefficient to measure how well the cluster represents the distances between specimens. This provides a linear correlation coefficient between the cophenetic distances obtained from the cluster, and the original dissimilarity matrix that was used to build the cluster. The output value must be close to 1 for a high-informative cluster (
Cluster analysis captures the multivariate structure of a dataset, but it does not unveil the patterns of variation behind the clusters it builds. We used Principal Component Analysis (PCA) to visualize and interpret patterns of morphometric variation among specimens. As seen below, PCA offers solutions for two elements that hamper the detection of patterns underlying morphometric variation among specimens: variable correlation and multidimensionality.
Morphological measurements are biologically linked to each other as they describe traits of an organism, and therefore, they are generally correlated (Zelditch et al. 2012). PCA creates new variables, or components, to eliminate such correlations. PCA components combine linearly the original measurements, are independent from each other, and will act as new dimensions/axes in the ordination space (
In the morphometric space (i.e., space defined by the measurements), PCA draws its first component along the line that comprises the highest proportion of variation among specimens. Consecutively, it derives the remaining components to encompass the highest variation after derivation of the previous components. This process continues until the number of components equals the number of original measurements (
The newly computed components are uncorrelated (i.e., orthogonal in the space), and ideally, the first components will capture most of the variation among specimens (
Eventually, PCA projects the position of each specimen onto the components (
We executed all the steps of the Principal Component Analysis on the R platform (
First, we checked the original measurements for the presence of correlations (function cor, stats package;
Function prcomp (scale set to TRUE; stats package) executed PCA analysis on the original measurement matrix. It also standardized our dataset to zero mean and unit variance, which prevents dominance of variables with higher variance in the analysis (
The data and R scripts underpinning the analysis presented above are deposited in the Dryad Data Repository at https://doi.org/10.5061/dryad.m7340.
Extended focus montage images were created with a Leica DFC 425 camera and LEICA APPLICATION SUITE software (version 3.8; Leica Microsystems, Switzerland), and are available online at AntWeb. In addition, scanning electron microscopy (SEM) was used for observations of smaller characters. We prepared specimens for SEM adapting the procedure used by
Workers kept in ethanol were washed in water and gently brushed to remove dirt particles, before being placed in 90% ethanol for 20 minutes. Specimens were then: (1) point mounted in a copper conductive triangle (TED PELLA, INC.) below the median and hind right coxae, and fixed in an SEM aluminum Zeiss stub (TED PELLA, INC.) via a double-sided adhesive conducting PELCO tab (TED PELLA, INC.); and (2) left to air dry for at least 12 hours before scanning.
Point-mounted dry specimens were submerged in warm water to dissolve the mounting glue before being placed in 90% ethanol, after which the same treatment described above was applied.
Specimens mounted on stubs were coated with gold-palladium—this procedure was not applied to rare taxa (i.e., poorly represented in collections). Images were taken using a LEO/Zeiss 1450 VP SEM field emission scanning electron microscope at CASC, using the high voltage mode (HV) at a voltage of 10 kV. Images of uncoated ants were taken using the SEM at a variable pressure secondary electron mode (VPSE) with the following configuration: VP target pressure around 20Pa, spot size around between 500 and 600, VPSE collector bias at 390V, and voltage at 20kV. At least three specimens of each species were imaged when permitted by the available number of specimens.
For Madagascar, species distributions were mapped over a shaded relief of the island, overlaid by an elevation layer and the outlines of five simplified ecoregion zones of the country (
For Seychelles, species distributions were mapped over a shaded-relief of the islands, overlaid by an elevation layer.
All of the following steps, unless otherwise noted, were performed on the R platform (
Obtaining and modifying ecoregions vector layers for Madagascar: In this study, ecoregion outlines of Madagascar are based on the vector data disclosed by the Terrestrial Ecoregions of the World (
Plottting maps: Function plot (raster package) drew the shaded relief of Madagascar and Seychelles, and overlaid them with the raw elevation layer. For Madagascar, function plot also overlaid the resuting image with the modified ecoregion layers. Function grey (grDevices package,
Note that extensive myrmecological exploration of Madagascar is ongoing; we encourage readers to consult detailed and regularly updated distribution data available on AntWeb.org, where existing and future distributions can be mapped interactively and at higher resolution then the maps presented here.
ANIC: Australian National Insect Collection, Canberra, Australia.
BMNH: The Natural History Museum, London, U.K.
CASC: California Academy of Sciences, San Francisco, California, U.S.A.
MCZC: Museum of Comparative Zoology, Harvard University, Cambridge, U.S.A.
NHMB: Naturhistorisches Museum, Basel, Switzerland.
NHMW: Naturhistorisches Museum, Vienna, Austria.
MHNG: Muséum d’Histoire Naturelle, Geneva, Switzerland.
MZSP: Museu de Zoologia da Universidade de Sao Paulo, Sao Paulo, Brazil.
USNM: National Museum of Natural History, Smithsonian Institution, Washington, D.C., U.S.A.
Stigmatomma as junior synonym of Amblyopone:
= Arotropus
Workers of Stigmatomma in the Malagasy bioregion – characters of the Amblyoponinae as described by
Holotype worker of Stigmatomma liebe sp. n. (CASENT0318428); dorsal face of the head. Image by F. A. Esteves; available at AntWeb.org
Mandibular teeth arrangement in two different species of Stigmatomma in the Malagasy bioregion.
Stigmatomma tsyhady sp. n. worker; lateral view (CASENT0121332). Image by F. A. Esteves; available at AntWeb.org
Abdominal segment VII of Stigmatomma sakalava worker sp. n. (CASENT0022146), lateral view, featuring stout spiniform setae on the apex of its hypopygium. Image by F. A. Esteves; available at AntWeb.org
The list of characters above forms an inclusive diagnosis of the genus, but no character can currently be pointed as unique for Stigmatomma.
1. In Stigmatomma, the total dental count (including teeth arranged in pairs) recorded for Malagasy species is 11–15, distributed from base to apex as follows: 1–3 single teeth, followed by 3–6 teeth pairs (generally fused at the base), a preapical (generally single) tooth, and an apical pointy tooth (
The most basal tooth is enlarged in the majority of species we studied, but not in all (
Teeth coupling generally occurs between teeth with similar dimensions (
Mandibles of Stigmatomma sakalava sp. n. worker; dorsal view (CASENT0022146). Arrows point to dorsal tooth couples, which increase in size towards the mandible's apex. Image by F. A. Esteves; available at AntWeb.org
Mandibular dentition arrangement of Stigmatomma pluto worker (ANTWEB1008502).
Among the other Amblyoponinae genera distributed in the Malagasy bioregion: Prionopelta has short and subtriangular mandibles, which are usually armed with three teeth on the apical half, so that basal and mastigatory margins are distinct (
Similarities and differences of the head among Adetomyrma, Mystrium, Prionopelta, and Xymmer in the Malagasy bioregion.
In addition to the similarities and differences among the shape and configuration of the mandibles, an enlarged mandibular basal tooth is absent in all other Malagasy Amblyoponinae genera (
2. Number and configuration of clypeal cuticular processes and associated dentiform setae vary among the evaluated species of Stigmatomma. All species present three to ten cuticular processes on the anterior margin of the clypeus. Each medial process bears one dentiform seta.
In half of the species (tsyhady species-complex members and Stigmatomma janovitsika sp. n.), the seta on the lateral-most process is laterodistally followed by a row of dentiform setae. These lateral rows extend laterad on the anterior clypeal margin, where it arises from flat cuticle (
However, the number of medial cuticular processes may vary within some species and sometimes within nest series. Thus, we did not use such variations to isolate individual species.
Among the other Amblyoponinae genera present in the Malagasy region, Mystrium, like Stigmatomma, also presents a single row of cuticular projections bearing dentiform setae on the anterior clypeal margin (
A pair of long setae is present on the anterior margin of the clypeus of all genera in the XMMAS clade in the Malagasy region, however, they are reduced and stouter in Mystrium (CASENT0002095).
3. The presence or absence of genal teeth is uniform within Stigmatomma species, and this character has relative importance to group species with similar morphology. In the Malagasy bioregion, this trait is present in all Mystrium species (
4. Despite the variation among species, the number of antennomeres is constant within the Stigmatomma species we studied. Adetomyrma, Mystrium, and Xymmer species present no variation for this character, with all having twelve antennomeres.
5. Under the stereomicroscope, the whole antenna is equally covered by setae in Adetomyrma, Prionopelta, Stigmatomma, and Xymmer (
6. Without dissection, the maxillary and labial palpomeres are often extremely difficult to count in the species we studied.
Regarding the number of maxillary and labial palpomeres in other Amblyoponinae members in the Malagasy region, the palpal formula is constant within Mystrium (4:3) and Prionopelta (2:2) (
The palpal formula published for the Adetomyrma worker caste is 3:3, but some species are only known by the male caste, which, depending on the species, may present palpomere counts of 2:2 and 2:3 (
Finally,
7. The presence or absence of the metanotal suture, and the degree of its impression, may vary within species, as well as within nest series of Stigmatomma in the Malagasy region. Given this, we did not use those variations to isolate individual species.
9. The number of mesotibial spur(s) is difficult to determine under stereomicroscopes when the anterior spur is reduced in size, and also because the posterior spur may be “replaced” by an enlarged, stout spiniform seta. SEM images allowed comparisons between the texture of enlarged spinifom processes and surrounding cuticle, thus enabling us to differentiate spur and seta (
Difference between a spur and an enlarged seta on the inner face of the mesotibial apex of Stigmatomma workers.
In the Stigmatomma we studied, the number of mesotibial spurs ranged from zero to two, and were generally constant within species. In one species, S. liebe sp. n., the number of mesotibial spurs visible under the stereomicroscope ranges from one to two. The anterior spur may be visible and developed, but it is vestigial in the majority of the specimens we evaluated. This variation was observed in specimens from the same nest series.
Regarding other members of the XMMAS clade, Stigmatomma pallipes (ANTWEB1008501; Nearctic region), S. pluto (ANTWEB1008502), Adetomyrma caputleae
Among the Amblyoponinae genera outside the XMMAS clade, Amblyopone australis
10. We confirm the presence of a longitudinal sulcus on the anterodorsal face of the mesobasitarsus in all species of Stigmatomma in the Malagasy region save S. tsyhady sp. n.
Within the XMMAS clade, this sulcus is present on the mesobasitarsus of Stigmatomma pallipes (ANTWEB1008501), S. pluto (ANTWEB1008502), Adetomyrma caputleae (ANTWEB1008494), Fulakora chilensis (ANTWEB1008496), F. mystriops (ANTWEB1008500), Myopopone castanea (ANTWEB1008551), and Xymmer muticus (ANTWEB1008499). We confirm present of this sulcus in only one Xymmer species in the Malagasy region. However, this character is difficult to visualize under a stereomicroscope when specimens are too small, as it occurs with Xymmer species, and its presence or absence may be better evaluated with an SEM microscope. This sulcus is absent in all Mystrium species we evaluated in the Malagasy region (CASENT0429914; CASENT0482698; CASENT0003281; CASENT0429897; CASENT0129838; CASENT0418314; CASENT0318933; CASENT0494274; CASENT0248701; CASENT0001158; ANTWEB1008554).
The sulcus on the anterior face of the mesobasitarsus is absent in Amblyopone australis (ANTWEB1008497), A. mercovichi (ANTWEB1008498), Apomyrma stygia (ANTWEB1008505), Onychomyrmex doddi (ANTWEB1008560), Prionopelta aethiopica (ANTWEB1008580), P. antillana (ANTWEB1008581), and P. concenta (ANTWEB1008513).
11. All Stigmatomma species present in the Malagasy bioregion present two well-developed metatibial spurs save S. liebe sp. n. In this species, the number of metatibial spurs visible under the stereomicroscope ranges from one to two. The anterior spur is visibly smaller than the posterior spur, and may be vestigial in some specimens. This variation was observed in specimens from the same nest series. A similar condition is found in Onychomyrmex hedleyi
In the XMMAS clade, Stigmatomma pallipes (ANTWEB1008501), S. pluto (ANTWEB1008502), Adetomyrma caputleae (ANTWEB1008494), A. venatrix, Fulakora chilensis (ANTWEB1008496), F. mystriops (ANTWEB1008500), Myopopone castanea (ANTWEB1008551), Mystrium voeltzkowi (ANTWEB1008554), and Xymmer muticus (ANTWEB1008499) possess two spurs on the metatibia.
Amblyopone australis (ANTWEB1008497), A. mercovichi (ANTWEB1008498), and Apomyrma stygia (ANTWEB1008505) possess two metatibial spurs. Onychomyrmex doddi (ANTWEB1008560) possesses two vestigial spurs at the apex of the metatibia. These spurs are small, stout, conic seta totally or partially concealed by a fovea. Prionopelta aethiopica (ANTWEB1008580) and P. antillana (ANTWEB1008581) have one spur, while P. concenta (ANTWEB1008513) presents no spurs.
12. Only one Stigmatomma species evaluated in this study (S. roahady sp. n.) presents a longitudinal sulcus on the anterior face of the metabasitarsus. The metabasitarsus of S. besucheti, while not presenting a sulcus on its anterior face, possesses two raised, parallel, not-well-developed longitudinal carinae with convergent apexes on its dorsal face.
This sulcus is present on the metabasitarsus of Myopopone castanea (ANTWEB1008551), and absent in Stigmatomma pallipes (ANTWEB1008501), S. pluto (ANTWEB1008502), Adetomyrma caputleae (ANTWEB1008494), A. venatrix, Fulakora chilensis (ANTWEB1008496), F. mystriops (ANTWEB1008500), and Xymmer muticus (ANTWEB1008499). It seems to be absent on the metabasitarsus of Xymmer in the Malagasy region. However, we cautiously affirm that, since this character is difficult to visualize under a stereomicroscope when specimens are too small, like those of Xymmer, it would be better evaluated under higher magnification. This sulcus is absent in all Mystrium species we evaluated in the Malagasy bioregion (CASENT0429914; CASENT0482698; CASENT0003281; CASENT0429897; CASENT0129838; CASENT0418314; CASENT0318933; CASENT0494274; CASENT0248701; CASENT0001158; ANTWEB1008554).
Among the Amblyoponinae genera that are not part of the XMMAS clade, the sulcus on the metabasitarsus is absent on Amblyopone australis (ANTWEB1008497), A. mercovichi (ANTWEB1008498), Apomyrma stygia (ANTWEB1008505), Onychomyrmex doddi (ANTWEB1008560), Prionopelta aethiopica (ANTWEB1008580), P. antillana (ANTWEB1008581), and P. concenta (ANTWEB1008513).
13. Arolium present on pro-, meso-, and metapretarsi in all species we studied. The same seems to apply to the other Amblyoponinae genera in the Malagasy region.
14. The petiole is sessile to subsessile in Adetomyrma and Mystrium; and subsessile to penduculate in Xymmer (
Presence or absence of petiolar penduncle in Adetomyrma, Mystrium, and Xymmer.
15. The constriction between pretergite and postergite of the abdominal segment III is scrobiculate in all Stigmatomma species but one. In Adetomyrma such a constriction is not visible; in Xymmer species the constriction is alveolate; and in Mystrium it is scrobiculate.
16. A prora is visible under a stereomicroscope in all Stigmatomma and Mystrium species in the Malagasy region; it seems to be absent in Adetomyrma and Xymmer.
17. Adetomyrma does not possess a constriction between the presclerite and postsclerite of abdominal segment IV. The constriction is scrobiculate in Mystrium and Stigmatomma, and alveolate in Xymmer.
18. Stout spiniform setae may be located on the apex of the hypopygium, surrounding the sting (
In the Malagasy region, all Mystrium species present two or four stout setae on the hypopygium (
Stout spiniform setae are also present on the hypopygium of Stigmatomma pluto (twelve setae, ANTWEB1008502), Fulakora chilensis (eight setae, ANTWEB1008496), and in F. cleae (
We introduce a morphological organization system for the species diversity of Stigmatomma in the Malagasy bioregion which is based upon the definition of informal species-groups, which may contain species-complexes when necessary. Groups and complexes are named after the most abundant species, and the groups we presently define only reflect what is seen in the Malagasy fauna.
besucheti group
besucheti (Baroni Urbani 1978) (Seychelles; Singapore?)
tsyhady group
sakalava complex
bolabola Esteves & Fisher sp. n. (Madagascar)
janovitsika Esteves & Fisher sp. n. (Seychelles)
sakalava Esteves & Fisher sp. n. (Madagascar)
tsyhady complex
irayhady Esteves & Fisher sp. n. (Madagascar)
liebe Esteves & Fisher sp. n. (Madagascar)
roahady Esteves & Fisher sp. n. (Madagascar)
tsyhady Esteves & Fisher sp. n. (Madagascar)
Stigmatomma besucheti (
The morphology of S. besucheti isolates the species from other Stigmatomma in the Malagasy bioregion, and we place it in its own group based on the following worker characters (asterisks flag unique characters within the genus in the Malagasy bioregion):
1. * Ten antennomeres;
2. * Two maxillary palpomeres (palpal formula: 2:2);
3. * Calcar of strigil completely pectinate;
4. * Anterior face of the calcar of strigil with squamiform microtrichia basally;
5. * Posterior face of the calcar of strigil glabrous;
6. * Weakly raised longitudinal parallel carinae present on the dorsal face of metabasitarsus, with convergent apexes;
7. * Petiolar proprioceptor zone reduced to a small concavity.
Workers with the following combination of characters (asterisks flag unique characters within the genus in the Malagasy bioregion):
1. * Twelve antennomeres;
2. * Four maxillary palpomeres (palpal formula: 4:3 or 4:2);
3. * Calcar of strigil not completely pectinate; basoventral lamella generally visible (in one species the lamella is reduced to a basal bud);
4. Anterior face of the calcar of strigil with straplike or tubiform microtrichia basally;
5. * Posterior face of the calcar of strigil with lanceolate microtrichia;
6. Absence of any longitudinal carina on the dorsal face of metabasitarsus;
7. * Petiolar proprioceptor zone a large, round concavity.
This group can be split into subgroups based on morphological similarities, here called species complexes.
Stigmatomma bolabola Esteves & Fisher, sp. n.
Stigmatomma janovitsika Esteves & Fisher, sp. n.
Stigmatomma sakalava Esteves & Fisher, sp. n.
Workers with the following combination of characters (character numbers are sequential to the species groups for sake of clarity in the character discussion):
8. Genal teeth present or absent;
9. Two labial palpomeres (palpal formula: 4:2);
10. Antler-like microtrichia present on posterior face of posterior metatibial spur;
11. Absence of fenestra on the subpetiolar process;
12. Stout spiniform setae present on the apex of hypopygium.
Stigmatomma irayhady Esteves & Fisher, sp. n.
Stigmatomma liebe Esteves & Fisher, sp. n.
Stigmatomma roahady Esteves & Fisher, sp. n.
Stigmatomma tsyhady Esteves & Fisher, sp. n.
Workers with the following combination of characters (character numbers are sequential to the species groups for sake of clarity in the character discussion; asterisks flag unique characters within the genus in the Malagasy bioregion):
8. Genal teeth present;
9. * Three labial palpomeres (palpal formula: 4:3);
10. Posterior face of posterior metatibial spur mostly glabrous;
11. * Fenestra present on the subpetiolar process;
12. * Absence of stout spiniform setae on hypopygium.
3. A reduced lamella on the basoventral margin of the calcar of strigil is often difficult to visualize under a stereomicroscope, and the calcar may appear completely pectinate while in reality it has a basal bud on the base of its ventral margin. Nonetheless, the proportion of lamellar tissue on the ventral margin of the calcar is constant within species, and was helpful to delimit certain species.
4-5. Presence and shape of microtrichia on anterior and posterior face of the calcar of strigil are not visible under a stereomicroscope. However, those characters are informative to diagnose groups of species.
6. The longitudinal parallel carinae on the dorsal face of the Stigmatomma besucheti metabasitarsus somewhat converge at their apexes; thus, the region between them appears groove-like in dorsal view. No other species of Stigmatomma in the Malagasy region presents such a character. However, one species, S. roahady, possesses a longitudinal sulcus on the anterior face of its metabasitarsus, and since its shape and location are different from the carinae on S. besucheti, we did not consider them homologous.
10. The presence and shape of microtrichia on the posterior face of the metatibial spur are not visible under a steromicroscope; however, it is informative to diagnose groups of species.
Amblyopone besucheti
Combination in Stigmatomma:
Worker (
Holotype of Stigmatomma besucheti (CASENT0101816); worker. Images by April Nobile; available at AntWeb.org
Head:
Mandibular baso-masticatory margin skirted dorsally by row of filiform setae; medially, by flexuous tongue-like setae; ventrally, by flexuous filiform setae, grading into flexuous tongue-like setae apically (
Head of Stigmatomma besucheti worker.
Mesosoma:
In dorsal view, mesonotum somewhat expanded laterally (
Mesosoma of Stigmatomma besucheti worker (CASENT0101970). Images by F. A. Esteves; available at AntWeb.org.
Legs:
Absence of lamella on basoventral margin of calcar of strigil (
Legs of Stigmatomma besucheti worker.
Metasoma:
Petiole sessile (
Petiole and gaster of Stigmatomma besucheti worker (CASENT0101970). Images by F. A. Esteves; available at AntWeb.org.
Sculpture:
Mandibular dorsal face costate-slightly catenate basally, grading into costate apically except for smooth apical portion (
Body sculpture in Stigmatomma besucheti worker (CASENT0101970). Image by F. A. Esteves, available at AntWeb.org.
Pilosity and color:
Suberect pilosity on head, dorsal face of mesosoma, lateral face of pronotum, petiolar tergite, and abdominal segments III, IV, V, and VI. Legs densely covered by subdecumbent pilosity. Suberect pilosity on anterior half of petiolar poststernite. Longer pilosity on abdominal segment VII. Body color yellow.
Character variation among specimens was minimal.
Unknown for the Malagasy region. However, a gyne of a putative Stigmatomma besucheti is known for Singapore, as presented below.
With characters of the besucheti species-group as described above and the following characters (asterisks flag unique characters within Stigmatomma in the Malagasy bioregion):
In the Malagasy bioregion, Stigmatomma besucheti is unique and easily recognized by: reduced number of antennomeres, palpal formula, head sculpture, absence of any enlarged process ressembling a spur on the apex of the mesotibia, petiolar proprioceptor zone reduced to a small concavity, and small body size. Further, it does not occur in sympatry with any other congener.
Stigmatomma besucheti is known by its type series, collected in Seychelles by Schauenberg in 1975 (
While no direct information about habitat/microhabitat exists, published records of other organisms collected by Schauenberg on La Digue island on 28.Jan.1975 indicate the type series of S. besucheti was probably extracted from soil samples submitted to Berlese funnels (
The two specimens from Singapore (a worker and a queen; CASENT0172194 and CASENT0195513, respectively) share remarkable similarities with the type specimens (e.g., antennomeres, general body shape and size, sculpture on the head, lack of any spiniform process on the mesotibial inner apex). However, those specimens differ in the following characters (corresponding characters of type specimens are presented within parentheses):
Dealated gyne of Stigmatomma cf. besucheti from Singapore (CASENT0195513). Images by F. A. Esteves; available at AntWeb.org
Despite these differences, we did not examine enough specimens of each form to evaluate character variation, and therefore cannot affirm they are different species. Also, while it seems improbable that a specialized predator would become an exotic species, it is noteworthy that: (1) the putative prey of Stigmatomma besucheti (i.e., geophilomorph centipedes) are widespread around the world and a major component of soil ecosystems (
In addition to the specimens collected in Singapore, there is single specimen collected in Sabah (Borneo; CASENT0235146) that resembles Stigmatomma besucheti in the number of antennomeres, head sculpture, mandible and clypeal configuration, size, and color, but differs in some significant characters of the petiole. Compared to S. besucheti, the anteroventral margin of petiolar tergite anterior dorso-latero-ventral carina is much shorter, and the shape of the subpetiolar process is different. Unfortunately, specimen CASENT0235146 was previously submitted to DNA extraction (
Worker (
Holotype of Stigmatomma bolabola sp. n. (CASENT0034580); worker. Images by April Nobile; available at AntWeb.org.
Head:
Mandibular baso-masticatory margin skirted dorsally by row of filiform setae; ventrally, by acuminate flattened-apex setae, and row of longer filiform setae (
Head of Stigmatomma bolabola sp. n. worker (CASENT0034744). Images by F. A. Esteves; available at AntWeb.org.
Mesosoma:
In dorsal view, mesonotum narrower than remaining mesosoma (
Mesosoma of Stigmatomma bolabola sp. n. worker (CASENT0034744). Images by F. A. Esteves; available at AntWeb.org.
Legs:
Basoventral fifth of calcar of strigil lamellar (
Legs of Stigmatomma bolabola sp. n. worker (CASENT0034744). Images by F. A. Esteves; available at AntWeb.org.
Metasoma:
Petiole sessile (
Petiole and gaster of Stigmatomma bolabola sp. n. worker. Images by F. A. Esteves; available at AntWeb.org.
Sculpture:
Mandibular dorsal face rugose-foveate basally, grading into costate-foveolate apically except for smooth apical portion (
Body sculpture in Stigmatomma bolabola sp. n. worker (CASENT0034744). Image by F. A. Esteves, available at AntWeb.org.
Pilosity and color:
Suberect pilosity on head, dorsal face of mesosoma, lateral face of propodeum, petiolar tergite, and abdominal segments III and IV. Petiolar poststernite mostly glabrous. Longer pilosity on abdominal segments V, VI and VII. Body color red-brown; apex of gaster and appendages orange-yellow.
Character variation on the specimens examined was minimal.
Unknown.
This taxon was referenced as Stigmatomma MG03 (specimen CASENT0034580) in
Worker
With characters of the tsyhady species-group and the sakalava species-complex as described above, and the following characters (asterisks flag unique characters within the genus in the Malagasy bioregion):
Stigmatomma bolabola may be confounded with S. sakalava by the following characters: absence of genal teeth, palpal formula, single mesotibial spur, head sculpture, shape of subpetiolar process, and presence of stout spiniform setae on the apex of hypopygium. However, it is easily recognized by the sculpture of its mesosoma lateral face and propodeal declivitous face, katepisternum shape, proportion of lamella on the basoventral margin of calcar of strigil, and distribution (since they do not occur in sympatry).
Bola-bola is the name that Malagasy people give to logs of rosewood, a plant of the genus Dalbergia (
Madagascar is home to 48 species of rosewood, of which 47 are endemic (
Due to international demand for rosewood, thousands of loggers have flooded into the national parks of Madagascar. In the process of extraction, new roads are built, and logging camps set up, which increases access to forests, fuels extraction of other resources, and accelerates general deforestation, illegal mining, and poaching (
The highest rosewood species richness in Madagascar is found in the northeastern rainforest, with seven species native to the SAVA Region and the Makira-Masoala Landscape (
The Makira component of the Makira-Masoala Landscape (Makira Forest Protected Area) is the only place in Madagascar where Stigmatomma bolabola has been found, in a collection effort encompassing more than 440 collection sites. Given that the health of the ecosystem is essential to protect S. bolabola habitat, here we plead for more effective protection of Malagasy rosewood.
Stigmatomma bolabola was collected in two localities of the Makira Forest Protected Area, in rainforest and montane rainforest habitats in the humid forests ecoregion of Madagascar (at 600 m and 1100 m respectively; following the classification of
Distribution map of Stigmatomma bolabola sp. n. in the Malagasy bioregion. Collection localities are mapped over the outlines of five simplified ecoregion zones of Madagascar: humid forests (dark green), subhumid forests (light green), dry deciduous forests (brown), succulent woodlands (orange), and spiny thickets (yellow).
Worker (
Holotype of Stigmatomma irayhady sp. n. (CASENT0042899); worker. Images by F. A. Esteves; available at AntWeb.org.
Head:
Mandibular baso-masticatory margin skirted dorsally by row of filiform setae; ventrally, by truncated filiform setae (
Head of Stigmatomma irayhady sp. n. worker. Images by F. A. Esteves; available at AntWeb.org.
Mesosoma:
In dorsal view, mesonotum lateral margins continuous with posterior remainder of mesosoma (
Mesosoma of Stigmatomma irayhady sp. n., worker (CASENT0458591). Images by F. A. Esteves; available at AntWeb.org.
Legs:
Basoventral three-fourths of calcar of strigil lamellar (
Legs of Stigmatomma irayhady sp. n. worker (CASENT0458591). Images by F. A. Esteves; available at AntWeb.org.
Metasoma:
Petiole sessile (
Petiole and gaster of Stigmatomma irayhady sp. n. worker. Images by F. A. Esteves; available at AntWeb.org.
Sculpture:
Mandibular dorsal face areolate-rugose basally, grading into costate apically except for smooth apical portion (
Mouthparts of Stigmatomma irayhady sp. n. worker (CASENT0458591), ventral view. Image by F. A. Esteves; available at AntWeb.org.
Pilosity and color:
Erect to subdecumbent pilosity on head. Erect to suberect pilosity on dorsal face of mesosoma, petiolar tergite, and abdominal segments III and IV. Erect pilosity on anterior half of petiolar poststernite. Longer pilosity on abdominal segments V, VI, and VII. Body color dark-brown to blackish; apex of the gaster orange; yellow-brown appendages.
No geographic pattern is seen in the variation on Stigmatomma irayhady, and characters such as body size, the presence of most basal masticatory tooth, number of dentiform setae on the anterior margin of the clypeus, presence and degree of development of metanotal suture, and presence and amount of digitiform cuticular projections on the ventral margin of the posterior mesotibial spur fluctuate even among specimens collected at the same locality.
Gyne (
Dealated gyne of Stigmatomma irayhady sp. n. (CASENT0458590); plate I. Images by Erin Prado; available at AntWeb.org.
Dealated gyne of Stigmatomma irayhady sp. n. (CASENT0458590); plate II. Images by F. A. Esteves; available at AntWeb.org.
Males: Unknown.
Worker
With characters of the tsyhady species-group and the tsyhady species-complex as described above, and the following characters:
Size, color, presence of genal teeth, palpal formula, presence of fenestra on the subpetiolar process, two mesotibial spurs, shape of microtrichia on posterior face of posterior metatibial spur, and absence of stout setae on the apex of hypopygium make it difficult to separate Stigmatomma irayhady from S. roahady and S. tsyhady.
However, S. irayhady possesses a sulcus on the anterodorsal face of the mesobasitarsus, and S. tsyhady does not; and it lacks a sulcus on the anterodorsal face of the metabasitarsus, which S. roahady has. Also, the ventral margin of the subpetiolar process decreases continuously posterad in S. roahady and S. tsyhady, while it has an obtuse angle at its midpoint in S. irayhady.
S. irayhady is sympatric with S. roahady in three localities: nearby Andranomay, close to Anjozorobe, and at the Binara Forest. It co-occurs with S. tsyhady at the Binara Forest.
The name is a compound of the Malagasy cardinal number iray, meaning one, and the Malagasy noun hady, meaning sulcus, ditch, or trench. It refers to the presence of a longitudinal sulcus on the anterior face of the mesobasitarsus, and the absence of a longitudinal sulcus on the anterior face of the metabasitarsus of that species. This is not unique among Stigmatomma species in the Malagasy bioregion, but distinguishes S. irayhady from the other two species most similar to it, S. tsyhady and S. roahady.
Stigmatomma irayhady was collected in montane rainforest habitats, above 1000 m, at the central to northern portions of the subhumid forests ecoregion of Madagascar (following the classification of
Distribution map of Stigmatomma irayhady sp. n. in the Malagasy bioregion. Collection localities are mapped over the outlines of five simplified ecoregion zones of Madagascar: humid forests (dark green), subhumid forests (light green), dry deciduous forests (brown), succulent woodlands (orange), and spiny thickets (yellow).
Worker (
Holotype of Stigmatomma janovitsika sp. n. (CASENT0161533); worker. Images by F. A. Esteves; available at AntWeb.org.
Head:
Mandibular baso-masticatory margin skirted dorsally by row of filiform setae; medially, by spatular setae; ventrally, by longer acuminate flattened-apex setae (
Head of Stigmatomma janovitsika sp. n. worker. Images by F. A. Esteves; available at AntWeb.org.
Mesosoma:
In dorsal view, mesonotum narrower than remaining mesosoma (
Mesosoma of Stigmatomma janovitsika sp. n., worker. Images by F. A. Esteves; available at AntWeb.org.
Legs:
Basoventral lamella of calcar of strigil reduced to a basal bud. Anterior face of calcar of strigil with tubiform microtrichia (
Legs of Stigmatomma janovitsika sp. n. worker; plate I. Images by F. A. Esteves; available at AntWeb.org.
Legs of Stigmatomma janovitsika sp. n. worker (CASENT0318418); plate II. Images by F. A. Esteves; available at AntWeb.org.
Metasoma:
Petiole sessile (
Petiole and gaster of Stigmatomma janovitsika sp. n. worker (CASENT0145426). Images by F. A. Esteves; available at AntWeb.org.
Sculpture:
Mandibular dorsal face rugose-foveolate basally, grading into costate apically, except for smooth apical portion (
Stigmatomma janovitsika sp. n. worker (CASENT0145426): ventral view of the mandibles, mouthparts, and anterior part of the head. Image by F. A. Esteves; available at AntWeb.org.
Pilosity and color:
Erect to subdecumbent pilosity on head, dorsal face of mesosoma, petiolar tergite, and abdominal segments III and IV. Petiolar poststernite mostly glabrous, with row of setae along lateral margins. Longer pilosity on abdominal segments V, VI, and VII. Body color orange-brown; light-orange appendages.
Under the stereomicroscope, there is no observable character variation on the specimens examined.
Gyne (
Dealated gyne of Stigmatomma janovitsika sp. n. (CASENT0161532); paratype; plate I. Images by F. A. Esteves; available at AntWeb.org.
Dealated gyne of Stigmatomma janovitsika sp. n. (CASENT0161532); paratype; plate II. Images by F. A. Esteves; available at AntWeb.org.
Male (
Male of Stigmatomma janovitsika sp. n. (CASENT0318447); plate I. Images by F. A. Esteves; available at AntWeb.org.
Male of Stigmatomma janovitsika sp. n. (CASENT0318447); plate II. Images by F. A. Esteves; available at AntWeb.org.
Male of Stigmatomma janovitsika sp. n. (CASENT0318446); plate III. Images by F. A. Esteves; available at AntWeb.org.
Left wings of Stigmatomma janovitsika sp. n. (CASENT0160792); male. Images by F. A. Esteves; available at AntWeb.org.
Right wings of Stigmatomma janovitsika sp. n. (CASENT0318446); male. Images by F. A. Esteves; available at AntWeb.org.
This taxon was referenced as Stigmatomma SC01 (specimen CASENT0159676-D01) in
Worker
With characters of the tsyhady species-group and the sakalava species-complex as described above, and the following characters (asterisks flag unique characters within the genus in the Malagasy bioregion):
Stigmatomma janovitsika is somewhat similar to S. bolabola and S. sakalava in palpal formula, shape of microtrichia on the posterior face of posterior metatibial spur, and absence of fenestra on the subpetiolar process.
However, it may be distinguished from them by: brush of filiform setae present on the corners of the clypeus (if the setae are removed, the region will be densely punctuate); presence of genal teeth; the mesepisternum is not divided into anepisternum and katepisternum; head sculpture; proportion of lamella on the baso-ventral margin of the calcar of strigil; long, stout, spiniform seta on the mesotibial inner face apex (resembling a spur under the stereomicroscope), followed apically by a cuticular deep fovea concealing a small, stout, truncated seta; and distribution, since it does not occur in sympatry with any of its congeners.
The name janovitsika is a portmanteau of Janovitz and vitsika (Malagasy name for ants), meaning the ant of Janovitz. Dr. Tyler W. Janovitz is a medical scientist interested in myrmecology, and generously supported this study.
Stigmatomma janovitsika specimens were collected in forest, mixed forest, and mixed forest near glacis (rocky outcrop) habitats, from 60 to around 700 m above sea level, on three granitic islands of the Seychelles (Conception, Mahé, and Silhouette;
Worker (
Holotype of Stigmatomma liebe sp. n. (CASENT0318428); worker. Images by F. A. Esteves; available at AntWeb.org.
Head:
Mandibular baso-masticatory margin skirted dorsally by row of filiform setae; medially, by spatular setae; ventrally, by filiform setae (
Head of Stigmatomma liebe sp. n. worker. Images by F. A. Esteves; available at AntWeb.org.
Mesosoma:
In dorsal view, lateral margins of mesonotum continuous with posterior remainder of mesosoma, or expanded laterally (
Mesosoma of Stigmatomma liebe sp. n., worker (CASENT0009102). Images by F. A. Esteves; available at AntWeb.org.
Legs:
Basoventral two-thirds to three-fourths of calcar of strigil lamellar (
Legs of Stigmatomma liebe sp. n. worker; plate I. Images by F. A. Esteves; available at AntWeb.org.
Legs of Stigmatomma liebe sp. n. worker (CASENT0009102); plate II. Images by F. A. Esteves; available at AntWeb.org.
Metasoma:
Petiole sessile (
Stigmatomma liebe sp. n. worker; metasoma. Images by F. A. Esteves; available at AntWeb.org.
Sculpture:
Mandibular dorsal face mostly costate-foveolate, except for smooth apical portion (
Stigmatomma liebe sp. n. worker (CASENT0009102): ventral view of the mandibles, mouthparts, and anterior part of the head. Image by F. A. Esteves; available at AntWeb.org.
Pilosity and color:
Erect to subdecumbent pilosity on head, dorsal face of mesosoma, petiolar tergite, and abdominal segments III and IV. Erect to suberect pilosity on anterior half and along lateral margins of petiolar poststernite. Longer pilosity on abdominal segments V, VI, and VII. Body color dark-yellow to orange; yellow appendages.
The great majority of specimens examined present just one visible meso- and metatibial spur under the stereomicroscope; however, variation in number of meso- and metatibial spurs is seen in specimens of the same nest series. When just one spur is present on the meso- or metatibia, it is always the posterior spur; in such cases, a bud-like cuticular projection is seen concealed by a fovea at the place where the anterior spur would be located. It seems to us that such a projection is a sensillum and not the basal portion of a broken spur, given the developmental plasticity exhibited by the anterior mesotibial spur, when it is present: anterior and posterior spurs may have the same length in some specimens, or anterior spur may be much shorter (in one specimen, it corresponds to one-quarter of the size of the posterior spur). However, we do not discard the possibility that the anterior meso- and metatibial spur may be easily broken, but we could not infer that based on the SEM images we possess.
No geographic pattern is seen in the variation of characters of Stigmatomma liebe, and body size, the presence of the most-basal masticatory tooth, number of dentiform setae on clypeal anterior margin, degree of mesonotum expansion, number of meso- and metatibial spur, and color fluctuates even on specimens collected in the same locality.
Gyne (
Gyne of Stigmatomma liebe sp. n. (CASENT0724177); plate I. Images by F. A. Esteves; available at AntWeb.org.
Gyne of Stigmatomma liebe sp. n. (CASENT0724177); plate II. Images by F. A. Esteves; available at AntWeb.org.
Male (
Male of Stigmatomma liebe sp. n. (CASENT0724171); plate I. Images by F. A. Esteves; available at AntWeb.org.
Male of Stigmatomma liebe sp. n. (CASENT0724171); plate II. Images by F. A. Esteves; available at AntWeb.org.
Male of Stigmatomma liebe sp. n. (CASENT0724171); plate III. Images by F. A. Esteves; available at AntWeb.org.
Male of Stigmatomma liebe sp. n. (CASENT0724171); plate IV - wings. Images by F. A. Esteves; available at AntWeb.org.
Stigmatomma liebe was referenced as Amblyopone sp.2 (specimen CASENT0500013) in
Worker
With characters of the tsyhady species-group and the tsyhady species-complex as described above, and the following characters (asterisks flag unique characters within the genus in the Malagasy bioregion):
Presence of genal teeth, palpal formula, presence of fenestra on the subpetiolar process, shape of microtrichia on the posterior face of posterior metatibial spur, and absence of stout setae on the apex of the hypopygium make Stigmatomma liebe similar to S. irayhady, S. roahady, and S. tsyhady.
However, the yellow color and smaller size differentiate it from the rest. Also, it possesses a sulcus on the anterodorsal face of the mesobasitarsus, while S. tsyhady does not; it does not have a sulcus on the anterodorsal face of the metabasitarsus, which is present in S. roahady; and the anterior metatibial spur is greatly reduced in size, meaning that in the great majority of specimens it is not visible under the stereomicroscope (when it is visible, its length corresponds to less than one-third of the length of the posterior metatial spur), while in S. irayhady it is always visible and much longer than half the length of the posterior metatibial spur.
Stigmatomma liebe is sympatric with S. roahady and S. tsyhady in four localities: at the Andohahela National Park, the Anosyenne Mountains, Andringitra Reserve, and the Ivohibe Special Reserve. It was not recorded at the localities S. irayhady was collected.
The name liebe is homage to Elizabeth (Liebe) R. Patterson, for all the support she and her husband (in memoriam) have given to the myrmecological work being done in Madagascar.
Stigmatomma liebe was collected in montane rainforest habitats, above 1100 m, at the southern portion of the humid forests ecoregion of Madagascar (following the classification of
Distribution map of Stigmatomma liebe sp. n. in the Malagasy bioregion. Collection localities are mapped over the outlines of five simplified ecoregion zones of Madagascar: humid forests (dark green), subhumid forests (light green), dry deciduous forests (brown), succulent woodlands (orange), and spiny thickets (yellow).