Nesomyrmex madecassus (Forel, 1892)

Csosz, Sandor & Fisher, Brian L., 2016, Taxonomic revision of the Malagasy Nesomyrmexmadecassus species-group using a quantitative morphometric approach, ZooKeys 603, pp. 105-130 : 117-120

Taxon classification Animalia Hymenoptera Formicidae

Nesomyrmex madecassus (Forel, 1892) Figs 10-12, Table 2

Type material investigated.

Syntype workers: CASENT0101667, (collection code: ANTC3246), CASENT0101687 (collection code: ANTC3247): [MADAGASCAR, Prov.] Antsiranana, Forêt d’ Andrangoloaka [Antananarivo, -18.91 N, 47.55 E], Madagascar (Sikora)", (CASENT0101667, CASENT0101687, MHNG);

Material examined.

Dark (wild type) phenotype: MADAGASCAR: BLF1626 (collection code: BLF1626, 3w, CAS), BLF1626(16) (collection code: BLF1626(16), 2w, CAS): Fianarantsoa, 29 km SSW Ambositra, Ankazomivady, N -20.77667, E 47.165, alt 1700 m, B.L. Fisher, 1_14_1998; CASENT0040463 (collection code: BLF09324, 1w, CAS): Antsiranana, Parc National de Marojejy, 25.4 km 30° NNE Andapa, 10.9 km 311° NW Manantenina, N -14.445, E 49.735, alt 2000 m, B.L. Fisher, 11_23_2003; CASENT0048441 (collection code: BLF10513, 2w, CAS): Toamasina, Analamay, N -18.80623, E 48.33707, alt 1068 m, Malagasy ant team, 3_21_2004; CASENT0049029 (collection code: BLF10704, 2w, CAS): Toamasina, Torotorofotsy, N -18.87082, E 48.34737, alt 1070 m, Malagasy ant team, 3_29_2004; CASENT0051178 (collection code: BLF10689, 2w, CAS): Toamasina, Torotorofotsy, N -18.87082, E 48.34737, alt 1070 m, Malagasy ant team, 3_28_2004; CASENT0058844 (collection code: BLF11968, 1w, CAS): Toamasina, Forêt Ambatovy, 14.3 km 57° Moramanga, N -18.85083, E 48.32, alt 1075 m, B.L. Fisher, 4_12_2005; CASENT0071372 (collection code: BLF13809, 1w, CAS), CASENT0071382 (collection code: BLF13794, 1w, CAS), CASENT0071385 (collection code: BLF13811, 1w, CAS), CASENT0071427 (collection code: BLF13798, 1w, CAS), CASENT0071431 (collection code: BLF13800, 1w, CAS), CASENT0071437 (collection code: BLF13785, 1w, CAS), CASENT0071439 (collection code: BLF13775, 1w, CAS): Fianarantsoa, Parc National d’Andringitra, Plateau d’Andohariana, 39.8 km 204° Ambalavao, N -22.18767, E 46.90083, alt 2150 m, B.L. Fisher et al., 4_16_2006; CASENT0097142 (collection code: MA-01-01D-01, 1w, CAS), CASENT0097143 (collection code: MA-01-01D-01, 1w, CAS): Diego-Suarez, Parc National Montagne d’Ambre [Petit Lac road], N -12.52028, E 49.17917, alt 1125 m, Irwin, Schlinger, Harin’H, 1_25_2001; CASENT0111762 (collection code: MG-29-06, 1w, CAS): Fianarantsoa, Miandritsara Forest, 40Km S of Ambositra, N -20.79267, E 47.17567, alt 822 m, Rin’ha, Mike, 1_5_2005; CASENT0112777 (collection code: MA-02-09C-60, 1w, CAS): Fianarantsoa, Belle Vue trail, Ranomafana National Park, Fianarantsoa Prov., N -21.2665, E 47.42017, alt 1020 m, R. Harin’Hala, 5_4_2003; CASENT0114296 (collection code: MA-02-09D-06, 1w, CAS): Fianarantsoa, JIRAMA water works near river, Ranomafana National Park, Fianarantsoa Prov., N -21.2485, E 47.45217, alt 690 m, R. Harin’Hala, 12_6_2001; CASENT0118350 (collection code: MG-29-04, 1w, CAS): Fianarantsoa, Miandritsara Forest, 40Km S of Ambositra, N -20.79267, E 47.17567, alt 822 m, Rin’ha, Mike, 11_14_2004; CASENT0122389 (collection code: BLF17425, 1w, CAS), CASENT0125701 (collection code: BLF17430, 1w, CAS), CASENT0125880 (collection code: BLF17420, 1w, CAS): Antananarivo, Kaloy, N -18.58998, E 47.65102, alt 1423 m, B.L. Fisher et al., 4_27_2007; CASENT0125872 (collection code: BLF17314, 1w, CAS): Antananarivo, Ambohimanga, N -18.76125, E 47.56447, alt 1361 m, B.L. Fisher et al., 4_26_2007; CASENT0127628 (collection code: BLF01989, 1w, CAS): Antsiranana, R.S. Manongarivo, 20.4 km 219° SW Antanambao, N -14.04667, E 48.40167, alt 1860 m, B.L. Fisher, 11_3_1998; CASENT0127627 (collection code: BLF01972, 3w, CAS): Antsiranana, Prov. Antsiranana R.S. Manongarivo 17.3 km 218° SW Antanambao, N -14.02167, E 48.41833, alt 1580 m, B.L. Fisher, 10_27_1998; CASENT0127629 (collection code: MA-01-01A-01, 1w, CAS): Diego-Suarez, Parc National Montagne d’Ambre [1st campsite], N -12.51444, E 49.18139, alt 960 m, Irwin, Schlinger, Harin’H, 1_21_2001; CASENT0127630 (collection code: ANTC8395, 2w, CAS): Antsiranana, RNI Marojejy, 11 km NW Manantenina, N -14.45, E 49.73333, alt 1875 m, E.L. Quinter, 11_13_1996; CASENT0127636 (collection code: ASS(03)-1, 2w, CAS): Fianarantsoa, Rés. Andringitra, Plateau d’Andohariana, base of Pic d’Ivangomena, N -22.2, E 46.9, alt 2050 m, Goodman leg., 9_3_1995; CASENT0127647 (collection code: BLF01755, 2w, CAS): Fianarantsoa, 8.0 km NE Ivohibe, N -22.42167, E 46.89833, alt 1200 m, B.L. Fisher (Sylvain), 11_3_1997; CASENT0136019 (collection code: BLF18083, 1w, CAS): Antsiranana, Parc National Montagne d’Ambre, Lac maudit, N -12.58502, E 49.15147, alt 1250 m, B.L. Fisher et al., 11_13_2007; CASENT0142139 (collection code: BLF20488, 1w, CAS), CASENT0142157 (collection code: BLF20480, 1w, CAS): Fianarantsoa, Parc naturel communautaire, 28.5 km SW Ambositra, N -20.78414, E 47.16699, alt 1780 m, B.L. Fisher et al., 5_21_2008; CASENT0212236 (collection code: BLF26175, 1w, CAS): Antsiranana, Parc National Montagne d’Ambre, N -12.51778, E 49.17957, alt 1000 m, B.L. Fisher et al., 3_6_2011; CASENT0227041 (collection code: BLF01989, 1w, CAS, CASENT0227040), CASENT0227050 (collection code: BLF01989, 1w, CAS), CASENT0227052 (collection code: BLF01989, 1w, CAS): Antsiranana, R.S. Manongarivo, 20.4 km 219° SW Antanambao, N -14.04667, E 48.40167, alt 1860 m, B.L. Fisher, 11_3_1998; CASENT0230550 (collection code: BLF26169, 1w, CAS), CASENT0245051 (collection code: BLF26169, 1w, CAS, CASENT0409551): Antsiranana, Parc National Montagne d’Ambre, N -12.51778, E 49.17957, alt 1000 m, B.L. Fisher et al., 3_6_2011; CASENT0274650 (collection code: BLF28278, 1w, CAS): Antananarivo, Réserve Speciale d’Ambohitantely, N -18.22444, E 47.2774, alt 1490 m, B.L. Fisher et al., 3_9_2012; CASENT0275845 (collection code: BLF28339, 1w, CAS): Antananarivo, Mandraka Park, N -18.9019, E 47.90786, alt 1360 m, B.L. Fisher et al., 3_11_2012; CASENT0409550 (collection code: BLF02398, 1w, CAS), CASENT0409551 (collection code: BLF02398, 1w, CAS): Antananarivo, 3 km 41° NE Andranomay, 11.5 km 147° SSE Anjozorobe, N -18.47333, E 47.96, alt 1300 m, Fisher, Griswold et al., 12_5_2000; CASENT0486880 (collection code: BLF09120, 1w, CAS), CASENT0487129 (collection code: BLF09369, 2w, CAS), CASENT0487141 (collection code: BLF09412, 2w, CAS), CASENT0487143 (collection code: BLF09412, 2w, CAS), CASENT0487177 (collection code: BLF09372, 2w, CAS), CASENT0487210 (collection code: BLF09416, 2w, CAS), CASENT0487357 (collection code: BLF09315, 4w, CAS): Antsiranana, Parc National de Marojejy, 25.7 km 32° NNE Andapa, 10.3 km 314° NW Manantenina, N -14.445, E 49.74167, alt 1575 m, B.L. Fisher, 11_22_2003; MCZENT0576254 (1w, MCZ): Antsiranana, 10k NE Antananarivo lac Alarobie, G.D. Alpert, 3_10_1991;

Ocher phenotype: CASENT0119572 (collection code: BLF15013, 1w, CAS), CASENT0119575 (collection code: BLF15088, 1w, CAS), CASENT0119580 (collection code: BLF15089, 1w, CAS): Fianarantsoa, Parc National Befotaka-Midongy, Papango 28.5km S Midongy-Sud, Mount Papango, N -23.84083, E 46.9575, alt 1250 m, B.L. Fisher et al., 11_19_2006; CASENT0149638 (collection code: BLF21513, 1w, CAS, CASENT0149638): Toliara, Réserve Spéciale Kalambatritra, N -23.4185, E 46.4583, alt 1365 m, B.L. Fisher et al., 2_8_2009; CASENT0148666 (collection code: BLF21476, 1w, CAS): Toliara, Réserve Spéciale Kalambatritra, Betanana, N -23.4144, E 46.459, alt 1360 m, B.L. Fisher et al., 2_8_2009; CASENT0192603 (collection code: BLF01626, 1w, CAS): Fianarantsoa, 29 km SSW Ambositra, Ankazomivady, N -20.77667, E 47.165, alt 1700 m, B.L. Fisher, 1_14_1998; CASENT0141296 (collection code: BLF20465, 1w, CAS): Fianarantsoa, Parc naturel communautaire, 28.5 km SW Ambositra, N -20.78414, E 47.16699, alt 1780 m, B.L. Fisher et al., 5_21_2008; CASENT0127621 (collection code: BLF01626, 4w, CAS): Fianarantsoa, 29 km SSW Ambositra, Ankazomivady, N -20.77667, E 47.165, alt 1700 m, B.L. Fisher, 1_14_1998; CASENT0127626 (collection code: BLF01989, 1w, CAS): Antsiranana, R.S. Manongarivo, 20.4 km 219° SW Antanambao, N -14.04667, E 48.40167, alt 1860 m, B.L. Fisher, 11_3_1998;

Description of workers.

Body color: brown; black; rarely yellow. Body color pattern: Body concolorous. If yellow, body concolorous, clava, femora and 1st gastral tergite darker. Absolute cephalic size: 692 [616, 763]. Cephalic length vs. Maximum width of head capsule (CL/CWb): 1.18 [1.13, 1.22]. Postocular distance vs. cephalic length (PoOc/CL): 0.46 [0.43, 0.48]. Postocular sides of cranium contour frontal view orientation: converging posteriorly. Postocular sides of cranium contour frontal view shape: convex. Vertex contour line in frontal view shape: straight; slightly concave. Vertex sculpture: main sculpture inconspuous, ground sculpture smooth. Gena contour line in frontal view shape: convex. Genae contour from anterior view orientation: converging. Gena sculpture: rugoso-reticulate with feeble areolate ground sculpture. Concentric carinae laterally surrounding antennal foramen: present. Eye length vs. absolute cephalic size (EL/CS): 0.26 [0.24, 0.28]. Frontal carina distance vs. absolute cephalic size (FRS/CS): 0.31 [0.29, 0.33]. Longitudinal carinae on median region of frons: absent. Smooth median region on frons: present. Antennomere count: 12. Scape length vs. absolute cephalic size (SL/CS): 0.78 [0.72, 0.82]. Median clypeal notch: variable. Ground sculpture of submedian area of clypeus: present. Median carina of clypeus: absent. Lateral carinae of clypeus: present. Metanotal depression: variable. Dorsal region of mesosoma sculpture: areolate ground sculpture, superimposed by dispersed rugae. Lateral region of pronotum sculpture: areolate ground sculpture, main sculpture dispersed costate. Mesopleuron sculpture: ground sculpture areolate, main sculpture absent. Metapleuron sculpture: ground sculpture areolate, main sculpture absent. Petiole width vs. absolute cephalic size (PEW/CS): 0.22 [0.19, 0.24]. Anterior profile of petiolar node contour line in lateral view shape: concave. Dorso-caudal petiolar profile contour line in lateral view shape: convex. Dorsal region of petiole sculpture: ground sculpture areolate, main sculpture absent. Postpetiole width vs. absolute cephalic size (PPW/CS): 0.35 [0.29, 0.39]. Dorsal region of postpetiole sculpture: ground sculpture areolate, main sculpture absent.

Diagnosis.

Workers of this species differ from that of Nesomyrmex gibber by having no mesothoracic hump, and from Nesomyrmex flavus sp. n. and Nesomyrmex nitidus sp. n. by its dark brown color versus the light yellow hue of the two latter species.

The dark color in madecassus populations is dominant across the entire known distributional area, and comprises ~95% of the examined material. However, a rare, lighter-colored madecassus phenotype (ocher phenotype) was also found in a few localities. There is no evidence, other than color, that would suport heterospecifity of these two discrete phenotypes of Nesomyrmex madecassus workers and no correlation was found between elevational cline and color. Only one mixed sample is known to include both ocher and dark phenotype. Ocher madecassus phenotypes are darker than the majority of Nesomyrmex flavus and Nesomyrmex nitidus workers and also differ from the latter species by having brown femora and a dark patch on the first gastral tergite.

Nesomyrmex madecassus workers (including ocher phenotypes) can be separated from those of Nesomyrmex flavus and Nesomyrmex nitidus using the ratio of postocular area to cephalic width including compound eyes (PoOC/CW), which yielded only three misclassified cases:

madecassus (n = 84) = 1.92 (1.77, 2.07), [5-95% percentiles: min. 1.85, max. 2.01]

flavus (n = 61) = 1.73 (1.53, 1.89), [5-95% percentiles: min. 1.60, max. 1.84]

nitidus (n = 79) = 1.73 (1.52, 1.85), [5-95% percentiles: min. 1.63, max. 1.83]

A more precise means to separate ocher madecassus phenotype from workers of Nesomyrmex flavus and Nesomyrmex nitidus may be necessary. In these cases, a discriminant D4 funtion (D4 = +0.0511*PoOC -0.0486*CW -0.0702*PEW +0.0435*PEL +8.3829) provides a moderately time consuming classification tool yielding non-overlapping ranges between madecassus workers and that of flavus and nitidus (morphometric data are given in micrometers):

madecassus D4 (n = 84) = -1.70 [-4.61, 0.26]

flavus D4 (n = 61) = +2.39 [0.42, 5.02]

nitidus D4 (n = 79) = +3.18 [0.51, 5.98]

Biology and distribution.

This species is known to occur in Madagascar’s rain forests at very high altitudes between 690 and 2150 m, mean: 1538 m (Fig. 3). This species is known to forage in low vegetation, nests can often be found in dead twigs, or rarely in leaf litter (leaf mold, rotten wood), or in rotten tree stumps.