Observations on the genus Terataner in Madagascar (Hymenoptera: Formicidae).
Psyche 99:117-127, 1992.
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OBSERVATIONS ON THE GENUS TERATANER IN
MADAGASCAR (HYMENOPTERA: FORMICIDAE)
Museum of Comparative Zoology
Harvard University, Cambridge, MA 02138
The present study was inspired by the analysis of endemism in Malagasy ants by William L. Brown (1973). The rare myrmicine ant genus Terataner, presently with twelve described species, is known only from the Ethiopian and Malagasy zoogeographical regions. Bolton (1981) revised the Ethiopian species of Terataner, and provided illustrations and a key to workers. In the same paper, Bolton described a new species of Terataner from Madagascar and included an illustrated key to workers from the Malagasy region. An ongoing study of Malagasy Terataner resulted in the discovery of many new species (Alpert, in prep.) and the first natural history data on any of the ants in this group. This new information sepa- rates Terataner into two distinct groups with fundamental biologi- cal differences.
The first group, containing four closely related arboreal species, occurs only in tropical West Africa. According to Bolton (1981, pers. comm.), these species construct nests in rotten parts of stand- ing timber, often located a considerable distance above the ground. The males in this group are unknown and the female reproductives, although presently undescribed, are morphologically typical ant queens. No other biological information is available on this group of ants.
The second, much larger, group of Terataner species nests near the ground and inhabits preformed plant cavities, such as hollow twigs and burrows of wood-boring insects. One species occurs in the Transvaal of South Africa, one in East Africa, one in the Sey- chelles, and five are currently recognized in Madagascar. The males, known from only a few species, are morphologically unusual. The newly discovered queens are wingless ergatoid Manuscript received 8 September 1992
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118 Psyche [vo~. 99
forms, distinguishable externally from workers only by very subtle characters. This extreme ergatoid condition is rare among ants in general (Peeters and Crewe 1985, Holldobler and Wilson 1990), and particularly rare in the Myrmicinae (Bolton 1986, Brandao 1987, Peeters 199 1). Observations on these Malagasy Terataner contribute to our understanding of the evolutionary biology of the genus, as well as the biogeography and biodiversity of ants from Madagascar.
MATERIALS AND METHODS
In a forthcoming revision of Malagasy Terataner (Alpert, in prep.), species names are given to the forms designated T. sp. a-d in this study. Individual foragers of T. sp, a were first discovered by William L. and Doris E. Brown, in 1977, in a vanilla plantation near the town of Sambava on the northeast coast of Madagascar. Subsequent trips by the author to the coastal lowlands and foothills of the Masoala Peninsula in the northeast of Madagascar (February 1990 and 199 1, July 1992) were successful in locating colonies of this species as well as three other species of Terataner (alluaudi, foreli and sp. b). In August of 1992, colonies of two additional species were studied, one from the Ankarana Reserve in the north (sp. c), and the other (sp. d) from the Lokobe Forest, Nosy Be in the northwest of Madagascar.
Complete Terataner colonies were collected into both 80% alcohol and Bouin's preservative. Field notes and photographs were taken of each nest site location. Field observations were made on foragers from each species, and representative colonies were brought back to the laboratory for further studies. Colonies were located by following individual workers return- ing to their nests and by searching the ground for twig nests. Ants entering twigs in search of prey items were occasionally mistaken for returning foragers. Nests sites were confirmed only when Ter- ataner ant brood was found associated with workers. After nest collection, the immediate area was examined for colony fragments, returning foragers and other ant nests.
Workers and ergatoid reproductives in a colony were dissected under a light microscope to determine their degree of reproductive development. The degree of ovarian development was measured,
19921 Alpert 119
and those with developed ovaries were examined for the presence of external queen characters.
Foragers of three undescribed species of Terataner were found at field study sites but their nests were not located. Data from com- plete colonies of six species; two previously described and four undescribed, are included in this study: T. alluaudi, the most common Terataner in northern Madagas- car, is a large (7.3 mm) black species with conspicuous orange legs. It is found from just above sea level (20 m) on the northeast and northwest coasts to about 500 m inland. It ranges from 12's near Antsiranana (Diego Suarez:type locality) in the north, to a lat- itude of 15's near Marofinaritra.
T. foreli is a medium-sized (5.3 mm) black and orange species distributed along the eastern coast of Madagascar from 14's to 19's latitude and from 50 to 800 meters altitude. Morphologically, it is more variable than other species presently known from Mada- gascar, and has the widest distribution. T. sp. a is very similar to T. alluaudi but is larger (7.9 mm) and has black, rather than orange, legs. T. sp. a has only been collected from the northeast coast of the Masoala Peninsula. Occurring in forested foothills from 50 m to 100 m altitude, its habitat is threat- ened by the advance of agriculture at these lower elevations. T. sp. b is a small (4.5 mm), entirely black species, closely related to T. foreli. It has only been found along the northeast coast of the Masoala Peninsula and a few kilometers inland. T. sp. c is restricted to the Lokobe forest, a "R6serves Naturelles Integrales" along the southeast coast of Nosy Be, an island off the northwest coast of Madagascar. The protection of this reserve is vital to the survival of this ant.
T. sp. d is restricted to the Ankarana forest in the "Rkserves Speciales" of north central Madagascar. The protection of this reserve is vital to the survival of this ant. Figure 1 illustrates the distribution of Terataner species included in this study. Colony Composition
All six Terataner species nest in plant cavities, typically in dead branches or twigs that are on the ground or in bushes close to the
Figure 1. Distribution of Terataner in Madagascar. (T. alluaudi = 1; T. foreli = 2; T. sp.a=3;T.sp.b=4;T.sp.c=5;T.sp.d=6)
ground. Different species of Terataner were often found nesting within a meter of one another in the same habitat. T. alluaudi, a widespread species, was found sympatrically with T. foreli and the more restricted species T. sp. a, T. sp. b, T. sp. c, and T. sp. d. Lar- vae, pupae and adults were packed together into a central cavity.
19921 Alpert 121
Only one or two entrances were found per nest, and these openings were typically guarded by workers. During nest analysis, no preda- tors, parasites, or inquilines were found. Occasionally, stored insect booty were found cached at one end of the nest. Seven complete nests of T. alluaudi were collected (Table 1). The nest sites of T. alluaudi consisted of a dead branch on the ground (4 cases), or a dead branch resting in vegetation close to the ground (3 cases).
Table 1. T. alluaudi colony size and composition. Nest # Eggs Larvae
1 65 130
2 0 14
3 19 16
4 26 29
5 17 19
6 25 11
7 10 15
Q-Pupae 0-Pupae Males Ergatoid Q
48 2 3 5
1 0 0 3
1 0 0 1
7 0 1 1
1 0 0 1
2 0 0 1
0 0 0 1
Nine complete colonies of T. foreli were collected (Table 2). T. foreli colonies typically were found in small twigs resting directly on the ground.
Table 2. T. foreli colony size and composition. .-. --
Nest # Eggs Larvae Workers ~-Pupae 0-Pupae Males Ergatoid Q --
3 8 1 0
2 10 23 12
2 0 0 1
3 11 10 7
1 0 0 1
4 0 6 10
0 0 0 1
5 15 16 10
6 0 0 1
6 1 7 12
2 0 0 1
40 19 6 0
8 0 8 22
6 0 0 1
7 1 I 3 0
- - - -- - - - - -
Four complete nests of T. sp. a were collected (Table 3). The branches used for nests by T. sp. a were always suspended above the ground by vegetation.
122 Psyche [vo~. 99
Table 3. T. sp. a colony size and composition. Nest # Eggs Larvae Workers Q-Pupae (7-Pupae Males Ergatoid 9 Eight complete nests of T. sp. b were collected (Table 4). T. sp. b nests close to the ground in the stems of bushes, or on the ground in small twigs.
Table 4. T. sp. b colony size and composition. Eggs Larvae Workers Q-Pupae (7-Pupae Males Ergatoid Q 0 25 27 3 1 0 1
20 2 1 46 9 0 1 1
8 9 16 3 0 1
24 65 5 5 12
0 0 1
47 8 9 24 6
6 0 1
20 4 1 22 16 0 0 1
39 41 28 17 0 0 1
2 1 8
19 3 0 0 1
Eight complete nests of T. sp. c were collected (Table 5). Nests were found in twigs on the ground, or in small stumps close to the ground.
Table 5. T. sp. c colony size and composition. Nest #
Workers Males Ergatoid Q
Three complete nests of T. sp. d were collected (Table 6). Nests were found in small twigs resting on the ground.
19921 Alpert 123
Table 6. T. sp. d colony size and composition. Nest # Eggs Larvae Workers Q-Pupae 0-Pupae Males Ergatoid Q --
1 10 3 7 11 3 0 0 1
23 8 1 0 0 1
3 0 9 3 0 0 0 1
No morphologically normal alate or dealate queens occur in any of the Malagasy Terataner species. Colonies are almost always monogynous with a single reproductive, an ergatoid queen, that differs only slightly from corresponding workers (Fig. 2). This remarkable reproductive lacks both wings and ocelli, and has an almost normal, worker-like thorax. The ergatoid queen is exter- nally distinguishable from workers only by very subtle characters (e.g., small spines or tubercles below the mesonotal groove; a unique pattern of rugae on the sides of the pronotum) that vary among species. Ergatoid queens have ovaries bearing two to three Figure 2. Ergatoid queen of Terataner alluaudi. Scale line, 1.0 mm.
124 Psyche [VOI. 99
ovarioles, and each ovariole contains a string of oocytes undergo- ing oogenesis. In contrast, no oocytes are present in workers. Males
Males were rare in colonies, never surpassed four per colony, and were found in only three of the six species. Terataner males are morphologically distinctive (Fig. 3). The alitrunk is unusually shaped such that the wings are attached abnormally low on its sides, yet the male is still capable of flight. The middle pair of legs is reduced in size relative to the other two pairs of legs. Males were present in nests throughout this study (July, August, February and March). When nests were opened for analysis, males some- times took flight. It is unknown whether males mate inside nests or whether they mate in the field with ergatoid queens. Figure 3. Male of Terataner alluaudi.
Scale line, 1.0 mm.
All species are diurnal, active from sunrise to sunset. During the months of January, February and March, the warm, rainy season in Madagascar, foraging activity was much greater than during July and August, which are cool and dry. Foragers for all six species spend most of their time searching the upper surface of vegetation close to the ground. When found, nests were usually located less than 5 meters from these foragers. Although Terataner workers forage individually, they will also sometimes initiate small group raids.
T. alluaudi raided other ants and termites that were nesting inside branches. T. foreli was found attacking small insects and beetle larvae in branches by chewing their way into the wood to reach their prey. T. sp. a was observed bringing in and caching large numbers of lepidoptera larvae as well as termites and other insects. T. sp. b was observed bringing in dismembered parts of insects. T. sp. c, and d were not observed raiding and their food sources are unknown.
Ergatoid queens, reported for the first time in the genus Ter- ataner, are present in all six Malagasy species studied. Thus the most probable mode of colony founding in these ants is budding, where a mated ergatoid queen and some workers leave an estab- lished nest and occupy a nearby plant cavity. Flightless queens severely restrict the dispersal ability of these ants and may account, in part, for the limited geographic distributions of some of these species. This mode of reproduction, combined with their preference for forested habitats, means that Malagasy Terataner may be extremely vulnerable to habitat destruction. Malagasy Ter- ataner share other ecological similarities: 1) small colony size, ranging from 3 to 89 workers; 2) workers that are general preda- tors which group raid the nests of other ants, termites, and attack live insects; and 3) nest sites in plant cavities such as twigs and hollow branches close to the ground. The presence of spider and clerid beetle mimics of several Terataner species (Alpert, unpub- lished data) suggests that workers are distasteful and/or formidable to vertebrate predators.
Psyche [vo~. 99
The significance of the disjunct biogeographical distribution of this genus is an open question. Have a few species dispersed to Madagascar from Africa and then secondarily radiated in a land devoid of driver ants and other competitors? Or, is Terataner a relict genus that was once widespread and is now restricted to a portion of the Ethiopian and Malagasy regions? It will be interest- ing to discover whether the Transvaal and East African Terataner have ergatoid queens similar to Malagasy species, or normal queens similar to those in West Africa. Many more species of Ter- ataner may be discovered when Madagascar is studied further. The ant biodiversity of this region of the world is far greater than expected based upon the number of described taxa (P. Ward, pers. comm.). If conservation efforts are successful, further research may answer some of these unresolved questions. Terataner species in Madagascar are very different from those in West Africa. West African Terataner are arboreal and have nor- mal, alate queens. In Madagascar, colonies nest in plant cavities near the ground, and reproduction is by means of ergatoid queens that are very similar to workers. Workers forage for live insect prey, and often group raid the nests of ants and termites. Males are morphologically unusual and are rare. This is the first report of ergatoid queens in the genus Terataner.
I thank Michael Kelley for the map, Kathy Brown-Wing for her scientific illustrations, and Stefan Cover and Jim Wetterer for their critical review of this manuscript. Ani Patel, Emile Rajeriarison, Pascal Rabeson, Samuel Rafanomezantsoa and Abner Kingman, Jr. assisted in locating ant colonies in Madagascar. This work was supported by the Archos Entomological Fund at Harvard University.
in prep. A revision of the genus Terataner from the Malagasy Region. BOLTON, B.
1981. A revision of six minor genera of Myrmicinae (Hymenoptera: Formici- dae) in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History), Entomology, 43(4): 245-307. 1986. Apterous females and shift of dispersal strategy in the Monomorium salomonis-group (Hymenoptera: Formicidae). Journal of Natural His- tory, 20(2): 267-272.
BRANDAO, C. R.
1987. Queenlessness in Megalomyrmex (Formicidae: Myrmicinae), with a discussion on the effects of the loss of true queens in ants. In J. Eder and H. Rembold, eds., Chemistry and biology of social insects (Pro- ceedings of the Tenth International Congress of the International Union for the Study of Social Insects, Munich, 1986), pp. 111-1 12. Verlag J. Peperny, Munich.
BROWN, W. L.
1973. A comparison of the Hylean and Congo-West African rain forest ant faunas. In B. J. Meggers, E. S. Ayensu, and W. D. Duckworth, eds., Tropical forest ecosystems in Africa and South America: a comparative review, pp. 161-185. Smithsonian Institution Press, Washington, D.C. HOLLDOBLER, B. AND E. 0. WILSON
1990. The Ants. The Belknap Press of Harvard University Press, Cambridge, Mass. xii + 733 pp.
1991. Ergatoid queens and intercastes in ants: two distinct adult forms which look morphologically intermediate between workers and winged queens. Insectes Sociaux. 38: 1-1 5.
PEETERS, C. AND R. CREWE
1985. Worker reproduction in the ponerine ant Ophthalamopone berthoudi: an alternative form of eusocial organization. Behavioral Ecology and Sociobiology, 18: 29-37.
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