Basiceros

Basicerotine (Formicidae: Basicerotini) ants has a disjunctive distribution, occurring in the New World (primarily Neotropical region, with one species in Florida, USA) and the Melanesian region (Australia, New Caledonia, Fiji, Papua New Guinea, Solomon Islands, Borneo, Malaysia, Indonesia, Singapore, Palau, Brunei and the Philippines). Brown & Kempf (1960) also studied material from this group collected at Botel Tobago Island (also referred as Orchid Island), south of Formosa. Of all genera present inside the tribe, only the species that compose Rhopalothrix and Eurhopalothrixdon't have exclusively neotropical distribution, with the possible earliest representatives from the genera of the tribe Basicerotini (Dietz, 2004). According to Brown & Kempf (op. cit.), probably there was a separation of the initial population of this ants, widely distributed (Indo-Australian, Neotropical and Neartic regions), for two large peripheral areas, where they settled and this event would be responsible in separating the two genera mentioned above. About Basicerotini, inconclusive molecular data suggested that this tribe is monophyly (Brady et al, 2006; Moreau et al, 2006), but only two genera belonging to this group were included in that study, with only one species each. However, some phylogenies have been performed using morphological data (Dietz, 2004; Baroni Urbani & De Andrade, 2007), indicating the monophyly of the tribe. However, Baroni Urbani & De Andrade (op. cit.), by considering Basicerotini as a junior synonym of Dacetini, argued that the separation would leave Dacetini as a paraphyletic tribe and claimed that "the homogeneity of the structural limits of this hypothetical tribe would result in loss of accuracy to what is commonly accepted for a valid tribes of ants. " The taxonomy of ants of the genus Basiceros suffered several nomenclatural changes. In 1860, Smith described a genus of ants,Ceratobasis (later to become Basiceros) with Ceratobasis singularis as type species by monotypy. The genus of Cerambycidae beetles Ceratobasis, however, had been described by Lacordaire in 1848. In 1906, Schulz proposedBasicerosas a replacement name to Ceratobasis, correcting this homonymy. Brown, in 1974, designates Basiceros as senior synonym of Aspididris. In 2007, the genusCreightonidris was also considered a junior synonym of Basiceros by Feitosa, Dietz and Brandão. Currently eight species of Basiceros are valid: B. conjugansBrown, 1974; B. convexiceps (Mayr, 1887);B. disciger (Mayr, 1887);B. manni Brown and Kempf, 1960; B. militaris (Weber, 1950);B. redux (Donisthorpe, 1939); B. scambognathus (Brown 1949) and B. singularis (Smith, 1858). Brown and Kempf (1960) made ​​the only revision to the genus. Synonyms were later diagnosed as well as the description of new species by several authors, cited below. Brown (1974) introduced amendments to Basiceros systematics (diagnoses and a reviewed key) and Feitosa et al. (2007) diagnoses and an updated key to the genre. Also in 2007, Baroni Urbani & De Andrade, using morphological data for phylogenetic proposal suggested the synonymy of all genera inside the tribe under Basiceros, claiming that "no explicit synapomorphy features Basiceros". In this work, the authors claim that they are aware that even the modification status of the tribe to the genus level will result in a poorly defined generic diagnosis when compared to most other genres, given the low number of unique synapomorphies that divided the gender of the other Dacetini the tribe, but defend this position by considering its proposal based on "minimal nomenclatural change in favor of maximum practical use." Therefore, there is a knowledge gap regarding the monophyly of the genus and the validity of synapomorphies proposed by Bolton (2003) and thus the phylogenetic relationship between species comprising the genus is a good topic of study. The integument of the genus Basiceros is rich in sculptures and different types of hairs, besides their representatives possess median sizes compared with ants in general, allowing studies under stereomicroscopy. Apparently all known species have a cryptobiotic habit and they are exclusively collected in South and Central America. Little is known about its natural history and until recently it was believed that ants of this genus were comparatively difficult to be collected (Longino, 1999); these ants cover themselves with soil particles, assuming a cryptic aspect against the ground in an extreme degree (Wilson & Brown, 1985), thanks to the accumulation of particles of soil and leaf litter, which adhere to a double layer of specialized standing hairs (spatulated and shorter decumbent to suberects setae). It is believed that these brush-like hairs can act as soil particles collectors (Hölldobler & Wilson, 1986). Furthermore, ants of this genus are considered to move slowly and exhibit thanatosis (they "pretend" to feign death, remaining still for a few minutes after being disturbed) (Hölldobler & Wilson, 1986). With regard to diet, Weber (1950) and Brown (1974) reported the termites as the basis for diet B. singularis - termites were observed being loaded into ant nests and also within the waste. Longino (1999) observing colonies ofBasiceros manni in Costa Rica noted that in garbage chambers inside nests there were unidentified gastropod shells. Although Wilson & Hölldobler (1986) have conducted laboratory experiments offering various food items to captive colonies of the species B. manni, the authors did not include gastropods in this set of offered items. Longino (1999) argues about the possibility of some form of prey specialization, suggesting that the long, narrow shape of the head and mandibles (triangular and massive) are adapted to predation on gastropods.