Diacamma cyaneiventre

Small colonies (214 workers ± 80 André et al. 2001) of this species can be found in open areas in southern India.

Distribution based on Regional Taxon Lists
Oriental Region: India.

Biology
André et al. (2006) - Diacamma cyaneiventre is a Ponerine ant with small colonies of about 214 ± 80 (±SD) workers (André et al., 2001), that inhabits open areas in southern India. Behavioral and genetic data suggest that monoandry should be the rule in Diacamma species (Peeters and Higashi, 1989; Fukumoto et al., 1989; André et al., 2001). The nests are long-lived underground structures (up to 50 cm, C. Peeters, unpubl. data) composed of many chambers. Nest entrances are surrounded by a conspicuous mound of soil and pebbles, and can thus easily be found. For purposes of thermoregulation, the workers regularly carry the brood in the upper chambers next to the nest entrance, as already noted in another Diacamma by Wheeler, 1915. An existing gamergate is replaced by a newly eclosed nestmate worker after the death of the existing queen or after colony fission. After a replacement, colonies go through short-lived periods in which two matrilines of sisters co-occur. This is a situation which can be described as serial polygyny.

In Diacamma, the single gamergate is replaced by one of her daughters (or occasionally by a sister). From a long-term genetic survey of nests of D. cyaneiventre, André et al. (2006) estimated the rate of gamergate turnover as well as the lifespan of workers and gamergate tenure using a maximum likelihood model developed for this purpose. We specifically compared the genotypes of two cohorts of workers sampled at 2 and 16 months interval from the same nests, using five microsatellite markers. To improve the accuracy of the estimates, we also used in the model the nests from the same population sampled only once and analysed by André et al. (2001). The model indicates that the possibility of the same nest not sheltering the same colony at two different sampling dates (colony turnover) was not significantly different from zero in our sample. The likelihood of the model was maximal for a probability of gamergate change pg = 0.005 per day (i.e. a gamergate tenure of 200 days) and a worker lifespan w = 60 days, indicating that the gamergate ‘s tenure is about 3 times longer than workers’ expected lifespan in the population studied. Moreover, the genetic analysis of the gamergate and brood in three colonies excavated completely, reveals that colony fission can occur just after a gamergate replacement with the sister of the new gamergate reproducing in the new propagule.

Doums et al. (2002) used both mitochondrial and microsatellite markers to assess the consequence of restricted female dispersal (due to the replacement of winged queens by gamergates) at three geographical scales: within a given locality (< 1 km), between localities within a given region (< 10 km) and between regions (> 36 km). Within a locality, a strong population structure was observed for mitochondrial DNA (mtDNA) whereas weak or nonexistent population genetic structure was observed for the microsatellites (around 5% of the value for mtDNA). Male gene flow was estimated to be about 20–30 times higher than female gene flow at this scale. At a larger spatial scale, very strong genetic differentiation for both markers was observed between localities — even within a single region. Female dispersal is nonexistent at these scales and male dispersal is very restricted, especially between regions. The phylogeographical structure of the mtDNA haplotypes as well as the very low genetic diversity of mtDNA within localities indicate that new sites are colonized by a single migration event from adjacent localities, followed by successive colony fissions. These patterns of genetic variability and differentiation agree with what is theoretically expected when colonization events are kin-structured and when, following colonization, dispersion is mainly performed by males.

Nomenclature

 *  cyaneiventre. Diacamma cyaneiventre André, 1887: 293 (w.) INDIA. Subspecies of rugosum: Forel, 1900d: 318. Revived status as species: Bingham, 1903: 78.