Ant diversity at Sunut forest , Khartoum , Sudan

Due to their scientific value as bioindicators, assessment of ant diversity is an important target of biological diversity research, especially in regions where conservation threats are substantial. In this paper, we present a preliminary investigation of the ant fauna at Sunut forest which is a natural forest located in the middle of Khartoum city, the capital of Sudan. Due to its location, the habitat at Sunut forest is increasingly threatened by human activities. Our goal is to provide a database to serve as a guide for future management and conservation research taking place at this forest. During the study period (May, June and July 2012), ten species of ants were collected and classified. The ant collection contained species with different habitat preferences, indicating that the environment at Sunut forest is highly heterogeneous.


INTRODUCTION
Biological indicators are species whose existence, physiology, behaviour or population dynamics reflect certain biotic or abiotic aspects of the environment and thus they can be used to monitor the state of ecological system through time (McGeoch, 1998).Bioindicators include a wide variety of species such as lichens, insects, copepods and microbial organisms and are used to monitor both terrestrial and aquatic environments.In conservation biology, bioindicators were proved to be a useful tool in monitoring and detecting changes in natural ecosystems, such as those caused by pollution and habitat disturbance (Rainio & Niemelä, 2003).Moreover, indicator species can also be used to monitor the ecosystem recovery following environmental rehabilitation projects (Majer, 1983).In biodiversity studies, surveying indicator species represent a simple, cost-effective method to estimate the species richness in the community (Colwell & Coddington, 1994).
Invertebrate communities represent robust indicators of the health of terrestrial environments.This is so because of their dominant biomass, extensive diversity in addition to their fundamental importance in the ecosystem function (Andersen, 1997).In particular, ants are used extensively as bioindicators, as their community composition and their response to habitat disturbance are both well-characterized (Andersen & Majer, 2004).In an analysis of various insect groups as potential bioindicators, ants scored highest (Brown, 1997).Changes in ant community structure following disturbance have been found to reflect changes in many other invertebrate communities, indicating the high sensitivity of this group to habitat change and their representation of other components in the ecosystem (Majer, 1983;Andersen, 1997).
Al-Sunut is a natural forest that borders the White Nile at the Mogran area, Khartoum.It is a poor savannah habitat that is seasonally submerged following the Nile flooding and thus considered as an inland wet land ecosystem (Altayeb & Hamed, 2003).The plant cover at the forest is dominated by Acacia nilotica trees.Sunut forest is characterized by rich biological diversity, as shown by previous surveys of avifauna and invertebrate fauna.Due to its location in the centre of a the crowded, urban region of Khartoum, Sunut forest is subjected to extensive human influence from various sources, including construction, agricultural and recreational activities taking place in the forest and its vicinity (Altayeb et al., 2013;Salah & Idris, 2013).As a consequence, the forest has become the focus of attention for many Sudanese conservationists and environmentalists.
Few studies have been conducted on the ant fauna of Sudan.As a consequence, a substantial amount of data on the diversity, the structure and the population dynamics of ant communities in Sudan should be accumulated prior to any realistic attempt to incorporate ants as bioindicators in a local conservation or rehabilitation project.Ant diversity in Khartoum state has been previously surveyed by Omer &Alam (2055) who found twenty five species.In the present study, we investigate the species richness of the ant community at a particular location within Khartoum state, that is, the Sunut forest.

Collection site
This study was carried out at the Sunut Forest (15° 35′N, 32° 30′E).The site is bordered by the new White Nile Bridge from the North, the industrial area from the South, the Ghaba Street from the East and the White Nile from the West.A long the river bank there is a narrow cultivated area extending between the forest and the river bank.

Collection of specimens
Ant specimens were collected manually using a paintbrush moistened with 5% formalin or by using fine forceps.The collected specimens were dropped and preserved in glass tubes containing 7% formalin.Collection was performed during the daytime between 9 a.m. and 5 p.m. Following collection, the specimens were examined under the microscope.

Identification of ant specimens
Taxonomic categorization of collected ant specimens was performed following the key of Bolton (1994).Identification was done by A. Omer.

Classification of ant species recorded at Sunut forest
Ten different species of ants (Family: Formicidae) have been identified in the current survey: