Distribution, abundance, population ratios and acoustic behaviour of conocephalus maculatus (orthoptera: tettigoniidae) in Kagera region North-Western Tanzania
Kashakuro, Reginald Silverius
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The longhorn grasshopper, Conocephalus maculatus (Le Guillou, 1841), is reported to be distributed over a wide range of grassland habitats in tropical Africa, Asia and Australasia. The species has gained attention in Asia as an important biological control agent of rice pests. In Tanzania, the species has been reported around Mount Kilimanjaro ecosystem with no reliable information in Kagera region, north-western Tanzania. The present study sought to bring to light the distribution, abundance, population ratios and acoustic behaviour, of this tettigoniid in Kagera region. The study was carried out in Bukoba, Karagwe, Kyerwa, Missenyi and Muleba districts at various randomly selected sites including; Maruku, Bugorora and Nshambya. It involved in-situ observation of the species for nine months from September 2014 to May 2015. A cross-sectional design was used in this study. Quadrat method, acoustic search, sweep-netting and direct hand-picking were applied in data collection. Distribution pattern was tested using the index of dispersion (ID). One-way ANOVA with LSD post hoc tests were used to analyse spatial and temporal variations in C. maculatus populations. Linear regression and Pearson`s correlation analyses were used to test the relationship of C. maculatus distribution, abundance and population ratios with ecological factors, and time of the day with sound signaling. Students` ttests were used to compare laboratory and field sound characteristics and also to test the significance in population ratios. Results revealed that distribution of this species was of aggregated nature (z = 3.09) and it was abundantly present in the area. Results also indicated a male-biased adult sex ratio (t = 3.473), a 1:1 nymph sex ratio (t = 1.107), and an adult-biased age ratio (t = 5.578). Distribution and abundance were positively related to temperature (r = 0.556; p < 0.0001) and grass vegetation (r = 0.49; p = 0.001) but inversely related to altitude (r = -0.611; p< 0.0001), humidity (r = - 0.341; p = 0.012), herbal vegetation (r = -0.340; p = 0.022) and shrubs (r = -0.387; p = 0.009). There were significant differences in abundances between the three sites in the order Nshambya < Maruku < Bugorora (f = 16.968; p < 0.0001). There were seasonal differences in abundance in the order Short dry < long rains < short rains (f = 5.591; p = 0.005). Results further revealed that sound signaling in C. maculatus was a daylight activity (r = 0.798, p = 0.000), which varied with environmental conditions. The results provide resourceful ecological information on the species. The study recommends the Tanzanian environmental authorities to enforce comprehensive conservation measures for grasslands which are a preferred habitat of this species.
- MST-Zoological Sciences