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Title: Species Composition of Ants (Hymenoptera: Formicidae) and Thermal Tolerance along Environmental Gradient in the Bale Mountains National Park (BMNP), Ethiopia
???metadata.dc.contributor.*???: Prof.Yalemtsehay Mekonnen
Ayele, Chirotaw
Keywords: ants, diversity, climate change;thermal tolerance, Camponotus negus, Camponotus acvapimensis, Bale Mountains National Park
Issue Date: Jan-2017
Publisher: Addis Ababa University
Abstract: This study was conducted to investigate the species composition of ants (Hymenoptera: Formicidea) and thermal tolerance of Camponotus negus and Camponotus acvapimensis in the Bale Mountains National Park (BMNP), Ethiopia. Ants were collected from different altitudes and habitats using manual search, baits and pitfall traps from December 14, 2013 to October 08, 2015. Heat and cold tolerance of ant colonies (C. negus) from different altitudes of the BMNP (Gaysay and Sanetti) and from Dilla (C. acvapimensis) was determined. The time taken (minutes) by ant colonies to lose mobility at a stressfully high temperature (knock-down resistance) of colonies were measured from each site as an index of heat tolerance. For heat tolerance experiment 10 to 12 individuals from each colony (for a minimum of 24 individuals per colony) were placed into two Petri dishes in identical water baths (Stuart digital water bath, RE300DB, Keison International Ltd, UK). Initially the temperature in both baths was set and maintained at 45 °C for 90 minutes. After 90 minutes, the temperature was raised by 5 °C, and continued to rise by 5 °C every 30 minutes thereafter until all ants had succumbed to heat stress. Time was recorded starting from the time the first ant completely lost mobility till the last ant stopped moving. The time required for an individual to recover from exposure to extremely low temperatures (chill-coma recovery) was used to assess cold tolerance of ants. For cold tolerance experiments, 24 to 27 ants from each colony were placed in a Petri dish covered in ice for 20 minutes. Then the time for each individual to recover from chill-comma was recorded. From a total of 162 sample collections made, 16 species under 8 genera and 4 subfamilies namely; Dorylinae, Formicinae, Myrmicinae and Ponerinae were identified. Subfamily Myrmicinae was the most diverse with nine species(56.25%) and the genus Tetramorium was the most speciose containing five species. C. negus was the most abundant species of 54.12% of the samples collected. The highest ant species diversity was observed in the altitude range of 2000– 2500 m followed by 3000– 3500 m and the lowest was in the altitude range of 2500– 3000 m and 3500–4000 m. Thus there was no clear pattern of species diversity with elevation. The highest ant species diversity was recorded from the rainforest. C. negus from Sanetti (3970 m) had high heat tolerance (143.52 ± 1.80 minutes) than from Gaysay (3040 m) (98.30 ± 1.82) minutes, but cold tolerance did not differ between the two sites. Colonies from Sanetti on average tolerated heat for additional 45 minutes compared to Gaysay. C. acvapimensis had similar heat tolerance as C. negus from Sanetti but it had very low cold tolerance which took 549.79 ± 18.77 seconds to recover from chill-comma compared to C. negus from both Gaysay and Sanetti which were 113.94 ± 19.40 and 84.04 ± 18.77 seconds respectively. C. acvapimensis needed nearly 5 times more time to recover from chillcoma compared to colonies of C. negus from Gaysay and 6 times than C. negus from Sanetti. Hence C. negus from Sanetti had higher heat and cold tolerance and may have higher potential to survive in the changing climate of BMNP. In conclusion, there was no clear pattern of species diversity with elevation and the diversity was the highest in the rainforest. C. negus from Sanetti had higher heat and cold tolerance and may has higher chance of survival in the changing climate.
Description: A Dissertation presented to the Department of Zoological Sciences in Fulfillment of the Requirements for the Degree of Doctor of Philosophy (Biology: Zoological Sciences)
Appears in Collections:Thesis-Zoological Sciences

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