| dc.description.abstract | The effects of forest disturbance on butterfly diversity in Kakamega Forest National
Reserve (K.F.N. R), Western Kenya were investigated by comparing butterfly species
composition and abundance in three habitat types within the reserve. The reserve was
greatly altered in the last two decades through selective commercial logging and clearing
for agricultural and pasture land leading to a mosaic of habitat types. The main objective
was to determine the effect of forest disturbance on butterfly species composition and
abundance in primary, secondary and Psidium habitat types. The primary habitat type
was least disturbed while the Psidium habitat type had the highest disturbance. The
secondary habitat type had intermediate disturbance. The number of butterfly species and
their abundance in each habitat type was determined by walking along five transects (100
m x 5 m) established in each habitat type. Air temperature, light intensity, relative
humidity, and butterfly nectar sources were recorded during butterfly transect count.
Vegetation composition in the three habitat types was determined by walking along a
transect (100m x 1m) established in each habitat type and recording the species of trees,
shrubs and their abundances. Five quadrats (lm x 1m) were established at intervals of
20m along a 100m transect in each habitat type. Herbaceous species and their abundance
were recorded in each quadrat. The secondary forest had the highest trees and shrub
diversity (HI = 4.46) while the Psidium habitat type had the highest herbs diversity (HI =
1.94). There was a significant difference in vegetation diversity between primary and
Psidium habitat type and between secondary and Psidium habitat type (t 0.05 (2) 978 = 1.854;
t 0.05 (2) 978 =1.962 respectively).
A total of 170 butterfly species comprising of 8,765 individuals were recorded from three
families in all the three habitat types. Secondary habitat type had the highest butterfly
diversity (H' = 5.13) whereas the Psidium habitat type had the lowest butterfly diversity
(HI= 4.83). A high similarity in butterfly species existed between the primary and
secondary habitat types (Morista's index of similarity (CA) = 0.78), while a high
dissimilarity existed between butterfly species recorded in the Psidium and the primary
(C" = 0.23;) and between Psidium and the secondary habitat type (CA = 0.28). This was
mainly due to invasion of the Psidium habitat type by open formation and savannah
.butterfly species. There were 21 species with an abundance of 100 individuals and above
in all three habitat types. A total of 46 butterfly species were found to prefer specific
habitat types which consisted of 16 species in the primary, 14 species in the secondary
and 16 species in Psidium. These species can be used as indicators of forest disturbance
in Kakamega forest. A total of 61 butterfly species were found to occur in all the three
habitat types.
Fluctuations in the number of butterfly species and their abundance from month to month
were not significant except in the Psidium habitat type (F 6, 28 = 4.78, P = 0.002). Monthly
changes in temperature led to a significant change in the monthly number of butterfly
species recorded in the primary and Psidium habitat type (r = 0.52, P = 0.05, N =7 and (r
= 0.57, P = 0.03, N =7). The correlation between butterfly nectar source abundance and
butterfly species and their abundance was not significant.
It was apparent that forest disturbance had a negative effect on butterfly species, but the
effect depended on the level of disturbance, which determined the microhabitat
conditions available for butterflies. | en |
