Spatio-temporal patterns of hover fly (Diptera: Syrphidae) diversity across three habitat types in KwaZulu-Natal, South Africa.
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Date
2022
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Abstract
Hover flies (Diptera: Syrphidae) are poorly studied in southern Africa and as a result, little is
known about their abundance throughout the year. Hover fly abundance is generally expected
to vary according to vegetation types, due to differences in the type and diversity of floral
resources, but this has not yet been investigated in South Africa. This study aims to investigate
temporal and spatial patterns of hover flies across three different, but adjacent habitats (forest,
grassland, and plantation) in KwaZulu-Natal (South Africa). This was done in two ways, first,
by analysing occurrence data from the Global Biodiversity Information Facility’s (GBIF)
database across months of the year. Second, by quantifying fly presence and abundance using
Malaise traps set up in three different habitats and supplemented with hand-netting data. The
Malaise traps were set up from October 2020 - September 2021 and were generally serviced
weekly. Hover flies were sorted and identified using available keys at the KwaZulu-Natal
Museum. The KZN GBIF database contained 11 tribes that represented three distinct
phenological patterns. The Karkloof GBIF dataset contained seven tribes that represented two
distinct phenological patterns. The field collection dataset contained eight tribes that
represented two distinct monthly patterns, although these slightly differed from the patterns
found in the GBIF data. Most records were from January, September and December whereas
few records were from May, June and July. Minimum-minimum, average-minimum, average
maximum and average temperature showed a positive correlation with hover fly abundance. In
terms of spatial patterns, grassland had the highest number of adult hover fly individuals (154),
followed by forest (106) and plantation (20). There was an overall effect of habitat type on both
the mean number of species and the number of individuals per trap per week. In addition,
Shannon’s diversity showed variation among the three habitat types whereas Simpsons
Evenness index showed no variation. The results show that hover fly populations remain active
throughout the year, but with distinct fluctuations in their abundance. They also show that
heterogeneous indigenous habitats such as grassland and forest represent high abundance,
diversity, evenness and richness of hover flies and this may be due to the diversity in available
microhabitats, compared to the plantation, which is a modified habitat that lacks microhabitat
diversity. Nonetheless, further studies should be undertaken in different regions of South Africa
to better understand the monthly patterns as well as the effect of habitat type on hover fly
diversity.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.