Population ecology and threats of bee species across vegetation types in Mgori Forest Reserve, Singida District, Tanzania
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Date
2024-05
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Sokoine University of Agriculture
Abstract
Bees are among pollinator groups of importance in promoting and
maintaining biodiversity and food production through provision of
pollination services. This makes identifying and monitoring
communities of bee species, a crucial step in the process of
conservation. Forest vegetation types are among determinant of bee
species composition and diversity. With the continued loss of
suitable habitats for bees, conservation of bee species should begin
with information on their presence. Mgori forest reserve is
surrounded by villages with farms planted with crops such as
sunflower, which is pollinator dependent, hence they benefit from
pollination services from bees inhabiting the forest. To ensure
inclusive conservation for the survival of bee species this study
aimed at determining the composition, diversity and threats of bee
species in Mgori forest reserve, across the vegetation types namely
open woodland, thickets and the mosaic of open woodland and
thickets, which are found within the forest reserve.
Systematic sampling was used in the study, whereby plots were
established in the forest. To collect bees on each plot, pan traps and
sweep nets were used.Threats to bees were also observed and
recorded on each plot, thereafter plots with observed threats were
characterised as disturbed plots and those with no observed threats
were characterised as undisturbed sites. Additionally, coordinates
and elevation point of the sites were also recorded. Bee species
composition was the list of bees identified. Bee species richness and
abundance were the number of species recorded and the number of
individuals per species respectively. Shannon-Wiener diversity index
was used to calculate the diversity of bees in the forest for disturbed
and undisturbed sites. Kruskal-Wallis test was used to compare
Richness and Abundance of bee species, across open woodland,
thickets and the mosaic of thickets and open woodland and the
Duncan post hoc was performed for both species richness and
abundance. Detrended correspondence analysis was used to find
the relationship between species composition and environmental variables and generalized linear mixed effect models were used to
find the relationship between environmental conditions and bee
species richness and abundance. All data was analysed through the
R Software. Threats to bees were described and presented through
graphs and tables using SPSS software. And then Chi-Square Test
was used for comparison across studied sites to determine the
variation of bee species richness and abundance between
undisturbed and disturbed sites.
A total of 508 bees were collected from the studies sites in Mgori
forest reserve; the Dominant family was the Halictidae family,
followed by the Apidae and Megachilidae was the least recorded
family. Species composition significantly varied between thickets
and open woodland types of vegetation, whereby open woodland
had higher composition, richness and abundance than thickets.
Environmental conditions were associated with species abundance
but not richness; particularly elevation had a significant influence on
species abundance.
On the influence of threats on bee species, the human threats
recorded were found to be consistent with resource needs in the
forest. The threats recorded were debarking, grazing, trails, logging,
fire scars and agricultural encroachment. The most consistent
evidence was the presence of trails in the forest and grazing across
all three vegetation types. The comparison of bee species richness,
abundance and diversity showed that, there was significant
difference in bees across the disturbed and undisturbed sites.
Whereby bees were more present in undisturbed sites than
disturbed sites. There was no difference in the calculated Shannon-
Wienner diversity index and abundance of bees between the
disturbed and undisturbed sites.
The study has revealed the composition of bees in Mgori forest
reserve, which can serve as information for future ecological study in
the forest. It has also revealed human threats in the forest that hinder conservation in the forest, as well as influencing the presence
of bees in the forest. Particularly their richness across space. In the
management of the forest, it is important to consider thickets and
open woodland vegetation types found within the forest, since they
serve as separate supplementary habitats to these forest species.
The apparent human threats in the forest threaten its conservation.
As a result, there is a need for the forest patrons and the
communities living adjacent to the forest, to work on improving the
guarding and conservation of the forest. This is because of the
benefits such as pollination services that can be obtained from Mgori
forest.
Description
MSc Dissertation
Keywords
Population Ecology, Bee Species Across Vegetation Types, Mgori Forest Reserve, Singida District, Tanzania