Tina Oduol: Lab Report Internal
Assessment
Biology
An investigation on the effect of the presence of the invasive species Lantana camara
on the biodiversity of native plants.
Background Information
Invasive species are organisms that are introduced to an area where they are not native, and
often outcompete local species, disrupting ecosystems. Their presence can interrupt
ecosystems, reduce biodiversity, and alter ecological balance. A key way invasive species
impact their surroundings is by competing with native plants for essential resources such as
light and water, which would lead to a decline in native plant populations.
Biodiversity is the variety of life in a particular area, and is often measured in terms of two key
components:
-​ Species richness - the number of different species in an area
-​ Species evenness - the abundance of each species present in an area
Both components are quite important for understanding the stability of ecosystems, In this
investigation biodiversity will be assessed using Simpson’s diversity index, which takes into
account both richness and evenness to provide a single value that reflects overall diversity.
The Invasive species chosen for this study is Lantana camara, an exotic plant species native to
Central and South America. It was later introduced to various parts of the world, including
Europe, Asia, and Africa for decorational purposes such as fencing. In Kenya, the species is
believed to have arrived during the colonial period. Lantana camara is a shrub that typically
grows up to 2 meters tall, though some specimens have reached heights of 6 meters under
favorable conditions. Its leaves are oval-structured and simple, with the stems being square or
rectangular in shape and often having small spines. Lantana camara has become a problem
because it’s an invasive plant that spreads quickly, outcompeting native species for resources
like light, water, and nutrients. It forms dense, tangled thickets that reduce biodiversity, disrupt
habitats, and make it harder for native plants and animals to survive. The study chosen to
conduct is focused on investigating the impact of Lantana camara on native plant diversity.
Specifically, whether areas where the species is present have lower species richness and
evenness compared to areas without it.
Lantana camara was chosen because it is one of the most widespread and damaging invasive
plant species in Kenya. The plant is often used for fencing in both rural and urban areas due to
the amount of thorns it has and its tolerance to drought. This makes it easy to locate and study
in real-world settings.
Two contrasting locations in western Kenya were selected for this study:
-​
-​
Mamboleo (Kisumu County) - an urban area where Lantana camara is commonly found
on roadside hedges
Ugenya (Siaya County) - a rural area where the plant thrives along fence lines and open
fields
These sites allow for a more accurate comparison of plant biodiversity in areas with differenc
levels of human disturbance, while still providing locations where Lantana camara is present
and absent.
Research Question: How does the presence of Lantana camara affect native plant biodiversity
in the area?
Hypothesis: Areas with Lantana camara will have lower native plant biodiversity (both in
species richness and evenness) compared to areas where the species is absent.
Variables:
-​ Independent variable: Presence or absence of Lantana camara
-​ Dependent variable: Biodiversity of native plant species (using Simpson’s Diversity
Index)
-​ Controlled variables:
-​ Time of sampling (mid-morning, same day)
-​ Weather conditions (dry and sunny)
-​ Camera device (same phone used)
Materials
-​ Phone (for taking photos) - why?
-​ Plant identification guide (PlantNet) why?
-​ Notebook for recording - why?
-​ Measuring tape - why?
Study sites
Sampling was conducted in two contrasting areas in western Kenya:
-​
-​
Urban site: Mamboleo, Kisumu County - areas with roadside hedges where the species
is commonly used for fencing.
Rural site: Ugenya, Siaya County - open fields and farm boundaries, where Lantana
camara grows freely.
At each site, I located and photographed areas where Lantana camara was visibly dominant,
and others where it was absent, to allow for a comparative analysis of biodiversity.
Sampling method:
The method that was used was photographic observation, where I identified multiple patches of
land (approximately 1–2 m² in size) in each location. At each patch, I photographed plant
communities from an angle where species diversity was clearly visible. I then selected 5
photographs from areas with Lantana camara present and 5 from areas without the species.
This visual method allowed for flexible sampling across areas where the species naturally
occurred without disturbing its ecosystem.
Data Collection and Processing:
Each photo was analyzed by identifying as many visible plant species as possible using
PlantNet, a plant identification guide. For each photo, I estimated:
-​
-​
Species richness: The number of visibly different species
Species evenness: Whether one or two species dominated the area
I also noted the approximate area that Lantana camara occupied, using a tape measure, and
whether the species appeared to crowd or shade out other plants. Due to the observational
nature of this study, data were assessed qualitatively and semi-quantitatively. The results were
used to explore patterns in plant diversity linked to Lantana camara presence.
Table 1: Raw data collected to determine species diversity with and without the presence of the
invasive species Lantana camara
Comparison of Species Richness Based on the Presence of Lantana
camara
Photo no.
Location
Lantana
camara
present?
Estimate
species
richness
Notes on dominance/
evenness
1 Mamboleo
yes
Lantana covers most of
2.5 the area
2 Mamboleo
yes
2.5 Dominated by Lantana
no
Mix of species, no single
6.5 dominant plant
no
A variety of plants,
relatively even
3.5 distribution
yes
Lantana present along
the fence, some native
5.5 shrubs
6 Ugenya
no
High diversity, wild
grasses, herbs, and
7.5 shrubs
7 Mamboleo
yes
Lantana is present near
2.0 the roadside
8 Ugenya
yes
Mostly Lantana, a small
3.0 number of weeds
3 Ugenya
4 Ugenya
5 Mamboleo
9 Ugenya
10 Mamboleo
no
6.0 Multiple native species
no
Mix of urban species,
5.0 moderate evenness
Table 2: Processed data showing the presence of Lantana camara in contrast to the
species richness of the area
Lantana
camara
presence
Species
richness
yes
2.5
yes
2.5
yes
5.5
yes
2.0
yes
3.0
no
6.5
no
3.5
no
7.5
no
6.0
no
5.0
Table 3: Processed data showing the calculated averages of the species richness in
areas with Lantana camara and areas without
Lantana
Presence
Average species
richness
yes
3.1
no
5.7
Graph 1: A bar chart of the processed data showing the average Plant Species Richness in
Areas With and Without Lantana camara
Data analysis
Based on the data collected, areas with Lantana camara present have substantially
lower species richness compared to areas without it. The mean species richness in
sites where Lantana camara was recorded was 3.1, while areas without the species had
a considerably higher mean of 5.7. In Lantana-dominated areas (e.g.,2 photos 1 and 2
from Mamboleo), only 2-3 species were observed, and the invasive shrub covered most
of the available space, resulting in low species evenness. In contrast, Lantana-free
areas, particularly in rural Ugenya (e.g., photos 3 and 6), contained a mic of grasses,
herbs, and shrubs, with no single species dominating, leading to higher species
richness values of up to 7.5. One exception to this trend was photo 5, where Lantana
camara was present along a fence, but the species richness was 5.5. This may be
because the invasive species one occupied a part of the area, allowing some native
shrubs to persist. Conversely, one of the Lantana-absent quadrats (photo 4) recorded a
lower richness than expected, with it being 3.5, and this could be possibly due to recent
disturbance of the area. Biologically, the reduced species richness in Lantana sites can
be explained by its competitive advantages. The invasive species forms dense thickets
that block nearby species of obtaining essential resources such as water, soul nutrients
and light. The species also releases allelopathic chemicals that inhibit the germination
and growth of other species, leading to competitive exclusion, where native plants are
unable to establish or survive. Areas without Lantana camara do not experience these
competitive pressures, allowing a more even distribution of species and a higher overall
richness. Overall, the data quite strongly supports the hypothesis that the presence of
Lantana camara reduces native plant species richness in both rural and urban settings,
with the most severe reductions being observed in areas where the species is the
dominant plant.
Evaluation
Strengths
Limitations
Data was collected from multiple sites,
representing different disturbance levels,
allowing for a clear comparison
Only species richness was measured, no
measure of evenness or abundance
Species were identified using a reliable
Areas sampled might not fully represent
guide, improving accuracy of identification the entire ecosystem, leading to potential
sampling bias
Sampling occurred under controlled
Human error in identifying species could
weather conditions, ensuring that external havelead to misclassification
factors would not influence data collection
Conclusion:
Overall, the investigation found that invasive plant species dominance is associated with
reduced plant species diversity, in both rural and urban areas. This supports the
hypothesis
Calculations
Experiment setup
Data Presentation
Observations
Data Processing:
Data Analysis
Evaluation:
Conclusion