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Biodiversity & Habitat Fragmentation Lab

Explore species diversity indices, the species-area relationship, and the effects of habitat fragmentation on biodiversity. Collect survey data, run island biogeography experiments, and investigate how wildlife corridors mitigate species loss.

Guided Experiment: Diversity Indices from Species Survey Data

How do you expect Simpson and Shannon diversity indices to differ between a community with even species abundances versus one dominated by a single species?

Write your hypothesis in the Lab Report panel, then click Next.

Controls

Species 1
Species 2
Species 3
Species 4
Species 5
Species 6
Species 7
Species 8
Species 9
Species 10
Noise Level10%

Results

S=10N=139S = 10 \quad N = 139
Simpson D (dominance)
0.1942
Simpson 1-D (diversity)
0.8058
Shannon H′
1.8678
Pielou Evenness J
0.8112
Species Richness
10 species

Rank-Abundance Curve

Data Table

(0 rows)
#TrialSpecies RichnessSimpson DShannon H′Evenness
0 / 500
0 / 500
0 / 500

Reference Guide

Diversity Indices

Simpson's Dominance Index measures the probability that two randomly selected individuals belong to the same species.

D=∑i=1Spi2D = \sum_{i=1}^{S} p_i^2

Shannon-Wiener Index accounts for both richness and evenness. Higher values indicate greater diversity.

H′=−∑i=1Spiln⁡(pi)H' = -\sum_{i=1}^{S} p_i \ln(p_i)

Pielou's Evenness ranges from 0 to 1, where 1 means all species are equally abundant.

J=H′ln⁡(S)J = \frac{H'}{\ln(S)}

Species-Area Relationship

One of ecology's most robust patterns. Larger areas support more species, following a power law.

S=cAzS = cA^{z}

Where S is species richness, A is area, c is a constant depending on the taxonomic group, and z typically ranges from 0.15 to 0.35 (often around 0.25 for oceanic islands).

On a log-log plot, this becomes a straight line with slope z.

log⁡S=log⁡c+z⋅log⁡A\log S = \log c + z \cdot \log A

Island Biogeography

MacArthur and Wilson's theory predicts that island species richness results from a balance between immigration and extinction.

Immigration rate decreases as the island fills with species, while extinction rate increases. The equilibrium is where these rates cross.

Near islands have higher immigration rates. Large islands have lower extinction rates. Together these predict that large, close islands hold the most species.

Habitat Fragmentation

When a continuous habitat is broken into smaller patches, total biodiversity declines even if total area is preserved. This happens because of edge effects, reduced population sizes, and isolation.

Each fragment behaves like a small island, supporting fewer species than the original whole. Wildlife corridors can partially restore connectivity by allowing species to disperse between fragments.

Fragmentation is one of the leading causes of biodiversity loss worldwide, making corridor design a key conservation strategy.