1. Disentangling the Patterns of Diversity in Invertebrate Communities
Along a Latitudinal Gradient
Avery Nickerson
Mentors: Dr. Adam Siepielski & Dr. Kate Boersma
References
Future Studies
Community Composition and
Environmental Factors
Introduction
Methods
Alpha Diversity
Results and Discussion
Hypotheses
Understanding how communities are structured is a
fundamental question in biology. Quantifying variation in
the composition of biological communities (beta
diversity), along spatial gradients can provide insight into
the mechanisms structuring communities. Beta diversity
can be quantified as the dissimilarity in community
structure among a set of sample units within a given
spatial extent. Variation partitioning of beta diversity can
reveal whether underlying environmental factors are
associated with certain community assemblages or that
these assemblages are simply a random subset of the
broader species pool. Disentangling these two
possibilities is key to understanding the underlying
processes that structure communities. To address this
question, we quantified the alpha and beta diversity of
aquatic invertebrate communities along a latitudinal
gradient and compared these patterns to various
environmental factors (Figure 1).
Figure 1: A map of the sample
locations
• Alpha and beta diversity of
aquatic invertebrate
communities will be greater at
lower latitudes than at higher
latitudes (Figure 2)
• Variation in community
structure will be correlated
with variation in environmental
factors
• Biological communities
• Collected invertebrates using a box sampler
(Figure 3)
• Identified invertebrates to family level
(Figure 4)
• Environmental variables
• Measured water composition using a probe
• Conductivity, Total Dissolved Solids, pH,
temperature, etc.
• Analyzed data using t-tests and
multivariate ordination methods
Figure 3: Containers used during
sample collection to hold and sort
samples
Figure 4a and Figure 4b: A Belostomatidae and a Dytiscidae, respectively, which are examples of
aquatic invertebrates
• Beta diversity increases with increasing geographic distance
between sites
• This pattern likely reflects differences in the regional
species pools among geographic locations along the
latitudinal gradient
• Beta diversity does not differ among sites within regions:
North or South (Figure 6)
• Could be due to small sample size
• Environmental variables (pH, total dissolved solids, and
conductivity) are associated with Beta diversity (Figure 6)
• Both species richness and Shannon diversity show significant
latitudinal patterns (Figure 7, Figure 8)
• Reflects expected difference in species composition
between Northern and Southern sites
• Local environmental variation is more important for
explaining variation in species composition among sites than
space alone
• These results suggest that different environmental factors
are important for explaining species composition among
sites than variation in community compositions between
sites
Figure 5: Freshwater pond where samples were
collected
Figure 6: Variation in community structure between Northern and Southern sites is
correlated with latitude, conductivity, total dissolved solids, and pH. (NMS: Stress = 0.151,
k = 2, p = 0.0196)
Figure 7: Species richness is higher in Southern sites than in Northern sites
(t-test: t = -4.8696, df = 15.875, p-value = 0.0001742)
Figure 8: Shannon diversity is higher in Southern sites than in Northern sites
(t-test: t = -3.6816, df = 15.113, p-value = 0.002196)
Figure 2: A visual representation of diversity. Alpha diversity is
the species richness of a community. Beta diversity is the
variation in species richness among multiple communities.
• Anderson, Marti J., Thomas O. Crist, Jonathan M. Chase, Mark Vellend, Brian D. Inouye, Amy L. Freestone, Nathan J. Sanders, Howard V.
Cornell, Liza S. Comita, Kendi F. Davies, Susan P. Harrison, Nathan J. B. Kraft, James C. Stegen, and Nathan G. Swenson. "Navigating the
Multiple Meanings of β Diversity: A Roadmap for the Practicing Ecologist." Ecology Letters 14.1 (2011): 19-28. Web.
• Astorga, Anna, Russell Death, Fiona Death, Riku Paavola, Manas Chakraborty, and Timo Muotka. "Habitat Heterogeneity Drives the
Geographical Distribution of Beta Diversity: The Case of New Zealand Stream Invertebrates." Ecology and Evolution 4.13 (2014): 2693-
702. Print.
Thank You!
• Thank you to the McCarthy Family and the Doheny
Foundation for funding my project through the Summer
Undergraduate Research Experience Program
• Thank you to the National Science Foundation for additional
funding
• Thank you to Dr. Adam Siepielski and Dr. Kate Boersma for
making this project possible and helping me every step of
the way
• Thank you to Team Enallagma for helping collect and
process samples
• Continue data collection to develop larger
sample size to better define variation within
regions
• Design manipulative experiments to determine
environmental drivers of differences in
community composition
• Further studies of Beta diversity in other regions
to further develop understanding of diversity
patterns
Figure 9: Freshwater pond
where samples were
collected