Disentangling the Patterns of Diversity in Invertebrate Communities Along a Latitudinal Gradient

Avery NickersonMentors: 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