UH Hilo biologist Natalie Graham researches ecological and evolutionary dynamics of the Hawaiian archipelago

Posted on by

Assistant Professor Graham studies how the structure of biological communities change over time, in particular, how anthropogenic changes are altering species interactions and potentially driving communities past ecological tipping points.

Natalie Graham pictured in cap, forest in background.
Natalie Graham (Courtesy photo)

By Susan Enright.

Natalie Graham, an assistant professor in the biology department at the University of Hawaiʻi at Hilo, researches arthropods of the Hawaiian archipelago in the hope to better understand what action should be taken to mitigate human impacts in the most vulnerable ecosystems. To achieve this, she studies how the structure of biological communities change over time, in particular, how anthropogenic changes are altering species interactions and potentially driving communities past ecological tipping points.

“I exploit the natural occurrence of age-structured terrains on the Hawaiian archipelago that represent communities in an assembly continuum at sites dating from 44 years to 5.5 million years in geological age,” says Graham about her work as a doctoral candidate in 2015-2021 at the University of California, Berkeley. She received her doctor of philosophy in 2021. She received her bachelor (2005) and master (2014) degrees from Sonoma State University.

Graham recently presented her research — on the importance of ecological and evolutionary dynamics in understanding how biodiversity accumulates through time — in person at a colloquium seminar hosted by University of Maryland’s entomology department.

Observing evolution

Graham explained in her recent presentation that interactions across space and time shape biodiversity, and while models have been developed to infer the dynamic processes shaping the evolution of communities, empirical data for understanding the interplay of ecology and evolution over long temporal scales are almost entirely lacking.

The Hawaiian archipelago provides an excellent backdrop for this research because each island is the result of the Pacific tectonic plate moving over a stationary “hot spot.” This means that each island began as a blank slate and represents a progressively longer amount of time that ecological and evolutionary processes have been able to shape present-day communities: younger islands tend to have communities with simpler networks and more generalized interactions, while older islands have more established, complex, and specialized interactions.

Studying ecological genetics on islands with different geological development times has the potential to increase understanding of interactions between species, and how they have changed over time. Plant-arthropod interactions are an excellent model for this type of research because of the tremendous diversity in species and life histories, meaning scientists can find many more species and more specialized relationships between arthropods and plants.

Chart showing island age gradient and increasing specialization.
Figure 1: As communities assemble over time, species will be added through ecological and evolutionary processes. Network size will increase over time and there will be a trend towards greater specialization. Recently introduced species (i.e., non-natives) evolved elsewhere would not have adapted to biotic and abiotic factors, thus limiting their specialization within communities at all stages of development. (Modified from Graham et al., 2023, via UMD)

Genomic data

Genomic data is among the most important methods to measure biodiversity. For many arthropods, relatedness between specimens can be difficult to discern by traditional identification methods.

For example, Graham can make use of high-throughput sequencing and DNA metabarcoding, a method to identify species in bulk collections of specimens using short segments of DNA. This result can be paired with plant morphological or genetic species identifications to find evidence of species biotic interactions.

Using DNA sequencing in this manner can provide important contextual information that can be combined with remote sensing information that can help with assessing the invasiveness or invasion potential of a species. Graham emphasizes that including morphological taxonomy and DNA barcoding of museum vouchers should be used in concert with DNA metabarcoding to verify results and to avoid under- or over-inflated biodiversity predictions from molecular methods alone.

Read the full story at the University of Maryland entomology department’s news site.

Story by Susan Enright, a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.

Share this story