Scientists look to Hawaii’s bugs for clues to origins of biodiversity

To Rosemary Gillespie, the Hawaiian Islands are a unique and ongoing series of evolutionary and ecological experiments. As each volcano rises above the waves, it is colonized by life from neighboring volcanoes and develops its own flora and fauna.

A new $2 million grant from the National Science Foundation (NSF) to the University of California, Berkeley, will allow Gillespie and her colleagues to focus on the islands’ insect and spider life in search of clues to how animals explore and settle into new niches, leading to increasing biodiversity over time.

One species of spider (Tetragnatha anuenue) on the Big Island of Hawaii shows an extraordinary diversity of color, that is matched by genetic variability. This variability seems to serve as the raw material for subsequent divergence and formation of new species over the course of tens or hundreds of thousand years. Photos by Rosemary Gillespie.“One of the most puzzling features of the high diversity of species on remote islands is that these species almost certainly arose from one or very few colonizers,” said Gillespie, director of UC Berkeley’s Essig Museum of Entomology. “How was variability regained after such genetic bottlenecks, and how did it give rise to ecological diversity?”

Their findings will answer questions not only about how communities have come together over the 700,000-year-lifespan of the Big Island, but also about the impacts of biological invasions. And, as the Hawaiian ecosystem adapts to a changing climate and a growing human population, the research will help develop successful conservation management practices and more effective programs in restoration ecology.

The grant is one of 14 totaling $26.4 million announced this fall by NSF’s Dimensions of Biodiversity program. It ties into the Berkeley Initiative on Global Change Biology (BiGCB), which looks at how biodiversity has responded in the past to environmental change in order to improve models for predicting the consequences of future environmental change.

“The islands of Hawaii are a great system for exploring how biodiversity changes in response to ecological change because it provides a chronological sequence of habitats from 0 to 1 million years ago on the Big Island, and further back in time as we go on to the older islands,” said Gillespie, co-director of BiGCB and professor of environmental science, policy and management. “The basic question is, ‘How do you go from an empty habitat on a newly emerged island to a complex mixture of populations like we see on the Big Island of Hawaii, where things are just starting, to a fairly discrete set of species like we see on Maui?’”

Colonizing volcanoes on the Big Island

The new study will focus initially on the five volcanoes that make up the island of Hawaii, which insects and spiders colonized during the past 1 million years. Gillespie and her colleagues expect to find a range of environments: from settled species in defined niches on the island of Maui, to discrete populations on Kohala, Hualalai and Mauna Kea, the oldest volcanoes of the youngest island, to muddled and still-evolving species on the youngest volcanoes, Mauna Loa and the still-erupting Kiluaea.

The researchers will collect DNA in search of genetic markers that will allow them to see how specific species and populations have adapted on volcanoes of different ages. The researchers will examine how species are continuing to adapt to an environment that experiences ongoing change – from new lava flows and landslides, for example — and settle into defined and recognizable species.

They hope to find out how quickly animals diverge in these new environments, and also whether the structure of the communities changes in a predictable way over time. This latter component makes use of a sophisticated ecological theory that looks at whether properties of communities are predictable.

“We are trying to see which animals get there first — something that eats plants or animals, dead or alive, for example — and whether the pattern of arrival and the community thus formed is predictable,” Gillespie said. “Then we can see how the community of organisms thus assembled might allow its members to diversify.”

In this way, Gillespie and her colleagues will be able to see how the interaction between the different parts of a community — such as predators, herbivores and parasites — are dictating divergence between populations and subsequent speciation.

UC Berkeley co-principal investigators are John Harte, professor of energy and resources, who will test theoretical models in ecology describing the numbers and types of animals in a given habitat; Patrick O’Grady, associate professor of environmental science, policy, & management and an expert on Drosophila flies; Rasmus Nielsen, professor of integrative biology, who will use molecular tools to look at how populations have expanded, contracted, diverged or otherwise changed over the lifetime of the island; and Neo Martinez, an affiliate of the energy and resources group, who will use new theoretical tools to explore how interactions between species change as a community develops.

Collaborators include evolutionary biologists Kerry Shaw at Cornell University, Diana Percy at the British Museum in London and Donald Price at the University of Hawaii in Hilo; and community ecologist Daniel Gruner of the University of Maryland, College Park.


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