Processes Dictating Biodiversity Dynamics Across Space and Time

Using islands of known age and isolation to assess the combined temporal and spatial dimension of biodiversity and determine patterns of diversification and associated community assembly and conservation challenges. Have been using an ecological community-level approach to look at arthropod biodiversity change through time in the Hawaiian Islands, seeking to identify those biological communities that are more vulnerable to invasion. The particular importance of the work is that it provided information on sensitivity to invasion and probability of extinction. We developed a “whole community metabarcoding” approach that allowed us to merge concepts from macroecology (species assembly, interaction networks) with an evolutionary approach to understand how sets of species adapt, multiply, and decline over time. The project continued through a NSF Rules Of Life grant to build a Model to Uncover Fundamental Processes Governing Biodiversity (2019-2024). Most recently this has developed into a NSF-funded project (2025), Biodiversity Dynamics: Linking Broad Scale Remote Sensing with Arthropod Metabarcoding Across a Geological Age Gradient in the Hawaiian Islands that uses a very standardized approach to examine gradients of habitat transformation across the Hawaiian Islands, looking at changes associated with both island age and disturbance. A particular current emphasis here is on how on-ground community-level measures of biodiversity are reflected in characteristics of the vegetation and how this in turn can be detected through broad scale remote sensing.

Adaptive Radiation of Spiders in the Hawaiian Islands

I am looking at extensive radiations of spiders in the Hawaiian Islands, in particular those in the genera Tetragnatha (Tetragnathidae), Theridion, Rugathodes, and Ariamnes (Theridiidae), Cyclosa (Araneidae), and linyphiids. In common with most Hawaiian spiders, representatives of these radiations remain largely unknown and undescribed. I have described many new species; so many more remain to be described. These species radiations encompass a huge spectrum of colors, shapes, sizes, ecological affinities, and behaviors. Within the Tetragnatha radiation, many species are web-building, with structural modifications of the abdomen that allow concealment in specific microhabitats, while other groups have abandoned the characteristic web-building behavior of the genus. With students, we are generating phylogenetic patterns of relationship for different clades and establishing relationships to mainland congeners, employing morphological and various molecular approaches. Using this information, we can test the role of morphological, ecological and behavioral attributes in dictating patterns of speciation. Results to date indicate that habitat associations play a key role in determining the level at which differentiation can occur within a lineage of spiders. Moreover, similar forms (“ecomorphs”) evolve repeatedly, resulting in the independent evolution of similar spider communities on each island .

Evolution of color diversity and color polymorphism in Happy face spiders

The Hawaiian happy face spider Theridion grallator exhibits a spectacular array of color morphs, which can be plain either 'yellow' or 'patterned' (red, black or white patches differing in form and extent, on the yellow background). In collaboration with Geoff Oxford (U. York, England) we have shown that in Maui populations color is controlled by simple Mendelian alleles, with 'yellow' morphs recessive to all patterned morphs. There is no evidence of associations of any morphs with a particular sex on Maui. On the island of Hawaii populations exhibit a similar array of morphs to those on Maui. However, unlike Maui, 4 of the most common morphs show sex limitation. We have also found that selection plays a role in maintaining the polymorphism. We are currently investigating the mechanisms whereby the genetic differences between populations might have arisen and the role of selection in reinstating diversity subsequent to colonization of an island. More recently we have found other spiders (esp. Theridion californicum from the west coast of California) which are remarkably similar to the happy face spider, with a similar set of color patterns, even with similar frequencies. And even in Hawaii, relative of the happy face spider are found on other islands, and also exhibit similar color polymorphisms.

Recent Grants

• NSF , Biodiversity Dynamics: Linking Broad Scale Remote Sensing with Arthropod Metabarcoding Across a Geological Age Gradient in the Hawaiian Islands. PI; co-PIs Iryna Dronova, Dan Gruner, Ryan Perroy, Jonathan Price, Natalie Graham  2025-2028

• Dept of Defense: Strategic Environmental Research & Development Program, A Predictive Model for Invasive Terrestrial Arthropod Species in the Indo-Pacific; co-PI; PI Mark Johnson, Natalie Graham. 2025-2028.

• NSF, IIBR RoL: Collaborative Research: A Rules Of Life (RoLE) Model to Uncover Fundamental Processes Governing Biodiversity; co-PI, PI AJ Rominger 2019-2025

• Peder Sather Grant, The dwarfs that crossed the Ocean: evolution and biogeography of Hawaiian linyphiids, 2022-2025, University of Bergen, University of California, Berkeley; with Dimitar Dimitrov, Gustavo Hormiga, Anui Sanz

• NSF DEB 2135502: IMEMEBA Workshop: Insights from Macro-Ecology and Macro-Evolution for Biodiversity Assessment. PI. 9/21-12/24. With Isaac Overcast, Mike Hickerson, Brian McGill

• Dept of Defense: Strategic Environmental Research & Development Program Next Generation Biosecurity Monitoring of Invasive Alien Arthropod Species; co-PI; PI George Roderick 05/2021- 01/2026. $2,963,770.

Publications: Google scholar

Lab members: Evolab

ORCID: link here

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