North Central Pacific Connectivity using eDNA

Large-scale comparisons of biodiversity can reveal ecological processes that shape and maintain community composition and potentially provide further insight to how the Hawaiian Archipelago is connected to the rest of the central Pacific. The Hawaiian Archipelago is one of the most isolated archipelagos in the world not just in terms of distance to the nearest archipelago but also because there is no direct current that can quickly transport larvae from surrounding archipelagos.

Visual surveys conducted in throughtout the Pacific show that the Hawaiian Archipelago has much less biodiversity compared to other Pacific Islands. However, these visual surveys often miss cryptic species and tend to focus on fish species or commercially important invertebrates. environmental DNA (eDNA) is a powerfool tool that can sample hundreds of species from a few samples using a non-invasive, inexpensive, and relatively fast method. eDNA methods can help reduce biases from visual surveys by detecting species across various life histories and taxonomic groups, including cryptic species. I have collected eDNA samples from archipelagos across the Central North Pacific including the Hawaiian Archipelago, the Line Islands, the Marshall Islands, Okinawa, Guam, Wake Island, and Johnston Atoll.

In order to get samples from Wake Island and Johnston Atoll, we had to take a research cruise across the Pacific to get to these extremely remote islands. We spent 3 weeks on the R/V Thompson collecting samples. I trained and led the eDNA team which consisted of 1 undergraduate student, 4 postbaccalaureates, and 2 graduate students.

In addition to documenting the patterns of biodiversity and shared species across all the islands sampled, I will be using the eDNA samples to identify community-wide genetic structure by locating shared genetic breaks. The location of concordant genetic breaks could be driven by geographic barriers, life histories (e.g., PLD, dispersal mode, habitat), or environmental change (e.g., sea level, temperature, and ocean current changes during last glacial maximum). To test for the influence of environmental changes, I will determine if there are many species with populations that are expanding or stable and approximate a date for any potential past extinction or dispersal events. To test if life histories are driving variation in population structure, I will use an ordination plot to identify significant factors. While these analyses have been done before in the central Pacific, I will be analyzing many more species than in previous studies, allowing for new insights on how current communities have been shaped by biological and historic environmental factors.

Read about it on UH News and on Big Island Now