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1. Evolutionary genomics of oceanic island radiations

   https://doi.org/10.1016/j.tree.2023.02.003  

   Cerca, José; Cotoras, Darko D.; Bieker, Vanessa C.; De-Kayne, Rishi; Vargas, Pablo; Fernández-Mazuecos, Mario; López-Delgado, Julia; White, Oliver; Stervander, Martin; Geneva, Anthony J.; et al (July 2023, Trends in Ecology & Evolution)
2. Island-wide characterization of agricultural production challenges the demographic collapse hypothesis for Rapa Nui (Easter Island)

   https://doi.org/10.1126/sciadv.ado1459  

   Davis, Dylan S; DiNapoli, Robert J; Pakarati, Gina; Hunt, Terry L; Lipo, Carl P (June 2024, Science Advances)

   Communities in resource-poor areas face health, food production, sustainability, and overall survival challenges. Consequently, they are commonly featured in global debates surrounding societal collapse. Rapa Nui (Easter Island) is often used as an example of how overexploitation of limited resources resulted in a catastrophic population collapse. A vital component of this narrative is that the rapid rise and fall of pre-contact Rapanui population growth rates was driven by the construction and overexploitation of once extensive rock gardens. However, the extent of island-wide rock gardening, while key for understanding food systems and demography, must be better understood. Here, we use shortwave infrared (SWIR) satellite imagery and machine learning to generate an island-wide estimate of rock gardening and reevaluate previous population size models for Rapa Nui. We show that the extent of this agricultural infrastructure is substantially less than previously claimed and likely could not have supported the large population sizes that have been assumed 

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3. Geological insights from the newly discovered granite of Sif Island between Thwaites and Pine Island glaciers

   https://doi.org/10.1017/S0954102023000287  

   Marschalek, James W.; Thomson, Stuart N.; Hillenbrand, Claus-Dieter; Vermeesch, Pieter; Siddoway, Christine; Carter, Andrew; Nichols, Keir; Rood, Dylan H.; Venturelli, Ryan A.; Hammond, Samantha J.; et al (February 2024, Antarctic Science)

   Large-scale geological structures have controlled the long-term development of the bed and thus the flow of the West Antarctic Ice Sheet (WAIS). However, complete ice cover has obscured the age and exact positions of faults and geological boundaries beneath Thwaites Glacier and Pine Island Glacier, two major WAIS outlets in the Amundsen Sea sector. Here, we characterize the only rock outcrop between these two glaciers, which was exposed by the retreat of slow-flowing coastal ice in the early 2010s to form the new Sif Island. The island comprises granite, zircon U-Pb dated to ~177–174 Ma and characterized by initial ɛ_Nd,⁸⁷Sr/⁸⁶Sr and ɛ_Hfisotope compositions of -2.3, 0.7061 and -1.3, respectively. These characteristics resemble Thurston Island/Antarctic Peninsula crustal block rocks, strongly suggesting that the Sif Island granite belongs to this province and placing the crustal block's boundary with the Marie Byrd Land province under Thwaites Glacier or its eastern shear margin. Low-temperature thermochronological data reveal that the granite underwent rapid cooling following emplacement, rapidly cooled again at ~100–90 Ma and then remained close to the Earth's surface until present. These data help date vertical displacement across the major tectonic structure beneath Pine Island Glacier to the Late Cretaceous. 

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4. Mycorrhizal types influence island biogeography of plants

   https://doi.org/10.1038/s42003-021-02649-2  

   Delavaux, Camille S.; Weigelt, Patrick; Dawson, Wayne; Essl, Franz; van Kleunen, Mark; König, Christian; Pergl, Jan; Pyšek, Petr; Stein, Anke; Winter, Marten; et al (December 2021, Communications Biology)

   Abstract Plant colonization of islands may be limited by the availability of symbionts, particularly arbuscular mycorrhizal (AM) fungi, which have limited dispersal ability compared to ectomycorrhizal and ericoid (EEM) as well as orchid mycorrhizal (ORC) fungi. We tested for such differential island colonization within contemporary angiosperm floras worldwide. We found evidence that AM plants experience a stronger mycorrhizal filter than other mycorrhizal or non-mycorrhizal (NM) plant species, with decreased proportions of native AM plant species on islands relative to mainlands. This effect intensified with island isolation, particularly for non-endemic plant species. The proportion of endemic AM plant species increased with island isolation, consistent with diversification filling niches left open by the mycorrhizal filter. We further found evidence of humans overcoming the initial mycorrhizal filter. Naturalized floras showed higher proportions of AM plant species than native floras, a pattern that increased with increasing isolation and land-use intensity. This work provides evidence that mycorrhizal fungal symbionts shape plant colonization of islands and subsequent diversification. 

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5. Oxygen Fugacity of Global Ocean Island Basalts

   https://doi.org/10.1029/2023GC011249  

   Willhite, Lori N; Arevalo, Ricardo; Piccoli, Philip; Lassiter, John C; Rand, Devin; Jackson, Matthew G; Day, James_M D; Nicklas, Robert W; Locmelis, Marek; Ireland, Thomas J; et al (January 2024, Geochemistry, Geophysics, Geosystems)

   Abstract Mantle plumes contain heterogenous chemical components and sample variable depths of the mantle, enabling glimpses into the compositional structure of Earth's interior. In this study, we evaluated ocean island basalts (OIB) from nine plume locations to provide a global and systematic assessment of the relationship betweenfO₂and He‐Sr‐Nd‐Pb‐W‐Os isotopic compositions. Ocean island basalts from the Pacific (Austral Islands, Hawaii, Mangaia, Samoa, Pitcairn), Atlantic (Azores, Canary Islands, St. Helena), and Indian Oceans (La Réunion) reveal thatfO₂in OIB is heterogeneous both within and among hotspots. Taken together with previous studies, global OIB have elevated and heterogenousfO₂(average = +0.5 ∆FMQ; 2SD = 1.5) relative to prior estimates of global mid‐ocean ridge basalts (MORB; average = −0.1 ∆FMQ; 2SD = 0.6), though many individual OIB overlap MORB. Specific mantle components, such as HIMU and enriched mantle 2 (EM2), defined by radiogenic Pb and Sr isotopic compositions compared to other OIB, respectively, have distinctly highfO₂based on statistical analysis. ElevatedfO₂in OIB samples of these components is associated with higher whole‐rock CaO/Al₂O₃and olivine CaO content, which may be linked to recycled carbonated oceanic crust. EM1‐type and geochemically depleted OIB are generally not as oxidized, possibly due to limited oxidizing potential of the recycled material in the enriched mantle 1 (EM1) component (e.g., sediment) or lack of recycled materials in geochemically depleted OIB. Despite systematic offset of thefO₂among EM1‐, EM2‐, and HIMU‐type OIB, geochemical indices of lithospheric recycling, such as Sr‐Nd‐Pb‐Os isotopic systems, generally do not correlate withfO₂. 

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