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11 August 2020 Temperate Eurasian Origins of Hawaiian Chenopodium (Amaranthaceae), Plus Description of a New Subspecies Endemic to Moloka‘i
Jason T. Cantley, Angela J. McDonnell, Jennifer Branson, Joseph Kobara, Stephanie R. Long, William Garnett, Christopher T. Martine
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Abstract

Hawaiian taxa of Chenopodium are tetraploids and are distinguished from other members of the circumglobally distributed genus by minute morphological characters. Because of these reasons, the geographic origin of Hawaiian Chenopodium has remained unclear. Across the Hawaiian Archipelago, taxa of Chenopodium are morphologically variable and grow in highly disparate xeric habitats, especially in terms of precipitation, temperature, wind, salt spray, and solar irradiation. Habitats include dry subalpine shrublands, sandy beach strands on atolls in the Northwest Hawaiian Islands, dry to mesic forests, and precipitously tall sea cliffs of northwestern Moloka‘i. From the Moloka‘i sea cliffs, which are battered by high energy winds, salt spray, and strong seasonal precipitation, we describe C. oahuense subspecies ilioensis as segregated from the widespread Hawaiian C. oahuense sensu lato. Morphometric analyses distinguish C. oahuense subsp. ilioensis by its strongly prostrate to scandent habit, thick succulent leaves, smaller average leaf size, limited lobing of the laminar margins, and smaller seeds. Phylogenetic analyses using two DNA regions (the plastid gene rpl32-trnL and nuclear ITS) of newly sequenced individuals of C. oahuense s. l. and C. oahuense subsp. ilioensis plus outgroup taxa support the monophyly of Hawaiian Chenopodium and reveal a geographic origin of temperate Eurasia. Two equivocal hypothetical scenarios are discussed regarding the likely sequence of events leading to the arrival of Chenopodium in Hawaiian Islands followed by possible in situ speciation of the Moloka‘i endemic C. oahuense subsp. ilioensis.

© Copyright 2020 by the American Society of Plant Taxonomists
Jason T. Cantley, Angela J. McDonnell, Jennifer Branson, Joseph Kobara, Stephanie R. Long, William Garnett, and Christopher T. Martine "Temperate Eurasian Origins of Hawaiian Chenopodium (Amaranthaceae), Plus Description of a New Subspecies Endemic to Moloka‘i," Systematic Botany 45(3), 554-566, (11 August 2020). https://doi.org/10.1600/036364420X15935294613473
Published: 11 August 2020
JOURNAL ARTICLE
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KEYWORDS
Chenopodioideae
Chenopodium oahuense
Chenopodium oahuense subsp. ilioensis
genome downsizing
halophyte
speciation
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