Syzygium thompsonii (Chamorro: atoto) is an endemic tree of the Mariana Islands of Guam, Rota, and Saipan[1] with a striking appearance due to its abundance of white flowers and edible fruit that grow directly from the trunk.

This differed from specimens from Rota and Saipan, which "tend to be slightly 4-angled and have buds (6-)7-8.5 mm long," suggesting these qualify as separate subspecies.

[8] The Smithsonian's US National Herbarium holds specimens from Saipan, collected from Water Cave and the north slope of Mt.

[11] Although the critically endangered Rota white-eye (Zosterops rotensis) is primarily insectivorous, it has been observed feeding on various fruits, including that of Syzygium thompsonii.

[14] A 2016-2017 survey of the Northwest Field in northern Guam observed 36 specimens of the federally threatened orchid, Tuberolabium guamense, growing on three Syzygium thompsonii trees.

[17] A 2013 forest inventory identified Syzygium thompsonii on only two of 48 island-wide plots, but estimated there were 178,000 trees on Guam (although with a substantial sampling error of 172,000).

"[15] Syzygium thompsonii is not mentioned by Charles Gaudichaud-Beaupré in his 1826 botanical review of the 1819 Freycinet Expedition of the Marianas,[19] nor by William E. Safford in his 1905 Useful Plants of Guam.

However, in 2012, Costion & Lorence disagreed with the merger, arguing that Syzygium trukense grows on volcanic soils of Chuuk, whereas the specimens on Guam is restricted to the northern limestone forest and has not been found growing in the volcanic soils of southern Guam.