SYNGONIUM HASTIFERUM
PROTOLOGUE: Syngonium hastiferum , published in Annals of the Missouri Botanical Garden 68: 595 (1982).
Syngonium hastiferum (Standley & L. O. Williams) Croat, comb. nov. Basionym: Philodendron hastiferum Standley & L. O. Williams, Ceiba 1:232. 1951. TvPE: Costa Rica, Puntarenas, forested hills above Esquinas, in region between Río Esquinas and Palmar Sur de Osa, Allen 5563 (US, holotype).
SYNONYMS:
HOMOTYPIC SYNONYMS: Philodendron hastiferum Standl. & L.O.Williams
DISTRIBUTION: Costa Rica: Costa Rica.
DISTRIBUTION NOTE: Costa Rica: Alajuela, Puntarenas, San José iNaturalist: Puntarenas.
SPECIES DESCRIPTION:
Nomadic vine; juvenile plants climbing; stems green, not glaucous, scandent; internodes to 25 cm or more long, ca. 1 cm diam., drying brown with thin flaking epidermis; smallest leaves with the petioles sheathed almost to the apex; blades broadly ovate. Intermediate stages with petioles 20–30 cm long, sheathed to beyond the middle, the unsheathed part of the petiole terete, becoming weakly flattened laterally toward the apex; blades becoming elliptic and weakly cordate, finally with hastate lobes like the adults, then increasing only in size. Adult plants appressed-climbing; internodes ca. 2.5 cm long, 1.5–2.5 cm diam. Leaves with petioles to 37–50 cm long, sheathed ca. 5/6 their length; sheath free-ending and emarginate at apex; blades elliptic-hastate or rarely 3-lobed with large confluent lateral lobes, gradually short-acuminate to narrowly acute at apex, deeply lobed at base, 20–48 cm long, 9.0–22.5 cm wide; anterior lobe 22–36 cm long, gradually constricted at base, sides broadly rounded; posterior lobes directed downward or slightly outward, narrowly triangular, somewhat unequal, longer lobe 2.5–12.0 cm long (from apex of petiole to tip of lobe), narrowly rounded at apex, shorter lobe 2–8 cm long; lateral lobes of 3-lobed leaves directed outward and upward, 16.5–20.0 cm long, 6.5–11.0 cm wide; sinus usually triangular at least in apical 2.5–3.5 cm, then broadly opening (when flattened), drying thin, upper surface brown, lower surface greenish brown; midrib flat or weakly sunken, 4 mm wide at base; primary lateral veins 7–15 per side, weakly raised, secondary and tertiary veins clearly visible; principal collective vein 8–12 mm from margin, weakly raised on lower surface; basal veins 3–5 pairs, basal rib not naked or only naked up to 1 cm.⁴
INFLORESCENCE:
Inflorescences erect at anthesis, 5–9 per axil; peduncle 13–20 cm long, 5–8 mm diam. (dried); spathe tube green on both surfaces, 4–7 cm long, 1.3–1.6 cm diam.; spathe blade greenish white, ca. 7 cm long, 2.2 cm diam. (unopened), acuminate at apex, gradually constricted near base; spadix sessile, white, 7.5–8.5 cm long; staminate portion of spadix more or less ellipsoid, 5.5 cm long, 13–15 mm diam., staminate flowers with synandrium truncate and obscurely 4-lobed at apex, lobes often obscurely emarginate at apex. Infructescences pendent, yellowish; not seen with mature fruit. Flowers July & November; Fruits seen March, September & November.⁴
ECOLOGY:
Syngonium hastiferum is endemic to Costa Rica (Puntarenas & San José) in Premontane wet forest, Tropical wet forest, and Premontane rain forest life zones at 20–680 m.⁴ altitude: 20–680 m
ETYMOLOGY:
From Latin hasta, "spear," and-fer, "bearing," referring to the hastate leaf blades with their outward-pointing basal lobes. The name was coined by Standley and Williams as Philodendron hastiferum and transferred to Syngonium by Croat in 1981.²
NOTES:
1. The species is a member of section Cordata and is characterized by its leaf blades being usually longer than broad, petioles sheathed much of the length of the petiole with the sheath free-ending and emarginate at apex, elliptic-hastate deeply basally lobed brownish drying blades which are triangular-acuminate at apex and gradually constricted at the base of the anterior lobe and with the narrowly triangular posterior lobes directed downward or slightly outward, with the sinus very narrow at the apex, 3 or 4 pairs of basal veins with the posterior rib naked only about 1 cm as well as by its up to 5 inflorescences, moderately long-pedunculate spathes with a green tube and greenish white blade and yellowish infructescences. Grayum (2003) reported that this is the only Costa Rican species with simple leaves that has the spathe tube green internally. Syngonium hastiferum is probably closest to Syngonium brewsterense from central Panama which differs by having the blade narrowly triangular sagittate-hastate and moderately constricted at the base of the anterior lobe with the sinus broadly spreading at apex, then turned inward to form a constriction as well as by having only 5 or 6 primary lateral veins per side. In contrast Syngonium hastiferum has narrowly ovate-elliptic blade which are scarcely or not at all constricted at the base of the anterior lobe and has the sinus very narrow at apex then flaring out with about 13 primary lateral veins per side. Croat & Grayum 59798 is unusual in being the only 3-lobed specimen of Syngonium hastiferum. In addition to having 3-lobed leaf blades it has a sinus that is sub-reniform rather than narrow. Despite these differences is seems to differ in no other way from simple-blades collections of the species.⁴
2. The only Syngonium with a field-confirmed pollinator. At La Gamba, Costa Rica, the sole pollinator is a plant bug, Neella sp. (Miridae), drawn by a volatile new to science, gambanol; bagged inflorescences set almost no fruit while every open one fruited.⁵
STORY:
STORY TITLE: The first flower known to be pollinated by a plant bug
For as long as anyone had thought about it, Syngonium was assumed to be pollinated the way its relatives are, by scarab beetles that spend a night inside the spathe. In 2022 a team led by Florian Etl reported from La Gamba, on the Pacific slope of Costa Rica, that Syngonium hastiferum is pollinated solely by a plant bug (Miridae: Bryocorinae) of the genus Neella, a species new to science. It was the first specialized plant-bug pollination system documented in any flowering plant.⁵
The evidence is unusually complete. Across 20 inflorescences the bugs averaged 146 individuals per inflorescence (20 to 515), with no other floral visitors beyond patrolling ants. Nine of ten bagged inflorescences set no fruit and the tenth made four seeds, while all 20 open inflorescences fruited, averaging 51 seeds. The attractant proved to be a molecule new to science, (Z)-3-isopropylpent-3-en-1-ol, named gambanol after the field station; synthetic gambanol on paper cones drew more than 900 Neella and no other insect. Bagged female-phase inflorescences, invisible to the bugs, still drew an average of 71.⁵
Everything about the beetle syndrome is inverted. Heat and scent come in the morning, between seven and nine, with the spadix up to 16 °C above the air; there are no food bodies; the pollen is spiny and is shed in strands that stick to the bugs. Bugs moved to a co-flowering Dieffenbachia aurantiaca picked up no pollen at all in 28 individuals tested. The cycle runs three days: the bugs enter the open chamber on days one and two, mate, and feed by piercing the tissue; on the morning of the third day the chamber closes, the upper spathe falls away, the bugs feed on the anthers, get dusted and leave. They are never trapped and come and go freely throughout.⁵
The question had been posed fifteen years earlier. Measuring thermogenesis in two other species in a Montreal greenhouse, Chouteau, Barabé and Gibernau noticed that a Syngonium spathe never loosens at pollen release, reasoned that a pollinator could not stay inside through the cycle, and closed with the sentence that the genus seemed to have two pollination syndromes, a conclusion that "must be verified through field studies."⁶ Earlier still, in an Aroid Profile on Syngonium steyermarkii, Croat and Bogner had looked at a spathe with no chamber at all and predicted pollination "by organisms other than by the large ruteline scarab beetles." Neither guessed a bug.
What the study does not show: no eggs or larvae were found in the inflorescences, so this is not a brood site, and heat was judged a secondary signal because synthetic gambanol alone matched the natural attraction.⁵
REFERENCES:
1. Plants of the World Online, Royal Botanic Gardens, Kew — Syngonium hastiferum
2. Annals of the Missouri Botanical Garden 68: 595 (1982) — protologue.
3. iNaturalist: Syngonium hastiferum
Additional photos from iNaturalist by mdoliveira, Marcel Esquivel, LostInCR, Nicolas Saenz and Randall Jiménez