Guayaba: an American fruit under indigenous cultivation, described in 1535 and carried round the tropics
Guava is a Neotropical fruit that modern work calls semi-domesticated. Oviedo's chapter on the guayabo, written in the Caribbean and printed in full in 1851, already records the two facts the genetics later supported: wild trees are smaller than cultivated ones because the Indians take care over them, and both Indians and Christians plant them in their holdings. He also records the astringent use against diarrhoea. The plant the Spanish carried outward is now invasive in much of the tropics.
Why this wins its question: Guava normally appears in English as a fruit that "originated in Central America and spread worldwide", with the spreading left agentless and the cultivation before 1492 left out. This object binds the two halves that are usually missing. From the sixteenth-century chapter, read from the page: wild guavas smaller than cultivated ones because the Indians take care over them, the crown of leaflets on the fruit, the six-year decline that forces replanting, the astringent use against flux of the belly, and the sentence in which Christians take up the Indians' orchard practice. From the peer-reviewed literature: semi-domestication proposed to begin in south-western Amazonia, the archaeological dates on two coasts, and the mechanism that actually moved the plant after 1492 - introduced livestock standing in for extinct megafaunal dispersers. It then prints the bill: invasiveness across the tropics, and the Galápagos case traced by microsatellites to three ornamental trees planted by a named settler about 1889. It also declines a priority claim it could have made loudly, and says why.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
The early account used here is capítulo XIX of libro VIII of Gonzalo Fernández de Oviedo's Historia general y natural de las Indias, "Del árbol llamado guayabo é su fructa", read from the Real Academia de la Historia edition printed at Madrid in 1851, tomo I, pages 304-305. The author was a royal official resident in Santo Domingo, and what these sheets are firm evidence of is the text as the Academy's editor established it from the codices, not the wording of the Seville sheets of 1535.
The chapter records a managed, not a wild, tree, and says who does the managing: "Hay muchos guayabos salvajes; pero son menores que los que se cultivan, en lo qual tienen mucho cuydado los indios" - there are many wild guavas, but they are smaller than the cultivated ones, in which the Indians take much care. The same page distinguishes two kinds and describes fruit both round and elongated, red or white inside, divided into four quarters of flesh.
The transfer into Spanish hands is recorded in one clause, without ceremony: "Los indios ponen estos árboles en sus heredamientos, é lo mismo haçen los chripstianos" - the Indians plant these trees in their holdings, and the Christians do the same. The husbandry was adopted before the fruit was liked, and the adoption is stated as observation rather than as achievement.
Modern synthesis reaches the same description of the plant's status by another road: guava is treated as semi-domesticated rather than fully domesticated, its domestication is proposed to have begun in the lowlands of south-western Amazonia, and it appears archaeologically on the Peruvian coast by about 7,000 years BP and in Mesoamerica by about 2,600 years BP, carried by human migration, exchange and trade long before 1492. The Amazonian origin is offered by its authors as a hypothesis from modelling and scattered archaeobotany, not as a settled result.
Oviedo's chapter also carries a medical use that the plant is still studied for: the fruit is good "para el fluxo del vientre, é restriñen, quando se comen no del todo maduras", good for flux of the belly, and binding when eaten not fully ripe - with the further instruction that they should then be somewhat hard so that the flux may cease.
That matters for a small point of bibliography which this object states with its uncertainty attached. The fullest modern review of guava's cultural history credits Francisco Cervantes de Salazar with the first mention of the fruit's medicinal use against diarrhoea and Cieza de León with its use for stomach illness in Colombia; it does not cite Oviedo, whose libro VIII was among the nineteen books printed at Seville in 1535 and who states the astringent use plainly. The priority is claimed here only as far as the evidence read goes: the 1851 text is an editorially established one, the 1535 sheets were not opened for this entry, and the review may have had a reason for its choice that it does not print.
The mechanism that carried guava out of the Americas after 1492 was partly accidental and is well identified: guava is a megafaunal fruit whose Pleistocene dispersers were extinct, and the introduced European livestock - kept on small farms as well as ranged - supplied new ones, so that the animals of the Columbian exchange spread the seed and enhanced gene flow between guava populations that had been isolated from each other. The plant travelled on the back of the cattle transfer as much as in anyone's hands.
Europeans did not take to it quickly, and Oviedo says why in terms a modern taster would recognise. Whoever is not accustomed to the fruit "no se agradará della, hasta que la continúe, por causa de los granillos" - will not like it until he keeps at it, because of the little grains, the hard seeds that must be swallowed. The modern review preserves the blunter European verdict of the period: "It stinks like a bug, and it was an abomination to eat it."
The husbandry Oviedo describes was demanding, which is part of why the cultivated tree is a real achievement rather than a found object. The trees age fast: past six years they are old, the fruit grows smaller and harsher every year, and "por tanto son de reponer ó plantar otros nuevos guayabos, y en buen territorio", so that a guava orchard is a thing continually replanted. The tree, he adds, rewards good soil and rarely does well in thin ground.
The cost belongs in the same entry as the transfer. "In numerous tropical and subtropical countries where guava is cultivated, it is often quite invasive", the review states, attributing this to the combination of clonal and sexual propagation and to seeds that stay viable a long time; colonial chroniclers in the Caribbean had already called it a plague.
One archipelago has the case documented down to the gardener. The first three guava trees in the Galápagos were planted for ornament by the settler Manuel J. Cobos on San Cristóbal about 1889-1890; guava is now one of the 37 highly invasive plants of the archipelago, has held uncultivated ground since the early 1900s, and microsatellite work finds that "the San Cristobal P. guajava population is the origin of the plague that spread over the four inhabited islands", with hybridisation threatening the endemic congener Psidium galapageium. Settlers "tried to eradicate any plant or seedling that appeared to be P. guajava, to no success."
What the sources read here cannot say is also worth stating. Oviedo describes cultivation in the Caribbean and on Tierra Firme but names no people, no orchard and no date for it; the genetic and archaeobotanical synthesis dates domestication only within millennia; and neither establishes when guava reached Africa, India or the Pacific, or by whose ships. The transfer is documented at both ends and thin in the middle.