New species of plants: Costa Rica, one endemic to the Osa

Publication Date: 
Wednesday, September 23, 2015
INOGO Newsletter, No. XV
Photo Credit: 
B.E. Hammel

Three new species of plants discovered in Costa Rica, one endemic to the Osa

After recent fieldwork and further scientific investigation by botanists, Costa Rica now claims three new species of plants discovered in the coffee family (Rubiaceae), one of which is endemic to the Osa Peninsula.

Surprisingly, for one of the most consumed products in the world, many would be hard-pressed to botanically describe the coffee plant (Coffea arabica) let alone identify it or some of its characteristics on farms, plantations, or in its native habitat. Botanically, the Rubiaceae family is known for its simple, opposite, and entire leaves (as opposed to compound, alternate, or lobbed respectively), which have loosely been the “rule-of-thumb” for the family. That is, when identified together these traits can help botanists and scientists in the field correctly identify a plant – sometimes among dozens or hundreds of species – down to the family, genus, or even species level.

In a recent article, “Three new species of Pentagonia (Rubiaceae) from southern Central America, one foreseen, two surprising”, published in August 2015 by Phytoneuron, the author Barry E. Hammel describes three news species in the Pentagonia genus that further diversify the family. This genus, already an exception to Rubiaceae with its “normal, mature leaves [that] are pinnately lobed to deeply pinnatified,” had just two out of 10 Pentagonia species known from Costa Rica with such leaves; now, Pentagonia gambagam, one of the recently discovered species adds a third. One of the other new species described is identified as Pentagonia gomez-lauritoi, which had previously been recognized and published as “Pentagonia sp. A”.

The third new species described is the most surprising as it completely deviates from the “rule” in the coffee family. Endemic to the Osa Peninsula, Pentagonia osapinnata was discovered by botanists Reinaldo Aguilar, N. Zamora, and Hammel, and has pinnately compound leaves (see picture above) with 8-10 leaflets (pinnae) per side, the first of its kind in the family. The species is considered a shrub or small, 4-6m un-branched tree that flowers in June and produces fruit in April. It occurs in “deep primary wet forest, on slopes and along ridges, sometimes at [the] edge of small ravines,” and is found between 200-280m. Etymologically, the species name is derived from its geographical origin and its description: “osa” for the canton from which it was collected, and “pinnata” for its pinnate compound leaves.

Even more surprising, P. osapinnata was actually first collected over 20 years ago in the same locality by the famous Costa Rican collector Gerardo Herrera, but was tentatively identified as another species (Pentagonia cf. lobata) and thus remained virtually unstudied. How and why this species evolved such divergent characteristics remains to be hypothesized, but hopefully now that it is receiving more scientific attention, the authors suggest, phylogenetic and molecular studies “will surely confirm the compound leaves of P. osapinnata to have evolved by way of relatives with simple, pinnatified-lobed leaves.”

Meaning, further genetic, taxonomic, and botanical work on these new species will reveal more insights and previously unrecognized relationships with other, perhaps undiscovered species. Certainly, the three new species of Rubiaceae in Costa Rica can serve as inspiration for the next generation of biologists, ecologists, and botanists ready to carry out fieldwork in pursuit of these answers.



Barry E. Hammel

Missouri Botanical Garden

P. O. Box 299

St. Louis, Missouri 63166-0299


Reinaldo Aguilar

Director - Vascular Plants of the Osa Peninsula, Costa Rica:

Los Charcos de Osa

Centro de Diversidad de Plantas Regionales.

Apdo # 76 - 8203,

Osa Peninsula,

Costa Rica.