Background:

Through explorations in south-central Sinaloa and review of iNaturalistMX, specimens were detected of a shrubby Jatropha with 3-5-lobed leaves that did not correspond to any known species.

Questions:

Are the Jatropha populations of south-central Sinaloa a new species? How many and which species of Jatropha are present in Sinaloa, Mexico?

Studied species:

Jatropha.

Study site and dates:

Sinaloa, Mexico, 2021-2024.

Methods:

Botanical collections and field photographs of Jatropha sp. nov. and J. purpurea were made. Specialized literature, herbarium specimens, and iNaturalistMX were consulted. Comparative plates, distribution maps, and identification keys of the shrubby, 3-5-lobed leafed Jatropha species in western and northwestern Mexico were prepared.

Results:

Jatropha marquezii is a new endemic species from Sinaloa. It is similar in habit to J. purpurea but differs in its yellowish-green corolla with long trichomes on the inner surface, conspicuously reflexed lobes, and practically no stipitate glands. It differs from J. bullockii by its uniseriate stamens and cupulate corolla. Fourteen species of Jatropha were documented for Sinaloa, of which Jatropha marquezii has the smallest range (< 30 km2) and J. purpurea occurs in the most threatened habitat.

Conclusions:

Jatropha marquezii sp. nov. is similar to J. purpurea and species of section Fremontioides. It is recommended that J. marquezii and J. purpurea be included as Endangered in the IUCN Redlist.

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