Euphorbia boliviana Rusby 1907

Euphorbia boliviana Rusby (1907: 442)

≡ Chamaesyce boliviana (Rusby) Croizat (1946: 291).

Lectotype (designated here):— BOLIVIA. s.l., s.d., M. Bang 2907 (NY barcode 00263308!; isolectotypes K barcode 000253892!, NY barcode 00263307!, US no. 799055 / barcode 00109300!).

Euphorbia boliviana is a small annual that is disjunct between the mountains of central Mexico and the Andes of Peru and Bolivia. Rusby described the species in an account of the plants collected by Miguel Bang during his botanical explorations of Bolivia in the late 1800s. The specimen designated here as lectotype was initially labeled as the holotype and has been treated as such (e.g., Mugnai et al. 2021). However, Rusby mentions in the protologue that Bang’s collection is “The same as Mandon 1064 and Mathews 502 ” without making a specific type designation. Thus, a lectotypification is warranted, and the Bang collection previously considered as the holotype is chosen.

It appears that neither Mandon 1064 nor Mathews 502 are at NY, where Rusby was a curator at the time he described Euphorbia boliviana. There is a collection of Mandon 1064 at G-DC (barcode G00310544 photo!), but this specimen is Euphorbia serpens Kunth (in Humboldt et al. 1817: 52) and scarcely coincides with the protologue description. Mathews 502 is at K (barcode K000253893 photo!). However, this specimen appears to be Euphorbia peruviana Wheeler (1939: 59) or a related species and also coincides little with the protologue description of Euphorbia boliviana. It bears an annotation by Derek Burch in 1971: “Cited by Rusby when publishing E. boliviana —as a joke?”. With regard to the Mandon specimen, it is possible that Rusby erred and meant to cite Mandon 1063, which is at NY (barcode 00263317!). It is an isotype of Euphorbia lasiocarpa Klotzsch (1843: 414) var. subprostrata Boissier in Candolle (1866: 1262), which I consider a synonym of E. boliviana.

Although Mugnai et al. (2021) treated E. boliviana as a synonym of Euphorbia hypericifolia Linnaeus (1753: 454), it is distinguished from the latter in being pubescent (vs. glabrous).