Euphorbia dressleri

[Melanie]

Euphorbia dressleri V. M. Steinm. nom. nov. (=Pedilanthus gracilis Dressler, Contr. Gray Herb. 182: 109-1957). A new name is required because of the existence of Euphorbia gracilis Loisel., published in 1807. The specific epithet dressleri honors Robert L. Dressler, renowned ochidologist who early in his career work on Euphorbiaceae and provided the monograph of Pedilanthus.

[Melanie]

possible extinct plant from Mexico

[Melanie]

Euphorbia dressleri V. W. Steinm.—This species was described (as Pedilanthus gracilis) by Dressler in 1957 based on a single collection (Hinton 10973, isotypes: MEXU!, MO!, NY!, P!). Hinton’s vague locality information reads “Guerrero, Distr. Galeana, Atoyac. Wooded hill. 240 m a.s.l. 25 Nov. 1937”. We made two visits to the area of Atoyac, in December 2002 and February 2003, and thoroughly searched the slopes of all the hills that met the following criteria: (1) They occurred in sufficient proximity to Atoyac that they could be construed as being located at “Atoyac”, sensu Hinton’s label; (2) The elevation corresponded to 500 m a.s.l. or lower; (3) The presence of at least some non-ruderal vegetation. Similar criteria have allowed us to relocate other Hinton localities. For example, the locality of a Cnidoscolus species in Michoacán, which Hinton described as “Villa Victoria, Distr. Coalcomán” (G. B. Hinton 13908, NY!) was collected less than two kilometers away from that village. If the type population of E. dressleri still exists, it seems likely that it would be within a similar radius around Atoyac.
We carefully searched numerous hills on both sides of the Atoyac River, including Cerro La Piedra, Cerro La Mina and canyons on their northern flanks, Cerro Rasca Viejo (the 360 m a.s.l. peak NNE of the dam on the Atoyac River), and the slopes of Cerro La Piedra del Diablo. Farther afield, we searched higher elevations in the vicinity of Agua Fría and between Cacalutla and the area of El Quemado and Cerro Prieto de Los Blanco. We also visited the low coastal hills (less than 100 m a.s.l.) to the southwest of San Jerónimo de Juárez, which can be seen from the vicinity of Atoyac.
Of the nearly 30 residents interviewed in the areas visited, all confirmed that a plant fitting the description given was not to be found in the local area. Many asserted that such a plant occurred higher in the mountains. We initially discounted these reports, because it is common for residents of seasonally dry areas to regard the evergreen vegetation of higher elevations as lusher and more diverse than the lowlands. However, because of the persistence of these reports, we extended our search to an elevational belt between 500 and 1500 m a.s.l. Indeed, Pedilanthus clade species do occur in the mountains above Atoyac, but they are not E. dressleri, as documented by collections of E. peritropoides (e.g., Olson and Cacho 996, MEXU!) and E. calcarata (G. Espinosa 9, and N. Turrubiate G. 110, FCME!) in the mountains northeast of Atoyac at approximately 1000 m where it shares the common name “zapatito de la virgen” or “zapatito de niño” with the cultivated E. tithymaloides. That we were able to locate slipper spurges in the area and that we were able to confirm that local people are aware of the plant when it is present suggest that our methods would have located E. dressleri if it still occurred in the hills around Atoyac. Additionally, staff of the FCME herbarium have been exploring the state for over 10 years for their Flora of Guerrero project but have never collected this species. Carauta (1989) would consider this species already extinct because it has not been collected for more than fifty years.
(A) Distribution. This species is only known from a single collection from an area less than 5 % of the Mexican territory (score = 4).
(B) Condition of habitat. There are apparently no existing sites suitable for this species, so the condition must be considered hostile (score = 3).
(C) Intrinsic biological vulnerability. We consider the vulnerability of this species to be high (score = 3). Although this species is only known from a unique collection and therefore its biological requirements are practically unknown, we can deduce likely factors that make it vulnerable. Some of these could be the low recruitment rate or low resistance to disturbance that might be inferred by our failure to relocate it in the highly altered forest of Atoyac.

(D) Impact of human activity. No primary forest remains in the area of Atoyac. Much has been cleared for agriculture and pasture, and all of the forests we visited receive heavy pressure from wood collectors. Extensive areas are covered with weedy secondary vegetation that is probably inappropriate for slipper spurges. Residents reported that the eradication of opium poppy and marijuana cultivation in the area involved aerial herbicide spraying and semicontrolled burns. We attribute our failure to locate E. dressleri and the lack of local knowledge of such a plant to this extensive perturbation that has virtually destroyed the lowland forests of Atoyac. The impact of humans on this species has clearly been high (score = 4).

www.explorelifeonearth.org/people/Olson%20et%20al%20AJB%202005%203.pdf

[koeiyabe]

plants.jstor.org/stable/10.5555/al.ap.specimen.mo-022135?searchUri=filter%3Dname%26so%3Dps_group_by_genus_species%2Basc%26Query%3DEuphorbia%2Bdressleri

Last collected specimen