Leuenbergeria guamacho

Range and seasonality

The species occurs in northern Colombia, Venezuela and part of the southern Caribbean region. It produces yellow flowers and is associated with seasonally dry communities, among others. Physiological measurements were made in Venezuela at Montecano and Arenales, sites with different patterns of water conditions. [2-WWW] [Edwards and Diaz 2006] [Leuenberger 2008]

The species was also recorded in the floristic study of Ciénaga de La Palmita in Zulia state. The paper describes a specific landscape and local communities. The VU category cited there comes from the Venezuelan red book. It is not equivalent to the current global IUCN category. [Vera 2025]

Habit and areole development

The plant forms a shrub or tree 4–8 m tall, with a short trunk and branched crown. Young shoots are green or reddish, later covered by pale brown periderm, a secondary covering tissue. On older branches, areoles elongate into small short shoots. They produce both spines and successive leaves, so foliage can renew on the previous year's part of the branch. [Leuenberger 1986, Pereskia guamacho description]

Yellow flowers distinguish this species from most leafy cacti. The similar Leuenbergeria aureiflora has flowers on distinct pedicels and larger seeds. In L. guamacho, flower attachment thus remains an important diagnostic feature, and seed structure also matters in fruiting material. Similar flower colour does not remove these differences. [Leuenberger 1986, P. guamacho and P. aureiflora descriptions]

Daytime photosynthesis and drought response

When water was available, leaves functioned mainly through the C₃ cycle, taking up CO₂ during the day. During prolonged drought in Arenales, nocturnal stomatal activity and increased acidity were detected. At Montecano, the corresponding measurement showed no such nocturnal increase. Both observations concern the same species under different field conditions. [Edwards and Diaz 2006]

Carbon isotope composition indicated a dominant contribution of C₃ photosynthesis to the overall balance. Nocturnal acid transformations thus show metabolic flexibility rather than a permanent shift of the whole plant to strong CAM. Stomata limited water loss, while the stem's ability to supply leaves with water remained an important part of the system's function. [Edwards and Diaz 2006]

Roots and underground reserves

A fleshy root over 1 m long and about 15 cm in diameter was documented in a young tree exposed in a roadside excavation in Venezuela. According to Leuenberger, the thickening probably developed from the main root. A storage root was later also observed in a seed-grown specimen in Berlin-Dahlem. The underground water store helps explain why leaf appearance does not always correspond directly to current rainfall. The author identified the importance of this reserve for the overall water balance as a hypothesis requiring measurements. [Leuenberger 2008]

Flowering in the field and greenhouse

In herbarium material, flowering was often associated with periods when plants were leafless. The author also observed flowering trees with leaves in the rainy season. Prolonged drying of a greenhouse specimen was insufficient to induce flowering. The proposed association with a combination of heat, drought and day length remained the author's hypothesis rather than a tested recipe for collections. [Leuenberger 2008]

Population variation

Analysis of 19 allozyme loci in 17 Venezuelan populations showed considerable genetic variation and relatively small differences between populations. Marker distribution allowed the authors to infer gene exchange and its relationship with distance. Pollinator flights and movements of individual seeds were not tracked directly. [Nassar et al. 2002]

Sources may use the names Pereskia guamacho and Pereskia colombiana. Current POWO links them to Leuenbergeria guamacho. Ecological, physiological and genetic results therefore remain assigned to one species even when publications use different names. [2-WWW]