Eulychnia acida

Name, range and separation of former varieties

Eulychnia acida Phil. is an accepted species in POWO. Its synonyms are Cereus acidus and Philippicereus acidus. The database gives a natural range from central Atacama to the northern part of the Valparaíso region. [2-WWW] [Merklinger et al. 2021]

The former E. acida var. elata and var. procumbens now correspond to separate species, E. elata and E. chorosensis, respectively. Data identified under these names were not automatically combined with this account. [2-WWW] [2-WWW]

The ecological studies described below concern tree-like plants from Coquimbo, including Quebrada Honda, Gualliguaica, La Coipa and the surroundings of Las Chinchillas reserve. Some populations lie inland, in a semiarid environment with winter rain. Their water supply differs from that of the coastal E. breviflora population studied for lichen effects. [Cares et al. 2018] [Salvatierra 2020] [Stanton et al. 2014]

Growth form and copao fruit

The tree-like growth form includes a trunk and numerous columnar, ribbed branches. Reproductive organs appear in their upper parts. In Merklinger and colleagues' morphological comparison, the flower of E. acida has a pericarpel without the dense hairiness characteristic of the E. breviflora group. The pale perianth may have pink or red-marked portions of its tepals. [Merklinger et al. 2021, p. 186, 256] [Salvatierra 2020, p. 186, 256]

The ripe fruit has fleshy, acid contents and numerous seeds. The dispersal study described an indehiscent fruit that falls when ripe. Whole fruits or exposed pulp reach various consumers. The durable covering and acid taste affect feeding behaviour, and passage through the digestive tract can preserve or destroy seeds. [Cares et al. 2018, p. 2, 4–6]

The cycle from areole to ripe fruit

Salvatierra observed three populations weekly from January 2006 to February 2007. Four outer stems pointing in different directions were marked on each plant. Eight stages were distinguished, from a woolly areole and enlarging bud, through perianth opening, to a young and ripe fruit. This allows development to be followed on a plant even when individual branches differ in phase. [Salvatierra 2020, p. 254–256]

Buds were observed from late Chilean autumn, and the main flowering period was from spring to summer. Fruit ripening began in summer. Buds, open flowers and fruits overlapped in time, particularly from spring onwards. Phase duration and organ number per stem differed between sites. The description refers to one monitored season in the Southern Hemisphere. [Salvatierra 2020, p. 258–261]

Flowers facing the equator

The 2017 study assessed the positions of 300 reproductive structures on 20 plants from two sites. The northern side predominated relative to both the whole plant and the axis of an individual stem. At this latitude, northern exposure faces the equator. Forming flowers on the illuminated side can bring them closer to photosynthetically active stem tissues. [Warren et al. 2017]

The authors presented more economical assimilate transport and flower warming as functional hypotheses. Measuring organ direction revealed an ordered pattern. This study did not directly examine sugar-flow rate, flower temperature or seed number after a change in exposure. These measurements are needed to assess the proposed mechanisms. [Warren et al. 2017]

The animal eating the fruit and the fate of the seed

In Las Chinchillas reserve, tracks near fruits set out indicated the tinamou Nothoprocta perdicaria, the mockingbird Mimus thenca and the degu Octodon degus. Birds pecked the fruits, and this trial did not demonstrate that they swallowed seeds. Degus took whole fruits to their burrows. In a feeding experiment, they destroyed almost all swallowed seeds. Their feeding therefore primarily involved consumption of pulp and seeds. [Cares et al. 2018, pp. 3–5]

Germination of seeds recovered from goat and guanaco faeces was compared with that of seeds taken directly from ripe fruits. Each group included 100 whole seeds sown. On moist gravel, at around 26°C and with a photoperiod of 14 hours of light and 10 hours of darkness, germination after 30 days was 60% after goats, 52% in the control and 13% after guanacos. Superiority of the goat group over the control was not demonstrated statistically. Different animal diets and selection of only intact seeds define the scope of this comparison. [Cares et al. 2018, pp. 3–5]

Young plants and shelter from shrubs

The abstract of earlier observations from 2009–2012 indicates that young E. acida, less than 30 cm tall, were found more often beneath selected shrubs than in open areas. A particular association involved Eriophyllum ambrosiodes (called Bahia ambrosioides in the publication). Under canopies, conditions were cooler and moister than in open places. The authors interpret this pattern as the action of nurse plants moderating the young cactus's microenvironment. [Cares et al. 2013, abstract] [2-WWW]

The path from a fruit to a new adult individual includes seed transport, germination and seedling survival in a suitable microhabitat. The field comparison in the 2018 study showed a larger proportion of young plants outside the reserve, where goats occurred. Since existing vegetation patches were compared, the result remains consistent with a possible contribution of goats to dispersal, while its magnitude also depends on establishment conditions. [Cares et al. 2018, pp. 4–6] [Cares et al. 2013, pp. 4–6]

Population variation and cultivation

The abstract of Jana and colleagues' study presents marked variation in morphological traits within and among three studied populations. ISSR marker analysis also showed diversity. ISSRs compare DNA fragments between repeated sequences. Agreement in part of the morphological and genetic pattern helps characterise the species' resources. Fruit shape or colour alone cannot reconstruct a plant's entire origin. [Jana et al. 2017, abstract]

Cultivation under cover uses the general conditions for columnar cacti described in the genus account. Sowing provides an opportunity to retain material provenance. The seed experiment confirms germination on a moist mineral substrate at a specified temperature and photoperiod. It assessed the effect of digestive passage, without comparing temperatures, substrates or year-round care. [1-WWW] [Cares et al. 2018]

Related articles

Materials from the author's archive

The species also appears in Konrad Szychowski's private material archive. [Kaktologia 2009b, file p. 9] [Kaktusy itd. 2008, file p. 7] [Neciu b.d., file p. 1]