Flowering within a short morning window
Jasminocereus thouarsii forms branched columns in the dry zone of the Galápagos. In 2001–2002, Jaramillo and colleagues studied a population beside the Charles Darwin station on Santa Cruz (J. thouarsii var. delicatus in the publication, now included in a single species in POWO). They observed 25 flowers on ten marked plants. All opened after 5.30 and closed by 10.00 local time. The authors found that they remained closed at night. [Jaramillo et al. 2010, Jaramillo et al., pp. 22–24][2-WWW]
The overlap between flower availability and visitor activity determined the opportunity for pollen transfer. Night observations covered four evenings in 2001, from 18.00 to 22.00. No insect visits to closed flowers were recorded then. The result complements older descriptions of nocturnal flowering, while remaining assigned to the population and seasons studied. [Jaramillo et al. 2010, pp. 22–24]
Three insects at the same flowers
Visits were observed on two profusely flowering plants in May of both years. Insects were recorded during the first twenty minutes of successive morning hours. Of 800 recorded visits, 54% were by the endemic bee Xylocopa darwini, 34% by the introduced fly Acrosticta apicalis and 12% by the endemic ant Camponotus planus. Visit intensity peaked at about 7.00. [Jaramillo et al. 2010, pp. 22–23]
The authors regarded the bee as the main participant in pollination. The reported proportions measure visit numbers and do not represent the percentage of seeds produced through each insect. The study did not compare fruit set following a single controlled visit. It identifies the most frequent visitor and the timing of flower contact, while keeping pollen-transfer effectiveness as a separate question. [Jaramillo et al. 2010, pp. 22–24]
Flower isolation explains the need for a vector
Ten buds on five plants were enclosed in pollination bags. Ten control buds on another five plants remained accessible to visitors. No isolated flower formed a fruit, while all controls fruited. Ripe fruits were collected after 22 days. They contained an average of 325 seeds, with a standard error of 15,3 across the ten fruits assessed. [Jaramillo et al. 2010, pp. 22, 24]
An external pollen-transfer agent was needed to obtain fruit in this experiment. Self-compatibility means the ability to be fertilised with the plant's own pollen, while autonomous self-pollination occurs without a pollen-carrying animal or intervention. The isolation test investigated the second process. The authors left self-compatibility unresolved. Comparison of controlled pollinations with self and cross pollen would resolve it. [Jaramillo et al. 2010, p. 24]
The same seed batch under four conditions
The next stage involved 1200 seeds from 25 ripe fruits. Each treatment had three replicates of one hundred seeds. The containers remained beside a laboratory window for four months, without additional lighting or heating. Seed preparation and germination substrate were varied. Seedlings were transplanted into soil upon reaching 5 mm. [Jaramillo et al. 2010, p. 22]
| Preparation | Substrate in the dish | Germination [%] |
|---|---|---|
| Soaking for 24 h at 25°C | Moist filter paper | 52,0 ± 10,2 |
| Soaking for 24 h at 60°C | Moist filter paper | 47,3 ± 8,1 |
| No soaking | Moist soil | 7,3 ± 3,0 |
| No soaking | Moist filter paper | 66,7 ± 8,6 |
The highest raw mean was obtained for unsoaked seeds on moist filter paper. Statistical analysis distinguished the poorly germinating soil treatment, while the three filter-paper treatments did not differ significantly. This comparison indicates the role of substrate conditions. Soaking, including at an elevated temperature, remains a tested treatment without a demonstrated increase in final germination compared with the unsoaked control on the same substrate. [Jaramillo et al. 2010, p. 24, Table 2]
Germination and seedling survival are successive stages
After transplantation into soil, the young plants were watered regularly and measured until April 2002. After eleven months, they were 9–25 mm tall. Mortality in individual treatments was 30–48%. Obtaining a seed capable of germination therefore does not yet establish the number of plants that will permanently join the adult population. [Jaramillo et al. 2010, pp. 22, 24, Table 2]
The Charles Darwin Foundation's 2025 nursery guide highlights the slow development of Jasminocereus and the need to control moisture during early germination. Excess water was linked to embryo rot and death. This practice concerns propagation of the archipelago's flora. It complements the substrate experiment by addressing seedling maintenance after emergence. [Jaramillo Díaz et al. 2025, pp. 86–87]
From a single season to population recruitment
At the Santa Cruz station, mean annual rainfall for 1982–2002 was 620 mm, but it varied greatly between years. The authors cited 2768 mm in 1983 and 63 mm in 1985. The mean alone therefore poorly describes the water input encountered by seeds at the site. Based on low germination in the soil treatment, they proposed that natural seedling establishment may be concentrated in years of heavy rainfall associated with El Niño. [Jaramillo et al. 2010, pp. 22, 24]
The study distinguished the need for a flower visit, seed germination capacity and subsequent seedling loss. The relationship with El Niño remains a hypothesis requiring long-term field data. Separating these stages allows slow recruitment of the tree-like cactus to be described through specific processes rather than attributed to a single seed trait. [Jaramillo et al. 2010, p. 24]
Full text of Jaramillo et al. 2010, pp. 21–25, and excerpts from the Charles Darwin Foundation's 2025 guide. The table and methods were compared with images of pages 22 and 24. The distinction between autonomous self-pollination and self-compatibility has been retained in accordance with the authors' discussion.
Insect pollinators of Jasminocereus thouarsii, an endemic cactus of the Galapagos Islands
Jaramillo P., Trigo M. M., Ramírez E., Mauchamp A., Insect pollinators of Jasminocereus thouarsii, an endemic cactus of the Galapagos Islands, Galapagos Research, 2010, 67:21-25
The study of a Santa Cruz population combines observations of morning flowering and visiting insects with flower isolation, a germination experiment and seedling growth measurements. It indicates a need for pollen transfer by an external agent, and separate limitations at the stages of germination and young plant survival. The discussion distinguishes the absence of autonomous self-pollination from undetermined self-compatibility, and proposes a relationship between population recruitment and irregular rainfall.
Plants of the World Online — Royal Botanic Gardens, Kew
Accepted names, synonyms and distribution. A citation beside a taxon leads to its record.
Accessed 2026-10-08.
Flora Nativa y Endémica de las Islas Galápagos. Guía de Propagación
[Jaramillo Díaz P., De Roy T., Calle-Loor A., Mayorga P., Sevilla C., Velasco N., Flora Nativa y Endémica de las Islas Galápagos. Guía de Propagación, Fundación Charles Darwin, 2025]
A propagation guide for Galápagos flora prepared from many years of experience in the Galápagos Verde 2050 programme. It combines local plant distribution, descriptions of structure and ecological importance with nursery guidance. The Jasminocereus profile on pages 86–87 discusses slow development and moisture control during early germination. The recommendations concern conditions in the archipelago.
