Ferocactus herrerae

Name, growth form and fruit

Plants of the World Online accepts Ferocactus herrerae as a separate species (formerly also F. wislizeni var. herrerae or F. wislizeni subsp. herrerae). Both historical combinations refer to the same plant in this treatment. Results for F. herrerae can therefore be sought under these names, while keeping them separate from studies of other F. wislizeni populations. [2-WWW]

The solitary stem changes from spherical to columnar. The description of material in the study of vivipary gives a height of up to about 2 m and a diameter of 45 cm. The elongated fruit is 4–6 cm long and 2.5–3 cm in diameter. Its wall remains fleshy, while the seed chamber is dry. Once mature, seeds lie loose within it and can spill out through an opening at the base. This structure matters when interpreting germination inside the fruit. [Aragón-Gastélum et al. 2013, p. 45]

Coastal plains and the seasonal water cycle

The natural range includes southwestern Sonora, Sinaloa and western Durango. The field account from northern Sinaloa describes plants on coastal plains and in mountainous areas. Coastal sites include places periodically flooded and saline places without flooding. Documentary photographs show individuals among Jatropha cinerea, Maytenus phyllanthoides, Agave angustifolia and Suaeda nigra. This is the specific setting of the study sites, rather than a list of obligatory companion plants. [2-WWW] [Aragón-Gastélum et al. 2013]

In the study area, rainfall was concentrated in July, August and September. The authors cited around 237 mm annually for San José and 391 mm for Los Mochis. These climate data describe two places used in the study. Differences in rainfall overlapped with differences in substrate and the plants' transplanting histories. Comparing the sites therefore requires consideration of this entire combination. [Aragón-Gastélum et al. 2013, p. 45, 47]

Germination while still on the mother plant

Here, vivipary means development of the radicle from a seed remaining inside the fruit. The resulting seedling is the offspring of sexual reproduction. In F. herrerae, this occurs despite the absence of juicy pulp surrounding the seeds. The authors considered the possibility that air entering the fruit chamber might provide sufficient humidity. The embryo's water source was not measured directly. The dry fruit chamber and fleshy wall therefore remain distinct elements of this explanation. [Aragón-Gastélum et al. 2013, p. 50]

Aragón-Gastélum and colleagues compared three transplanted groups of plants. San José was the control site, with 21 individuals. At Pueblito, 19 plants received extra watering during the dry season. At UAS, 17 plants originating from a non-saline rocky area were planted and then irrigated with added seawater. Fruits were collected in 2007–2008, and at UAS only in 2008. In the irrigated groups, each plant received a total of 240 l of liquid in six portions. This amount describes an experiment on adult plants in the ground. [Aragón-Gastélum et al. 2013, p. 47]

In the combined results from both seasons, at least one fruit with germinating seeds was found in 56% of control plants and 82% of watered plants. At UAS, all nine individuals that produced fruits had viviparous fruits. The other eight plants in this group experienced flower or fruit mortality. The proportions of viviparous fruits were 7.6%, 16.7% and 43%, respectively. The authors found a statistical difference in this proportion between UAS and the other two sites, while the two lower results belonged to one statistical group. [Aragón-Gastélum et al. 2013, p. 47, 49–50]

At UAS, more frequent germination inside fruits accompanied lower fruit production. About seven fruits per fruiting plant were produced there on average, compared with about eighteen in the other two groups in 2008. Each treatment was represented by one site, and plant origin and transplanting time differed. The study documents an association between vivipary and moist, saline conditions. The contribution of salts alone to this phenomenon remains entangled with the other differences between sites. [Aragón-Gastélum et al. 2013, p. 49–50]

From fruit to population recruitment

Germination inside the fruit shortens part of the path between a mature seed and a seedling. For this species, how often such a seedling leaves the fruit, roots and survives in the field remains an open question. The experiment cited counted fruits and the germinating seeds inside them. The authors did not compare subsequent survival of viviparous offspring and offspring from ordinary sowing. The ecological benefit of vivipary in F. herrerae therefore requires data on these later stages. [Aragón-Gastélum et al. 2013, p. 50–51]

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