Bonellia nervosa (C. Presl) B. Ståhl & Källersjö

Bonellia nervosa is a shrub belonging to the Theophrastaceae family. It was formally known as Jacquinia nervosa and later J. pungens. B. nervosa is found in deciduous and semi-deciduous dry forests from southern Mexico to Panama (Zuchowski et al. 2007). It exhibits an inverse pattern of leaf phenology where it drops its leaves during the rainy season and produces leaves during the dry season. It has characteristic needle-shaped, waxy leaves that protect the leaves from herbivory (Janzen 1970). It’s narrow, orange-red flowers are sometimes believed to be pollinated by hummingbirds, but no observations of hummingbirds visiting the plant have been recorded (Janzen 1983). Due to its flowers’ pungent scent, it has also been suggested that it may be insect pollinated (Zuchowski et al. 2007). It produces bitter tasting green fruits that ripen into sweet, orange mature fruits that are dispersed by frugivorous birds and rodents (Janzen 1970).

The population is essentially continuous on the pacific coast of the Central American lowlands from southern Jalisco, Mexico to northern Panama (Janzen 1970, Zuchowski et al. 2007).

B. nervosa is a woody shrub with multiple trunks and branches. It rarely grows higher than 4 m tall (Janzen 1970). Unlike many other tropical plants, the taproots do not extend out laterally, but grow down into the clay that lies beneath the nutrient rich surface soil. For 2-meter tall adult plats, the taproot grows at least 3 meters down into the ground (Janzen 1970, Oberbauer 1985). Thus, there appears to be no root competition between B. nervosa and other understory plants.

One branch shoot is usually produced per branch per year, but several long branches often radiate from a single cluster of leaf axils (Janzen 1970). The branches of B. nervosa range from 0.1-15 cm, with two different peak branch lengths. The shorter branches have an average length of 0.5 cm and have 1-7 leaves in a tight whorl. The longer branches have an average length of 7 cm and have 14-15 leaves along their distal half. These longer branches are responsible for a slight increase in crown height and volume each year (Janzen 1970).

B. nervosa has stiff, sclerophyllous, needle-shaped leaves with a sharp spine at the end. These spines are 5-10 centimeters long. The bitter, unpalatable taste of the leaves and the presence of spines protect the plant from herbivory (Janzen 1970).

Birds are the main disperser of B. nervosa seeds. When the birds eat the fruit, the hard seeds pass through the gut undamaged and germinate in about 2 weeks. Rodents like agoutis, coatis, and squirrels also disperse B. nervosa seeds because they either spit them out or swallow them whole. Thus, B. nervosa experiences virtually no seed predation (Janzen 1970). B. nervosa can also regenerate from stump sprouts after it has been cut down (Janzen 1970).

The flowers are orange-red in color, stiff, waxy, and mildly fragrant. Flower buds are visible within approximately one month after the leaves are produced (Janzen 1970).Smaller individuals usually have fewer flowers than larger individuals, but there is great variation in the amount of flowers produced. For an average-sized individual, the total number of flowers varies between 100-900 (Janzen 1970).

B. nervosa produces spherical, green fruits 2-3 cm in size during the first part of the dry season, from the end of November to February (Janzen 1970, Chaves and Avalos 2014). They taste soapy and bitter and are even used as fish poisons in western Mexico (Standley 1923). During the last three months of the rainy season, the fruits mature and become orange and sweet. The ripe fruits are indehiscent and have a thick hard rind. The fruit has a sweet juicy endocarp and 2-10 smooth, flattened, oval seeds inside (Janzen, 1983). Once mature, they are eaten by birds and rodents. Based on a sample of 102 fruits, B. nervosa shrubs produce 9-90 seeds with an average of 9.56 seeds per fruit (Janzen 1970).

B. nervosa experiences little damage from herbivores because of its leaves’ protective spines and bitter taste, and the leaf crop often remains completely undamaged throughout the entire dry season (Janzen 1970). However, chewing beetles from the genus Epicauta, specialists on B. nervosa, concentrate their herbivory on young leaves. In individuals that harbored these beetles, young leaves lost an average of 36.77% of their leaf area (Chaves and Avalos 2014).

B. nervosa avoids attack by leafcutter ants by making jacquinoic acid, an ant repellent compound in its leaves (Okunade and Weimer 1985).

B. nervosa is a heliophile, meaning that it thrives in large amounts of sunlight (Janzen 1983). Adult and juvenile B. nervosa drop their leaves approximately 2 weeks after the overhead canopy has closed in, and 4 weeks after the rainy season starts. Within the first eight weeks of heavy rains, leaf drop is nearly complete (Chaves and Avalos 2006, Janzen 1970). The shrub is initially inconspicuous in its leafless phase because of the circular patch of yellow and white dead leaves that surround the base of the trunk. At the beginning of the rainy season the taproot, trunk, branches, and twigs have the highest starch content because the plant must store reserves for the period when it is photosynthetically dormant (Janzen 1970). The plant’s starch reserves fall steadily during the rainy season. Hot rainy seasons can cost the plant up to 50% of the stem’s carbohydrate reserves. Since the plant has a long thick taproot instead of lateral roots, it is also unable to harvest litter or upper soil reserves (Janzen 1983).

The shrubs remain leafless until the end of the rainy season when leaf wilt and some leaf drop begins in the canopy (Janzen 1970, Reich and Borchert1984, Sobrado 1986). For the lower Guanacaste province of Costa Rica, this means that the plants produce a new crop of leaves from late November to early December. Most branch elongation occurs while new leaves are produced (Janzen 1970). Leaf numbers are related to light availability. Maximum leaf production occurs during peak solar radiation in the middle of the dry season. Decreasing day length causes flower bud emergence and leaf flushing (Chaves and Avalos 2006). B. nervosa is the only plant species in Costa Rica that displays this pattern of inverse leafing phenology (Chaves and Avalos 2006).

Hummingbirds pollinate B. nervosa flowers (Janzen 1970). When the flowers initially open, the anther covers the stigma so that the hummingbird’s upper beak will carry pollen. After a few days, the anthers move outward to expose the stigma and allow the hummingbird’s beak to reach it (Janzen 1970).

Bonellia nervosa là một loài thực vật có hoa trong họ Anh thảo. Loài này được (C.Presl) B.Ståhl & Källersjö mô tả khoa học đầu tiên năm 2004.