Tiliaceae
PIENE DE MICO
Common, evergreen (or briefly deciduous), understory tree (10-15 m) named for the round, bristle-covered fruits that fill its canopy during the dry season. A fast growing pioneer that is among the first trees to grow in an area that has been disturbed, Piene de Mico is a prototypical secondary forest species. Road and trail-sides, as well as and young woodlands, typically harbor large numbers of these trees.
Description: Piene de Mico has a bent, though still vertically ascending and roughly cylindrical trunk (to 60 cm in diameter). Very thin buttresses arise from the bole about a meter above the ground and wind away from it in an intricate, serpentine pattern. Bole and buttresses are clad in extremely smooth, often glossy bark, carrying an unusual pale green, silvery or whitish hue, and textured by vertical lenticels. Branching occurs along the upper half of the trunk. Upwardly angled, they create a thin, small, and irregularly-shaped crown. Peine de Mico’s simple, alternate leaves are variable in size, though large, averaging 27 cm long and 10 cm wide. They are arranged in two, horizontally oriented tiers, along either side of the slightly zig-zag twig. Of overall elliptical shape (their widest point is off-center and distally displaced), the blades have finely serrate margins and end in well-developed, narrow drip-tips (2.5 cm). Leaf veins, petioles, and twigs (and, to a lesser extent, blade surfaces) are densely populated by long (2 mm) golden or reddish brown hairs. Foliage yellows and is shed during the dry season months of January and February. Trees then remain bare until new growth begins in April. By May, all trees boast a luxuriously green and fresh cover of pristine leaves.
Flowers grow in short cymes from leaf axils. Buds are bulb-shaped and covered with the same dense pubescence as the leaf veins and twigs. Each open flower (3 cm in diameter and 2 cm long) consists of five long, thick sepals with glossy, yellow inner surfaces; five narrow, yellow petals that, though free, project forward and often form a tube-like corolla; a tight bunch of bristly stamens; and a central pistil. Quite aromatic, Apeiba flowers smell pleasantly of roses. Piene de Mico trees are fertile during 75% of the year, with the most prolific flowering activity occurring from July to November. Blossoms are absent only during the driest part of the summer season – a three month period stretching from late February until late May. Despite this continuous fertility, new Apeiba fruits cannot be observed in the crowns until late November or December – seven months after the flowering season began. (Fertilized flower ovaries are assumed to remain dormant during this time). Then, small, green spheres (2-3 cm) covered with flexible, finely barbed spines (1 cm) finally begin to appear. Now growing rapidly, they reach their full diameter of 7 cm by February. Exposed to the hot summer sun in the nearly leafless canopy, the still green capsules slowly brown and begin to fall from the trees in a process that lasts through early May. The hollow, thin-walled comb houses a crusty ball comprised of hundreds of small (2 mm) seeds. The combs remain on the forest floor and eventually may break open along three, pre-formed seams. Apeiba seeds begin germinating with the first drenching rains of mid-May – sometimes while still within the combs.
Similar Species: Due to a number of unusual and uniquely identifying characteristics, Peine de Mico is unlikely to be confused with any other tree in Manuel Antonio. When walking though disturbed areas, look for the combs – either in the trees or on the ground around them; for the yellow flowers that are almost always present; for the thin, wavy, smooth-barked buttresses; and for the large, densely-pubescent leaves. Goethalsia meiantha is another Tiliaceae species of the secondary forest whose leaves resemble those of Apeiba, however they lack hairy pubescence. Furthermore, Goethalsia’s winged fruits bear no similarity to Apeiba’s combs, and the former species is only fertile during July, August, and September.
Natural History: As mentioned previously, Piene de Mico is a secondary forest species that thrives in disturbed sites offering abundant sunshine. Apeiba trees generally grow rapidly and are relatively short-lived, surviving for less than 40 years.
Their briefly deciduous habit provides them with some drought resistance – a beneficial feature for a tree that frequents exposed, unsheltered ecosystems. By decreasing the movement of air immediately adjacent to blade surfaces, leaf hairs also help to diminish the transfer of moisture to dry breezes moving through the canopy.
Apeiba flowers are pollinated by insects, most notably from the Hymenoptera order. Lacking anything edible, fruits are most likely dispersed as hitchhikers since their bristles seem to be of the appropriate design (equipped with barbs) and length to cling to animal fur – though their large size would seem to preclude long trips. Certainly a passing monkey in a tree, or a foraging mammal on the ground could inadvertently snare an occasional comb and transport it at least a short distance. Though most fruits would surely never be affected in this way, the rare and lucky recipient of a ride would contain enough seeds to give the species at least a fighting chance in a new – hopefully sunny – location. Interestingly, the pods are indehiscent and therefore dependent upon some external source of mechanical energy (a crushing footstep?) to be opened.
The timing of fruit-fall to coincide with the beginning of the long wet season enables Apeiba seedlings to germinate immediately and to get as well established as possible before the onset of the next dry season – an often life-threatening time for any plant with a shallow root system.
Uses: Allen (1956) says that Apeiba wood is soft and white and not used. The bark has fibers that can be employed in robe making.
Distribution: In Manuel Antonio National Park (MANP), Piene de Mico is widely distributed along all trailsides and within patches of dry, secondary forest. A few have been seen in undisturbed forest as well. Apeiba ranges throughout all of tropical America.
Trees of Costa Rica's Pacific Slope 
