Heliconia

The simple leaves of these plants are 15–300 cm (6 in–10 ft). They are characteristically long, oblong, alternate, or growing opposite one another on nonwoody petioles often longer than the leaf, often forming large clumps with age.[6] The leaves in different positions on the plant have a different absorption potential of sunlight for photosynthesis when exposed to different degrees of sunlight.[7] They also look like lobster claws.

Heliconia rostrata growing in West Bengal, India

H. rostrata inflorescence close up

Their flowers are produced on long, erect or drooping panicles, and consist of brightly colored, waxy bracts, with small true flowers peeping out from the bracts. The growth habit of heliconias is similar to Canna, Strelitzia, and bananas, to which they are related. The flowers can be hues of reds, oranges, yellows, and greens, and are subtended by brightly colored bracts.[6]

The flowers' shape often limits pollination to a subset of the hummingbirds in the region. They also produce ample nectar that attract these birds.[6][8]

Fruits are blue-purple when ripe and primarily bird dispersed.[9] Studies of post-dispersal seed survival showed that seed size was not a determinant. The highest amount of seed predation came from mammals.[10]

Although Heliconia are almost exclusively pollinated by hummingbirds, some bat pollination has been found to occur. Heliconia solomonensis is pollinated by the macroglosine bat (Melonycteris woodfordi) in the Solomon Islands. Heliconia solomonensis has green inflorescences and flowers that open at night, which is typical of bat pollinated plants. The macroglosine bat is the only known nocturnal pollinator of Heliconia solomonensis.[14]

Many bats use Heliconia leaves for shelter. The Honduran white bat, Ectohylla alba, utilizes five species of Heliconia to make diurnal tent-shaped roosts. The bat cuts the side veins of the leaf extending from the midrib, causing the leaf to fold like a tent. This structure provides the bat with shelter from rain, sun, and predators. In addition, the stems of the Heliconia leaves are not strong enough to carry the weight of typical bat predators, so shaking of the leaf alerts roosting bats to presence of predators.[15] The bats Artibeus anderseni and A. phaeotis form tents from the leaves of Heliconia in the same manner as the Honduran white bat.[16] The neotropical disk-winged bat, Thyroptera tricolor, has suction disks on the wrists which allow it to cling to the smooth surfaces of the Heliconia leaves. This bat roosts head-up in the rolled young leaves of Heliconia plants.[17]

Heliconias provide shelter for a diverse range of insects within their young rolled leaves and water-filled floral bracts. Insects that inhabit the rolled leaves often feed upon the inner surfaces of the leaf, such as beetles of the family Chrysomelidae. In bracts containing small amounts of water, fly larvae and beetles are the dominant inhabitants. In bracts with greater quantities of water the typical inhabitants are mosquito larva. Insects living in the bracts often feed on the bract tissue, nectar of the flower, flower parts, other insects, microorganisms, or detritus in the water contained in the bract (Siefert 1982). Almost all species of Hispini beetles that use rolled leaves are obligate herbivores of plants of the order of Zingiberales, which includes Heliconia. These beetles live in and feed from the rolled leaf, the stems, the inflorescences, or the unfurled mature leaves of the Heliconia plant. In addition, these beetles deposit their eggs on the leaf surface, petioles of immature leaves, or in the bracts of the Heliconia.[18] Furthermore, some wasp species such as Polistes erythrocephalus build their nest on the protected underside of large leaves.[19]

Hummingbirds are the main pollinators of heliconia flowers in many locations. The concurrent diversification of hummingbird-pollinated taxa in the order Zingiberales and the hummingbird family (Trochilidae: Phaethorninae) starting 18 million years ago supports the idea that these radiations have influenced one another through evolutionary time.[20][21] At La Selva Research Station in Costa Rica, specific species of Heliconia were found to have specific hummingbird pollinators.[22] These hummingbirds can be organized into two different groups: hermits and non-hermits. Hermits are the subfamily Phaethornithinae, consisting of the genera Anopetia, Eutoxeres, Glaucis, Phaethornis, Ramphodon, and Threnetes.[23] Non-hermits are a catch-all group of other hummingbirds that often visit heliconias, comprising several clades (McGuire 2008). Hermits are generally traplining foragers; that is, individuals visit a repeated circuit of high-reward flowers instead of holding fixed territories[22][24] Non-hermits are territorial over their Heliconia clumps, causing greater self-pollination.[22] Hermits tend to have long curved bills while non-hermits tend to possess short straight bills, a morphological difference that likely spurred the divergence of these groups in the Miocene era.[25][26] Characteristics of Heliconia flowers that select for either hermit or non-hermit pollinator specificity are degree of self-compatibility, flowering phenology, nectar production, color, and shape of flower.[27][28][25] The hummingbird itself will choose the plants its feeds from on the basis of its beak shape, its perch on the plant, and its territory choice.[29]

Hummingbird visits to the Heliconia flower do not affect its production of nectar.[30] This may account for the flowers not having a consistent amount of nectar produced from flower to flower.

Different Heliconia species have different flowering seasons. This suggests that the species compete for pollinators. Many species of Heliconia, even the newly colonized species, are visited by many different pollinators.[31]