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Spiral gingers (Costaceae)

Understory monocots closely related to true gingers (Zingiberaceae), and included in the superfamily Zingiberales. Species of Amazonian Costaceae (CostusDimerocostus and Monocostus) are usually referred to as spiral gingers due to the arrangement of their leaves which maximize exposure to sunlight. Some species also have red/purple pigments on the lower surface of leaves to better capture what little light makes it to the forest floor. Fruits, foliage and roots of some species are spicy-fragrant (ginger-like). Pollination is by bees and hummingbirds. 

Costus amazonicus - understory of terra firme (non-flooding) forest

Costus arabicus - high light environments along rivers, habitat edges and disturbed areas. The cordate leaf base is characteristic of this species.

Costus asplundii - medium light levels on terra firme. Seeds often germinate in the persistent bracts at the ends of the stems. One of the larger species of Costus in our area - to at least 3 meters.

Costus erythrocoryne - a conspicuous plant that can be locally common in higher light areas on upland soils.

Costus krukovii (aff.) - a rare understory species known from a couple of locations at Madre Selva. We've never encountered it in flower. The pleated leaves set it apart from any other Costus in the area. 

Costus scaber - common in both seasonally flooded and upland habitats, and in both high- and low-light conditions. Ants tend to be abundant on the inforescences and may nest in them, hence the build-up of debris on the spikes. No doubt ants are feeding from nectaries on the spike and/or flowers, and giving some of protection from herbivores. 

Costus sinningiiflorus - a short, high-light Costus of terra firme. Formerly classified as C. guaniensis. This species has velvety-soft leaves.

Costus spiralis - high-light edges in terra firme. Distinguished from C. scaber by the flowers being turned inward toward the axis of the stem.

Costus whiskeycola (probably!) - low growing plant of dark understory upland forest. Similar (but not identical) to plants found in Colombia and Ecuador, and may be a different species. Found at Santa Cruz.

Costus whiskeycola (aff.) - A single population known from Madre Selva, similar to the C. whiskeycola from Santa Cruz, but with distinctive silvery-gray upper surfaces to the leaves. We have not encountered this plant in flower, and it may be a variety of C. whiskeycola, or a distinct species. 

Dimerocostus appendiculatus - a tall (to 5 m) plant of upland forest. Leaf tips are conspicuously elongate.

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