Photo Dennis Stevenson
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The Cycad Pages
Zamia polymorpha

Zamia polymorpha "D.W. Stev., A. Moretti & Vázq. Torres", Delpinoa n.s. 37-38: 3-8 (dated 1995) (1998).
"TYPE: Belize. Cayo: 22 Jan 1989, D. Stevenson et al. 1119 (holo NY; iso BRH, FTG, MO, NY, U)."[NY][NY][NY][NY]


Etymology: The specific epithet, Z. polymorpha, is derived from the fact that the species exhibits extreme variability in leaf and leaflet morphology

Historical notes: This species, first collected at the turn of the 20th century, was known from only three herbarium specimens which in turn were not assigned to a species. Intensive field work in the late 1980's revealed many large populations throughout the Yucatan Peninsula and Belize. Those plants and in some cases individual leaves that are exposed to full sun are shorter, more narrow, coriaceous, and have leaflets that are lanceolate and finely serrate. In contrast, those plants, and in some cases individual leaves, that are in deep shade have longer, broader, subcoriaceous to papyraceous leaves and have leaflets that are elliptic to suboblanceolate. Those plants growing under intermediate conditions exhibit leaf morphologies that are intermediate between these two extremes. This variability in leaf morphology was observed in all eleven populations studied. Moreover, it was in all cases correlated with habitat so that the extremes can be thought of as sun and shade forms. This is supported by the fact that both extremes were observed in a few cases to exist on the same plant where one leaf was exposed to full sun and another was highly shaded. This in turn supplied enough material for a thorough comparison with other species and the recoginition of its status as a new species.

Distinguishing features: In many aspects many individual plants of Zamia polymorpha are most similar to Z. loddigesii Miq. These include general growth habitat, the presence of 2-3 leaves, leaf size and shape, and leaflet size and texture. However, both the pollen and ovulate strobili differ from Z. loddigesii in color, overall shape and the morphology of the individual sporophylls. The pollen cones of Z. loddigesii are brown at pollen shedding and have microsporophylls with a large terminal facet that obscures the presence of the six small lateral facets. In contrast, Z. polymorpha has light tan to tan pollen cones at pollen shedding and microsporophylls with a small terminal facet and six prominent lateral facets. The ovulate strobilus of Z. loddigesii is gray to very light tan and cylindrical with a prominent prolonged and constricted acuminate, sterile tip (see for example the color photograph on page 286 in Jones, 1993) whereas the ovulate strobilus of Z. polymorpha is tan to brown and ovoid with a gradual, acute, sterile tip. Other plants of Z. polymorpha appear similar in leaflet morphology and texture to plants of Z. furfuracea L. fil. but they lack the distinctive pubescence that characterizes mature leaflets of Z. furfuracea as well as the obovate leaflets that generally characterize Z. furfuracea.

Distribution and habitat: Zamia polymorpha is endemic to the Yucatan Peninsula of Mexico and along the eastern coast of Belize extending westward up to 500 m on the eastern slope of the Maya mountains.

Conservation: Zamia polymorpha seems to do well in mildly disturbed habitats where the plants are numerous with good seed set and seedlings establishment. Not listed in the 1997 IUCN Red List of Threatened Plants.
Photo Ken Hill
Photo Ken Hill

Description:

Stem subterranean, subglobose, to 10 cm diam.

Cataphylls ovate, 3-4 cm long, 1.5-2.5 cm wide.

Leaves 2-3 (1-4), 0.5-1.5 m long; petiole 15-50 cm long, sparsely to densely prickled; rachis with 3-12 pairs of leaflets.

Leaflets lanceolate to oblanceolate, cuneate basally, acute to subacuminate apically, margins serrate in the upper two-thirds, the larger median ones 20-30 cm long, 2-8 cm wide.

Pollen cones tan, cylindrical to ovoid-cylindrical, 6-10 cm long, 2-4 cm diam.; peduncle 2-4 cm long.

Microsporophylls with sterile tip composed of six slightly inclined facets surrounding a small, centrally depressed terminal facet, sporangia present on abaxial surface only.

Seed cones tan to brown, cylindrical to ovoid-cylindrical, 10-15 cm long, 5-7 cm diam.

Seeds light-red to red, 1.5-2 cm long, 0.5-0.8 cm diam.

2n = 17, 22, 23, 24, 25, 26, 27, and 28.


The Cycad Pages

© 1998-2012 Royal Botanic Gardens Sydney
Written and maintained by Ken Hill 1998-2010
Maintained by Leonie Stanberg and Dennis Stevenson 2010-2012
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