. The Caribbean forester. Forests and forestry Caribbean Area Periodicals; Forests and forestry Tropics Periodicals. J 4-i\UARY - June 1960 13. Figure 1. — Variation in mahogany leaves and fruit from mixed population, from left to right: typical small-leaf (Swietenia mahagoni), intermediate (S. mahagoni x macrophylla?), and typical bigleaf (S. macrophylla). ulation, as a rule consisting of thousands of biotypes arranged in a pattern of local pop- ulations, ecotypes, and geographic sub-species. Most widespread forest tree species appear to be composed of geographical clines or moder- ately dist
. The Caribbean forester. Forests and forestry Caribbean Area Periodicals; Forests and forestry Tropics Periodicals. J 4-i\UARY - June 1960 13. Figure 1. — Variation in mahogany leaves and fruit from mixed population, from left to right: typical small-leaf (Swietenia mahagoni), intermediate (S. mahagoni x macrophylla?), and typical bigleaf (S. macrophylla). ulation, as a rule consisting of thousands of biotypes arranged in a pattern of local pop- ulations, ecotypes, and geographic sub-species. Most widespread forest tree species appear to be composed of geographical clines or moder- ately distinct geographic ecotypes (35). A species population to a geneticist, ac- cording to Darlington (6) usually consists of hundreds to thousands of genotypes, and all fertilizations except those between members of the same genotype result in hybrids. To the Geologist and geographer, species consist of local races, ecotypes and geographical sub- species . Intraspecific hybrids are recognized between such groups, but lesser differences are not considered. The taxonomist is con- cerned with interspecific hybrids when he encounters occasional individuals (Fi) and swarms of back crosses (3). NATURAL VARIATION The three recognized species of mahog- any- are relatively isolated from each other 2/ Swieten;a mahagoni Jacq., S. humilis Zucc S. macrophylla King. geographically in their natural distributions. Each species in turn is divided into subgroups of interbreeding populations by partial or complete discontinuities in distribution. Con- siderable differences within each species have been reported from different parts of their re- spective ranges (21). In addition to wide variation in the leaves, flowers, and fruit of a particular species, there are also differences in the structure and other characteristics of the wood. This variation has been largely at- tributed to differences in rate of growth due to environmental conditions. However, species which have been broken up into many sep
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