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Differentiation among insular and continental populations of Coccothrinax argentata (Arecaceae): Evidence from DNA markers and a common garden experiment

Abstract:

The palm Coccothrinax argentata occurs on both the southern Florida mainland and the Florida Keys, but the populations are morphologically distinct. The mainland populations tend to be shorter in stature than the insular populations. We tested the hypothesis that differences in stature were the result of genotypic selection because of different environmental conditions between the mainland and the Keys. We used a combined approach of morphological data gathered from a long-term common garden experiment and ISSR molecular data. After eleven years, the common garden plants are exhibiting differences in stature, but the differences are not associated with provenance. In addition, plants from different source populations have differences in ISSR profiles. We reject the hypothesis that differences in stature are solely the result of differences in environment. Morphological and molecular data do not exhibit clearly defined discontinuities that could be used to distinguish the populations as separate taxa. This study is the first common garden experiment with palms, which are long-lived and slow-growing, and the first to examine genetic differences between plant populations from mainland Florida and Florida Keys.