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A phylogenetic analysis of all the intrageneric taxa of the genus Dioon Lindley (Zamiaceae) was undertaken by using chloroplast DNA restriction fragment length polymorphism analysis. Wagner parsimony analysis on a 187 character matrix yielded two equally parsimonious trees, differing only for the position of D. caputoi. The consensus tree has two well‐defined major clades. The first is composed of D. mejiae, D. rzedowskii, and D. spinulosum; the second is composed of D. califanoi, D. caputoi, D. edule var. angustifolium, D. edule var. edule, D. holmgrenii, D. merolae, D. purpusii, D. tomasellii var. sonorense, and D. tomasellii var. tomasellii. A phenetic analysis of the same data showed results broadly congruent with the cladistic analysis. This resulting phylogeny is partially congruent with morphological data and is also compatible with the biogeography of the genus. Modem species of Dioon may have evolved as a consequence of a very fast succession of vicariance events that mainly occurred during the early Cenozoic. The short time between each of these events may not have allowed the accumulation of a large number of morphological synapomorphies for the groups of species.

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In the present paper a Random Amplified Polymorphic DNA (RAPD) investigation was carried out on DNAs from five Crocus sativus L. (saffron) accessions cultivated in different countries and on six closely related Crocus species. Aims of the study are to check whether cultivated saffron has maintained a constant genomic organisation and to clarify its relationships with possible ancestor species. For the fifteen primers, which produced positive results, DNAs of saffron corms from different accessions present the same amplification pattern, in accordance with the similar DNA content and base composition pointed out in previous studies. The amplification of the seven Crocus species DNAs with twenty-one primers provided 217 repeatable and interpretable fragments, which were scored for presence/absence and employed for a cluster analysis. Results indicated that C. sativus is very closely related to C. cartwrightianus and also similar to C. thomasii. This result, concurring with part of the previous evidence, would rule out the hypothesis of close relationships between C. sativus and C. pallasii.