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-(Malpighiaceae: correlations between habit, fruit type and basic chromosome number). The family Malpighiaceae presents species with different habits, fruit types and cytological characters. Climbers are considered the most derived habit, followed, respectively, by the shrubby and arboreal ones. The present study examines the relationship between basic chromosome numbers and the derivation of climbing habit and fruit types in Malpighiaceae. A comparison of all the chromosome number reports for Malpighiaceae showed a predominance of chromosome numbers based on x=5 or 10 in the genera of sub-family Malpighioideae, mainly represented by climbers with winged fruits, whereas non-climbing species with non-winged fruits, which predominate in sub-family Byrsonimoideae, had counts based on x=6, which is considered the less derived basic number for the family. Based on such data, confirmed by statistic assays, and on the monophyletic origin of this family, we admit the hypothesis that morphological derivation of habit and fruit is correlated with chromosome basic number variation in the family Malpighiaceae.Key words -Malpighiaceae, Malpighioideae, Byrsonimoideae, chromosome number, habit, fruit types RESUMO -(Malpighiaceae: correlações entre hábito, tipo de fruto e número cromossômico básico). A família Malpighiaceae apresenta diferentes tipos de hábito, frutos e caracteres citogenéticos. Em geral, espécies lianas são consideradas as mais derivadas, seguidas, respectivamente, pelas arbustivas e arbóreas. O presente estudo propõe para Malpighiaceae uma relação entre a variação do número cromossômico básico e a derivação do hábito trepador e da morfologia dos frutos. Para estabelecer esta relação analisamos todas as contagens de cromossomos já relatadas para a família Malpighiaceae, sendo que a freqüência relativa destas contagens foi calculada para todos os gêneros estudados. Esta comparação mostrou a predominância de números cromossômicos baseados em x=5 ou 10 na sub-família Malpighioideae, predominantemente composta por lianas com frutos alados, enquanto que espécies de outros hábitos, com frutos não alados, apresentaram contagens baseadas em x=6, considerado o número básico menos derivado para a família, predominante na sub-família Byrsonimoideae. Baseados em consistentes dados estatísticos, e também na origem monofilética da família, admitimos a hipótese de que as derivações do hábito e dos tipos de fruto estão diretamente relacionadas com a variação do número cromossômico na família Malpighiaceae.Palavras-chave -Malpighiaceae, número cromossômico, número básico, hábito, tipos de fruto

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Summary Cytogenetic and reproductive assays were carried out on a population of annatto (Bixa orellana) of Southeastern Brazil. The reproductive data indicate that B. orellana is self-compatible but preferentially alogamous and entomophylous. No apomictic fruits were obtained from emasculated flowers. Fruits formed exclusively by self-pollination were smaller and had fewer seeds than those obtained by open pollination, highlighting the importance of pollination for annatto seed production. The meiotic process was analyzed and some abnormalities observed resulted in only some sterile pollen (1.9%) with no significant reduction of fertility. The cytogenetic studies showed the haploid chromosome number n=7 and the diploid number 2n=14, with a remarkable bimodal karyotype. FISH with 45S rDNA and 5S rDNA probes showed that these loci do not occur in synteny. Both probes hybridized in the proximal regions of the short arm of pair 1 (45S) and pairs 4 and 6 (5S). One pair of 5S rDNA sites presented larger signals in FISH than the other pair. These karyological features suggest that fusion of chromosomes and amplification of DNA segments played an important role in karyotype evolution of B. orellana.

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