Chromosomal and reproductive barriers among three species of Cleome L. from Ile‐Ife, Nigeria

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Cleome rutidosperma DC, C. viscosa L. and C. gynandra L. have been observed to sometimes grow sympatrically in Ile‐Ife, Nigeria. Here, we investigated the genetic relationship and reproductive barriers among these species through cytological, reproductive biology and hybridization studies. A chromosome number of 2n = 2x = 34 was observed in C. gynandra, while 2n = 2x = 20 was documented in C. viscosa and C. rutidosperma. Two simultaneous cytokineses were observed in meiotic chromosomes of all three species and no chromosomal aberrations were observed. The seed germination percentage increased over the course of 12 months in C. gynandra, while a loss of seed viability was observed with increasing storage time in C. viscosa and C. rutidosperma. Reciprocal crosses were characterized by heavy flower drops and embryo abortion and no viable F1 seed was obtained. The lowest percentage of fruit set, 4% and 2.3%, was observed in C. viscosa × C. rutidosperma and C. viscosa × C. gynandra, respectively. The results demonstrate that although the species appear to share the same pollinators, strong post‐zygotic reproductive isolation mechanisms have been established, thereby making the exchange of genes difficult. In addition, the species‐specific inherent mechanisms of seed dormancy might have a strong influence on the distribution of these species