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Evolution of floral monosymmetry is thought to be a major driving force of angiosperm radiation, making angiosperms the most successful land plant group in terms of species richness. Monosymmetry evolved from a polysymmetric ancestor repeatedly in different angiosperm lineages, where it likely facilitated diversification through the interaction with insects. Most monosymmetric taxa are thus dominated by monosymmetric members. However, in the Brassicaceae, only few members develop a monosymmetric corolla with two petal pairs of unequal size, making them an ideal system to study the evolution of molecular mechanisms enhancing flower complexity. Monosymmetry is controlled by the TCP transcription factors that belong to the CYC2 clade in distantly related taxa. In Iberis amara, the first crucifer analyzed in terms of monosymmetry development, unequal corolla formation is due to a stronger CYC2 clade gene expression in the smaller adaxial petals compared with the larger abaxial ones. Phylogenetic reconstruction of the crucifer family reveals that the monosymmetric genera Iberis, Calepina, and Teesdalia belong to one major crucifer lineage. Monosymmetry is most pronounced in Iberis and less so in Calepina and Teesdalia, with a positive dosage-dependent correlation between the strength of a CYC2 expression difference and the extent of monosymmetry formation. An early adaxial CYC2 expression in floral meristems, observed in many distantly related taxa, might have facilitated the repeated evolution of CYC2-controlled monosymmetry. Comparison of early and late CYC2 expression in monosymmetric and polysymmetric crucifers representative for the four major crucifer lineages reveals that an adaxial CYC2 expression in floral meristems is likely ancestral for the Brassicaceae. However, it got lost in all analyzed monosymmetric members and is, as such, not a prerequisite for the establishment of corolla monosymmetry in crucifers. Here, monosymmetry evolved via a heterochronic CYC2 expression shift from an ancestral early adaxial expression in floral meristems to an adaxial CYC2 transcript accumulation later in petal development. This study emphasizes the potential of regulatory changes in the evolution of morphological novelties, like corolla monosymmetry in the Brassicaceae. In combination with a corymboid inflorescence, monosymmetry might have served as a key invention driving diversification in the genus Iberis comprising more than 20 monosymmetric species.

Traditional assays (germination and vigour), as well as biochemical assays using isozyme loci, were performed to evaluate the effect of different seed storage conditions in Coincya rupestris, Iberis pectinata, Moricandia moricandiodes and Vella pseudocytisus . Seeds had been stored for 24–30 years under long-term (LT) and short-term (ST) conditions. Fresh seeds of the same species from natural populations (NP) were also collected in 1996 and used for comparison. Isozyme loci were used as markers of genetic deterioration and to determine the genetic diversity of samples. The germinability, vigour and enzyme activity of LT samples were comparable to values obtained using freshly collected NP samples, showing the effectiveness of the long-term storage conditions.

Noncrop borders surrounding field crops may enhance biological control of insect pests by drawing pests away from the crop and by providing a suitable habitat for natural enemies. We quantified the effects of borders of flowering Iberis umbellata L. (candytuft) on cabbage pest and predator abundance by repeatedly sampling arthropod abundance in plots of Brassica oleracea L. I. umbellata provides potential food for crucifer herbivores as well as nectar and pollen resources for predators. Although I. umbellata harbored large populations of hemipteran predators, few of these predators were found on the adjacent crop plants. Iberis borders did not change the abundance of crop pests within the crop but had mixed effects on natural enemies. Interestingly, the spatial distribution of Pieris rapae L. and Trichoplusia ni (Hubner) eggs on B. oleracea differed significantly between treatments, indicating that the presence of flowering I. umbellata may have altered the movement and oviposition behavior of these lepidopteran pests. Our results point to the importance of considering predator and pest movement when investigating how alternative habitats, such as flowering borders, affect arthropod population dynamics.