The ndh genes are represented by yellow arrows or truncated yellow arrows; blue, protein-coding genes; green, tRNA; red, rRNA; grey, genes of unknown function. Parallel lines indicate areas reduced in size. A. Comparison of genes detected in the SSC regions in different Alismatales. The tree is a consensus of those published elsewhere and is included only to illustrate phylogenetic relationships among the species. All members of the family Araceae (light blue) possess a complete set of ndh genes. In the family Hydrocharitaceae (dark blue), the ndh genes are retained in Elodea canadensis but missing in Najas. The dashed lines represent sequences retrieved by targeted-PCR in other Najas species. B. Schema of the IR/SSC region in Najas flexilis and Elodea canadensis. C. SSC regions in orchids (blue) and parasitic plants (dashed blue, Orchidaceae; dashed orange, Solanales; dashed yellow, Lamiales). The ‘loss as a suite’ pattern in these groups is equivalent to the example reported here for Najas flexilis.