Abstract
In the course of molecular systematic studies of Lauraceae we received a sample of a plant cultivated under the name Cinnamomum porrectum in the Botanical Garden Munchen-Nymphenburg. Preliminary determinations, both morphologically based on the Flora of China (Li & al. 2008) and by chloroplast sequences (psbA-trnH spacer, trnK intron including matK gene, trnL intron, trnL-trnF spacer and trnQ-rps16 spacer) obtained by Sanger sequencing suggested that it was C. camphora, still the plant looked different from other individuals of C. camphora cultivated in the botanical gardens of Berlin, Hamburg, Mainz, Munich and Oldenburg. Attempts to sequence the more informative nuclear internal transcribed spacer repeatedly led to mixed signals. We therefore used Illumina sequencing on a set of pre-amplified molecular markers (ITS, trnK 3′ and 5′ intron, trnL intron, and the intergenic spacers psbA-trnH, trnL-trnF, as well as parts of the trnQ-rps16 spacer), and downloaded available sequences of C. camphora and C. parthenoxylon from GenBank for comparison. Considerable differences were found among these sequences, but the haplotype groups do not coincide with the current species determinations. Particularly the internal transcribed spacer sequences are rather diverse, suggesting possible misidentifications, contaminations, and/or a common gene pool that is larger than anticipated. Concerning the plant in question, our results suggest that it may be a hybrid, with C. camphora as the maternal and another species, possibly C. parthenoxylon, as the paternal parent.Citation: Rohwer J. G., Trofimov D., Mayland-Quellhorst E. & Albach D. 2019: Incongruence of morphological determinations and DNA barcode sequences: a case study in Cinnamomum (Lauraceae). – Willdenowia 49: 383–400. doi: https://doi.org/10.3372/wi.49.49309Version of record first published online on 4 December 2019 ahead of inclusion in December 2019 issue.
Highlights
In the Lauraceae, intraspecific hybrids are well known, especially among different varieties of the avocado, Persea americana Mill. (e.g. Furnier & al. 1990)
Many of the leaves of the specimen in question were slightly larger than described for those two species, up to 15 cm long and 7 cm wide, with petioles up to 4 cm, compared to a maximum of 10 × 6 cm described for C. micranthum and 12 × 5.5 cm described for C. camphora, both with 3 cm petioles
The result of the Illumina sequencing in the plant in question was the same for the chloroplast markers investigated, i.e. the by far most frequent reads for all of them were identical with the result of the Sanger sequencing (Cinnamomum camphora cp group #1, but trnL intron sequence like cp group #2)
Summary
In the Lauraceae, intraspecific hybrids are well known, especially among different varieties of the avocado, Persea americana Mill. (e.g. Furnier & al. 1990). K. Allen), but some of these “species” (P. drymifolia, P. nubigena) have been treated as varieties of P. americana by Kopp (1966), and all of them appeared to be part of P. americana in a wider sense in the analysis of Furnier & al. Many of the leaves of the specimen in question were slightly larger than described for those two species, up to 15 cm long and 7 cm wide, with petioles up to 4 cm, compared to a maximum of 10 × 6 cm described for C. micranthum and 12 × 5.5 cm described for C. camphora, both with 3 cm petioles. The leaves of the specimen in question were elliptic to lanceolate-elliptic, usually with an acute to attenuate base, compared to mostly ovate-elliptic leaves with a broadly cuneate to rounded base in C. micranthum and C. camphora, at least on flowering branches. We applied high-throughput (Illumina) sequencing to a set of pre-amplified molecular markers including ITS, in order to identify the secondary signal in ITS and to investigate if there was a secondary signal in the chloroplast markers as well
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