Maria A. Galkina and Yulia K. Vinogradova
Tsitsin Main Botanical Garden of Russian Science Academy, Botanicheskaya 4, Moscow, Russia
Bidens decipiens Warnst. is a hybrid between the native European B. cernua L. and the North American invasive B. frondosa L. It has been grown in Europe since the end of the 19th century and was found in Russia at the beginning of the 21st century (Galkina & Vinogradova 2017). This species is included in “The Plant List” as B. connata Muehl. ex Willd., but European specimens differ from the type variety (B. connata var. connata) from the natural distribution range – there are no ray flowers in the inflorescence, the first real leaves are less narrow than the American specimens, clearly petiolate, with less numbers of denticles along the margin; the denticles are big and irregularly located, and the outer bracts of involucres clearly phylloid, 3–6 cm long (Mayorov & Vinogradova 2013). Earlier, we studied the macromorphological features of B. decipiens individuals in Russia. Some morphological features were noted to be intermediate between invasive B. frondosa and the native B. cernua L. We hypothesized the hybrid origin of B. decipiens and tested it using the ISSR analysis. Our data confirmed that B. decipiens can be regarded as a complex of hybrids and backcrosses and B. frondosa and B. cernua are the parental species of this taxon (Galkina & Vinogradova 2017). However, it will be necessary to recognize paternal and maternal species of this hybrid. Therefore, we performed the analysis of the nucleotide sequences using the nuclear and chloroplast DNA sites of these taxa. We collected 30 samples of B. decipiens, B. frondosa and B. cernua in Russia and Belarus. Bidens cernua is distinguished from B. frondosa on some nucleotide substitutions in the ITS sequence; most samples of B. decipiens are characterized as ambivalent in most of these substitutions. This result reflects the heterozygosity and hybrid origin for B. decipiens. However, some samples from the Kaliningrad district and the sample from Moscow city only have ambivalent sequences in a few cases. Hence, these samples cannot be regarded as hybrids F1 and F2. These samples are very similar to B. cernua. We presume that the introgressions for these samples are due to backcrosses. Next, we analyzed the nucleotide sequences of the trnL-trnF intergenic noncoding spacer of chloroplast DNA. All B. frondosa samples have deletion from seven nucleotides as compared with B. decipiens and B. cernua. Bidens decipiens does not differ from B. cernua in trnL-trnF sequence. As a result, B. cernua is the maternal species and B. frondosa is the paternal species for B.decipiens.
Galkina M. A. & Vinogradova Yu. K. (2017) Hybridization of alien and aboriginal taxa of Bidens L. genus in Eastern Europe. Biol. Bull. 44: 406–411.
Mayorov S. R. & Vinogradova Yu. K. (2013) Formation of secondary distribution range and intraspecific variability of Bidens connata. In: 12th Reunion on Ecology and Management of Alien Plant Invasions, September 22–26, 2013, p. 119, Pirenopolis, Brazil.