Crataegus bretschneideri (Rosaceae), a separate species endemic to Northeast of China

<p><span><i>Crataegus b</i></span><span><i>retschneideri</i> is considered a variety of <i>Crataegus pinnatifida</i>, but it has also been proposed as a separate species. We used ITS and three cpDNA sequence fragments (<i>psbA-trnH, trnG-trnS, trnH-trnK</i>) to perform maximum parsimony, maximum likelihood, Bayesian interence and neighbor-joining molecular phylogenetic tree analysis with 108 individuals of 19 hawthorn (<i>Crataegus</i>) species and 4 outgroups (<i>Malus</i>). ITS, cpDNA and cpDNA-ITS molecular phylogenetic trees constructed using 4 methods have similar consistency respectively.</span></p> <p><span>In the cpDNA-ITS molecular phylogenetic tree, <i>C. bretschneideri</i> is an independent clade separated from <i>Crataegus maximowiczii </i>and <i>C. pinnatifida</i>, which provides a separate species condition. In the ITS (nuclear inheritance) molecular phylogenetic tree, <i>C. bretschneideri</i> and <i>C. pinnatifida</i> are closely related and are distantly related to <i>C. maximowiczii</i>. The cpDNA (maternal inheritance) molecular phylogenetic tree indicated that <i>C. bretschneideri</i> is closely related to <i>C. maximowiczii</i> but distantly related to <i>C. pinnatifida</i>. Furthermore, the 108 <i>Crataegus</i> individuals belonged to 15 chloroplast haplotypes, as determined using the DNASP analysis; <i>C. bretschneideri</i> and <i>C. maximowiczii</i> have the same chloroplast haplotype, H1; <i>C. pinnatifida </i>contains three haplotypes, H13-H15. Taken together with previous results of our laboratory, we confirm that <i>C. bretschneideri</i> is not a variety of <i>C. pinnatifida,</i> but a separate species that gradually developed from natural hybrid offspring in mixed forest areas with <i>C. maximowiczii</i> as the female parent and <i>C. pinnatifida</i> as the male parent. </span></p>