Two independent genetic markers support separation of the myxomycete Lycogala epidendrum into numerous biological species

ABSTRACT

Lycogala epidendrum is one of the most widely known myxomycete species and the first-ever discovered representative of this group. Using 687 original DNA sequences from 330 herbarium specimens from Europe, Asia, North and Central America, and Australia, we constructed the first detailed phylogenies of the genus Lycogala, based on two independently inherited genetic markers, the ribosome small subunit 18S rRNA nuclear gene (18S rDNA) and the mitochondrial cytochrome oxidase subunit I gene (COI). In both phylogenies, L. epidendrum appeared to be a polyphyletic group, represented by numerous clades. The four other recognized species of the genus (L. confusum, L. conicum, L. exiguum, and L. flavofuscum) are scattered between branches corresponding to L. epidendrum. A barcode gap analysis revealed 60 18S rDNA phylogroups of L. epidendrum, which are distant from each other not less than from other species of the genus Lycogala. For 18 of these phylogroups with both 18S rDNA and COI sequences available, recombination patterns were analyzed to test for reproductive isolation. In contrast to the results of a simulation assuming panmixis, no crossing between ribosomal and mitochondrial phylogroups was found, thus allowing the conclusion that all tested phylogroups represent biospecies. More than one third (39.6%) of the studied specimens share a single 18S rDNA phylogroup, which we consider to be L. epidendrum s. str. This group displays the broadest geographic distribution and the highest intraspecific genetic variability. Nearly all (93.3%) of the remaining non-singleton 18S rDNA phylogroups are restricted to certain continents or even regions. At the same time, various reproductively isolated phylogroups occur sympatric at a given location.

KEYWORDS:

• Amoebozoa
• biospecies
• cryptic species
• marker gene
• morphospecies
• Myxogastrea
• phylogeny
• reproductive isolation
• Reticulariaceae
• species delimitation

ACKNOWLEDGMENTS

Carrying out this research would not have been possible without the scientific community providing us with collections of Lycogala. Loans from numerous colleagues allowed us to study collections from many different regions of the world. Among these were N. Ambec (Canada), Yury Bengus (Ukraine), Thomas E. E. Dela Cruz (Philippines), Eva Heinrich (Germany), E. Lomp (Germany), Edvin Johannesen (Norway), P. Eitmann (Germany), Maria F. B. M. Eloreta (Philippines), Arturo Estrada-Torres (Mexico), Anastasia Glagkikh (Ukraine), Georgios Konstantinides (Greece), Mariia D. Leontieva (Ukraine), Yuliana Leshchenko (Ukraine), Sarah J. Lloyd (Australia), Vasyl B. Malanyuk (Ukraine), B. Mazur (Poland), Oleksandra Nikitina (Ukraine), Dora Panayotova (USA), Stanislav V. Sarzhevsky (Ukraine), Teresa and John van der Heul (Australia), Vitaliy Vyunyk (Ukraine), and Steve Wendt (Canada). We especially thank Yury Ishchenko and Yury Novozhilov (both Russia), Shuanglin Chen and Min Li (both China), and Carlos Rojas Alvarado (Costa Rica).

We are infinitely grateful to all the brave defenders of Ukraine, thanks to whom we were able to complete this publication.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00275514.2022.2133526

Additional information

Funding

This study was supported by an Alexander von Humboldt foundation grant for experienced scientists awarded to D.L. Laboratory procedures were in part supported by a grant within the DFG (Deutsche Forschungsgemeinschaft (German Research Foundation)) graduate school “Response” [RTG2010] to M.S.