Speciation in progress? A phylogeographic study among populations of Hemitrichia serpula (Myxomycetes)

Abstract

Myxomycetes (plasmodial slime molds, Amoebozoa) are often perceived as widely distributed, confounding to the “everything is everywhere” hypothesis. To test if gene flow within these spore-dispersed protists is restricted by geographical barriers, we chose the widespread but morphologically unmistakable species Hemitrichia serpula for a phylogeographic study. Partial sequences from nuclear ribosomal RNA genes (SSU) revealed 40 ribotypes among 135 specimens, belonging to three major clades. Each clade is dominated by specimens from a certain region and by one of two morphological varieties which can be differentiated by SEM micrographs. Partial sequences of the protein elongation factor 1 alpha (EF1A) showed each clade to possess a unique combination of SSU and EF1A genotypes. This pattern is best explained assuming the existence of several putative biospecies dominating in a particular geographical region. However, occasional mismatches between molecular data and morphological characters, but as well heterogeneous SSU and heterozygous EF1A sequences, point to ongoing speciation. Environmental niche models suggest that the putative biospecies are rather restricted by geographical barriers than by macroecological conditions. Like other protists, myxomycetes seem to follow the moderate endemicity hypothesis and are in active speciation, which is most likely shaped by limited gene flow and reproductive isolation.

Genetic barcoding of dark‐spored myxomycetes (Amoebozoa)—Identification, evaluation and application of a sequence similarity threshold for species differentiation in NGS studies

“…Therefore, sequences of the protein elongation factor 1 alpha (EF1A, chromosomal) and the COI gene have been used as markers complementary to SSU. In the few available studies, the patterns obtained were largely congruent with those obtained for the SSU marker (Dagamac et al., ; Feng & Schnittler, ; Feng et al., ; Fiore‐Donno et al., ), and so it seems reasonable to establish the SSU sequence as a DNA marker for ePCR studies. Attempts to develop a marker universal for myxomycetes have failed due to the large divergence between two basal subgroups, called the dark‐ and the bright‐spored myxomycetes (Fiore‐Donno et al., , ).…”

“…() found intraspecific differentiation within Lamproderma puncticulatum and L. columbinum using a larger fraction (659 bp) of the SSU gene combined with ITS sequences and EF1A markers. Similarly, intraspecific subclades were found for L. ovoideum (M. Borg Dahl et al., unpublished results), for the bright‐spored species Tubifera ferruginosa (Leontyev et al., ) and Hemitrichia serpula (Dagamac et al., ). In all these cases, scanning electron microscopy images of spores revealed that genetic subclades showed consistent differences in spore ornamentation.…”

Diversity patterns, ecological associations and future of research on Costa Rican myxomycetes

“…Ecological associations are an important element to contextualise and support biogeographical (i.e. Dagamac et al 2017) or taxonomic (i.e. Walker et al 2015a) studies and to promote applied lines of research on myxomycetes (i.e.…”

Inclusion of myxomycetes in the Red Data Book of Ukraine: feasibility, selection criteria and recommended species

“…Тож, хоча ареали цих видів охоплюють різні континенти, вони усюди трапляються лише у рідкісних та вразливих біотопах. Нарешті, по-третє, для деяких видів доведене розділення на географічні раси із суттєво відмінними генофондами (Rojas, Stephenson, 2017;Dagamac et al, 2017), і деякі з цих рас можуть потребувати охорони.…”