The extraordinary variation of the organellar genomes of the Aneura pinguis revealed advanced cryptic speciation of the early land plants

Abstract

Aneura pinguis is known as a species complex with several morphologically indiscernible species, which are often reproductively isolated from each other and show distinguishable genetic differences. Genetic dissimilarity of cryptic species may be detected by genomes comparison. This study presents the first complete sequences of chloroplast and mitochondrial genomes of six cryptic species of A. pinguis complex: A. pinguis A, B, C, E, F, J. These genomes have been compared to each other in order to reconstruct phylogenetic relationships and to gain better understanding of the evolutionary process of cryptic speciation in this complex. The chloroplast genome with the nucleotide diversity 0.05111 and 1537 indels is by far more variable than mitogenome with π value 0.00233 and number of indels 1526. Tests of selection evidenced that on about 36% of chloroplast genes and on 10% of mitochondrial genes of A. pinguis acts positive selection. It suggests an advanced speciation of species. The phylogenetic analyses based on genomes show that A. pinguis is differentiated and forms three distinct clades. Moreover, on the cpDNA trees, Aneura mirabilis is nested among the cryptic species of A. pinguis. This indicates that the A. pinguis cryptic species do not derive directly from one common ancestor.