Speciation and Species Separation in Hordeum L. (Poaceae) Resolved by Discontinuous Molecular Markers¹

Abstract

Amplified fragment length polymorphisms (AFLPs) were used to evaluate the capacity of discontinuous markers to reveal genetic structure within Hordeum, a challenging higher plant genus from the standpoint of natural systematics. Phylogenies of 63 accessions encompassing nine species from four Hordeum sections were inferred from polymorphisms scored at 600 loci. Phylogenies based on sequences from the nuclear internal transcribed spacer (ITS) region were constructed for comparison, but revealed severe sampling errors inherent to single genes. Although superior by virtue of providing genome‐wide estimates of genetic similarity, the adoption of AFLPs in infrageneric studies requires caution. Comigrating AFLP bands studied here could be divided on the basis of band intensity variation into two types that are □ 100 % identical and < 40 % identical in DNA sequence, respectively, in infrageneric comparisons. Thus, the careful selection of AFLP bands to be analyzed bears heavily upon their phylogenetic utility. Within the H. murinum complex, which encompasses three morphologically distinct subspecies, AFLP data from 37 accessions reveal unexpected genetic differentiation between H. murinum, glaucumpopulations to the east and west of Alexandria (Egypt), suggesting the presence of allopatric speciation in the wake of human settlement.

Analysis of eggplant (Solanum melongena)-related germplasm: morphological and AFLP data contribute to phylogenetic interpretations and germplasm utilization

“…Discontinuous markers (RFLPs, RAPDs, AFLPs and SNPs) can provide a measure of genetic distances to establish phylogenetic relationships among taxa Aggarwal et al 1999;Rodriguez et al 1999;El Rabey et al 2002). In biosystematic studies of Solanum section Petota, Kardolous et al (1998) proved that molecular markers such as AFLPs are more informative and reliable than morphological markers.…”

“…In the same study, it has been reported that the AFLP technique is suitable at the intraspecific level, while the interspecific phylogenies might be less reliable due to an increasing chance of the co-migration of non-homologous DNA fragments. Recent results using AFLP markers to align genetic maps from different potato genotypes (Rouppe van der Voort et al 1997), and to study Hordeum taxa (El Rabey et al 2002), proved that co-migration of bands defines similarity due to ancestry also at an interspecific level. In this study the combined use of morphological and AFLP data made possible: (1) the establishment of a genetic distance between accessions; (2) the reclassification of several taxa that were previously misidentified; (3) the new classification of eight out of nine Solanum sp.…”

Genetic and morphological differentiation between Melica ciliata L. and M. transsilvanica Schur (Poaceae) in Europe reveals the non-presence of M. ciliata in the Polish flora

“…str., based on overall genome dissimilarity, could be considered as conclusive references in future study of phylogeographic and taxonomic patterns in M. ciliata complex. Recently, the usefulness of AFLP markers for plant natural systematic in Hordeum murinum complex [76] or in Festuca brachyphylla complex [3] was found.…”

Reconstructing patterns of reticulate evolution in angiosperms: what can we do?

“…(2003) used AFLP data to test hybrid origin in several taxa (Begonia, Mangifera, Nepenthes and Lausium) and these data permitted the reconstruction of relations with the putative parents. Despite many examples where AFLP data are considered useful in phylogenetic studies (e.g., Kardolus & al., 1998;El-Rabey & al., 2002;Spooner & al., 2005), the application of these data (and similar single-locus markers) in infrageneric studies requires caution. One major concern involves the difficulty in assessing homology between the co-migrating fragments of more distant taxa (El-Rabey & al., 2002; but see Crawford & Mort, 2004).…”

“…Despite many examples where AFLP data are considered useful in phylogenetic studies (e.g., Kardolus & al., 1998;El-Rabey & al., 2002;Spooner & al., 2005), the application of these data (and similar single-locus markers) in infrageneric studies requires caution. One major concern involves the difficulty in assessing homology between the co-migrating fragments of more distant taxa (El-Rabey & al., 2002; but see Crawford & Mort, 2004). Therefore, the general value of the use of these markers in assessing hybrid origin remains questionable as only the successful cases tend to get published (but see Krauss & Hopper, 2001, who report that high genetic variability made it difficult to distinguish between different hybrid scenarios).…”