Genetic variation and gene flow in Alpine diploid and tetraploid populations of Lotus (L. alpinus (D.C.) Schleicher/L. corniculatus L.). I. Insights from morphological and allozyme markers

Abstract

The altitudinal distribution, morphology, phenology and allozyme polymorphism at 12 loci were studied in diploid and tetraploid populations of Lotus growing at over 1800 m in the French Alps to clarify relationships between these cytotypes. In general, diploids occurred at higher elevation than tetraploids, although some sites at intermediate elevation contained both cytotypes, diploids predominating in the upper part and tetraploids in the lower part of the contact area. Evidence for an autopolyploid origin of the tetraploids was provided by tetrasomic inheritance at two enzyme loci, although no tetravalents were observed at meiosis. Diploid and tetraploid plants shared morphological traits distinct from those of other Lotus species and showed differences in size, which may be attributable to chromosome doubling. The diploid cytotype, L. alpinus, may thus be the ancestor of the Alpine tetraploids. Both cytotypes showed nearly identical suites of alleles at all loci and very similar genetic parameters, except for heterozygosity, which was higher in the tetraploid plants. However, the occurrence of few alleles specific to each ploidy level indicated limited gene flow between cytotypes, probably as a result of spatial segregation and variation in flowering time. Of the individuals in a tetraploid population, 25% showed morphological traits similar to those observed in L. corniculatus, suggesting genetic introgression between the two tetraploid species.

Disentangling phylogeography, polyploid evolution and taxonomy of a woodland herb (Veronica chamaedrys group, Plantaginaceae s.l.) in southeastern Europe

“…(Gauthier et al, 1998) or Taraxacum sect. Ruderalia (Calame and Felber, 2000), nor was there obvious habitat differentiation between the cytotypes, as has been shown for Anthoxanthum alpinum (Felber-Girard et al, 1996), Claytonia virginica (Lewis and Suda, 1976), Dactylis glomerata (Lumaret et al, 1987) or Senecio carniolicus (Hülber et al, 2009).…”

Sympatric diploid and hexaploid cytotypes of Senecio carniolicus (Asteraceae) in the Eastern Alps are separated along an altitudinal gradient

“…1). (Gauthier et al 1998). (Felber-Girard et al 1996), Chamerion angustifolium Schemske 1998, 2000) and Ranunculus adoneus (Baack 2004).…”

Spatial ecological and genetic structure of a mixed population of sexual diploid and apomictic triploid dandelions

“…As a result of hybrid inviability, coexisting cytotypes are expected to show some form of reproductive isolation. Genetic studies have proven that reproductive isolation is present in polyploid complexes with sympatric cytotypes such as Arrhenatherum elatius (Petit et al ., 1997) and Plantago media (Van Dijk & Bakx‐Schotman, 1997), but absent in others such as the Lotus alpinus/corniculatus complex (Gauthier et al ., 1998a,b). In Taraxacum sect.…”

“…in flowering time), will lead to reproductive isolation between two cytotypes. Such reproductive isolation has been found in several polyploid complexes (Petit et al ., 1997; Van Dijk & Bakx‐Schotman, 1997; Gauthier et al ., 1998a), but genetic studies show that in Taraxacum section Ruderalia this is not the case. Menken et al .…”