Natural hybridization in tropical spikerushes of Eleocharis subgenus Limnochloa (Cyperaceae): Evidence from morphology and DNA markers

C3 -C4 intermediates may be of hybrid origin - a reminder

The currently favoured model of the evolution of C₄ photosynthesis relies heavily on the interpretation of the broad phenotypic range of naturally growing C₃ -C₄ intermediates as proxies for evolutionary intermediate steps. On the other hand, C₃ -C₄ intermediates had earlier been interpreted as hybrids or hybrid derivates. By first comparing experimentally generated with naturally growing C₃ -C₄ intermediates, and second summarising either direct or circumstantial evidence for hybridisation in lineages comprising C₃ , C₄ and C₃ -C₄ intermediates, we conclude that a possible hybrid origin of C₃ -C₄ intermediates deserves careful examination. While we acknowledge that the current model of C₄ photosynthesis evolution is clearly the best available, C₃ -C₄ intermediates of hybrid origin, if existing, should not be used for further analysis of this model. However, experimental C₃  × C₄ hybrids potentially are excellent systems to analyse the genetic differences between C₃ and C₄ species and, also using segregating progeny, to study the relationship between individual photosynthetic traits and environmental factors.

Merging Fargesia dracocephala into Fargesia decurvata (Bambusoideae, Poaceae): implications from morphological and ITS sequence analyses

Aims

Fargesia decurvata is closely allied with F. dracocephala and differs in 5 major characters (i.e. the culm sheath blade base shape, the width of the culm sheath blade base, the auricle shape, and the lower surface of leaf blade) in Fargesia. It is difficult to distinguish these two species because of existing of transitional statements of characters. The aims of this paper are to (i) investigate whether the variation of the characters is continuous or not; (ii) reveal whether the publishment of F. dracocephala was the result of discontinuous sampling of F. decurvata or not.

Methods

Ten populations of F. decurvata and F. dracocephala were investigated in their entire distribution (including type localities). The statements of 5 major characters were measured from 693 annual and 693 perennial culms of 231 individuals in 10 populations, and analyzed at population, individual and culm levels. UPGMA cluster analysis was carried out based on 29 characters from 10 populations of F. decurvata and F. dracocephala and 2 populations of F. qinlingensis as outgroup. The ITS sequences were also sequenced and analyzed.

Important Findings

Five major characters exhibited great variation not only at population level, but at individual level within a population, even the culm level within an individual and in different parts of the same culm. Cluster analyses showed that 10 populations of F. decurvata and F. dracocephala were not divided into two species, but they were well separated with outgroup. There was no difference in floral organ between F. decurvata and F. dracocephala. MP and NJ trees based on ITS sequences showed the same results with the cluster analysis on morphological characters. All the facts indicated that the publishment of F. dracocephala was the result of discontinuous sampling of F. decurvata, and F. dracocephala should be treated as the synonym of F. decurvata.