title: The base number of 'loxoscaphoid' Asplenium species and its implication for cytoevolution in Aspleniaceae.
abstract: OBJECTIVE
  'Loxoscaphoid' Asplenium species are morphologically a remarkably distinct group of Aspleniaceae. Except for two preliminary chromosome counts of Asplenium theciferum, the cytology of this group of species has, however, been largely unstudied.
  
  
  METHODS
  Chromosome counts were obtained by acetocarmine squash preparations of one mitotic cell and several meiotic cells. Relative DNA content of gametophytic and sporophytic cells was determined by flow cytometry. The phylogenetic placement of A. loxoscaphoides, A. rutifolium s.l. and A. theciferum s.l. was investigated through an analysis of rbcL sequences.
  
  
  RESULTS
  The dysploid base number is reported to be x = 35 in Asplenium centrafricanum, A. loxoscaphoides, A. sertularioides and A. theciferum. Analysis of rbcL sequences confirms that 'loxoscaphoids' nest robustly within Asplenium. Several high ploidy levels exceeding the tetraploid level were found in A. theciferum s.l. and A. rutifolium s.l. All taxa proved to be sexual.
  
  
  CONCLUSIONS
  Four base numbers are known at present for Aspleniaceae: x = 39, 38, 36 and 35. The dysploid base number x = 35 found in the 'loxoscaphoid' Asplenium spp. sheds a novel light on the cytoevolution of the whole family. We postulate a recurrent descending dysploid evolution within Aspleniaceae, leading to speciation at the (sub)generic and species/group level.
authors.affiliation: Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Bellefroid
authors.forename: S Khadijah
authors.initials: SK
authors.lastname: Rambe
authors.forename: Olivier
authors.initials: O
authors.lastname: Leroux
authors.forename: Ronald L L
authors.initials: RL
authors.lastname: Viane
mesh_terms: D005075:Biological Evolution; D032461:Chromosomes, Plant / Q000235:genetics; D029624:Ferns / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D011003:Ploidies