Karyomorphological analyses and heterochromatin characteristics disclose phyletic relationships among 2n = 32 and 2n = 36 species ofOrchis (Orchidaceae)

Is floral divergence sufficient to maintain species boundaries upon secondary contact in Mediterranean food-deceptive orchids?

“…Consequently, allopatric speciation has been suggested to be the most important speciation mechanism in these Mediterranean orchids (Cozzolino et al, 2004;Cozzolino and Scopece, 2008). This hypothesis was further supported by the observation that closely related food-deceptive orchid species often have asymmetric karyotypes (Cozzolino et al, 2004) or even different chromosome numbers (D'Emerico et al, 1996;Moccia et al, 2007), which may indicate that reproductive isolation evolves most likely as a consequence of the fixation of chromosomal changes in allopatric populations (Cozzolino et al, 2004), rather than by the gradual accumulation of negative epistatic interactions. However, identifying the mechanisms that cause speciation can best be done at an early stage of divergence, before speciation has gone to completion.…”

“…In this study, we investigated a secondary contact zone between two closely related Mediterranean food-deceptive orchids with similar karyotypes (D'Emerico et al, 1996) to assess whether floral trait differences that have evolved in allopatry are sufficient to confer reproductive isolation on secondary contact. Overall, we found that hybridization and strong genetic admixture occur in the two investigated sympatric populations, together with an apparent lack of postzygotic isolation mechanisms.…”

“…The distribution ranges overlap only in Sicily and Corsica where the two species form hybrid zones in which the assignment of individuals to parental species can be difficult. Despite their clear divergence in morphology (in particular spur length) and ribosomal DNA sequence (Cafasso et al, 2001), these two taxa show very similar karyotypes (D'Emerico et al, 1996). The majority of Mediterranean food-deceptive orchids that occur in sympatry have divergent karyotypes that cause strong postzygotic isolation and prevent extensive hybridization and introgression (Cozzolino et al, 2004).…”

Phylogeny and Evolution of Orchis and Allied Genera Based on ITS DNA Variation: Morphological Gaps and Molecular Continuity

“…For all taxa included in the Ophrys and Serapias clades, reports indicate n ϭ 18, with the exception of Serapias lingua (n ϭ 36, one of the few tetraploid species of the genus) and O. papilionacea (n ϭ 16). All taxa included in the O. italica and Platanthera clades are n ϭ 21 and Dactylorhiza and Gymnadenia are n ϭ 20 (Cauwet-Marc and Balayer, 1984;Bianco et al, 1989;Del Prete et al, 1991;D'Emerico et al, 1992D'Emerico et al, , 1996D'Emerico, pers. comm.).…”

Karyotype and C-band Analysis in Two Species of Genipa L. (Rubiaceae, Gardenieae Tribe).

“…An association of heterochromatin gain with telomeric C-band amount, life form and evolutive degree have been seen in some groups of related species such as Anacyclus (Schweizer and Ehrendorfer 1983), or Capsicum (Moscone et al 1993) Orchis (D'Emerico et al 1996). The most considered advanced species possess high amount of heterochromatin and also predominant telomeric C-bands.…”