Genetic variation and natural hybridization betweenOrchis laxiflora andOrchis palustris (Orchidaceae)

Arduino, Paola; Verra, Federica; Cianchi, R.; Rossi, Walter; Corrias, Bruno; Bullini, L.

doi:10.1007/bf00985819

Cited by 49 publications

(45 citation statements)

References 24 publications

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“…To date, studies of these orchids have mainly focused on strictly related, hybridizing species by evaluating the strength of inviability and/or sterility of their hybrid progenies, which is the nature of post-zygotic barriers (Arduino et al 1996;Pellegrino et al 2005;Cozzolino et al 2006). In this context, sympatric food-deceptive species pairs for which natural hybrids have never been observed represent a suitable model to explore whether their reproductive isolation depends upon pre-or postpollination mechanisms, or both.…”

Section: Introductionmentioning

confidence: 99%

Strong post-pollination pre-zygotic isolation between sympatric, food-deceptive Mediterranean orchids

2010

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Mediterranean orchids that grow in admixed, co-flowering populations, and frequently show hybrid progenies are interesting to use to study the nature and the strength of post-zygotic barriers. However, examination of pre- and post-pollination pre-zygotic isolating mechanisms requires sympatric, co-flowering species pairs that do not produce hybrid swarms. In this study, we analyzed a contact zone between Orchis italica and O. papilionacea, in which hybrid forms have never been reported, although hybridization between members of their groups of appurtenance has been signaled. We investigated pre-pollination barriers observing the floral phenology of both species and identified pollinators by means of molecular analysis of pollinaria collected on the insects captured in the study site. Post-pollination barriers were tested performing manual crosses in order to evaluate pollen germination/pollen tube growth in vivo and fruit and seed formation. Floral phenologies of O. italica and O. papilionacea display nearly overlapping trends, and two common pollinators have been identified by molecular analysis of pollinaria. Thus, pre-pollination barriers are very weak or nonexistent. Bidirectional crosses have shown that the growth of heterospecific pollen tubes is fully blocked in stigmatic cell layers. Since no fruit formation was detected in bidirectional interspecific crosses, we assume that reproductive isolation between the examined species is fully guaranteed by post-pollination pre-zygotic mechanisms acting at stigmatic level. Such condition has been rarely described and may mask the potential action of post-zygotic mechanisms.

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Section: Introductionmentioning

confidence: 99%

Strong post-pollination pre-zygotic isolation between sympatric, food-deceptive Mediterranean orchids

2010

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“…These results were interpreted as the consequence of habitat fragmentation, inbreeding, founder effects, and genetic drift. However, widespread and outbreeding orchids without a known history of population fragmentation showed similarly high genetic differentiation among populations, including Cypripedium parviflorum (G ST ϭ 0.23, Wallace and Case 2000), Orchis laxiflora (G ST ϭ 0.12, Arduino et al 1996), and Tolumnia variegata (G ST ϭ 0.11, Ackerman and Ward 1999). These values, together with those reported by Hamrick and Godt (1996) for 16 orchid species (mean G ST ϭ 0.087), are consistently higher than those found within Ophrys.…”

Section: Fig 4 Genotype Assignment Tests Based On Cavalli-sforza's mentioning

confidence: 99%

Gene Flow Across Species Boundaries in Sympatric, Sexually Deceptive Ophrys (Orchidaceae) Species

Soliva

Widmer²

2003

Evolution

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Abstract. Orchids of the genus Ophrys (Orchidaceae) are pollinated by male bees and wasps through sexual deception. The Ophrys sphegodes group encompasses several closely related species that differ slightly in floral morphology and are pollinated by different solitary bee species. Populations representing different species of the O. sphegodes group often flower simultaneously in sympatry. To test whether gene flow across the species boundaries occurs in these sympatric populations, or whether they are reproductively isolated, we examined the distribution of genetic variation within and among populations and species of this group. We collected at each of five different localities in southern France and Italy two sympatric, co-flowering Ophrys populations, representing six Ophrys species in total. The six microsatellite loci surveyed were highly variable. Genetic differentiation among geographically distant populations of the same species was lower than differentiation among sympatric populations of different species. However, the strength of genetic differentiation among species was among the lowest reported for orchids. Genotype assignment tests and marker-based estimates of gene flow revealed that gene flow across species boundaries occurred and may account for the low observed differentiation among species. These results suggest that sexual deceit pollination in Ophrys may be less specific than thought, or that rare mistakes occur.

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“…In this respect it is worth noting that while orchid species share biological attributes such as small, mostly dust-like seeds, they are also a large, heterogeneous and diverse group (Arditti, 1992;Rudall and Bateman, 2002). The Orchidaceae contains ca 19 000 species encompassing an exceptionally wide range of reproductive strategies, variation in generation times, and includes both narrow endemic and widespread species, Rossi et al (1992);8, Case (1993);9, Case (1994); 10, Arduino et al (1995);11, Peakall and James (1995); 12, Arduino et al (1996); 13, Peakall and Beattie (1996);14, Sharma and Jones (1996);15, Sun (1996); 16, Hollingsworth and Dickson (1997); 17, Reinhammar and Hedrén (1997); 18, Arft and Ranker (1998);19, Case et al (1998);20, Aagaard et al (1999); 21, Ackerman and Ward (1999);22, Nielsen and Siegismund (1999); 23, Thornhill (1999);24, Wong and Sun (1999); 25, Alexandersson and Å gren (2000); 26, Chung and Chung (2000); 27, Ehlers and Pedersen (2000) . We have not attempted to standardise here as in some cases the raw data are unavailable, and there is also a strong correlation between measures.…”

Section: Population Differentiationmentioning

confidence: 99%

Population genetic structure in European populations of Spiranthes romanzoffiana set in the context of other genetic studies on orchids

Forrest

Hollingsworth

et al. 2003

Heredity

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Spiranthes romanzoffiana Cham. is restricted in Europe to the British Isles, where it is recognised as a conservation priority species due to frequent extirpation of populations along with no evidence of seed set; vegetative reproduction has been invoked as the sole means of perpetuation and dispersal. To investigate the reproductive ecology of this species, 17 populations have been sampled for chloroplast microsatellites and amplified fragment length polymorphisms (AFLPs). These markers revealed a previously unsuspected genetic-geographic split in the species, which correlates with differences in patterns of within-population variation. Northern populations were fixed for one chloroplast haplotype but showed high levels of AFLP genotypic diversity consistent with sexual reproduction (proportion of genotypes distinguishable, P D ¼ 0.98). More southerly populations showed fixed differences from the northern populations in their chloroplast haplotype and for 10 AFLP markers. They harboured only 12 unique multilocus genotypes among 113 individuals from six populations (P D ¼ 0.11). These genotypes differed mostly by single bands, and none by more than 4/138 loci, with identical multilocus genotypes occurring in widely separated populations. This uniformity in southern populations is consistent with agamospermous or autogamous reproduction, and/or an extreme population bottleneck. Finally, the observed patterns of population differentiation in S. romanzoffiana are compared with other studies of orchids, revealing a wide range of values that belie recent contrasting published generalisations that claim that orchids show either higher, or lower, levels of population differentiation than other plant families.

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Genetic variation and natural hybridization betweenOrchis laxiflora andOrchis palustris (Orchidaceae)

Cited by 49 publications

References 24 publications

Strong post-pollination pre-zygotic isolation between sympatric, food-deceptive Mediterranean orchids

Strong post-pollination pre-zygotic isolation between sympatric, food-deceptive Mediterranean orchids

Gene Flow Across Species Boundaries in Sympatric, Sexually Deceptive Ophrys (Orchidaceae) Species

Population genetic structure in European populations of Spiranthes romanzoffiana set in the context of other genetic studies on orchids

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