Orchid diversity: an evolutionary consequence of deception?

Cozzolino, Salvatore; Widmer, Alex

doi:10.1016/j.tree.2005.06.004

Cited by 457 publications

(402 citation statements)

References 56 publications

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“…This finding sharply contrasts with the common observation of postmating isolation mechanisms (such as pollen-stigma incompatibilities that impede fruit formation following interspecific pollinations, for example, Scopece et al, 2007) between sympatric food-deceptive orchid species. Such postmating isolation mechanisms have been proposed to evolve in secondary contact zones to avoid the waste of gametes because of interspecific matings (Dobzhansky, 1940), a common event among orchid species that share pollinators (Cozzolino and Widmer, 2005a).…”

Section: Discussionmentioning

confidence: 99%

“…Reproductive barriers in this orchid group have been investigated in much detail in recent years (reviewed in Cozzolino and Widmer, 2005a;Cozzolino and Scopece, 2008). These studies revealed that hybrid zones among Mediterranean food-deceptive orchids are typically dominated by F1 hybrids and often contain only few backcross individuals (reviewed in Cozzolino and Widmer, 2005b).…”

Section: Introductionmentioning

confidence: 99%

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

Zitari

Scopece

Helal³

et al. 2011

Heredity

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Analyzing the processes that determine whether species boundaries are maintained on secondary contact may shed light on the early phase of speciation. In Anacamptis morio and Anacamptis longicornu, two Mediterranean orchid sister-species, we used molecular and morphological analyses, together with estimates of pollination success and experimental crosses, to assess whether floral isolation can shelter the species' genomes from genetic admixture on secondary contact. We found substantial genetic and morphological homogenization in sympatric populations in combination with an apparent lack of postmating isolation. We further detected asymmetric introgression in the sympatric populations and an imbalance in cytotype representation, which may be due either to a difference in flowering phenology or else be a consequence of cytonuclear incompatibilities. Estimates of genetic clines for markers across sympatric zones revealed markers that significantly deviated from neutral expectations. We observed a significant correlation between spur length and reproductive success in sympatric populations, which may suggest that directional selection is the main cause of morphological differentiation in this species pair. Our results suggest that allopatric divergence has not led to the evolution of sufficient reproductive isolation to prevent genomic admixture on secondary contact in this orchid species pair.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Zitari

Scopece

Helal³

et al. 2011

Heredity

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“…Chemosensory pollinator isolation: In flowering plants pollinated by specific pollinators, pollinator shifts can reduce the relative amount of heterospecific pollen reaching the stigma (Grant, 1994;Cozzolino and Widmer, 2005;Rieseberg and Willis, 2007). Floral odour is an important trait used by many plants to attract pollinators.…”

Section: Caribbean/ Africa Rest_of_the_worldmentioning

confidence: 99%

On the scent of speciation: the chemosensory system and its role in premating isolation

2008

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Chemosensory speciation is characterized by the evolution of barriers to genetic exchange that involve chemosensory systems and chemical signals. Here, we review some representative studies documenting chemosensory speciation in an attempt to evaluate the importance and the different aspects of the process in nature and to gain insights into the genetic basis and the evolutionary mechanisms of chemosensory trait divergence. Although most studies of chemosensory speciation concern sexual isolation mediated by pheromone divergence, especially in Drosophila and moth species, other chemically based behaviours (habitat choice, pollinator attraction) can also play an important role in speciation and are likely to do so in a wide range of invertebrate and vertebrate species. Adaptive divergence of chemosensory traits in response to factors such as pollinators, hosts and conspecifics commonly drives the evolution of chemical prezygotic barriers. Although the genetic basis of chemosensory speciation remains largely unknown, genomic approaches to chemosensory gene families and to enzymes involved in biosynthetic pathways of signal compounds now provide new opportunities to dissect the genetic basis of these complex traits and of their divergence among taxa.

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“…The flowers of orchids are of considerable morphological diversity, and their reproduction and development have intrigued scientists for centuries (Brown, 1810;Brown, 1831;Darwin, 1862;Rolfe, 1909;Garay, 1960;Chen, 1982;Cozzolino and Widmer, 2005). For instance, Darwin and others interested in the morphological evolution of the orchid flower employed information on the vascularization pattern of the flower organs to infer the relationships of homology with those of flowers of other petaloid monocots (Brown, 1810;Brown, 1831;Darwin, 1862;Lindley, 1840;Nelson, 1967).…”

Section: The 'Orchid Code'mentioning

confidence: 99%

Conserved differential expression of paralogous DEFICIENS‐ and GLOBOSA‐like MADS‐box genes in the flowers of Orchidaceae: refining the ‘orchid code’

2011

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SUMMARYIn flowering plants, class-B floral homeotic genes encode MADS-domain transcription factors, which are key in the specification of petal and stamen identity, and have two ancient clades: DEF-like and GLO-like genes. Many species have one gene of each clade, but orchids have typically four DEF-like genes, representing ancient gene clades 1, 2, 3 and 4. We tested the 'orchid code', a combinatorial genetic model suggesting that differences between the organs of the orchid perianth (outer tepals, inner lateral tepals and labellum) are generated by the combinatorial differential expression of four DEF-like genes. Our experimental test involves highly sensitive and specific measurements, with qRT-PCR of the expression of DEF-and GLO-like genes from the distantly related Vanilla planifolia and Phragmipedium longifolium, as well as from wild-type and peloric Phalaenopsis hybrid flowers. Our findings support the first 'orchid code' hypothesis, in that absence of clade-3 and -4 gene expression distinguishes the outer tepals from the inner tepals. In contrast to the original hypothesis, however, mRNA of both clade-3 and -4 genes accumulates in wild-type inner lateral tepals and the labellum, and in labellum-like inner lateral tepals of peloric flowers, albeit in different quantities. Our data suggest a revised hypothesis where high levels of clade-1 and -2, and low levels of clade-3 and -4, gene expression specify inner lateral tepals, whereas labellum development requires low levels of clade-1 and -2 expression and high levels of clade-3 and -4 expression.

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Orchid diversity: an evolutionary consequence of deception?

Cited by 457 publications

References 56 publications

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

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

On the scent of speciation: the chemosensory system and its role in premating isolation

Conserved differential expression of paralogous DEFICIENS‐ and GLOBOSA‐like MADS‐box genes in the flowers of Orchidaceae: refining the ‘orchid code’

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