Floral evolution: One-sided evolution or two? A reply to Ennos

Hodges, Scott A.; Whittall, Justen B.

doi:10.1038/hdy.2008.12

Cited by 8 publications

(12 citation statements)

References 30 publications

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“…This is a commonly reported axis of specialization; for example, nectar is often secreted at the base of long tubular corollas or spurs (see Hodges and Arnold 1995;Hodges 1997;Muchhala 2006b). Specialization along this axis may result in a coevolutionary spiral or serial pollinator switches, as appears to be the case for the long spurs of some orchid and columbine flowers and their long-tongued pollinators (Darwin 1877;Nilsson et al 1987;Nilsson 1988;Wasserthal 1997;Whittall and Hodges 2007;Ennos 2008;Hodges and Whittall 2008).…”

Section: Divergence In Attraction Systems (Rewards and Advertisements)mentioning

confidence: 94%

Associations between floral specialization and species diversity: cause, effect, or correlation?

2008

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It has been proposed frequently, from Darwin's time onwards, that specialized pollination increases speciation rates and thus the diversity of plant species (i.e. clade species richness). We suggest here that the correlation between clade species richness and floral specialization is real, but that clade species richness is frequently the cause, not the result of floral specialization. We urge a broader, variance-partitioning perspective for assessing the causes of this correlation by suggesting four models of how the diversityspecialization correlation might come about: (1) floral specialization promotes initial reproductive isolation (''Initial-RI'' model), (2) floral specialization promotes reinforcement of reproductive isolation upon secondary contact (''Reinforcement'' model), (3) floral specialization reduces the extinction rate by promoting tighter species packing (''Extinction'' model), (4) floral specialization is the result of high clade species richness, which increases the number of related species in communities, and thus selects for floral character displacement (''Character-Displacement'' model). These hypotheses are evaluated by comparing the relationships between species richness, speciation mechanisms, and pollination precision, accuracy, and specialization in the broader literature and, more specifically, in four study systems: Dalechampia (Euphorbiaceae), Collinsia (Plantaginaceae), Burmeistera (Campanulaceae), and Stylidium (Stylidiaceae). These systems provide stronger support for the character-displacement hypothesis, wherein local species diversity drives the evolution of specialized pollination. Although the two reproductive-isolation hypotheses may hold for plants like orchids, with extremely precise pollination systems, the reproductive character-displacement hypothesis seems likely to be more important for plant groups with less precise pollination systems.

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Section: Divergence In Attraction Systems (Rewards and Advertisements)mentioning

confidence: 94%

Associations between floral specialization and species diversity: cause, effect, or correlation?

2008

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“…In addition, models of the tempo of evolution strongly indicated the concentration of spur-length evolution at times of speciation. Thus, as with the broad correlation between the evolution of spurs themselves and species diversity, this study suggests that spur length is intimately linked with the speciation process, at least in North American species of Aquilegia (38,39). Functionally, matching of spur length to tongue length has been shown to be adaptive because Aquilegia flowers with artificially shortened spurs have less pollen removed from their anthers, and presumably deposited on their stigmas, because of the body of the pollinator being held further away from the flower (40).…”

Section: Evolutionary Trends In Aquilegiamentioning

confidence: 99%

Adaptive radiations: From field to genomic studies

Hodges

Derieg

2009

Proc. Natl. Acad. Sci. U.S.A.

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Adaptive radiations were central to Darwin's formation of his theory of natural selection, and today they are still the centerpiece for many studies of adaptation and speciation. Here, we review the advantages of adaptive radiations, especially recent ones, for detecting evolutionary trends and the genetic dissection of adaptive traits. We focus on Aquilegia as a primary example of these advantages and highlight progress in understanding the genetic basis of flower color. Phylogenetic analysis of Aquilegia indicates that flower color transitions proceed by changes in the types of anthocyanin pigments produced or their complete loss. Biochemical, crossing, and gene expression studies have provided a wealth of information about the genetic basis of these transitions in Aquilegia. To obtain both enzymatic and regulatory candidate genes for the entire flavonoid pathway, which produces anthocyanins, we used a combination of sequence searches of the Aquilegia Gene Index, phylogenetic analyses, and the isolation of novel sequences by using degenerate PCR and RACE. In total we identified 34 genes that are likely involved in the flavonoid pathway. A number of these genes appear to be single copy in Aquilegia and thus variation in their expression may have been key for floral color evolution. Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level. The genetic dissection of other adaptive traits in Aquilegia should also be possible soon as genomic resources such as whole-genome sequencing become available.anthocyanins ͉ evolutionary trend ͉ flower color ͉ hybrid zone A daptive radiations have played, and continue to play, a central role in the development of evolutionary theory. After his exploration of the Galapagos Islands, Darwin recognized that variants of species were confined to specific islands. In particular, Darwin (1) noted that mockingbirds he collected on different islands represented 3 distinct forms and that all of the forms were similar to mockingbirds from the mainland of South America. He further noted that the different islands were within sight of one another, all quite similar in their habitats, and apparently geologically young. Based on these observations, Darwin (2) began to suspect that species gradually became modified. Thus, began his search for a process that could account for such observations, leading to his formulation of the theory of natural selection.Key to Darwin's suspicion of common ancestry was the close proximity of environmentally-similar islands comprising the Galapagos archipelago. In fact, many classic examples of adaptive radiations involve islands or lakes; notable examples include Darwin's finches of the Galapagos, honeycreeper birds and silversword plants of Hawaii, and cichlid fish of lakes Malawi and Victoria in Africa. The power of these examples for inferring the force of natural selection in evolution stems from the marked diversity in form and function among ...

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“…In allogamous orchids, the plants rely on animals for the transportation and deposition of pollen. About four‐fifth of all orchid species are pollinated by animals, mostly insects (Van der Pijl and Dodson , Grimaldi ), although there are various transitions between complete allogamy and some degree of autogamy (Tałałaj and Brzosko , Claessens and Kleynen , Jacquemyn et al ). Pollinators may be attracted by various rewards like pollen, nectar, oil or food‐hairs (Kull et al ), but in European orchids, nectar is the main reward.…”

Section: Introductionmentioning

confidence: 99%

“…Pollinators may be attracted by various rewards like pollen, nectar, oil or food‐hairs (Kull et al ), but in European orchids, nectar is the main reward. Nectar is a key component in the relationship between plants and pollinators (Lenaerts et al ), and in orchid flowers it can be secreted on the inflorescences (Subedi et al ), sepals (Subedi et al , Karremans et al 2015), lip, lip base or in an elongation of the lip, or the spur (Kocyan et al ). The place where nectar is presented greatly influences the visitor spectrum: an orchid with easily accessible and copious nectar like Neottia ovata (L.) Bluff & Fingerh.…”

Section: Introductionmentioning

confidence: 99%

Pollination ofHabenaria tridactyliteson the Canary Islands

Claessens

Bacallado²,

Bogarín

et al. 2019

Nordic Journal of Botany

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We investigated the pollination of Habenaria tridactylites, an endemic orchid of the Canary Islands. The entirely green, widely open flowers have a long spur containing nectar. We carried out fieldwork, a molecular clock analysis, herbarium surveys, identified pollinators by both morphology and DNA barcoding, and measured the length of floral spurs and insect tongues using a combination of traditional and innovative micro‐CT scanning methods to 1) determine the pollinator of this orchid and 2) investigate correlations between local mean spur length and age, altitude and longitude of the island. Habenaria tridactylites was found to be pollinated on Tenerife by both small and intermediate sized moth species with variable tongue lengths and mostly belonging to Geometridae and to a lesser extent Crambidae, Erebidae, Noctuidae and Tortricidae. Of the sixteen moth species identified, nine are endemic to the Canary Islands or Macaronesia. The different local populations of H. tridactylites on the islands of Gran Canaria, El Hierro, La Gomera, La Palma and Tenerife with different ages and distances from mainland Africa, did not show a significant correlation of mean spur length and altitude, but did show a significant and positive linear correlation with longitude and the geological age of the island. The latter is congruent with the evolutionary arms race theory first proposed by Darwin, suggesting that flowers gradually evolve longer spurs and pollinators longer tongues.

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Floral evolution: One-sided evolution or two? A reply to Ennos

Cited by 8 publications

References 30 publications

Associations between floral specialization and species diversity: cause, effect, or correlation?

Associations between floral specialization and species diversity: cause, effect, or correlation?

Adaptive radiations: From field to genomic studies

Pollination ofHabenaria tridactyliteson the Canary Islands

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