COMPETITION FOR POLLINATORS AND EVOLUTION IN CENTAUREA

Lack, Andrew

doi:10.1111/j.1469-8137.1976.tb04675.x

Cited by 32 publications

(25 citation statements)

References 17 publications

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“…The severe drought of summer 1976 followed by the cold wet spring of 1977 probably contributed to this decline and it seems that the numbers were only beginning to build up again in 1978 and 1979. In 1975 the bumblebees were discriminating in favour of C. scabiosa but the honeybees in favour of C. nigra (Lack, 1976), a different picture from 1978 and 1979 and perhaps this varies with the numbers of insects present.…”

Section: Insect Visitsmentioning

confidence: 96%

“…In 1975 on Hod Hill no measurements were made on nectar, but bumblebees, particularly B. lapidarius, were abundant (Lack, 1976). In 1977 the only bumblebees I saw in 3 days on Hod Hill in mid-August were three B. terrestris (or B. lucorum).…”

Section: Insect Visitsmentioning

confidence: 99%

“…The possession of ray florets makes the capitula larger (about 4 cm across compared with 1-5 to 2 cm for rayless capitula), and perhaps more attractive to insects. It also causes the capitula of C. nigra to resemble those of C scabiosa and I have suggested earlier (Lack, 1976) that rayed C. nigra may be 'mimicking' C. scabiosa. To investigate the importance of the ray florets for the insects, on Hod Hill the number of insect visits to untouched rayed capitula was compared with the number of capitula from which the rays had been removed.…”

Section: Introductionmentioning

confidence: 96%

“…nigra and ssp. nemoralis and do not possess ray florets (see Marsden-Jones and Turrill, 1954;Lack, 1976). The possession of ray florets makes the capitula larger (about 4 cm across compared with 1-5 to 2 cm for rayless capitula), and perhaps more attractive to insects.…”

Section: Introductionmentioning

confidence: 99%

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COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.

Lack

1982

New Phytologist

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SUMMARY Observations are presented on: (a) the numbers of insects foraging on Centaurea scabiosa and Centaurea nigra per available capitulum of each species; (b) the numbers of insect visits to each capitulum of C. scabiosa and C. nigra in 30 min intervals; (c) the numbers of insect visits to rayed capitula compared with ray less capitula; (d) the number of successful pollinations. The study was carried out on the Devil's Ditch, Cambridgeshire where C. nigra is rayless, and on Hod Hill, Dorset where C. nigra is rayed, with a few results from a garden trial set out in the Cambridge Botanic Garden. In the counts of insects in each area of the Devil's Ditch the numbers recorded feeding on each Centaurea species per capitulum were approximately proportional to the nectar reward of each species. On Hod Hill the number of insect visits to C. nigra plants from which rays had been removed was half to three‐quarters of the number of visits to rayed capitula. This is very similar to the difference on the Devil's Ditch between the number of visits to C. scabiosa (rayed) and C. nigra (rayless), and this difference may therefore be a result simply of the possession of ray florets in C. scabiosa but not in C. nigra. The difference between the two species on Hod Hill was greater (C. scabiosa receiving two to three times as many visits as C. nigra) although C. nigra possesses ray florets and therefore resembles C. scabiosa. Some bees were observed visiting C. scabiosa selectively on Hod Hill but none did so on the Devil's Ditch. On the Devil's Ditch both species had similar numbers of styles successfully fertilized on nearly all dates. Hod Hill on most dates a similar number of styles was fertilized in each species, but on a few dates C. scabiosa had more successful fertilizations than C. nigra. It is concluded that competition for pollinators is not a strong selective factor in Centaurea on the Devil's Ditch but may be a factor promoting the later flowering and the possession of ray florets in C. nigra on Hod Hill. Competition for pollinators may have been more important as a selection pressure in the past when less suitable habitat was available.

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Section: Insect Visitsmentioning

confidence: 96%

Section: Insect Visitsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.

Lack

1982

New Phytologist

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“…According to Lack (1976), the presence of radiant peripheral fl orets in the related C. nigra L. is directly related to competition for pollinators (mainly Bombus sp., cf. Hegland & Totland, 2004) with a larger species of Centaurea with similar ecological preferences, C. scabiosa L. Radiate heads in C. nigra predominate in populations which grow in presence of C. scabiosa, while non-radiated heads predominate in stands of C. nigra alone.…”

Section: Morphologymentioning

confidence: 99%

Two additions to the Jacea-Lepteranthus complex: parallel adaptation in the enigmatic species Centaurea subtilis and C. exarata

Hilpold¹,

Garcia‐Jacas²,

Vilatersana³

et al. 2009

Collect. Bot

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Centaurea subtilis from south east Italy and C. exarata from south west Iberia were classifi ed in the AcrolophusPhalolepis group and therein in section Maculosae. A molecular survey based on ITS sequence data indicates that both species should rather be placed in the Jacea-Lepteranthus group instead. This placement is consistent with the chromosome number of the two species, which is x = 11 like the rest of species of the Jacea-Lepteranthus group, and differs from the x = 9 of the other taxa included in sect. Maculosae. These results confi rm previous suggestions on the unnaturality of sect. Maculosae. Centaurea exarata and C. subtilis are quite different from the other species of Jacea-Lepteranthus in some striking morphological characters, which we hypothesize to be the result of parallel adaptation to dryer climates. The lack of competitors for pollination might be a good explanation for the partial or even total loss of showy fl owers in these two species.Key words: Acrolophus; Compositae; ITS; Jacea-Lepteranthus; karyology; Maculosae; morphology; showy fl owers. ResumenDos adiciones al complejo Jacea-Lepteranthus: adaptaciones paralelas en las enigmáticas especies Centaurea subtilis y C. exarata.-Centaurea subtilis del sureste de Italia y C. exarata del suroeste de la Península Ibérica fueron clasificadas anteriormente en el grupo Acrolophus-Phalolepis y dentro de él en la sect. Maculosae. Una revisión molecular basada en secuencias de la región ITS indica que ambas deberían clasifi carse en el grupo Jacea-Lepteranthus. Este cambio es coherente con el número cromosómico de las dos especies, que tienen x = 11 como el resto de las especies del grupo Jacea-Lepteranthus y no x = 9 como las especies del grupo Acrolophus-Phalolepis. Estos resultados confi rman advertencias anteriores sobre el carácter artifi cial de la sect. Maculosae. Centaurea exarata y C. subtilis son bastante diferentes de las otras especies de Jacea-Lepteranthus en algunos caracteres morfológicos importantes, resultado, según nuestra hipótesis, de adaptaciones a un clima más árido. La reducción o total pérdida de las fl ores estériles radiantes podría ser una adaptación a la falta de especies competidoras en la polinización.Palabras clave: Acrolophus; cariología; Compositae; fl ores estériles; ITS; Jacea-Lepteranthus; Maculosae; morfología. ResumDues addicions al complex Jacea-Lepteranthus: adaptacions paral·leles en les enigmàtiques espècies Centaurea subtilis i C. exarata.-Centaurea subtilis del sud-est d'Itàlia i C. exarata del sud-oest de la Península Ibèrica han estat classifi cades en el grup Acrolophus-Phalolepis i, dins d'aquest grup, a la secció Maculosae. Una revisió molecular basada en seqüències de la regió ITS indica que ambdues espècies haurien de classifi car-se en el grup Jacea-Lepteranthus. Aquest canvi és coherent amb el nombre cromosòmic de les dues espècies, que tenen x = 11 com la resta de les espècies del grup Jacea-Lepteranthus i no x = 9 com les espècies del grup Acrolophus-Phalolepis. Aquests resultats confi...

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Autogamy and Competition for Pollinators in Hepatica Americana (Ranunculaceae)

Motten

1982

American J of Botany

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Hepatica americana is one of the earliest flowering vernal herbs in the deciduous forests of piedmont North Carolina. Unlike most other members of the spring wildflower community, its flowers are nectarless and autogamous. The number of insect visits a flower receives varies markedly through the blooming season and is lowest when H. americana is in full bloom. Potential for outcrossing as measured by the seed set of emasculated flowers follows the same pattern. The mid‐season decline in insect‐pollination is most likely the result of competition with Erythronium umbilicatum, which flowers concurrently with H. americana and is much more attractive to the solitary bees that are the principal early season pollen vectors. Because of this competitive disadvantage, seed set of H. americana in piedmont North Carolina would be pollination‐limited if the flowers were not autogamous. Autogamy may also be favored by flowering early in the spring before pollinators are available. Opportunities for outcrossing in H. americana are primarily the result of protogyny and blooming earlier than competitors.

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COMPETITION FOR POLLINATORS AND EVOLUTION IN CENTAUREA

Cited by 32 publications

References 17 publications

COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.

COMPETITION FOR POLLINATORS IN THE ECOLOGY OF CENTAUREA SCABIOSA L. AND CENTAUREA NIGRA L.

Two additions to the <i>Jacea-Lepteranthus</i> complex: parallel adaptation in the enigmatic species <i>Centaurea subtilis</i> and <i>C. exarata</i>

Autogamy and Competition for Pollinators in Hepatica Americana (Ranunculaceae)

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