Fruit polymorphism in ephemeral species of Namaqualand. I. Anatomical differences between polymorphic diaspores of two Dimorphotheca species

Beneke, Karen; Teichman, Irmgard von; Rooyen, M.W. van; Theron, G.K.

doi:10.1016/s0254-6299(16)30791-8

Cited by 17 publications

(6 citation statements)

References 20 publications

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“…This is in line with other studies of seed heteromorphic plants that have also shown the existence of such a tradeoff within seeds (e.g. Venable & Lawlor, ; McEvoy, ; Beneke et al ., ; Imbert, ). Individual‐level tradeoffs are usually predicted as the result of biophysical constraints (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…In Dimorphotheca , central fruits are disk‐shaped, winged and appear adapted for wind dispersal. By contrast, peripheral fruits are nut‐like and do not possess any adaptations for dispersal (Beneke et al ., ; De Waal, ). O. grandiflorum individuals produce only peripheral fruit, but some possess wing‐like appendages, presumably to aid wind dispersal.…”

Section: Methodsmentioning

confidence: 99%

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Dispersal, dormancy and life‐history tradeoffs at the individual, population and species levels in southern African Asteraceae

2015

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SummaryDispersal and dormancy are important risk-reducing strategies in unpredictable environments. Negative covariation between these strategies is theoretically expected, but empirical evidence is limited and inconsistent. Moreover, covariation may be affected by other lifehistory traits and may vary across levels of biological organization.We assessed dispersal (vertical fall time of fruits, a proxy for wind dispersal ability) and dormancy (germination fractions measured during germination trials) in populations of 15 annual and 12 perennial wind-dispersed species in six Asteraceae genera from South Africa.Dormancy was higher in annuals than in perennials, whereas fall time was largely determined by evolutionary history. Controlling for phylogeny, dispersal and dormancy was negatively associated across species and life-history categories. Negative covariation between dispersal and dormancy was not evident at either the individual level (except for seed heteromorphic species) or the population level.Our study provides rare empirical support for the theoretical expectation of tradeoffs between dormancy and the alternative risk-reducing strategies, perenniality and dispersal, but refutes the expectation of increased dispersability in perennials. Although negative covariation between dispersal and dormancy at the species level appears not to be a simple consequence of upscaling individual-level mechanistic tradeoffs, our findings suggest that selection for one strategy may constrain evolution of the other.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Dispersal, dormancy and life‐history tradeoffs at the individual, population and species levels in southern African Asteraceae

2015

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“…winged pericarp in disc seed morphs, or escape in time, e.g. dormancy enforced by the greater mechanical and chemical resistance of heavily lignified pericarps in ray seed morphs ( Beneke et al . 1992 ).…”

Section: Discussionmentioning

confidence: 99%

Carry‐over of enhanced ultraviolet‐B exposure effects to successive generations of a desert annual: interaction with atmospheric CO2 and nutrient supply

Musil

Midgley

Wand

1999

Global Change Biology

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The performance of fifth generation offspring of a desert annual (Dimorphotheca sinuata DC.) were compared in the absence of UV‐B, under variable atmospheric CO2 and nutrient supply, after four consecutive generations of concurrent exposure of their progenitors to UV‐B at ambient (seasonal range: 2.55–8.85 kJ m–2 d–1) and enhanced (seasonal range: 4.70–11.41 kJ m–2 d–1) levels. Offspring of progenitors grown under elevated UV‐B exhibited a diminished photosynthetic rate, a consequence of a reduced leaf density, and diminished foliar levels of carotenoids, polyphenolics and anthocyanins. Conversely, nonstructural carbohydrate and chlorophyll b levels were increased. Altered physiology was accompanied by reduced apical dominance and earlier flowering, features generally considered under photomorphogenic control, increased branching and inflorescence production and greater partitioning of biomass to reproductive structures, but diminished seed production. Many of these changes were magnified under nutrient limitation and intensified under atmospheric CO2 enriched conditions. The latter disagrees with current opinion that elevated CO2 may reduce detrimental UV‐B effects, at least over the long‐term. Observed correlations between seed production and polyphenolic, especially anthocyanin, levels in offspring, and indications of diminished lignification (thinner leaves, less robust stems and fewer lignified seeds set) all pointed to the involvement of the phenylpropanoid pathway in seed formation and plant structural development and its disruption during long‐term UV‐B exposure. Comparisons with earlier generations revealed trends with cumulative generations of enhanced UV‐B exposure of increasing chlorophyll b and nonstructural carbohydrates, decreasing polyphenolics and biomass allocation to vegetative structures, and diminishing seed production despite increasing biomass allocation to reproductive structures. Notwithstanding some physiological compensation (increased chlorophyll b), the accumulation and persistence of these ostensibly inherited changes in physiological and reproductive performance suggest a greater impact of elevated UV‐B on vegetation, primary production and regeneration over the long‐term than presently envisaged.

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“…Heterocarpy is an extremely widespread phenomenon in Asteraceae (Beneke et al 1992). Different cypsela morphs may show different strategies in dispersion and germination and enable species to adapt to changeable environments (Jeffrey 2009).…”

Section: Discussionmentioning

confidence: 99%

Micromorphology of an involucral bract and cypselae of the endemic and relict species Amphoricarpos elegans Albov (Asteraceae, Cardueae) from the Caucasus

et al. 2020

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In this study, micromorphology of an involucral bract and inner and outer dimorphic cypselae of the relict Amphoricarpos elegans, endemic from western Caucasus, is examined using a scanning electron microscope (SEM) and presented here for the first time. The middle involucral bract is nearly glabrous, with a reticulate-rugulose surface and an oblong-obtusate mucro. Both cypselae exhibit similar features, viz., narrowly oblong-cylindrical or obovate shape with more or less conspicuous longitudinal ribs, an adaxial detachment area, an asymmetrical carpopodium, absence of a pericarp crown and a barbate-aristate pappus made up of narrow, subulate, basally smooth and apically barbate bristles. However, some differences are evident. The outer cypsela is glabrescent and flattened, with an obscure outline of epidermal cells lacking an end wall and with a sunken periclinal surface and striatereticulate structure. Also, the outer cypsela has two entire, narrow, lateral wings, rounded above; and less numerous pappus bristles in one row. In contrast to this, the inner cypsela has a distinct outline of the epidermal cells, which are rod-shaped with a short acute end wall, a swollen periclinal surface and reticulate structure. The pappus of the inner cypsela possesses many more bristles organised in two rows (a biseriate pappus). Also, slightly pentagonal or round nectary remnants are found in the centre of the upper part of the inner cypsela. The taxonomic value of the analysed characters is briefly discussed.

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Fruit polymorphism in ephemeral species of Namaqualand. I. Anatomical differences between polymorphic diaspores of two Dimorphotheca species

Cited by 17 publications

References 20 publications

Dispersal, dormancy and life‐history tradeoffs at the individual, population and species levels in southern African Asteraceae

Dispersal, dormancy and life‐history tradeoffs at the individual, population and species levels in southern African Asteraceae

Carry‐over of enhanced ultraviolet‐B exposure effects to successive generations of a desert annual: interaction with atmospheric CO2 and nutrient supply

Micromorphology of an involucral bract and cypselae of the endemic and relict species Amphoricarpos elegans Albov (Asteraceae, Cardueae) from the Caucasus

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