Phenotypic plasticity and biomass allocation pattern in three Dryopteris (Dryopteridaceae) species on an experimental light-availability gradient

Abstract

We were interested in whether the contrasting regional distribution patterns of three congeneric, frequently co-occurring fern species (Dryopteris carthusiana, D. dilatata and D. expansa) could be explained by differential biomass allocation strategies and different phenotypic plasticities to light availability. The morphology and habitat preference of these ferns are known to be very similar, but in Estonia, their frequencies of occurrence differ sharply--Dryopteris carthusiana is common, D. expansa grows in scattered localities, and D. dilatata is rare. We grew the species under different levels of illumination (100, 50, 25 and 10% of full daylight) in an experimental garden to compare their autecological responses to shading. After one growing season there were clear interspecific differences in total plant biomass accumulation--D. carthusiana > D. expansa > D. dilatata--indicating the possible competitive inferiority of the latter at the young sporophyte stage. D. expansa was the least shade-tolerant, with biomass decreasing sharply under less than 50% illumination; D. dilatata was the most shade-tolerant, with similar growth at all illumination levels. In relative biomass allocation patterns, the most notable differences among species were in the relative shares of biomass stored in rhizomes. In D. carthusiana and D. expansa this share was nearly constant and independent of the illumination conditions. D. dilatata allocated very little biomass into rhizome in deep shade, but was able to increase this share more than twofold in 50% light. Dryopteris dilatata was clearly shown to be morphologically the most plastic of the three. In four traits--rhizome mass, frond:below-ground biomass ratio, stipe length and specific leaf area--its degree of ontogenetic plasticity to light was significantly higher than that of D. expansa and D. carthusiana. While the general performance (biomass production) of species in the experiment coincided with that observed in nature, the results of plasticity estimation were somewhat surprising--it is difficult to explain the inferior performance of a species (D. dilatata) through high morphological plasticity. Probably, the species is rare either because of certain climatic restrictions, or because it is presently expanding its distribution and is in the phase of invading Estonian understory communities.

Biological Flora of the British Isles: Dryopteris carthusiana, D. dilatata and D. expansa

“…The results of a study in which the three species were grown on a light‐availability gradient in an experimental garden (Rünk & Zobel 2007) were generally in agreement with the distribution of the three species in the British Isles (see ). There were clear interspecific differences in total plant growth and biomass allocation in different shade treatments.…”

“…When the effect of plant size (biomass) was removed, D. dilatata appeared to be the most plastic of the three. In four traits (rhizome mass, frond/below‐ground biomass ratio, stipe length and SLA), its degree of ontogenetic plasticity was significantly higher than that of D. expansa and D. carthusiana (Rünk & Zobel 2007).…”

“…According to the results of a garden pot experiment on a light‐availability gradient (10, 25, 50 and 100% of full daylight), sporophytes of D. carthusiana , D. dilatata and D. expansa grown together performed differently in different light conditions (Rünk & Zobel 2007). D. dilatata was morphologically the most plastic species of the three.…”

Leaf form and photosynthetic physiology of Dryopteris species distributed along light gradients in eastern North America

“…The remaining five eastern North American species are allopolyploids, formed over the last 13 million years via hybridization and genome doubling involving three of the extant North American diploids and one extinct progenitor (Sessa, Zimmer & Givnish ; Table ). Tani & Kudo (, ), and Tessier & Bornn () have examined biomass allocation and the contributions of overwintering leaves to carbon uptake in several Dryopteris species, and Rünk, Zobel & Zobel () and Rünk & Zobel () have compared growth and survival of a few European species as a function of edaphic conditions and light availability, but no rigorous study of photosynthetic adaptations to light regime has been undertaken for the North American group, despite their strikingly different habitats and leaf morphologies.…”

Growth and morphology of three forest understorey species (Calluna vulgaris, Molinia caerulea and Pteridium aquilinum) according to light availability

“…ferns (Rünk and Zobel, 2007). In the results of Den Ouden (2000), the decrease in the frond mass is assumed to be linked to a decrease in the investment in the support tissues of the fronds, i.e.…”