Insights Into the Inside – A Quantitative Histological Study of the Explosively Moving Style in Marantaceae

This study aims to identify the histological basis for the extraordinary, fast movement of the style in Marantaceae. Although this explosive pollination mechanism was subject of many studies, quantitative measurements to document volumetric changes have never been conducted. Based on physical parameters and limitations (poroelastic time), the movement itself is by far too fast to be explained by turgor changes solely. Therefore, we address the hypothesis that the style contains elastic structures to store energy allowing the fast movement. We provide an experimental approach in Goeppertia bachemiana to identify histological differences of styles in various states, i.e., steady, unreleased, and released state. Cross and longitudinal sections were used to reconstruct the cell volume in different sectors of the style. Histological data were discussed with respect to a putative water shift (turgor movement) and elastic instabilities that were proposed to explain the style movement of Marantaceae. Current data show, that the upper epidermis is under tensile stress in the unreleased state. After style release, the lower side of the style revealed an enormous water up-take. According to our results, we hypothesize that the fast style movement of G. bachemiana is likely based on an elastically stretched upper epidermis, whereas a “soaking tissue” at the lower side presumably mediates the up curling of the style. The experimental data show that at least for G. bachemiana, physical limitations such as the poroelastic time are suitable parameters to predict movements that are based on elastic instabilities

Cambios fenológicos constantes en la creación de un hotspot de biodiversidad: la flora del cabo

The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record

Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

Background The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record

Floral synorganization and its influence on mechanical isolation and autogamy in Marantaceae

The flowers of Marantaceae (∼550 species) exhibit a highly derived pollination mechanism within Zingiberales, with a rapid and irreversible style movement based on a close synorganization of different floral parts. Given the complexity of the structure, we assume that little variation is possible if functionality is to be maintained. To test this, we investigated how much floral diversity exists in the clade and whether this diversity potentially influences the breeding system and placement of pollen on the pollinator. Flowers of 66 species covering the five major phylogenetic clades of the family were analysed. All species are similar in their basic flower construction: the fleshy staminode forms the tunnel-shaped roof of the flower and narrows the tube with stiff swellings, and the hooded staminode holds the style under tension and narrows the flower entrance with its trigger appendage. Despite morphological diversity of the pollination apparatus, functionality is maintained by coordinated variation of the fleshy and hooded staminodes. Autogamy is usually avoided by herkogamy. However, in a few exceptions, subtle morphological changes alter the breeding system from allogamy to autogamy. Variable floral proportions allow for differential pollen deposition potentially causing mechanical isolation between sister taxa. This study clearly illustrates that structural variation is not only present in the highly synorganized flowers of Marantaceae, but that it also creates potentially new options for evolutionary diversification. © 2012 The Linnean Society of London.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Developmental Changes in Time and Space Promote Evolutionary Diversification of Flowers: A Case Study in Dipsacoideae

Diversification in flower shape and function is triggered by the high plasticity of flower meristems. Minute changes in space and time can profoundly affect the formation of adult structures. Dipsacoideae provides an excellent model system to investigate the evolutionary aspects of temporal and spatial changes in flower development due to its small size, the resolved phylogenetic framework, and significant diversity of perianth form and merosity. In the present study, we investigated the sequence of floral organ initiation and quantified the interactions between flower meristem expansion and petal primordium size in eight species representing two major clades of Dipsacoideae. Our quantitative study indicates the plasticity of the flower meristem for the regulation of pentamery either due to a decrease in petal primordium size (Scabiosa) or an increase in flower meristem size (Pterocephalus and Lomelosia) compared to tetramerous flowers. According to our results, temporal shifts of organ initiation during flower evolution contribute to the morphological diversity of perianth. Sepal reduction in members of the Dipknautids is paralleled by a delay in sepal initiation. The multiplication of sepals in Lomelosia and Pterocephalus is correlated with an extension of initiation time. Some heterochronies in early development do not affect adult morphology. The effects of a temporal change in early development can be enhanced, reduced, or eliminated by later changes of the growth rate during development. Our results confirm the hypothesis that the interaction between timing and space plays an important role for evolutionary diversification of flowers

Ontogenetic and phylogenetic diversii cation in Marantaceae

The Marantaceae Petersen (31 genera; ~530 ssp. Andersson, 1998) are a pantropically (80% America; 11% Asia; 9% Africa: Kennedy, 2000) distributed family of perennial herbs and lianas found in the understory of tropical lowland rainforests. They are characterized by a unique pollination mechanism combining secondary pollen presentation with an explosive style movement (Kunze, 1984; Claßen-Bockhoff, 1991; Claßen-Bockhoff and Heller, 2008a). The specific pollen transfer mechanism is found in conjunction with a high synorganization of morphologically modified floral elements and has been postulated to be a key innovation responsible for the radiation of the Marantaceae (Kennedy, 2000). Flowers in Marantaceae are trimerous, with inconspicuous sepals and petals and extremely modified elements in the two androeceal whorls (Fig 10.1). In the outer whorl one or two petaloid ‘outer staminodes’ act as the showy organs of the flowers. The three elements of the inner whorl are functionally differentiated into: (1) a single (monothecate) anther, (2) a ‘fleshy (callose) staminode’ and (3) a ‘hooded (cucullate) staminode’ (Kunze, 1984; Claßen-Bockhoff, 1991). These organs closely interact with the style resulting in secondary pollen presentation, set-up of tension and finally the explosive pollination mechanism (e.g. Gris, 1859; Delpino, 1869; Schumann, 1902; Yeo, 1993; Claßen-Bockhoff and Heller, 2008a, b; Ley, 2008; Pischtschan and Claßen-Bockhoff, 2008; Fig 10.2). As the style movement demands a high degree of synorganization of floral parts and synchronization with the pollinator and as the movement is irreversible, providing the flowers with a single opportunity for pollination, one should expect rather uniform structures across the whole family, as slight morphological deviations might result in a loss of operability. However, the high degree of floral diversity in the Marantaceae contradicts this expectation (Kunze, 1984; Kennedy, 2000; Claßen-Bockhoff and Heller, 2008a; Ley, 2008). It instead raises the questions: how far are elements of a functional unit allowed to vary without jeopardizing the reproductive success, and has the variation of the flowers influenced speciation in the family?SCOPUS: ch.binfo:eu-repo/semantics/publishe

Evolution in African Marantaceae - Evidence from phylogenetic, ecological and morphological studies

The Marantaceae (∼530 spp.) are one of the most species rich families within the order Zingiberales which incites the search for evolutionary factors favoring speciation. A positive influence on their divergence is ascribed to their unique explosive pollination mechanism which has been proposed to be a key innovation. To test this hypothesis phylogenies of the two major African clades (Sarcophrynium and the Marantochloa clade) were established based on data from nuclear (ITS, 5S) and chloroplast (trnL/trnL-F) DNA for an almost complete taxon sample. The phylogeny was used to parsimoniously reconstruct morphological and ecological traits and gographic distribution patterns. The resulting molecular relationships of the genera are congruent with the existing family phylogeny. As in previous studies the species Ataenidia conferta is nested within Marantochloa so that a new circumscription of Marantochloa is proposed leading to the new name Marantochloa conferta .Hybridization events, adaptation to different pollinators, and Pleistocene climatic fluctuations are hypothesized evolutionary factors fostering speciation in the African clades. The explosive pollination mechanism might have played an important role in optimizing the mating system but did certainly not force speciation directly through mechanisms of reproductive isolation. © Copyright 2011 by the American Society of Plant Taxonomists.SCOPUS: ar.jinfo:eu-repo/semantics/publishe