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Evolution and pollination of Madagascan and African Dalechampia
... The complexity of the interactions between plants and animals might suggest they would be evolutionarily conservative. (Armbruster, 1993;Goldblatt, et al. 1995;Johnson, 1995). The first system forms the basis of the present contribution. ...
... In the process of collecting the reward the bees contact the staminate and pistillate flowers and effect pollination (Armbruster, 1984(Armbruster, , 1988Armbruster et al. 1989). A few species appear to offer only pollen as a reward for pollen-collecting bees or pollen-feeding beetles (Armbruster et al., 1993). ...
... 60 Dalechampia species were made at field sites in Mexico, Belize, Costa Rica, Panama, Venezuela, Ecuador, Peru, Brazil, Tanzania, South Africa, and Madagascar. Dates of study and exact field location can be found in Armbruster (1988b), Armbruster and Mziray (1987), and Armbruster et al (1993). Floral and leaf secretions were analyzed using thin-layer chromotography, flash chromotography, HPLC, integrated gas chromotgraphy-mass spectrometry, and NMR (see Armbruster et al. 1989Armbruster et al. , 1995. ...
This chapter examines homoplastic evolution from an ecological perspective with the help of the Dalechampia vines. In particular, it focuses on the evolution of plant-animal relationships. The complexity of the interactions between plants and animals might suggest that they would be evolutionarily conservative. Recent analysis of three different plant-pollinator systems (Dalechampia [Euphorbiaceae], Lapeirousia [Iridaceae], Disa [Orchidaceae]) indicates that plant-animal interactions may often be evolutionarily labile and exhibit considerable homoplasy. The biological properties and processes that contribute to high homoplasy of ecological characters are also discussed in the chapter. Historical analysis of Dalechampia evolution suggests that homoplasy is common in characters with ecological significance. Three reasons seem to be responsible for this: strong selective pressures, character reversals, and parallelisms. It appears that natural selection interacts with the “internal” factors that influence the generation of novel phenotypes, and they act together to generate “biases” in the pattern of diversification. Another conclusion is that characters of ecological importance are often of little systematic utility. Although homoplasy is problematic in phylogeny estimation, it is obviously an important part of the evolutionary process. It remains particularly important to identify the processes that cause homoplasy and to analyze them in conjunction with determining the roles of genetic and developmental constraint, natural selection, and chance in evolution.
... A few species of Dalechampia produce monoterpene fragrances as pollinator rewards (Armbruster and Webster 1979, Whitten et al. 1986, Armbruster et al. 1989, Armbruster 1993). These fragrances attract and reward male euglossine bees (Apidae: Euglossini), which collect them probably as precursors for sex pheromones Whitten 1983, Armbruster et al. 1989). ...
... These fragrances attract and reward male euglossine bees (Apidae: Euglossini), which collect them probably as precursors for sex pheromones Whitten 1983, Armbruster et al. 1989). A few species (e.g., D. shankii, D. liesneri) appear to be pollinated by pollen-collecting bees or, in Madagascar, pollen-feeding beetles (Armbruster 1993, Armbruster et al. 1993. ...
... This event was followed by extensive speciation in at least two separate evolutionary lines. Pollination by male euglossine bees has evolved several times from resin-reward ancestors (Armbruster 1993). ...
To evaluate possible evolutionary links between plant-herbivore and plant-pollinator relationships, defense and reward characteristics and pollination ecology were mapped onto a morphologically estimated phylogeny of 42 species of Dalechampia. This procedure generated detailed hypotheses about the evolution of anti-herbivore defense and pollination systems. These hypotheses were tested using the results of chemical analyses and bioassays of foliar and floral secretions. Multiple lines of defense appear to have evolved in sequence in Dalechampia. The first defense system to originate was deployment of triterpene resins to defend the staminate flowers. This feature was a preaptation (preadaptation) that allowed the evolution of a resin-based, pollinator-reward system. Thus pollination by resin-collecting bees originated as a 'transfer exaptation' (a new function replaced the old). This hypothesis is supported by anti-herbivore activities of floral resins and by chemical similarity of floral defense and reward resins. After the resin defense of flowers was lost by conversion into a reward system, there followed (in evolutionary time) a sequence of defensive innovations. These included nocturnal closure of large, involucral bracts to protect both staminate and pistillate flowers. Phylogenetic analysis showed that the large bracts themselves probably originated as a floral advertisement system, and the bracts assumed a defensive function through 'addition exaptation' (a new function was added to the old). Additional lines of defense to evolve were deployment of resin to defend the developing ovaries and seeds (an addition exaptation), deployment of sharp, detaching trichomes on enveloping sepals to defend developing seeds (apparent adaptations), closure of involucral bracts around the developing fruits and seeds (an addition exaptation), and deployment of resin to defend the leaves and growing shoot tips (also an addition exaptation). Support for this scenario also derives from the chemical similarities of sepal, foliar, and floral resins, and the anti-herbivore properties of foliar resins. It appears that at least one pollinator-reward system originated by modification of a defense system, and several defense systems originated by modification of pollinator reward and advertisement systems. Thus exaptations have been important in the origin of new defense and pollination systems, and each system has significantly influenced the evolution of the other on several occasions.
... Dalechampia vines exhibit 1 or 2 origins of lateral-facing, 2 origins of pendent, and 1 origin of upward-facing inflorescences as a result of peduncle bending. In this group, lateral blossom orientation is associated with pollination by female bees collecting floral resin or pollen, pendent orientation is associated with pollination by fragrance-collecting male euglossine bees, and upward orientation is associated with pollination by beetles (see figure 15.2;Armbruster 1993;Armbruster et al. 1993;Plebani et al. 2015). ...
Essays on evolvability from the perspectives of quantitative and population genetics, evolutionary developmental biology, systems biology, macroevolution, and the philosophy of science.
Evolvability—the capability of organisms to evolve—wasn't recognized as a fundamental concept in evolutionary theory until 1990. Though there is still some debate as to whether it represents a truly new concept, the essays in this volume emphasize its value in enabling new research programs and facilitating communication among the major disciplines in evolutionary biology. The contributors, many of whom were instrumental in the development of the concept of evolvability, synthesize what we have learned about it over the past thirty years. They focus on the historical and philosophical contexts that influenced the emergence of the concept and suggest ways to develop a common language and theory to drive further evolvability research.
The essays, drawn from a workshop on evolvability hosted in 2019–2020 by the Center of Advanced Study at the Norwegian Academy of Science and Letters, in Oslo, provide scientific and historical background on evolvability. The contributors represent different disciplines of evolutionary biology, including quantitative and population genetics, evolutionary developmental biology, systems biology, and macroevolution, as well as the philosophy of science. This plurality of approaches allows researchers in disciplines as diverse as developmental biology, molecular biology, and systems biology to communicate with those working in mainstream evolutionary biology. The contributors also discuss key questions at the forefront of research on evolvability.
Contributors:J. David Aponte, W. Scott Armbruster, Geir H. Bolstad, Salomé Bourg, Ingo Brigandt, Anne Calof, James M. Cheverud, Josselin Clo, Frietson Galis, Mark Grabowski, Rebecca Green, Benedikt Hallgrímsson, Thomas F. Hansen, Agnes Holstad, David Houle, David Jablonski, Arthur Lander, Arnaud LeRouzic, Alan C. Love, Ralph Marcucio, Michael B. Morrissey, Laura Nuño de la Rosa, Øystein H. Opedal, Mihaela Pavličev, Christophe Pélabon, Jane M. Reid, Heather Richbourg, Jacqueline L. Sztepanacz, Masahito Tsuboi, Cristina Villegas, Marta Vidal-García, Kjetil L. Voje, Andreas Wagner, Günter P. Wagner, Nathan M. Young
... The African and Madagascan species have been moderately well studied in terms of ecology and reproduction, although these studies also attempted to address questions about floral evolution and biogeographic history (e.g. Armbruster and Mziray 1987;Armbruster and Steiner 1992;Armbruster 1993Armbruster , 1994Armbruster et al. 1993Armbruster et al. , 2009Armbruster et al. , 2012Armbruster and Baldwin 1998;Plebani et al. 2015). ...
... Despite the great morphological variation, most Dalechampia can be easily recognized by their pseudanthial inflorescences being subtended by pairs of often showy involucral bracts (Webster and Armbruster 1991). The pseudanthium comprises a staminate pleiochasium with four to about 50 staminate flowers and a separate subinflorescence of one to three pistillate flowers (Pax and Hoffmann 1919;Armbruster et al. 1993;Webster 2014). The most recent synopsis of Neotropical species was published by Webster and Armbruster (1991). ...
Abstract—A new species of Dalechampia from southeastern Brazil, belonging to Dalechampia sect. Dioscoreifoliae, is described and illustrated here. Dalechampia margarethiae is a twining vine occurring exclusively in Esp´ırito Santo state. Its pseudanthia are similar to those of D. peckoltiana and D. pentaphylla, but D. margarethiae differs in a set of important characters, including having cylindrical, down-curved style tips, staminate flowers at anthesis having unreflexed sepals with stamens born on unelongated columns, whitish floral resin, and simple, entire, cordate leaves.
For the ongoing revision of Dalechampia sect. Dioscoreifoliae, we proceed with the lectotypification of D. juruana, D. luetzelburgii, D. schottii and D. schottii var. trifoliolata.
Revisionary studies of Dalechampia sect. Dalechampia have revealed the need to lectotypify D. colorata and that it represents a distinct species rather than a synonym of D. tiliifolia. Dalechampia karsteniana is interpreted to be a synonym of D. colorata.
In his treatise on the structure and fertilization of flowers, Sprengel (1793) described in great detail how the structures of flowers are designed for efficient function in attracting pollinating insects and placing pollen on, and receiving it from, them. Sprengel also noted that there may be conflicting requirements on floral design: Flowers also need to protect pollen and nectar from rain. Flower design must therefore represent a compromise between these competing functions. Thus, Sprengel anticipated an area of modern interest: the role of constraints and adaptive compromise in the evolution of morphology (see review by Arnold, 1992). The focus of Sprengel’s book, however, was on the optimality of floral design for efficient pollination.
Three new species of Dalechampia are described. Two are placed in section Rhopalostylis and the third is placed in a new section Brevicolumnae. The phylogenetic relationships among the species of the two sections and the species' relationships to members of other sections are estimated. Section Rhopalostylis appears to be paraphyletic, but recognition of additional sections is unwarranted at this time. Descriptions and key to the 10 species in the two sections are provided. Pollination biology, ecology, phenology, and distribution, when known, are given for each species.
Floral morphology often directly influences interactions with pollinators, but less is known about the role of extrafloral structures. We studied the relationship between bract motility, floral structural specialization and
pollination in Dalechampia aff. bernieri, an endemic Madagascan species with floral structures indicating specialized buzz-pollination.Wemeasured circadian bract angles in 47 inflorescences from 11 plants of D. aff. bernieri; in addition, we recorded any flower-visiting insects observed. The inflorescences hadmotile bracts with mean angles varying from about 50° at 00h00 to about 90° at 10h45. They were visited by buzz-pollinating Nomia viridilimbata bees (Halictidae), but also by non-buzz-pollinating Liotrigona bees (Apidae). The temporal pattern of bractmotility observed in D. aff. bernieri may
represent an extra-floral specialization to reduce visitation by non-pollinating visitors while maximizing visitation by diurnal buzz-pollinating bees.
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