A synopsis of the neotropical species of Dalechampia (Euphorbiaceae)

WEBSTER, G. L. & ARMBRUSTER, W. S., 1991. A synopsis of the neotropical species of Dalechampia ( Euphorbiaceae ). The characters used in inferring phylogenetic relationship in Dalechampia are discussed, and a consistent terminology is devised for the parts of the distinctive pseudanthial inflorescences. The infrageneric classification is radically modified, with the 92 provisionally accepted binomials for the neotropical taxa referred to six sections: Rhopalostylis, Dioscoreifoliae, Cremophyllum, Coriaceae, Tiliifoliae and Dalechampia. As here interpreted, section Dalechampia includes 53 species in five subsections; one new subsection, Convolvuloides , is described.     

Revision of Maranta subgen. Maranta (Marantaceae)

Maranta subgen. Maranta includes species related to M. arundinacea L. It is characterized by aerial shoots with a strong monopodial tendency, absence of root tubers, simple inflorescences or few-branched, often diffuse synflorescences, florescences with few, herbaceous spathes, and comparatively large, distinctly pedicellate flowers. There are occasional exceptions to all these characters. Most species are partial selfers, only two or three being allogamous. Sixteen species are recognized, eight of which are new: M. linearis, M. sobolifera, M. lindmanii, M. zingiberina, M. incrassata, M. rupicola, M. amazonica , and M. tuberculata. The new species are described, and all species are defined and discussed, data being given about distribution and habitat. Growth habit and rhizome structure are essential taxonomic characters, but leaf shape and indument distribution are more useful characters for routine identification. Of the species referred to subgen. Automaranta by Schumann in Das Pflanzenreich, three are excluded: M. cordata, M. pohliana , and M. foliosa.     

Decorative sterile flowers in nine Japanese species of Viburnum (Adoxaceae) and their influence on pollinator visits

Framed inflorescences are unique arrangements in which a cluster of small fertile flowers is surrounded by several larger, decorative sterile flowers. Viburnum (Adoxaceae) species vary in their inflorescence arrangements; some species exhibit framed inflorescences, whereas others do not. We hypothesize that the decorative flowers increase the pollinator-attracting functions of the inflorescences; as proved by previous studies, they additionally function as landing-sites for pollinators. To test our hypotheses, field manipulation experiments were carried out for nine Viburnum species, three with inherently framed inflorescences and six without them: sterile flowers were removed and mounted on species with and without framed inflorescences, respectively. Results show that inflorescences with decorative flowers had higher visit rates than inflorescences without them, and that insect flower visitors did not show landing preference for either flower type. These results suggest that decorative flowers appeared only in a subset of Viburnum species to increase their pollination chances by, mainly, enhancing the attractiveness of the inflorescence. It is likely that species without framed inflorescences use other attraction-enhancing mechanisms, such as a high flowering synchrony within a single cluster of fertile flowers, a trait found in most studied species without decorative flowers.     

Production of food bodies on the reproductive organs of myrmecophytic Macaranga species (Euphorbiaceae): effects on interactions with herbivores and pollinators

In protective ant–plant mutualisms, plants offer ants food (such as extrafloral nectar and/or food bodies) and ants protect plants from herbivores. However, ants often negatively affect plant reproduction by deterring pollinators. The aggressive protection that mutualistic ants provide to some myrmecophytes may enhance this negative effect in comparison to plant species that are facultatively protected by ants. Because little is known about the processes by which myrmecophytes are pollinated in the presence of ant guards, we examined ant interactions with herbivores and pollinators on plant reproductive organs. We examined eight myrmecophytic and three nonmyrmecophytic Macaranga species in Borneo. Most of the species studied are pollinated by thrips breeding in the inflorescences. Seven of eight myrmecophytic species produced food bodies on young inflorescences and/or immature fruits. Food body production was associated with increased ant abundance on inflorescences of the three species observed. The exclusion of ants from inflorescences of one species without food rewards resulted in increased herbivory damage. In contrast, ant exclusion had no effect on the number of pollinator thrips. The absence of thrips pollinator deterrence by ants may be due to the presence of protective bracteoles that limit ants, but not pollinators, from accessing flowers. This unique mechanism may account for simultaneous thrips pollination and ant defense of inflorescences.     

The inflorescences structure of Cyperus L. section Luzuloidei Kunth (Cyperaceae)

In the present work the inflorescences of 12 species of Cyperus sect. Luzuloidei Kunth sensu Kükenthal were analyzed using the methodology and terminology of Troll's school. All the inflorescences studied are polytelic (indeterminate). The inflorescences are anthela-like or capitate, and can be terminal or pseudolateral. Below the main florescence a paracladial zone is present. In this zone three types of branching were observed, i.e. normal, accessory-axillar and prophyllar branching, whose position vary among the different species. In the paracladial zone a subzone of long paracladia and a subzone of short paracladia were observed. In the short paracladial subzone the spikelets are clustered in fascicles, which can be serial, prophyllar or mixed. Variation in length and position of pherophylls, length of prophyll, number and degree of branching were noticed. The systematic value of the inflorescences in the section Luzuloidei is discussed.     

Flowering dynamics of Orchis morio L. and Herminium monorchis (L.) R.Br, at two sites in eastern England

Information taken from two long-term demographic studies on Orchis morio L. and Herminium monorchis (L.) R.Br, is used to explore some of the factors which influence flowering. The proportion of plants which flowered each year varied considerably between species, flowering in O. morio exceeding 40% in all years except one over an 18 year period; over a 30 year period (1966–95), the number of plants of Herminium in flower never exceeded 36% of the population and no inflorescences were produced in 1977 and 1991. The relationship between flowering in Herminium in a given year and the monthly rainfall and temperature for the current and 3 previous years was analysed using logistic regression. Best fits were obtained using data for the summer months in the previous year, with an increasing flowering rate with rainfall and a decline with temperature. It is hypothesized that drought and high temperatures in the summer reduce leaf area and cause premature senescence and the death of leaves, with the result that not enough carbohydrates are stored to enable plants to support or initiate inflorescences the following year. For species such as Orchis morio which produce leaves in the autumn and remain green, summer drought causes no problems as they have no above ground organs. Factors which influence flowering in this species are as yet unknown.     

Thrips pollination of androdioecious Castilla elastica (Moraceae) in a seasonal tropical forest

Androdioecy is a rare sexual system in nature, as predicted theoretically. Among the androecious species reported so far, Castilla elastica (Moraceae) is unique in that flowers are unisexual and staminate and pistillate flowers on cosexual plants are produced on different inflorescences. In addition, inflorescence structure of staminate inflorescences on males and staminate and pistillate inflorescences on cosexes is markedly different. Staminate inflorescences on males are bivalvate, while staminate inflorescences on cosexes are "fig-like" and urceolate. Pistillate inflorescences are discoidal. The difference may reflect different roles and requirements of the three inflorescences in pollination and protection from herbivores. This study reports thrips pollination of C. elastica, demonstrated by a pollinator introduction experiment. Thrips pollination of the species may be an example of mutualism originating from plant-herbivore interactions. In the Moraceae, shifts from simple herbivores on flowers to pollinators might have occurred many times, evolving into diverse pollination systems including the fig-fig wasp mutualism. The family, of which little is known about pollination systems, provides interesting and unique opportunities to study evolution of pollination systems and roles of nonpollinating associates of inflorescences.     

Limonium cedrorum sp. nov. (Plumbaginaceae) from Lebanon

Limonium cedrorum Domina & Ramondo, a new species belonging to the L. palmare aggr., is described and illustrated from the inland near Becharre (Lebanon). Its relationships with morphologically close taxa are discussed. Limonium cedrorum differs from L. sieberi and L. postii mainly by looser inflorescences and larger flowers. It differs from L. galilaeum by longer outer bract and longer scale below the first inflorescence branch, few sterile branches, thicker base of the inflorescence and denser spikes, and from L. graecum by the shape of the inflorescence, longer basal internodes and the shape of the calyx.     

Functional significance of the dark central floret of Daucus carota (Apiaceae) L.; is it an insect mimic?

In Daucus carota L. (Apiaceae) the florets comprising the central umbellet of inflorescences are usually pink or dark purple, presenting a marked contrast to the surrounding umbellets, which are generally white. The number of dark florets varies, and some inflorescences have no dark florets. It has been proposed that the dark florets function as an insect mimic, and in so doing serve to attract insects to the flower. In contrast, other authors, Darwin included, suggest that they are functionally redundant. The present study examined whether the dark florets attract insects, and also whether this effect can be replicated by replacing these florets with an insect. At the study site in Portugal the predominant insect visitor was the beetle Anthrenus verbasci L. (Dermestidae), which is similar in size and shape to the dark florets. Large inflorescences and those with more dark florets attracted more beetles than small inflorescences and those with fewer or no dark florets. Inflorescences with the dark florets removed attracted fewer beetles visitors compared with intact inflorescences. Inflorescences in which the dark florets were replaced with one or a cluster of five dead, freeze-killed A. verbasci attracted more beetles than inflorescences from which the dark florets had been removed. Replacement of the dark florets with a relatively large Meloid beetle resulted in the attraction of markedly fewer A. verbasci . We conclude that the dark florets can act as an insect attractant for some insect groups by acting as an insect mimic, and that they are adaptive, in contrast to the speculations of Darwin.     

A comparison of floral resource exploitation by native and invasive Argentine ants

Ants are often considered antagonists when they visit flowers because they typically steal nectar without providing pollination services. Previous research on ant–flower interactions on two species of South African Proteaceae in the Cape Floral Kingdom revealed that the invasive Argentine ant (Linepithema humile), but not native ants, displace other floral arthropod visitors. To determine how common Argentine ant use of inflorescences is, how Argentine and native ant visits differ in the numbers they recruit to inflorescences, and what factors may affect Argentine and native ant foraging in inflorescences, I surveyed 723 inflorescences in 10 species in the genera Protea and Leucospermum across 16 sites and compared ant presence and abundance in inflorescences with abundance at nearby cat food and jam baits. Argentine ants were the most commonly encountered ant of the 22 observed. Argentine ants, as well as six species of native ants were present in all inflorescences for which they were present at nearby baits. Mean Argentine ant abundance per inflorescence was 4.4 ± 0.84 (SE) ants and similar to that of Anoplolepis custodiens and Crematogaster peringueyi, but higher than observed for the other most commonly encountered native ants, Camponotus niveosetosus and Lepisiota capensis. Both Argentine ants and A. custodiens were more likely to be found foraging in spring and under humid conditions, and in inflorescences closer to the ground, with lower sucrose concentrations, and with a greater proportion of open flowers. Argentine ants were more likely to be found in Protea inflorescences, whereas A. custodiens and L. capensis more often visited Leucospermum inflorescences. Considering its displacement of floral arthropods and widespread use of Proteaceae inflorescences, the Argentine ant could be posing a serious threat to plant and pollinator conservation in this biodiversity hotspot.     

Evolution and homology of bird pollination syndromes in Erythrina (Leguminosae)

Erythrina L. (Leguminosae: Phaseoleae) is a pantropical genus of over 100 species, all of which are either hummingbird or passerine pollinated. Phylogenetic hypotheses based on morphological and chloroplast DNA restriction site characters suggest that shifts from passerine to hummingbird pollination have occurred a minimum of four times in the genus. In hummingbird-pollinated species the inflorescences are held upright, the flowers are arranged radially along the axis, and the narrow standard petal is conduplicately folded to form a pseudotube. In most of the passerine-pollinated species, the inflorescences are held horizontally, the flowers are secund, and the standard petal is open so that the nectar and androecium are easily visible and accessible. Nectar amino acid concentrations and sucrose to hexose ratios are closely associated with pollination mode. Despite the general resemblance in flower and inflorescence morphology among species with the same pollination type, homology assessment reveals that petal morphology and size, and calyx and pollen morphology differ. Morphological characters, even if comprising modifications associated with adaptive pollination systems, therefore provide useful phylogenetic information.     

Why be a rewarding trap? The evolution of floral rewards in Arum (Araceae), a genus characterized by saprophilous pollination systems

Plant species of the genus Arum typically have lure-and-trap pollination systems that are saprophilous (i.e. attracting flies or beetles searching for breeding sites in decaying organic matter). They have been assumed to always attract and trap their pollinators by deception because the inflorescences provide unsuitable breeding grounds for pollinators. The present study explored the possibility that one species, Arum creticum Boiss. & Heldr., which has yellow, sweet-smelling inflorescences, rewards its pollinators and that this increases its success in attracting pollinators over its close relative, Arum idaeum Coust. & Gadoger. The relationship between rewards provided, floral structure, insect attraction, and pollen import and export was examined in two naturally occurring sympatric populations of A. creticum , A. idaeum , and their natural hybrids. The results showed that plants providing more pollen were visited by larger numbers of females of a mining bee Lasioglossum marginatum Brullé as well as adults and nymphs of a hemipteran bug Dionconotus cruentatus creticus Heiss. In A. creticum , L. marginatum was found to be a better outcrossing vector than D. cruentatus in areas where both pollinators occurred because L. marginatum individuals carried more pollen on their bodies and travelled greater distances between inflorescences, thus increasing the potential for outcrossing. The finding that floral rewards may result in increased fitness, compared to nonrewarding systems that rely on attracting saprophilic pollinators, suggests that it is possible for rewarding species to evolve from saprophilous systems.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 257–268.     

Metamerism,heterochrony, and inflorescence morphology of the Pithecellobium-complex (Leguminosae: Mimosoideae: Ingeae)

The diverse inflorescence morphology of species in the Pithecellobium-complex is shown to be a result of: 1) the organization of the components of the inflorescence and their relative positions; 2) the hierarchical relationship of the axes of the inflorescences and the position they assume in total tree architecture; and 3) heterochronic development of the components of the inflorescence. It is shown that the typological system of nomenclature of inflorescences leads to false assumptions of homology and therefore must be discarded. The morphology of inflorescences is discussed in terms of metamerism, and the term Repeating Growth Unit (RGU) is introduced and is defined as the smallest complete sequence of metamers produced by a meristem. A module is defined as the sequence of RGUs produced by a meristem. An inflorescence is defined as that sequence of metamers in an RGU which participates in the production and/or presentation of flowers and fruit. Heterochrony, proleptic and sylleptic buds, and shoot dimorphism are discussed and their role in modifying inflorescence morphology in the Pithecellobium-complex is illustrated. Examples from the Pithecellobium-complex are provided which demonstrate the various modifications of the inflorescence that result from the interaction of these various phenomena.     

The Bizarre Inflorescence of Norantea brasiliensis (Marcgraviaceae): Visits of Hovering and Perching Birds1

The pollination biology of Norantea brasiliensis (Marcgraviaceae) was studied in the rain forest of southeastern Brazil. This plant presents bizarre, brush-type racemous inflorescences bearing numerous flowers and extrafloral cup-shaped nectaries. Flower anthesis is diurnal, nectar production is continuous and copious, and the sticky pollen is readily removed by visitors during the first morning hours. The ruby-coloured inflorescences were visited by eight species of hummingbirds (Trochilidae), and 10 species of passerine birds (three Coerebidae and seven Thraupidae). Hummingbirds hovered while probing for nectar and touched flowers occasionally, whereas passerine birds perched and made contact with flowers habitually. Due to differences in flower-visiting and general foraging behaviour, perching birds act as better pollen vectors than hovering birds. The inflorescence of Norantea brasiliensis seems well fitted for pollination by passerine birds, and the hexose-dominated nectar supports this idea. Pollination syndrome trends within Marcgraviaceae may stem from insect-pollinated, condensed and spike-like inflorescences which would give rise to bird-pollinated, brush-type inflorescences. From the same basic condensed inflorescence, bat-pollinated umbelliform inflorescence may be derived from bird-pollinated, pendulous and corymb-like inflorescences. These postulated inflorescence types are found among the extant species of Marcgraviaceae.     

Organographic and ontogenetic studies on the inflorescence ofLespedeza cuneata (Dum.-Cours.) G. Don (Leguminosae)

Structure of inflorescence and its variation were organographically and ontogenetically studied inLespedeza cuneata (Dum.-Cours.) G. Don. An axillary inflorescence of the species forms a compound inflorescence which is composed of three or four component inflorescences. Each component inflorescence bears four (rarely six), three, two, or one flowers. Based on the arrangement of inflorescence phyllomes, the component inflorescence with four flowers is interpreted as a pseudoraceme bearing two shortened lateral shoots (partial inflorescences) each of which has two flowers. The component inflorescence with one flower appears to be terminated by the flower and to compose the cyme. Organographic observations revealed that the terminally located flower is not truly terminal, but axillary in origin. Ontogenetic observations showed that the apices of component inflorescence and partial inflorescence exist in early developmental stages in spite of variation in the form of component inflorescence. The terminally located flower in the cyme-like inflorescence was thus demonstrated to be laterally borne on the partial inflorescence axis. The component inflorescence composing the cyme-like one inL. cuneata is a reduced form in the number of partial inflorescences and of flowers from the pseudoraceme. The cyme-like inflorescence inL. cuneata resembles the inflorescence ofKummerowia.