Madagasikaria (Malpighiaceae): a new genus from Madagascar with implications for floral evolution in Malpighiaceae

Madagasikaria andersonii is described here as a new genus and species of Malpighiaceae from Madagascar. The phylogenetic placement of Madagasikaria was estimated by using combined data from ndhF and trnL-F chloroplast sequences and phytochrome (PHYC) and ITS nuclear sequences. It forms a strongly supported clade with the Malagasy endemic genera Rhynchophora and Microsteira. Despite nearly identical floral morphology among species in this clade (here called the madagasikarioid clade), these genera are easily distinguishable on the basis of their fruits. The schizocarpic fruits of Madagasikaria have distinctive mericarps. Each mericarp has a lateral wing, which completely encircles the nut, and a peculiar dorsal wing, which folds over on itself. The morphology of this fruit suggests that the homology of the unusual wing in Rhynchophora is lateral in nature and represents a reduced wing similar to the lateral wing in Madagasikaria. Taxa in the madagasikarioid clade all appear to be morphologically androdioecious and functionally dioecious, producing both staminate and "bisexual" (i.e., functionally carpellate) individuals. This condition appears to be exceedingly rare in flowering plants and has important implications for floral evolution within Malpighiaceae. Neotropical Malpighiaceae are pollinated by specialized oil-collecting anthophorine bees of the tribe Centridini and exhibit highly conserved floral morphology despite tremendous diversity in fruit morphology and habit. These oil-collecting bees are absent from the paleotropics, where most members of the Malpighiaceae lack both the oil glands and the typical floral orientation crucial to pollination by neotropical oil-collecting bees. The madagasikarioids represent one shift from the neotropical pollination syndrome among Old World Malpighiaceae.     

New taxa of Malpighia (Malpighiaceae) from Mexico and the West Indies

Malpighia romeroana var.nayaritensis is described from Nayarit, México, andM. albiflora subsp.antillana andM. nummulariifolia subsp.oblongifolia from the West Indies.     

A new species of Byrsonima (Malpighiaceae) from Panama

Byrsonima dressleri is newly described as endemic to the low cloud forests of Panama adjacent to the Canal Zone. Its closest relationship appears to be with those taxa of the Guayana Highland and Amazonia.     

A new species of Jubelina (Malpighiaceae) from Central America

The first species of Jubelina known from Central America is namedJubelina wilburi, described, illustrated, and compared with its nearest relative,J. uleana of Peru.     

Three new species of Hiptage (Malpighiaceae) from Thailand

Three new species, Hiptage calcicola, H. gracilis , and H. monopteryx are described. A key to the species of Hiptage found in Thailand is provided.     

New evidence of floral elaiophores and characterization of the oil flowers in the subtribe Oncidiinae (Orchidaceae)

Elaiophores seems to be uncommon in Orchidaceae; however, the number of known species with floral oil glands has increased in recent years, principally in Oncidiinae. Oil rewards are used by bees of the tribes Centridini, Tapinotaspidini and Tetrapediini. Our aims were to identify the presence of elaiophores and to describe their structure in species of Gomesa, Grandiphyllum and Trichocentrum, and to compare our results with other studies of elaiophores in Oncidiinae. We selected a set of characters presumably associated with oil production in flowers of Oncidiinae, which were evaluated using a cluster analysis to identify different floral morphologies of the oil flowers. The correlation between morphological types of oil flowers and species of pollinators was examined. The cluster analysis distinguished two groups of species, one of them principally linked with pollination by bees of genus Centris and the other type associated to species of Paratetrapedia and Tetrapedia. The evaluation of these results into a phylogenetic framework of the Oncidiinae, adding more evidence that species of this subtribe with similar floral morphology associated with floral oil secretion arise in many independent clades, in parallel evolution with the oil-bee pollination.     

风筝果镜像花的雌雄异位变化及传粉生态型的形成

亚洲特有植物风筝果(Hiptage benghalensis)镜像花(mirror-image flowers)的雌雄异位变化极大, 柱头与可育花药的空间距离在海南岛与云南西双版纳种群仅有2-4 mm, 而在贵州及云南东南部种群可达10-12 mm。为验证 “镜像花雌雄异位的变化是各个地理种群受到传粉昆虫体型大小选择的结果”假说, 本文开展了传粉生态学与分子生物学研究, 探讨风筝果不同地理种群的雌雄异位变化是否与当地传粉者体型相关, 是否有着遗传基础, 以及是否形成了“传粉生态型”(pollination ecotype)。结果表明, 雌雄异位程度大的贵州种群和云南东南部种群, 其传粉者也是体型较大的木蜂(Xylocopa nasalis)和熊蜂一种(Bombus sp.); 雌雄异位程度小的海南岛种群和云南西双版纳种群的传粉者则是体型较小的大蜜蜂(Apis dorsata)、西方蜜蜂(A. mellifera)。除了雌雄异位的明显分化(F = 53.69, P < 0.01)之外, 花柱长度也在这两类种群之间差异显著(F = 12.5, P < 0.05), 与传粉昆虫身体长度密切相关。通过叶绿体ycf1b、rbcL和细胞核ITS 3个DNA片段的序列分析, 由大型蜂传粉的雌雄异位程度较大的3个种群(贵州和云南东南部种群)遗传关系极近, 与小型蜂传粉种群(雌雄异位较小的海南岛种群和云南西双版纳种群)存在明显的遗传分化。这些结果显示, 风筝果不同地理种群的镜像花雌雄异位程度的变化可能是适应局域不同体型大小的传粉昆虫的选择结果, 而且种群间出现了基因流的隔断, 可能与大型蜂、小型蜂传粉的两种生态型有关。镜像花通过雌雄异位的变化适应不同地域的传粉者而形成传粉生态型, 这种传粉生态型及其传粉隔离机制可能是风筝果属物种形成与维持的一个重要原因。     

A new species of Hiptage (Malpighiaceae) from Nujiang Gorge,southwest China

Hiptage lushuiensis, a new species from the Hengduan Mountains, northwestern Yunnan Province, China, is described and illustrated here. This species was found growing at the margin of an open forest in the Nujiang Gorge of Lushui City. Hiptage lushuiensis is distinctive for its pink petals, 2 or more calyx glands, and large and pink samara with white hairs. This species is isolated in the deep gorge (25°51′N, 98°51′E, altitude 917 m), at the northern edge distribution range of the genus. These distinctive morphological differences and the geographic isolation suggest a history of long-distance dispersal and allopatric speciation. Hiptage lushuiensis has a shorter filament but larger herkogamy than related species, suggesting that H. lushuiensis may have adapted to other pollinators with short but fat body such as Amegilla or Bombus spp.     

A new species of Heteropterys (Malpighiaceae) from the semideciduous forests of Bahia, Brazil

Heteropterys andersonii, related to seriesMetallophyllis Nied., is described as new and illustrated.

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Resumen   Heteropterys andersonii, relacionada a sérieMetallophyllis Nied., é descrita como nova e ilustrada.

     

A presumed case of functional convergence between the flowers of Schizolobium parahyba (Fabaceae) and species of Malpighiaceae

Flowers of Malpighiaceae have a flag petal with a sturdy base that Centridini bees clasp with their mandibles to free their legs and thus be able to harvest oil. We found that the yellow, nectariferous flowers of Schizolobium parahyba (Fabaceae) have a forward-flexed upper petal with a sturdy claw and an adnate filament. Two Centris species were among the most frequent bee visitors to S. parahyba flowers. These bees clasped the adnate filament and the claw of the upper petal with their mandibles and extended their mouthparts into the corolla to take nectar. During the visit they leaned on, or loosely grabbed, the stamens. Blooming in the same area and period were two yellow-flowered Stigmaphyllon species (Malpighiaceae) whose pollen was also found on loads carried by the Centris bees. The flexion and the sturdiness of the upper petal claw of Schizolobium parahyba flowers may be viewed as a trait that suits the mandible clasp of Centris bees. Although this clasp is not needed when the bees visit S. parahyba flowers, it is vital when the bees exploit flowers of the Malpighiaceae. We suggest that the sturdy claw and the adnate filament of S. parahyba may be viewed as an instance of presumed functional convergence with the upper petal of Malpighiaceae.     

Five new species of Heteropterys (Malpighiaceae) from Central and South America

Five-new taxa ofHeteropterys H. B. K. subsect.Aptychia Nied. are described, illustrated, and mapped:H. andina from Peru;H. minutiflora from Costa Rica; andH. bullata, H. capixaba, andH. oberdanii, from the Atlantic coastal forest of Brazil. The affinities and diagnostic characters of each species are discussed.     

Accelerated rates of floral evolution at the upper size limit for flowers

Evolutionary theory explains phenotypic change as the result of natural selection, with constraint limiting the direction, magnitude, and rate of response [1]. Constraint is particularly likely to govern evolutionary change when a trait is at perceived upper or lower limits. Macroevolutionary rates of floral-size change are unknown for any angiosperm family, but it is predicted that rates should be diminished near the upper size limit of flowers, as has been shown for mammal body mass [2]. Our molecular results show that rates of floral-size evolution have been extremely rapid in the endoholoparasite Rafflesia, which contains the world's largest flowers [3]. These data provide the first estimates of macroevolutionary rates of floral-size change and indicate that in this lineage, floral diameter increased by an average of 20 cm (and up to 90 cm)/million years. In contrast to our expectations, it appears that the magnitude and rate of floral-size increase is greater for lineages with larger flowered ancestors. This study suggests that constraints on rates of floral-size evolution may not be limiting in Rafflesia, reinforcing results of artificial- and natural-selection studies in other plants that demonstrated the potential for rapid size changes [4-6].     

A New Species of Pterandra (Malpighiaceae) from the Guayana Highland

Pterandra sericea, a new species from southeastern Venezuela and western Guyana, is described, illustrated, and compared with its nearest relative,P. flavescens, another species of the Guayana Highland.     

Barnebya,A new genus of Malpighiaceae from Brazil

The new genusBarnebya is described and illustrated and its systematic position in the Malpighiaceae is discussed, especially its similarity in some respects to the primitive subfamily Byrsonimoideae and in other respects to the Old World genusAcridocarpus. Two species are recognized,B. dispar comb. nov. andB. harleyi sp. nov.; these are described and illustrated and a key is provided for their distinction.     

A novel chlorinated diphenyl ether from Byrsonima microphylla (Malpighiaceae)

The isolation is described of an unusual chlorinated diphenyl ether named methyl 3,5-dichloro-6-(6-hydroxy-4-methoxy-3-methoxycarbonyl-2-methylphenoxy)-2-hydroxy-4-methylbenzoate that was obtained from the trunk of Byrsonima microphylla (Malpighiaceae). The structure was elucidated by a spectroscopic data analysis, and the presence of this compound in heartwood was confirmed by HPLC and HPTLC analyses.     

Impacts of floral gender and whole-plant gender on floral evolution in Ecballium elaterium (Cucurbitaceae)

Investigation of gender specialization in plants has led to several theories on the evolution of sexual dimorphism: reproductive compensation, based on enhanced reproductive efficiency with gender specialization (flowers should be larger on dioecious plants); Bateman's Principle, based on sex-specific selection (display for pollinator attraction in males and seed set in females); and intersexual floral mimicry, based on mimicry of a reward-providing gender by a non-reward providing gender (reduced dimorphism in dioecious plants due to increased spatial separation of male and female flowers). These theories were evaluated in Ecballium elaterium, which contains two subspecies, elaterium (monoecious) and dioicum (dioecious). Our results show that flowers of the dioecious subspecies are larger and allocate more to reproductive organs than do flowers of the monoecious subspecies. Both subspecies are sexually dimorphic (male flowers larger than female flowers). Variance in flower size among populations is greater in the dioecious subspecies. Finally, there is sufficient genetic variation to enable ongoing response to selection; genetic correlation constraints on independent response of female and male flowers may be stronger in the monoecious subspecies. Our findings provide support for aspects of all three theories, suggesting that the evolution of floral dimorphism is based on a complex interplay of factors.     

New Passalora species on Peixotoa (Malpighiaceae) from the Brazilian Cerrado

Four new Passalora species were found on leaves of Cerrado native plants of the genus Peixotoa (Malpighiaceae). Two of the new Passalora species (P. peixotae-reticulatae and P. cerradensis) belong in Section Mycovellosiella, while P. peixotoae-goianae and P.brasilianensis belong in Section Phaeoramularia.     

Floral organogenesis and floral evolution of the Lecythidoideae (Lecythidaceae)

The subfamily Lecythidoideae of Lecythidaceae (Brazil nut family) is a dominant group in neotropical forests, especially those of Amazonia. New World members of the family have large showy flowers that are either polysymmetric or monosymmetric. In this study, floral organogenesis of all 10 neotropical genera was examined using SEM. Our observations of floral development are put into the context of a molecular phylogeny based on sequences of the ndhF and trnL-F genes (Am. J. Bot. 94: 289-301). Floral evolution of the subfamily is explained as having undergone four different levels of complexity in regard to floral symmetry. The basal most genera, Grias and Gustavia, have polysymmetric flowers. At level two, represented only by Couroupita, monosymmetry is established through the expression of abaxial dominance and the development of an androecial hood; at this level, abaxial dominance impacts the perianth and androecium, but not the gynoecium. At the third level, monosymmetry is developed in groups of Couratari and Cariniana domestica; but, in the Allantoma/Cariniana decandra lineage, a reversal back to polysymmetric flowers, resulting from a gradual weakening of abaxial dominance, and the loss of the hood has occurred. Finally, in level four, including Bertholletia, Corythophora, Eschweilera, and Lecythis, monosymmetry is so strongly expressed that the gynoecium is also influenced by abaxial dominance. In this group, the hood is complicated in both structure and function, and the floral axis is changed from straight to slightly inclined. This study demonstrates that the development of floral abaxial dominance is the proximate cause of monosymmetry in the Lecythidoideae. We suggest that monosymmetric flowers are more efficiently pollinated, and therefore the bees and bats that pollinate the monosymmetric flowers in this group are ultimately responsible for the monosymmetry.     

Developmental morphology of female flowers of Gyrostemon and Tersonia and floral evolution among Gyrostemonaceae

Floral simplifications and specializations in the evolution of Gyrostemonaceae have confused the systematics of the family. Recent phylogenetic analyses have demonstrated their placement among Capparales. This investigation presents a phylogenetic analysis of Gyrostemonaceae, demonstrating that Codonocarpus and Gyrostemon form a clade that is the sister group of Cypselocarpus, Tersonia, and Walteranthus. These phylogenetic results and data on development of Gyrostemon and Tersonia are used to discuss the morphology and evolutionary diversification of female flowers of Gyrostemonaceae. The uniseriate perianth of Gyrostemonaceae consists of four to eight tepals with an unusual lateral to median developmental sequence. The female flowers of Gyrostemon and Tersonia display no distinctive evidence of an androecium, although the former has late-forming, primordium-like structures positioned between the tepals and gynoecium that may be the vestiges of either a second perianth series or the androecium. The gynoecium of Gyrostemonaceae is syncarpous, although the two main clades in the family differ in the expression of ovarian synorganization. The Codonocarpus–Gyrostemon clade is unusual in having largely separate carpels that are only syncarpous because the ventral side of each is formed by the flank of the floral apex. All Gyrostemonaceae, however, incorporate the flank of the floral apex as the ventral side of the carpel, and this is the location of ovule development. On the basis of its placement in a clade that includes Tersonia and Walteranthus, the uniloculate and uniovulate gynoecium of Cypselocarpus may be pseudomonomerous. All Gyrostemonaceae have large stigmas that are typical of anemophilous taxa, and they differ from most other Capparales in this attribute. Among Capparales, Gyrostemonaceae may be most similar to Ochradenus (Resedaceae), which also appears to be anemophilous. It is unclear whether the similarities of Ochradenus and Gyrostemonaceae are homologies, indicative of a close relationship between the two groups, or evolutionary parallelisms associated with separate shifts to anemophily.