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Drawings and floral diagram of Dialium guianense. a. Floral diagram and formula. b. Mature stamens showing reflexed filaments and longitudinal anther dehiscence. c. Flower bud just prior to anthesis, sepals removed. d. Flower bud prior to anthesis. e. Detail of style and stigma. f. Compound leaf. g. Section of inflorescence showing cymose units. Vouchers: b, G.I. Manriquez 2649 (MO); c-e, Rabelo 3118 (NY); f, Coronado et al. 2026 (MO); g, Krukoff 6262 (MO).
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The Caesalpinioideae are widely variable in their floral ontogeny, and among caesalpinioids, members of the polyphyletic tribe Cassieae are particularly diverse. Within the Cassieae, the monophyletic Dialiinae clade is also marked by a high degree of organ loss, particularly in the largest genus, Dialium. The purpose of this work is to explore the...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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... Mature morphology (Fig. 4) This South American species produces thyrsoid inflorescences ( Fig. 4g). Pedicellate flowers are subtended by bracts and preceded by opposite, early-caducous bracteoles situated on the lower half of the pedicel (Fig. 4c). The pentamerous calyx is imbricate in bud (Fig. 4d), becoming reflexed at anthesis. Sepals are uniform at the base and tomentose on all surfaces. The corolla is absent (Fig. 4a). The androe- cium consists of two stamens in the adaxial lateral positions, situated along the rim of a broad receptacular disc. Anthers are basifixed, widely ovate, and have sagittate bases (Fig. 4b). Dehiscence is latrorse, along longitudinal slits, opening completely at the distal tip. The sessile carpel contains two ovules. It is densely velutinous and sits toward the abaxial side of the expanded receptacle (Fig. 4a, c). The slender, distally glabrous style curves adaxially, ending in a small, terete stigma (Fig. 4e). The fruit is a one-to two-seeded, indehis- cent drupe. Leaves are imparipinnately compound with alternate leaflet insertion (Fig. ...
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Native vegetation fragments embedded in anthropogenic landscapes are increasingly threatened by land‐use intensification. Managing disturbance regimes and nutrient inputs may help maintain species diversity in such remnants. Yet, it is unclear the extent to which changes in resource availability due to reduced capture by resident plants and/or incr...
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... A comparative floral ontogenetic study of Tachigali and related genera would be an interesting topic for future research, perhaps even the key to unveiling the floral homology in the tribe Sclerolobieae, as has previously been shown to be successful in revealing affinities in various other florally disparate legume genera (e.g., Tucker and Kantz 1997;Prenner and Klitgaard 2008;Zimmerman et al. 2013;Bruneau et al. 2014;Prenner et al. 2015;Prenner and Cardoso 2017). For example, in legume subfamily Detarioideae, which houses a large collection of florally diverse genera of predominantly tropical trees, new floral ontogenetic synapomorphies (Prenner and Cardoso 2017), as well as a remarkable evolutionary lability of some floral traits, have been revealed (Bruneau et al. 2014;Ojeda et al. 2019). ...
Despite recent advances in revealing the evolutionary history of speciose tropical plant clades, many species radiations are still poorly understood phylogenetically. One of these is the species-rich neotropical genus Tachigali (~ 90 spp.), a caesalpinioid legume lineage of mostly ant-housing canopy trees that has diversified in the tropical rainforest biome across the Andean foothills, Amazon basin, and Atlantic Coastal Forest of Brazil. It is also ecologically dominant across the fire-prone savanna vegetation of the Brazilian Cerrado. The taxonomic history of Tachigali has long been confounded with the genus Sclerolobium, with the two differing in floral symmetry. Here, we reconstruct the phylogeny of Tachigali using densely sampled Bayesian and maximum likelihood analyses of nuclear ribosomal (ITS/5.8S) and plastid (matK and trnL intron) DNA sequences for 67 species. All phylogenetic analyses support Tachigali as monophyletic. We recognize a broad circumscription of Tachigali encompassing species exhibiting both radially and bilaterally symmetrical flowers, and we suggest that the traditional generic concept of Sclerolobium should be abandoned. The poor resolution in the Tachigali phylogeny is suggestive of rapid diversification, which has been observed in other species-rich rainforest-inhabiting plant clades across the Neotropics.
... On the other hand, the reduction or proliferation of organs located in the perianth whorls, especially the petals, have been described and analyzed from an ontogenetic point of view, most commonly in species of Dialioideae (Falcão et al. 2020;Zimmerman et al. 2013), Detariodeae (Bruneau et al. 2014;Kochanovski et al. 2018;Pedersoli et al. 2010;Tucker 2000), Papilionoideae (Leite et al. 2015;Paulino et al. 2013), and other Caesalpinioideae species (Prenner 2004;Tucker 1988Tucker , 1990Tucker , 1992a. Regarding the mimosoid clade (with polysymmetric flowers, in contrast to monosymmetric flowers in previously mentioned clades), little is known about the ontogenetic pathways that lead to the reduction or proliferation of organs, especially of the perianth organs. ...
... In Fabaceae, some cases of extreme reductions of floral organs have been reported, such as Dialium L., Apuleia Mart., and Dicorynia Benth. (Dialioideae), (Falcão et al. 2020;Zimmerman et al. 2013), or subtle reductions of floral organs in Amhertsia Muro, Hymenaea L., and Copaifera L. (Detarioideae), in which two sepals of a pentamerous calyx are fused, leading to a tetramerous pattern in anthesis (Kochanovski et al. 2018;Pedersoli et al. 2010;Tucker 2000). Further, there is the case of species of basal lineages of Papilionoideae, in which the corolla undergoes extreme reduction to one petal or complete absence of petals (Leite et al. 2015;Moço and Pinheiro 1999;Paulino et al. 2013;Tucker 1990). ...
The genus Mimosa L. (Leguminosae; Caesalpinioideae; mimosoid clade), comprising more than 500 species, is an intriguing genus because, like other members of the mimosoid clade, it presents an enormous variation in floral characteristics and high merism lability. Thus, this study aimed to elucidate the floral development and identify which ontogenetic pathways give rise to merism variation and andromonoecy in Mimosa caesalpiniifolia, M. pudica, M. bimucronata, and M. candollei. Floral buds at various stages of development and flowers were collected, fixed, and processed for surface analysis (SEM). The development of the buds is synchronous in the inflorescences. Sepals appear simultaneously as individualized primordia in M. caesalpiniifolia and in reversed unidirectional order in M. bimucronata, with union and formation of an early ring-like calyx. Petal primordia appear in unidirectional order, with a noticeably elliptical shape in M. caesalpiniifolia. The wide merism variation in Mimosa results from the absence of organs from inception in the perianth and androecium whorls: in dimerous, trimerous, or tetramerous flowers, the additional organs primordia to compose the expected pentamerous flowers are not initiated. The haplostemonous androecium of M. pudica results from the absence of antepetalous stamens from inception. In the case of intraspecific variations (instabilities), there is no initiation and subsequent abortion of organs in the events of reduction in merosity. In addition, extra primordia are initiated in supernumerary cases. On the other hand, staminate flowers originate from the abortion of the carpel. Mimosa proved to be an excellent model for studying merism variation. The lability is associated with actinomorphic and rather congested flowers in the inflorescences. Our data, in association with others of previous studies, suggest that the high lability in merism appeared in clades that diverged later in the mimosoid clade. Thus, phylogenetic reconstruction studies are needed for more robust evolutionary inferences. The present investigation of ontogenetic processes was relevant to expand our understanding of floral evolution in the genus Mimosa and shed light on the unstable merism in the mimosoid clade.
... Androcalymma, together with the Asian genus Uittienia Steenis (1948: 418), are the only two genera of Dialioideae and one of the few in Fabaceae that have not been molecularly sampled in phylogenetic studies for the family so far, having its relationship with the other taxa of the group inferred only from morphological data (Dwyer, 1958;Koeppen, 1963;Zimmerman et al. 2017). Androcalymma is a potentially pivotal taxon to understand several morphological relationships within a subfamily characterized by intense floral variation and specializations (Tucker, 1998;Zimmerman et al., 2013;Falcão et al., 2020b;in prep). ...
... The presence of uncinate trichomes in the flower, as mentioned by Falcão et al., (2020b); here observed on anthers ( Figure 6I), margins of sepals and surface of gynoecium, which also has larger non-uncinate trichomes ( Figure 6N). Dicorynia presents uncinate trichomes on the anther surface (Falcão et al. 2022;In prep), Apuleia on the anthers, filaments, and hypanthium surfaces (Zimmerman et al., 2013;Falcão et al., 2020b), Distemonanthus on the sepals and anthers (Falcão et al., in prep), Dialium on anthers, carpels, and nectariferous disk (Tucker 1998;Zimmerman et al., 2013;Falcão et al., in prep), Uittienia also present such trichomes in their carpel and receptacle and Zenia in their anthers (Falcão et al., in prep). The first five genera form a clade (Figure 7) and the relations of the last two are not well known but this character can be a potential synapomorphy for all those genera except Zenia, on which it would be a possible example of convergence (Falcão et al., 2020b;present work;in prep). ...
... The presence of uncinate trichomes in the flower, as mentioned by Falcão et al., (2020b); here observed on anthers ( Figure 6I), margins of sepals and surface of gynoecium, which also has larger non-uncinate trichomes ( Figure 6N). Dicorynia presents uncinate trichomes on the anther surface (Falcão et al. 2022;In prep), Apuleia on the anthers, filaments, and hypanthium surfaces (Zimmerman et al., 2013;Falcão et al., 2020b), Distemonanthus on the sepals and anthers (Falcão et al., in prep), Dialium on anthers, carpels, and nectariferous disk (Tucker 1998;Zimmerman et al., 2013;Falcão et al., in prep), Uittienia also present such trichomes in their carpel and receptacle and Zenia in their anthers (Falcão et al., in prep). The first five genera form a clade (Figure 7) and the relations of the last two are not well known but this character can be a potential synapomorphy for all those genera except Zenia, on which it would be a possible example of convergence (Falcão et al., 2020b;present work;in prep). ...
Androcalymma Dwyer, a monospecific and morphologically unique genus on the legume subfamily Dialioideae, stands out as one of the less known genera of Fabaceae, not being molecularly sampled in phylogenetic studies of the family until now, which led to an uncertain position among other taxa in its clade. Androcalymma glabrifolium, endemic to a small and hardly accessible area in the Brazilian Amazon rainforest, was collected once in 1936 and never seen after that, even being conjectured as possibly extinct. Here we describe a recent expedition searching for this enigmatic and rare tree that brought to light an extant population of the species in an indigenous area where it still thrives. The fruits of Androcalymma are here described and illustrated for the first time, as also its flowers’ colors and several other new characters. Here we present its first photographic register, and its DNA is compared to other Dialioideae bringing a solid relationship with the also Amazonian genus Dicorynia, a grouping sustained here by many known and newly discovered morphological characteristics. SEM analyses of flowers and fruits, conservation assessments indicating the critically endangered situation of the genus, taxonomic descriptions, and geographic, systematic, and ecological comments are made.
... Furthermore, during field surveys, reproductive characteristics are generally not visible and only trunks and leaves can be observed. Leaves in Dialium can contribute to distinguishing species from each other [56]. For example, distinction of Dialium heterophyllum from other species in the Amazonian Basin is done by its reduced rachis and unifoliate to trifoliate leaves [20]. ...
During inventories of lesser-known timber species in eastern Gabon, a new Dialium morphospecies was discovered. To discriminate it from the two other 2–5 leaflets Dialium species, 25 leaf traits were measured on 45 trees (16 Dialium pachyphyllum, 14 Dialium lopense, 15 Dialium sp. nov.). Nine wood chemical traits, as well as infrared spectra, were also examined on harvestable trees (four Dialium pachyphyllum and four Dialium sp. nov.). This study revealed seven discriminant leaf traits that allowed to create a field identification key. Nine significant differences (five in sapwood and four in heartwood) in terms of wood composition were highlighted. The use of the PLS-DA technique on FT-IR wood spectra allowed to accurately identify the new morphospecies. These results provide strong support for describing a new species in this genus. Implications for sustainable management of its populations are also discussed.
... Detailed analysis of ontogenetic series indicates, that similar final condition (e.g., absence of petals) is conditioned by unequal degree of reduction. While there are no signs of corolla initiation in Cordyla, apetalous Swartzia, and Dialium (Tucker, 2003a;Zimmerman et al., 2013;Sinjushin, 2018), the primordia of four or five petals emerge but have no further development in Crudia and Amburana (Tucker, 2001;Leite et al., 2015). Sometimes rudimentary petals persist (Copaifera-Detarioideae) or rarely unfold (Ceratonia) (Tucker, 1992;Pedersoli et al., 2010). ...
... In fasciated flowers of Lupinus, paired stamens may emerge instead of solitary ones, and these pairs in one whorl alternate with single or twin stamens of the other whorl . Similar morphology, although untypical for legumes, is found in very unstable flowers of Mendoravia (Dialioideae) (Zimmerman et al., 2013). Two adaxial petals in Swartzia dipetala seemingly emerge from a joint blastozone, as well as two carpels in flowers of the same species. ...
The contemporary evolutionary developmental biology includes molecular phylogeny, studies on morphology and morphogenesis, genetics, and genomics. The most reliable conclusions about main trends of floral evolution can result from investigations of highly polymorphic group, which is precisely characterized from the positions of both modern systematics and molecular developmental biology. The legume family, Leguminosae, is a group of such kind. It demonstrates an outstanding variation in flower structure. The
ancestral floral structure in this family includes monosymmetry, pentacycly, pentamerous perianth and androecium, and a monomerous gynoecium. However, distinct evolutionary lineages resulted in origin of polysymmetric perianth, different patterns of staminal reduction or polymerization, as well as multicarpellate
gynoecium. A strikingly high level of homoplasy is found in Leguminosae. Besides the existing evolutionary tendency to stabilize floral structure, the exact “instability syndrome” evolved repeatedly, associated with a polysymmetry and characterized with a highly variable number and position of floral organs.
... Обращение к онтогенетическим данным показывает, что сходное конечное состояние, например отсутствие лепестков, обусловлено неодинаковой степенью редукции. Если у Cordyla, безлепестных Swartzia и Dialium нет никаких признаков заложения недостающих лепестков (Tucker, 2003a;Zimmerman et al., 2013;Sinjushin, 2018), то у Crudia и Amburana примордии четырех или пяти лепестков формируются, но не развиваются (Tucker, 2001;Leite et al., 2015). Иногда сохраняются (Copaifera, Detarioideae) или изредка развиваются (Ceratonia) рудименты лепестков (Tucker, 1992;Pedersoli et al., 2010). ...
... Так, при фасциации цветка у Lupinus вместо одиночных тычинок могут развиваться пары, и именно пары тычинок одного круга чередуются с одиночными или парными тычинками другого (Sinjushin et al., 2019). Сходная, хотя и совершенно не типичная для Бобовых картина наблюдается в очень нестабильных по числу органов цветках Mendoravia, Dialioideae (Zimmerman et al., 2013). Вероятно, производными единой бластозоны являются два адаксиальных лепестка и единой же -два плодолистика у Swartzia dipetala. ...
[This review will be also published in English soon. Русский текст доступен по запросу]
Современная эволюционная биология развития включает в свой инструментарий молекулярную филогению, изучение морфологии и морфогенеза, генетику и геномику. Эволюцию цветка удобно изучать на примере высокополиморфной группы, охарактеризованной с позиций современной систематики и молекулярной биологии развития. Такой группой является семейство Бобовых (Leguminosae),
демонстрирующее исключительное разнообразие в строении цветка. Исходный план строения цветка в семействе – зигоморфный, пятикруговой, с пятичленными околоцветником и андроцеем, с одночленным гинецеем. Однако в разных эволюционных линиях независимо возникают актиноморфный околоцветник, различные варианты редукции или полимеризации андроцея, многочленный гинецей. Отмечается чрезвычайно высокий уровень гомоплазии. Помимо эволюционной тенденции к стабилизации структуры цветка, неоднократно формируется своеобразный синдром нестабильности, связанный с актиноморфной симметрией и характеризующийся вариабельными числом и положением органов цветка.
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The contemporary evolutionary developmental biology includes molecular phylogeny, studies on morphology and morphogenesis, genetics, and genomics. The most reliable conclusions about main trends of floral evolution can result from investigations of highly polymorphic group, which is characterized from the positions of both modern systematics and molecular developmental biology. The legume family, Leguminosae, is a group of such kind. It demonstrates an outstanding variation in flower structure. The ancestral floral structure in this family includes monosymmetry, pentacycly, with pentamerous perianth and androecium, and a monomerous gynoecium. However, distinct evolutionary lineages resulted in origin of polysymmetric perianth, different patterns of staminal reduction or polymerization, as well as multicarpellate gynoecium. A strikingly high level of homoplasy is revealed in Leguminosae. Besides the existing evolutionary tendency to
stabilize floral structure, the exact “instability syndrome” evolved repeatedly, associated with a polysymmetry and characterized with a highly variable number and position of floral organs.
... This reduction reaches extreme degrees in several Dialium species, which have entirely lost their corolla or have a single vestigial petal and only two adaxial stamens. Nonetheless, a tremendous meristic variation can occur within the genus, with some species presenting trimerous calyx and corolla, and the number of stamens reaching up to 10 (Rojo, 1982;Zimmerman et al., 2013;LPWG, 2017;Falcão et al., 2016;2020;in prep). The small globose fruits, known as camaras, are a variation of the samara and samaroid found in closely related genera (Spjut, 1994;Falcão et al., 2016), and, together with the reduced flowers, make Dialium a genus difficult to be morphologically recognizable as belonging to the family Fabaceae. ...
In this work, we describe Dialium heterophyllum, a new species for the largest genus in the diverse and morphologically unique legume subfamily Dialioideae. Dialium, with 32 species, has its highest diversity in tropical Africa and Asia, with four species accepted until now in the Neotropics. The fifth species described here reinforces the idea that a large portion of the Neotropical diversity, notably in the Amazon, is still unknown. Dialium heterophyllum is restricted to the south of the Amazon Basin in Brazil and Bolivia, areas under intense anthropic pressure in recent years. Due to its floral morphology, the species appears to be closely related to the other Neotropical species of the genus, differing by its reduced leaf rachis with unifoliolate to trifoliolate leaves, generally opposed to sub-opposed leaflets, the terminal leaflet much longer than the lateral ones (when present) and than the leaf rachis. We provide illustrations, distribution maps, a conservation risk assessment and an identification key.
... Mendoravia Capuron and two of the four species of Storckiella Seem. show organ proliferation in the calyx, corolla and/or androecium (Zimmerman, Prenner & Bruneau, 2013b, Zimmerman et al., 2017, Dialium hexasepalum Harms shows proliferation in the calyx with six or seven sepals (Harms, 1915;Rojo, 1982), and Dicorynia shows proliferation in the sporangia of the anthers (Koeppen, 1967). ...
... Tucker (1998), working on Dialium, Labichea Gaudichaud-Beaupre ex DC. and Petalostylis Benth., was the first to address the intense and varied reduction of floral organs and whorls in the clade ontogenetically, revealing examples of reduction as a result of different ontogenetic processes, such as the absence of floral organs since initiation, fusion of organs during development and examples of suppression. Zimmerman et al. (2013b) supplemented the ontogenetic studies of the group with analyses of four other Dialium spp. and the monospecific genera Poeppigia and Mendoravia, finding relatively similar organogenetic patterns to those in Dialium, such as the common absence of abaxial organs in the corolla and androecium. ...
... and the monospecific genera Poeppigia and Mendoravia, finding relatively similar organogenetic patterns to those in Dialium, such as the common absence of abaxial organs in the corolla and androecium. Mendoravia is one of the few genera in the subfamily showing floral organ proliferation (12 stamens) and, despite the great variation in forms of initiation of whorls among genera, the absence of organs is much more common than suppression (Zimmerman et al., 2013b). Another common pattern found is the bidirectional initiation of the calyx, with the median abaxial sepal being the first one to differentiate in Petalostylis and several Dialium spp. ...
The goal of this study was to better understand the origin and development of flowers and inflorescences in the newly established subfamily Dialioideae, an unusual and morphologically variable clade of Fabaceae due to its varied levels of floral reduction. We present here the complete ontogenetic series for two species characterizing different levels of floral reduction: Apuleia leiocarpa, an andromonoecious species with trimerous flowers; and Martiodendron fluminense, a species lacking the inner whorl of stamens. We also performed a literature review and herbarium specimen survey of the inflorescence and floral morphology of the other 15 genera in Dialioideae. Among the exclusive traits of Apuleia found here are the absence of two sepals and petals from initiation, the simultaneous initiation of the sepals (never before documented for Dialioideae), the absence of carpel initiation in staminate flowers and the formation of the carpel in the staminal whorl of monoclinous flowers, with the presence of a nectariferous hypanthium in both flower types. In Martiodendron the two exclusive traits are the heteromorphic development of stamens of the outer whorl, with the abaxial one being the last to elongate, and the possible initiation of an inner staminal whorl, which stops developing immediately thereafter and is no longer visible at anthesis. Among the potential synapomorphies for the subfamily are the absence of bracteoles and a pair of bracts subtending a triad of flowers or inflorescence axes, the distichous anthotaxy of the thyrsoid inflorescences, the bidirectional initiation of the sepals and the simultaneous initiation of the stamens.
... Here, we provide a detailed assessment of the apparently simple and small, but structurally complex flowers of Tachigali, a large genus of neotropical trees that has early diversified in the Caesalpinioideae phylogeny. Early-branching genera across all legume subfamilies have been largely marked by conspicuous changes in floral morphology involving symmetry, reduction or proliferation of stamens and petals, multicarpellate gynoecium and petals that can be free and equal or highly differentiated and connate (e.g., Pennington et al. 2000;Prenner and Klitgaard 2008;Cardoso et al. 2012aCardoso et al. , b, 2013aZimmerman et al. 2013;Bruneau et al. 2014;Paulino et al. 2014;Leite et al. 2015;Prenner et al. 2015;Prenner and Cardoso 2017). In contrast to such floral evolutionary lability among closely related genera of earlybranching legume clades, major changes in floral architecture at genus level seem to be rare. ...
Comparative studies of floral development and morphology have largely contributed to the understanding of taxonomic classification, phylogenetic relationships and evolutionary trends across many angiosperm clades, particularly in the florally diverse family Leguminosae (alternatively Fabaceae). This study aimed to characterize the middle to late stages of floral development and morphological variation of the caesalpinioid genus Tachigali, an evolutionary radiation of predominantly neotropical rainforest trees. Floral buds and flowers of five representative species from Tachigali were analyzed under stereo microscopy, light microscopy and scanning electron microscopy to evaluate informative morphological and developmental characters. Although the genus displays relatively small flowers measuring up to 14 mm long, they are variable in terms of symmetry, structure and size, which have influenced the main taxonomic subdivisions among the species. Here, we show that the floral architecture of Tachigali involves a double whorl of stamens, anthers with dome-shaped connective extension and monosymmetrical hypanthium, owing to the unequal development of its wall at different stages of the floral ontogeny. Such developmental patterns are likely new diagnostic floral characters of Tachigali in the context of the early diverging caesalpinioid clades and reaffirm the circumscription of the genus in order to include the species previously classified within Sclerolobium.
... In one group, both stamen and gynoecial primordia are initiated in a single flower, and one set of sexual organs is later arrested during the development. This type of development occurs in some legumes (Tucker 1998;Zimmerman et al. 2013), Zea (De Long and Calderon-Urrea 1994), and Andropogoneae (Poaceae; Le Roux and Kellogg 1999), among others (Luo et al. 2017). In the other group, either gynoecial or stamen primordia are initiated, but not both. ...
Key message
Xanthoceras sorbifolium is apparently andromonoecious but exhibits a cryptically monoecious breeding system. Sexual differentiation in male and functional female flowers occurs 2 weeks before flowering.
Abstract
Individual trees of Xanthoceras sorbifolium bear male and morphologically bisexual flowers but functionally female flowers, and show labile sex expression. Investigations of the floral development are of significant value for understanding the breeding system and elucidating the systematic relationships. We studied floral development of male and bisexual flowers using scanning electron and light microscopy. The early stages of floral development were essentially the same, and all floral organ primordia were initiated in the two types of flowers of X. sorbifolium. Later, the stamens in bisexual flowers and the gynoecium in male flowers were aborted. We divided floral development into nine stages. Morphological differences between male and bisexual flowers appeared first at stage 8, when the style elongated obviously and the stigma papillae began to expand in the bisexual flowers but not in the male flowers. Ovule development was arrested shortly after formation of megaspore mother cells or during meiosis in the male flowers, whereas anther development was aberrant in the bisexual flowers. Morphologically bisexual flowers of X. sorbifolium do not have male function and are functionally female. Comparison of floral developmental characters did not support the separation of the Chinese monotypic genus Xanthoceras from the family Sapindaceae.
