FIGURE 5 - uploaded by Marcus José de Azevedo Falcão
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Dialium guianense (Aubl.) Sandwith. A. Example of common leaf morphology: 7-9 small leaflets strongly alternate, elliptical shape, cuneate to obtuse basis, long leaf rachis, similar size between leaflets; B. Example of common leaf morphology: 6 big leaflets, ovate to elliptical shape, obtuse to truncate basis. A: Prance, G.T. 1737; B: Hopkins, M.J. 1533. Source: A: Reflora; B: INPA. Scale bar: 10cm.
Source publication
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 tha...
Context in source publication
Context 1
... leaflet shape of D. guianense is quite variable, D. heterophyllum, as well as D. rondoniense, D. congestum and D. hexaestaminatum, present a much more stable set of characters. While D. guianense has predominantly elliptical or ovate leaflets with cuneate, obtuse, truncate or cordate base, D. heterophyllum has mostly lanceolate terminal leaflets with obtuse or truncate base (a very rare combination in D. guianense) and a smaller proportion of specimens with ovate shape and cordate base (never cuneate) ( Figure 5). ...
Citations
... Continuing the recent systematic studies on the subfamily Dialioideae, notably in the Neotropical region (Falcão et al., 2016;2020a;2023;in prep.), the genus Androcalymma Dwyer (1958: 295) points out as the least known and least collected among the 17 genera that constitute this pantropical subfamily (LPWG 2017). Six of the genera in the subfamily occur in the Americas: Dialium Linnaeus (1767: 56), Apuleia Martius (1837: 123), Dicorynia Bentham (1840;82-83), Martiodendron Gleason (1935: 141), Poeppigia C. Presl (1830: 15) and Androcalymma, with the last five being endemic to this region. ...
... Taxonomic analysis:-The morphological analyses were made mainly through a stereomicroscope and scanning electron microscopy , also using data obtained in previous studies on other genera of Dialioideae for comparative purposes. Detailed specifications on such methods and lists of examined specimens for other Dialioideae genera can be found in Falcão et al. (2016;2020a;2020b;2023). ...
... 5. Flowers of Androcalymma and Dicorynia are white, while flowers in Martiodendron are yellow. The petals are also white in Apuleia, Distemonanthus, and several species of Dialium (Figures 4E-I;5A-B;Falcão et al., 2020a;2020b;2023). It is important to note that, now knowing the phylogenetic position of Androcalymma, we can indicate that such character is restricted to a clade that contains the genera above except Martiodendron (Figure 7). ...
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.
... Martiodendron excelsum, on the other hand, is the only species of the genus that is strongly associated with riverine habitats; it occurs most often in seasonally inundated varzeas, as well as in campinaranas, whereas M. elatum and M. parviflorum, which have geographical distributions adjacent to that of M. excelsum, are more associated with upland "terra firme" forests. It is also worth noting that the majority of Martiodendron species do not seem to be related to flooded environments, despite being associated with regions close to large river courses, a pattern also observed in the related genus Apuleia (Falcão et al., in prep) and Dialium (Falcão et al., 2016;2020b), while M. excelsum presents a distributional pattern more similar to the related genus Dicorynia (Falcão et al., 2022). ...
... These observations, combined with the relatively reduced samara wings of the species relative to other members of the genus, indicate an evolutionary shift away from anemochoric dispersal, which presumably is the dominant form of seed dispersal in the other species of the genus, toward hydrochoric dispersal. Transitions to hydrochoric dispersal via floating fruits are postulated for several other taxa of Dialioideae found in seasonally inundated riverine forests and/or close to rivers, including some species of Dialium, Dicorynia, and Apuleia (Falcão et al., 2016;2020b;2022;in prep). Other examples of mainly anemochoric groups with shifts towards hydrochory are found in other subfamilies of Leguminosae like in the genera Machaerium Pers. ...
Martiodendron (Leguminosae/Fabaceae) is a Neotropical genus of trees and shrubs comprising five species. It is characterized by its yellow pentamerous corolla, four to five long poricidal anthers and large, attractive red samaras; it represents an intermediate stage of floral reduction among the 17 genera of the subfamily Dialioideae, which display diverse floral morphologies including different types of reduced flowers in the perianth and androecium. The last taxonomic revision of Martiodendron was published some 60 years ago and there is frequent misidentification of specimens in herbaria, databases, and floristic works with mistreatment of taxa and unclear geographic distributions. Thus, circumscriptions of the species and varieties of the genus require reassessment in light of the substantial new data that has become available during the last several decades. Here, we synthesized morphological, geographical, and ecological data on the genus to produce a modern integrative taxonomic treatment. Our taxonomic concepts are underpinned by analysis of 352 herbarium specimens and substantial fieldwork in South America. We recognize five species and four varieties of Martiodendron. All of these taxa display high levels of morphological and geographical cohesion. One of the varieties, M. mediterraneum var. concinnum, is described as new to science. Detailed descriptions of each recognized taxa are accompanied by illustrations, distribution maps, conservation status assessments, and complete nomenclatural treatments with four new lectotypifications. An identification key and a morphometric analysis of fruits are also provided.
... 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]. Using the 7 significant leaf traits to classify this species seems therefore relevant. ...
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.
Recent severe droughts, extreme floods, and increasing differences between seasonal high and low flows on the Amazon River may represent a twenty-first-century increase in the amplitude of the hydrologic cycle over the Amazon Basin. These precipitation and streamflow changes may have arisen from natural ocean–atmospheric variability, deforestation within the drainage basin of the Amazon River, or anthropogenic climate change. Tree-ring reconstructions of wet-season precipitation extremes, substantiated with historical accounts of climate and river levels on the Amazon River and in northeast Brazil found in the Brazilian Digital Library, indicate that the recent river-level extremes on the Amazon may have been equaled or possibly exceeded during the preinstrumental nineteenth century. The “Forgotten Drought” of 1865 was the lowest wet-season rainfall total reconstructed with tree-rings in the eastern Amazon from 1790 to 2016 and appears to have been one of the lowest stream levels observed on the Amazon River during the historical era according to first-hand descriptions by Louis Agassiz, his Brazilian colleague João Martins da Silva Coutinho, and others. Heavy rains and flooding are described during most of the tree-ring-reconstructed wet extremes, including the complete inundation of “First Street” in Santarem, Brazil, in 1859 and the overtopping of the Bittencourt Bridge in Manaus, Brazil, in 1892. These extremes in the tree-ring estimates and historical observations indicate that recent high and low flow anomalies on the Amazon River may not have exceeded the natural variability of precipitation and streamflow during the nineteenth century.
Significance Statement
Proxy tree-ring and historical evidence for precipitation extremes during the preinstrumental nineteenth century indicate that recent floods and droughts on the Amazon River may have not yet exceeded the range of natural hydroclimatic variability.
