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Diversity of flowers in Apocynaceae. (A) Aspidosperma pyrifolium, Aspidospermateae; (B) Hancornia speciosa, Willughbeieae; (C) Couma rigida, Willughbeieae; (D) Tabernaemontana solanifolia, Tabernaemontaneae; (E) Condylocarpon isthmicum, Alyxieae; (F) Thevetia peruviana, Plumerieae; (G) Allamanda puberula, Plumerieae, (H) Wrightia coccinea, Wrightieae; (I) Adenium obesum, Nerieae; (J) Mandevilla atroviolacea, Mesechiteae; (K) Pentopetia grevei, Periplocoideae; (L) Secamone parviflora, Secamonoideae; (M) Ceropegia tihamana, Ceropegieae; (N) Orbea lutea, Ceropegieae; (O) Calotropis procera, Asclepiadinae; (P) Oxypetalum rusticum, Oxypetalinae [Photos of panels (A–G,I,J,O,P) by Rapini; panels (H,K–N) by Meve].
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Apocynaceae (the dogbane and milkweed family) is one of the ten largest flowering plant families, with approximately 5,350 species and diverse morphology and ecology, ranging from large trees and lianas that are emblematic of tropical rainforests, to herbs in temperate grasslands, to succulents in dry, open landscapes, and to vines in a wide variet...
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Apocynum venetum L. is an endangered perennial species mainly distributed in the semi-arid lands and plays an important role in protecting ecological environment; meanwhile, it is also widely used as a traditional Chinese medicine. While physiological changes of seed germination under drought stress have been conducted, the adaptive mechanism to se...
Chemical investigation of the EtOAc-soluble extract of the leaves of Apocynum venetum allowed the isolation of seven flavonoids including a new compound named 4′-hydroxy-7- O-(4-hydroxybenzyl)-3-methoxy-6-prenylflavone (1) and six known compounds (2–7). The structures of these compounds are elucidated by spectroscopic and physico-chemical analyses....
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... 12,[15][16][17][18][19] This particular case reflects an evolution directly related to the plasticity of the protodermis which, together with the emergence of the pollinia, seems to have been mainly responsible for the high 14,20 giving rise to thousands of species distributed almost worldwide. 21,22 Among the different parts of the flower having secretory tissues, the style head stands out for its fundamental importance for pollination in Apocynaceae. 15,[22][23][24] Style head ...
... 21,22 Among the different parts of the flower having secretory tissues, the style head stands out for its fundamental importance for pollination in Apocynaceae. 15,[22][23][24] Style head ...
... The style head is ubiquitous in Apocynaceae, 12,22,24 and is one of the main morphological synapomorphies of the family. It forms from a postgenital fusion of the apices of the two carpel primordia during flower development. ...
Nuptial glands are very diverse and associated with different pollination mechanisms. The greater the specifici-ty in the pollen transfer mechanism from anther to stigma, the greater the morphological elaboration of flowers and functional complexity of the nuptial glands. In Apocynaceae, pollination mechanisms reached an extreme specificity, a fact that was only possible due to an extreme morphological synorganization and a profusion of floral glands. Although these glands are of different types, the vast majority have secretory cells only in the epi-dermis. In general, these epidermal cells produce many different compounds at the same time, and previous studies have demonstrated that in the style head, the functional complexity of epidermis has become even greater. Four types of style head are found in the family, which have different degrees of functional complexity in relation to the secretion produced and pollen dispersal mechanism. The secretion is fluid in types I, II and III, and the pollen is dispersed and adhered to the pollinator by the secretion produced by the style head. In type IV, the secretion hardens and acquires a specific shape, moulded by the spatial constraints of the adjacent floral organs. This evolutionary alteration is accompanied by changes in the structure and arrangement of the secre-tory cells, as well as in pollen aggregation and position of stigma. Histochemical analysis has shown that the secretion is mixed and highly complex, especially in the style head type IV, where the secretion, called translator , is formed by a rigid central portion, which adheres to the pollinator, and two caudicles that attach to two pollinia. The translator has a distinct composition in its different parts. Further studies are needed to answer the new questions that have arisen from the discovery of this highly functional complexity of the secretory tissue.
... Overall, both regions presented higher range sizes than forests. The two results follow the trend of recent radiation of the family from forests to drier environments (Bitencourt et al. 2021), with niche conservatism potentially playing an important role in the differences observed in the richness patterns of forests and savannas. Considering solely the savanna environments included in our analysis, the widespread distribution observed for some species can also be linked to the overall simpler topography of the region. ...
... Apocynaceae are hypothesized to have originally occupied wet forests in austro-and boreotropical latitudes until the Eocene-Oligocene climate transition, later developing multiple adaptations (e.g. wind-dispersed, twining, pollinia-bearing) that allowed them to disperse into open vegetation types (Bitencourt et al. 2021). For lianas, our result follows that reported for different families and other regions of the world since they are usually not as abundant in shrublands as they are in forest-type physiognomies (Harper et al. 2005). ...
... In addition, the distribution of species richness was positively associated with a latitudinal gradient (Fig. 1B), the highest richness cell values being observed in tropical latitudes between 14°S and 10°S, and the mean richness values being higher in subtropical latitudes between 22°S and 26°S. These results show that most of the diversity of the group is concentrated in tropical and subtropical forests, following previous quantifications of Apocynaceae diversity in the Neotropics (BFG 2015) and the biogeographical and evolutionary trends reported for the family (Bitencourt et al. 2021). In these environments, the complexity of the forest structure has been hypothesized to enhance the diversification of climbing modes and, consequently, to increase the species richness of lianas. ...
Brazilian moist forests and savannas are some of the most species-rich biomes in the Neotropics. In the transition zones between these regions, ecotones often accumulate even higher taxonomic diversity. However, whether these ecotonal communities consist of overlapping species widespread from the neighbouring biomes or a specific set of locally adapted species still needs to be clarified. Regional differences in species richness may be influenced by factors such as species' environmental tolerances, life forms, or species’ range sizes. To investigate the species richness found in ecotones, we used the ‘milk-weed’ family (Apocynaceae), which comprises both widespread and narrowly distributed trees, lianas, and shrubs, as a model to evaluate if (i) their observed richness in ecotones is promoted by widespread species or by locally adapted species; (ii) trees, lianas, and shrubs show different richness patterns in savannas, ecotones, and forests; and (iii) species found in ecotones have broader environmental tolerances than other species in the family. We used a taxonomically curated georeferenced dataset to compare the range sizes of 643 species of Apocynaceae from 73 genera listed for Brazil, comprising 298 species with a liana life form and 345 trees, herbs, or shrubs. We recorded 335 predominantly forest species, 56 savanna species, and 152 ecotone species, for which we quantified species richness, areas of occurrence, precipitation, and temperature ranges and tested for differences in range sizes and environmental tolerances between habits and ecoregions. Our results indicate that (i) Apocynaceae species occurring in ecotones have wider geographical ranges than species not occurring in ecotones; (ii) lianas showed higher area-weighted richness in ecotones than other life forms; and (iii) species found in ecotones had broader environmental tolerances than species restricted to moist forests or savannas. These results indicate that the species richness found in ecotones between savannas and moist forests in Brazil is not necessarily a consequence of higher endemism and local adaptation but may also be a result of overlapping ranges of widespread species typically associated with neighbouring biomes. Together, our findings add to our understanding of ecotones and biomes as continuous, gradual biogeographical transitions instead of sharply defined ecological units.
... Apocynaceae, the dogbane family, are one of the ten largest families in angiosperms, comprising 378 genera and more than 5000 species (Endress et al., 2018). The majority of species in this family are found in tropical and subtropical regions of the world, and they exhibt wide diversity in terms of their habitats, growth forms and morphological characteristics (Fishbein et al., 2018;Ollerton et al., 2019;Bitencourt et al., 2021). Furthermore, many Apocynaceae species have high economic values. ...
Apocynaceae are one of the ten species-richest angiosperm families. However, the backbone phylogeny of the family is yet less well supported, and the evolution of plastid genome structure has not been thoroughly studied for the whole family. Herein, a total of 101 complete plastomes including 35 newly sequenced, 24 reassembled from public raw data and the rest from NCBI GenBank database, representing 26 of 27 tribes of Apocynaceae, were used for comparative plastome analysis. Phylogenetic analyses were conducted using a combined plastid data matrix of 77 protein-coding genes from 162 taxa, encompassing all tribes and 41 of 49 subtribes of Apocynaceae. Plastid genome lengths ranged from 150,897 bp in Apocynum venetum to 178,616 bp in Hoya exilis. Six types of boundaries between the inverted repeat (IR) regions and single copy (SC) regions were identified. Different sizes of IR expansion were found in three lineages, including Alyxieae, Ceropegieae, and Marsdenieae, suggesting multiple expansion events of the IRs over the SC regions in Apocynaceae. The IR regions of Marsdenieae evolved in two ways: expansion towards the large single copy (LSC) region in Lygisma + Stephanotis + Ruehssia + Gymnema (Cosmopolitan Clade), and expansion towards both LSC and small single copy (SSC) region in Dischidia-Hoya alliance and Marsdenia (Asia-Pacific Clade). Six coding genes and five non-coding regions were identified as highly variable, including accD, ccsA-ndhD, clpP, matK, ndhF, ndhG-ndhI, trnG(GCC)-trnfM(CAU), trnH(GUG)-psbA, trnY(GUA)-trnE(UUC), ycf1, and ycf2. Maximum likelihood and Bayesian phylogenetic analyses resulted in nearly identical tree topologies and produced well-resolved backbone relationships. Fifteen clades in the Apocynaceae backbone were identified. The subfamily Periplocoideae were embedded in the Apocynoid grade and were sister to the Echiteae-Odontadenieae-Mesechiteae clade with high support values. Three tribes (Melodineae, Vinceae, and Willughbeieae), the subtribe Amphineuriinae, and four genera (Beaumontia, Ceropegia, Hoya, and Stephanotis) were not resolved as monophyletic. Our work sheds light on the backbone phylogenetic relationships in the family Apocynaceae and offers insights into the evolution of Apocynaceae plastomes using the most densely sampled plastome dataset to date.
... With about 3400 species, 181 genera, 17 subtribes, and 5 tribes (Asclepiadeae, Ceropegieae, Eustegieae, Fockeeae, Marsdenieae), this subfamily comprises 60% of all species in the family Apocynaceae (Fishbein & al., 2018;Endress & al., 2019). In addition to its ancestral African distribution (Bitencourt & al., 2021), four independent radiation events occurred in the Americas (Rapini & al., 2003), of which onethe speciesrich MOG-clade comprising subtribes Metastelmatinae, Oxypetalinae and Gonolobinae, along with five smaller subtribes of the tribe Asclepiadeaeincludes 75% of all American Asclepiadoideae species (Rapini & al., 2007;Silva & al., 2012;Endress & al., 2019) (Fig. 1). While Secamonoideae are mostly woody with predominantly lianescent or twining growth forms and to a lesser extent also small erect shrubs (Endress & al., 2019), Asclepiadoideae are defined by a wide array of non-woody life forms. ...
... These various woody and non-woody growth forms thrive in habitats ranging from lowland rainforests in Southeast Asia to diverse, often disturbed, forests and shrublands in Africa and the Americas (Endress & al., 2019). Interestingly, Bitencourt & al. (2021) observed a family-wide evolutionary transition in habitat occupation, ranging from stable and dense tropical rainforests typical of the rauvolfioids and some apocynoids, towards highly diverse twining lineages in more open, semi-arid, pioneer vegetation in Asclepiadoideae. ...
The Apocynaceae subfamilies Secamonoideae and Asclepiadoideae have undergone several transitions during their evolution with regard to growth form and degree of woodiness. In this study, we present a wood anatomical overview of both subfamilies that complements previous work on the remaining Apocynaceae. Detailed microscopic wood descriptions using light and scanning electron microscopy were performed on 60 species that cover most Secamonoideae genera and all major woody Asclepiadoideae lineages. Our observations are in line with subfamilial and (sometimes sub)tribal delimitations. Furthermore, we present for the first time an overview of the estimated number of shifts from herbaceousness to (phylogenetically) derived woodiness in Asclepiadoideae, along with a derived woody species list with distribution and habitat information. In total, at least 168 derived woody species resulting from at least 28 independent woodiness transitions were found, with drought possibly being one of the main drivers of most of these transitions.
... While the DIVALIKE model reconstructs tropical Asia as ancestral area for the tribe (though with a rather high probability for Africa or Africa-tropical Asia, suppl. Fig. S16), the DEC model gives widespread Africa-tropical Asia as ancestral area, a result also obtained by Bitencourt & al. (2021). In our analysis, stem age of Marsdenieae is estimated to be somewhat younger (30.2 Ma) than in with 39.5 Ma, and crown age somewhat older (28.8 Ma vs. 22.8 Ma) than in . ...
A densely sampled molecular phylogeny of the pantropical, predominantly forest‐dwelling tribe Marsdenieae (Apocynaceae) is presented, including almost a quarter of the ca. 740 species. Sampling focused on resolving the circumscription of Marsdenia, which ranges from Marsdenia sensu Bullock with less than 10 Asian species closely related to the type, M. tinctoria, to Marsdenia sensu Forster, with ca. 300 species distributed throughout the range of the tribe, encompassing the genera Cionura, Dregea, Gongronema, Gymnema, Leichhardtia, Stephanotis, and Wattakaka as synonyms. All analyses resolve two well‐supported clades: an Asia‐Pacific Clade that includes the large epiphytic Dischidia‐Hoya alliance and a number of Marsdenia species, among them the type M. tinctoria, and a Cosmopolitan Clade that includes most of the rest of Marsdenieae with several moderately to well‐supported subclades that span the entire geographic range of Marsdenieae. The position of two small genera, Rhyssolobium (southern Africa) and Sicyocarpus (Madagascar), is ambiguous. Given this topology, a monophyletic Marsdenia s.l. would subsume all species of Marsdenieae. Instead, we propose a classification that maintains Dischidia and Hoya as distinct genera. We revise generic circumscriptions, reducing Marsdenia s.str. to a small clade of Asian species. Two new genera, Gongreos gen. nov. and Gongronemopsis gen. nov., are described, with two and nine species, respectively. A total of twenty‐six new combinations, one new name, and six new synonyms are proposed. Three neotypes and eleven lectotypes are selected, and one 2nd step lectotypification is carried out. Diagnostic morphological characters for identified clades are discussed. Biogeographic analysis retrieves tropical Asia as most likely ancestral area for Marsdenieae, with widespread tropical Asia‐Africa almost equally likely. The first‐branching lineages in both major clades are tropical Asian; the Asia‐Pacific Clade comprises a sizeable radiation in the Pacific area, with two dispersals from Australia to New Caledonia. The Cosmopolitan Clade comprises several genera (Gongronemopsis, Gymnema, Stephanotis, Telosma) widespread in Africa and tropical Asia, and some also in Madagascar, and the New World genus Ruehssia.
... While the DIVALIKE model reconstructs tropical Asia as ancestral area for the tribe (though with a rather high probability for Africa or Africa-tropical Asia, suppl. Fig. S16), the DEC model gives widespread Africa-tropical Asia as ancestral area, a result also obtained by Bitencourt & al. (2021). In our analysis, stem age of Marsdenieae is estimated to be somewhat younger (30.2 Ma) than in with 39.5 Ma, and crown age somewhat older (28.8 Ma vs. 22.8 Ma) than in . ...
Using the Apocynaceae as an example, the present paper demonstrates how the new tool Rhakhis highlights taxonomic problems in a large vascular plant family and, at the same time, invites specialists in the family to solve these problems with the aim of producing an up‐to‐date taxonomy. This taxonomy can then be used to estimate species and genus numbers, thus approaching the goal of completing our picture of the diversity surrounding us and providing a solid basis for science and conservation. The most recent estimates for genus and species number in the Apocynaceae are provided.
Apocynum pictum Schrenk is a semi-shrub of the Apocynaceae family with a wide distribution throughout the Tarim Basin that holds significant ecological, medicinal, and economic values. Here, we report the assembly of its chromosome-level reference genome using Nanopore long-read, Illumina HiSeq paired-end, and high-throughput chromosome conformation capture sequencing. The final assembly is 225.32 Mb in length with a scaffold N50 of 19.64 Mb. It contains 23,147 protein-coding genes across 11 chromosomes, 21,148 of which (91.36%) have protein functional annotations. Comparative genomics analysis revealed that A. pictum diverged from the closely related species Apocynum venetum approximately 2.2 million years ago and has not undergone additional polyploidizations after the core eudicot WGT- event. Karyotype evolution analysis was used to characterize interchromosomal rearrangements in representative Apocynaceae species and revealed that several A. pictum chromosomes were derived entirely from single chromosomes of the ancestral eudicot karyotype. Finally, we identified 50 members of the well-known stress-responsive WRKY transcription factor family and used transcriptomic data to document changes in their expression at two stages of drought stress, identifying a number of promising candidate genes. Overall, this study provides high-quality genomic resources for evolutionary and comparative genomics of the Apocynaceae, as well as initial molecular insights into the drought adaptation of this valuable desert plant.
Diante da atual crise da biodiversidade e visto que os recursos para sua conservação são limitados, estabelecer áreas prioritárias tem se mostrado um recurso-chave e, ao mesmo tempo, desafiador. Os métodos tradicionais são contestáveis, já que o número de espécies e o endemismo são indicadores pobres do nível de ameaça das regiões.
