The Rhabdodendraceae family has a single genus, Rhabdodendron, which contains three species with exclusively South American distribution: R. amazonicum (Spruce ex Benth.) Huber, R. macrophyllum (Spruce ex Benth.) Huber, and R. gardneranum (Beth.) Sandwith. Rhabdodendron amazonicum exhibits remarkable morphological plasticity and is widely distributed across the Amazonian vegetation mosaic. This study aims to analyze the spatial distribution and morphological variation of R. amazonicum populations across distinct phytophysiognomies in western Pará, including seasonal forest, savanna, and campinarana. For sampling, a 100 × 100 m plot was established within each phytophysiognomy, totaling 59 collected individuals. Plant height and the following leaf variables were measured in triplicate: leaf blade and petiole lengths, as well as medial, apical, and basal widths. The normality and homogeneity of variances were assessed using the Shapiro-Wilk and Levene tests followed by ANOVA, Welch ANOVA, and Kruskal-Wallis analyses. For multivariate ordination, non-metri multidimensional scaling (NMDS) was applied. Rhabdodendron amazonicum occurs in all three phytophysiognomies with distinct densities, being most abundant in the savanna. Populations of R. amazonicum from the savanna and seasonal forest are morphologically more homogeneous than those of the campinarana, reflecting the complex taxonomic characterization of the species. NMDS analyses clearly segregate the campinarana from the savana phytophysiognomies, demonstrating that the R. amazonicum population is more adapted to the savanna while tolerating other environments reflecting its morphological plasticity, and suggesting that individuals in the campinarana are likely forming a subgroup undergoing speciation, given the population's geographic isolation.

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Mesembryanthemum cordifolium , a perennial plant with crassulacean acid metabolism (CAM) in the Aizoaceae family, has significant ornamental and medicinal values. In this study, we reported the first complete chloroplast genome sequence of this species. The total genome size was 153,734 bp in length, including a large single-copy (LSC) region of 85,692 bp, a small single-copy (SSC) region of 18,212 bp, and a pair of inverted repeat (IR) regions of 24,915 bp by each. The overall GC content of the M. cordifolium chloroplast genome was 37.08%. The genome encodes 131 genes, comprising 87 protein-coding genes (PCGs), 36 transfer RNA genes (tRNAs), and eight ribosomal RNA genes (rRNAs). Phylogenetic analysis shows this species was relatively close to M. crystallinum . This chloroplast genome sequence will be valuable for species discrimination and for understanding phylogenetic relationships within the genus Mesembryanthemum .

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Background Baolia H.W.Kung & G.L.Chu is a monotypic genus only known in Diebu County, Gansu Province, China. Its systematic position is contradictory, and its morphoanatomical characters deviate from all other Chenopodiaceae. Recent study has regarded Baolia as a sister group to Corispermoideae. We therefore sequenced and compared the chloroplast genomes of this species, and resolved its phylogenetic position based on both chloroplast genomes and marker sequences. Results We sequenced 18 chloroplast genomes of 16 samples from two populations of Baolia bracteata and two Corispermum species. These genomes of Baolia ranged in size from 152,499 to 152,508 bp. Simple sequence repeats (SSRs) were primarily located in the LSC region of Baolia chloroplast genomes, and most of them consisted of single nucleotide A/T repeat sequences. Notably, there were differences in the types and numbers of SSRs between the two populations of B. bracteata. Our phylogenetic analysis, based on both complete chloroplast genomes from 33 species and a combination of three markers (ITS, rbcL, and matK) from 91 species, revealed that Baolia and Corispermoideae (Agriophyllum, Anthochlamys, and Corispermum) form a well-supported clade and sister to Acroglochin. According to our molecular dating results, a major divergence event between Acroglochin, Baolia, and Corispermeae occurred during the Middle Eocene, approximately 44.49 mya. Ancestral state reconstruction analysis showed that Baolia exhibited symplesiomorphies with those found in core Corispermoideae characteristics including pericarp and seed coat. Conclusions Comparing the chloroplast genomes of B. bracteata with those of eleven typical Chenopodioideae and Corispermoideae species, we observed a high overall similarity and a one notable noteworthy case of inversion of approximately 3,100 bp. of DNA segments only in two Atriplex and four Chenopodium species. We suggest that Corispermoideae should be considered in a broader sense, it includes Corispermeae (core Corispermoideae: Agriophyllum, Anthochlamys, and Corispermum), as well as two new monotypic tribes, Acroglochineae (Acroglochin) and Baolieae (Baolia).

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Rhabdodendraceae is recorded for the first time in the vascular flora of Colombia and the upper Río Negro basin, based on collections of Rhabdodendron amazonicum from the upper Cuyarí river, Guianía department, Colombia, and the upper Isana (Içana) river, Amazonas state, Brazil, respectively. These two localities extend considerably the northwesternly distribution of this taxon inside the Amazon Basin. Notes about the phytogeography (e.g. insights as to why this species has not yet been found between Manaus and the confluence of the Guainía and Casiquiare rivers), the habitats of R. amazonicum, and an updated overview of the known specimens using a geographic distribution map of this taxon is also included. The discovery of this family in the upper Río Negro region, demonstrates the value of field work through alliances between private initiatives and the Kuripaco nation.

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A new genus Limadendron (Leguminosae, Papilionoideae, Brongniartieae) from northern South America is described and illustrated. The new genus is segregated from Poecilanthe based on a previous phylogenetic analysis. Limadendron is sister to Cyclolobium and differs from it mainly by its woody dehiscent legumes contrasting with the winged samaroid fruits of the latter. Two new combinations, Limadendron amazonicum (Ducke) Meireles & A. M. G. Azevedo and Limadendron hostmannii (Benth.) Meireles & A. M. G. Azevedo, are proposed. A distribution map and an identification key for the species are also provided.

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