Vanilla is a pantropical genus of 130 vine species, most of which are nomadic. It is most diverse in Brazil, which hosts thirteen endemic species, including two in the Amazon, its second-richest domain. Vanilla exhibits high morphological diversity, although identifying species requires flowers. Since the vegetative anatomy of Vanilla is still poorly understood, our objective was to conduct a comparative study of the leaves of eight species occurring in the Amazon, belonging to two subgenera: Vanilla subgen. Membranacea (V. acuta and V. mexicana) and Vanilla subgen. Vanilla (V. appendiculata, V. lindmaniana, V. odorata, V. phaeantha, V. planifolia and V. pompona), using standard protocols for light and scanning electron microscopy. We identified anatomical characters for Vanilla species, noting that the presence and type of crystalliferous idioblasts and crystal types proved most significant in distinguishing between them. For example, V. appendiculata lacks crystals, V. odorata has prismatic crystals, and V. phaeantha has prismatic crystals and raphides in the leaf blade. Other characters can be used to separate groups of taxa within the sample, such as the following: absence/presence of a hypodermis; and absence/presence, type, and location of crystals. The findings provide new diagnostic information for vegetative Vanilla, which is crucial for conservation efforts in Brazil’s Amazon, and offers a year-round tool for researchers studying this commercially important plant. This updated structural data is expected to guide future, larger systematic studies of the genus.
Hydnora is a highly unusual genus of holoparasitic plants in the family Hydnoraceae comprising 10 species across Africa and the Middle East. Species concepts and relationships within the genus have historically been poorly defined, in part due to a paucity of morphological characters available for species delimitation. Here, we present the most comprehensively sampled nuclear phylogenomic study of Hydnora to date. We employ the Angiosperms353 target capture approach, using 34 nuclear loci to generate the species tree. Our results provide strong molecular support for all four recently proposed subgenera of Hydnora, demonstrating that even a limited set of morphological traits can be used to delimit lineages within the genus. We estimate ancestral states for these taxonomically informative characters within the Hydnoraceae and provide molecular evidence to clarify some of the long-standing taxonomic uncertainty within the widespread Hydnora abyssinica complex. We analyse gene tree discordance in the results and discuss our results in the context of these conflicting studies. The phylogenetic hypotheses presented here are the most widely sampled to date, and provide a framework for future ecological and evolutionary research into this enigmatic family of parasitic plants.
This study aimed at exploring the usefulness of pollen in the taxonomy of brambles (Rubus subgen. Rubus), focusing on the diversity of palynological traits among diploids, polyploids, hybrids, and horticultural cultivars. Using light microscopy and scanning electron microscopy, we examined 62 samples representing six diploid species, 16 polyploid taxa, nine hybrids, and three cultivars from various geographic regions. Quantitative traits—polar axis length (P), equatorial diameter (E), P/E ratio, ectocolpi length (Lc), and exine thickness along the polar axis (Exp)—were measured and statistically analysed to evaluate intraspecific and interspecific variation and to explore correlations with ploidy levels. Our results revealed significant morphological differences within and among the four studied groups. Diploid species exhibited smaller pollen grains and greater intra- and interspecific variability than polyploids, supporting the hypothesis that pollen size correlates with ploidy level. Pollen shape was predominantly subprolate and prolate, but shape alone proved unreliable for species discrimination. Exine ornamentation was largely homogeneous across taxa, characterised by striate-perforate patterns, which limited its diagnostic value. Pollen size traits showed positive significant correlations with ploidy levels. Contrast analyses between parental species and hybrids indicated that hybridisation influences pollen morphology, with some hybrids displaying intermediate or distinctive characteristics. In addition, reproductive mode (sexual vs. apomictic) did not significantly affect pollen traits at the same ploidy level. Overall, pollen morphology, particularly size-related traits, can be used as supplementary traits in Rubus taxonomy, e.g. in ploidy determination. However, they must be combined with additional data for reliable species distinction.
Cytogenetic data remain limited for many lineages of Cactaceae, constraining our understanding of chromosome evolution in this diverse family. Here, we combine newly generated cytogenetic and genome size data for Armatocereus mataranus subsp. ancashensis with a comparative dataset of ribosomal DNA (rDNA) organization across Cactaceae to examine patterns of locus number and chromosomal distribution. rDNA loci were analysed using fluorescence in situ hybridization (FISH) with 5S and 45S probes, and nuclear DNA content was estimated by flow cytometry. Somatic cells exhibited 2n = 22 chromosomes, consistent with a diploid condition based on x = 11. Two 5S rDNA loci were located on different chromosome pairs, while a single terminal 45S rDNA locus was detected on another pair. The diploid genome size was estimated at 2C = 2.73 pg, and flow cytometric profiles indicated the presence of endopolyploidy. Comparative analyses across Cactaceae show that rDNA locus number and chromosomal distribution in A. mataranus subsp. ancashensis are broadly consistent with patterns reported in both Cactoideae and Opuntioideae. These findings place the cytogenetic characteristics of this taxon within a broader comparative context and highlight patterns of both conservation and variation in rDNA organization across Cactaceae. Finally, these data may be useful as a cytogenetic reference for future conservation studies on A. mataranus subsp. ancashensis.
Jatropha excisa is found throughout the Chaco phytogeographical province in Argentina, Bolivia, and Paraguay, but its taxonomic boundaries are unclear. This study investigates whether J. excisa comprises more than one species, examining genetic variation and morphological traits, its genetic diversification over time, its native or introduced status in the Chaco, and its distinctiveness from J. gossypiifolia. We analyzed nuclear (ITS) and chloroplast (trnL-trnF) genes from 52 individuals across 32 locations. The results revealed 12 nuclear alleles grouped into four clusters and 29 chloroplast haplotypes with no clear geographic structure. Phylogenetic analysis identified four major clades diverging between 1.8 and 8.1 million years ago, with one clade corresponding to J. excisa and another to J. thyrsantha, indicating at least two distinct species. The findings suggest an ancient divergence among allele groups and a slow geographic expansion of J. excisa over the last 150,000 years. This research supports recognizing J. excisa as a distinct native species in the Chaco, diverging from J. gossypiifolia around 18 million years ago, and emphasizes the need for further studies on hybridization and genetic flow among Jatropha species for conservation efforts.
