Most angiosperm flowers and vegetative shoots of land plants have an acropetal sequence of organ initiation, namely, the more proximal the organ position, the earlier its primordium appears in ontogeny. This is apparently the ancestral condition for angiosperm flowers. An acropetal sequence is the only way in which pre-patterning of organs along a spiral can be established and the only documented sequence of visible organ initiation in spiral flowers. This constraint is absent for whorled flowers, in contrast to whorled vegetative shoots. Non-acropetal developmental sequences are known from both species-rich angiosperm clades with flowers that are predominantly (eudicots) or exclusively whorled (monocots). Deviations from a strict acropetal pattern can be interpreted as sequence heterochronies, related to early termination of the floral meristem and subsequent fractionation of the floral apex into organ primordia. Monocots provide a useful opportunity to generate a large-scale comparative analysis of sequence heterochronies in floral evolution. We recognize several patterns of heterochronic shifts in monocot flowers. An ‘external’ pattern is related to the influence of extrafloral structures such as a flower-subtending bract, creating a delay in initiation of outer whorl organ(s) in the abaxial sector. All ‘internal’ patterns lack any obvious external influence; they include: (1) basipetal organ initiation in wind- and water-pollinated flowers, associated with overall perianth reduction; (2) basipetal organ initiation in secondarily multistaminate androecia (some palms and some Alismataceae) and secondarily multicarpellate gynoecia (some Triuridaceae); (3) non-acropetal patterns associated with common primordia, mostly tepal-stamen (occasional instances in six monocot orders); (4) simultaneous initiation of two neighbouring whorls lacking common primordia (some Alismatales, Dioscoreales, Pandanales, Poales). We propose a typification of common primordia, recognizing tangential and radial types, the latter being either bilobed or entire at the earliest stages. The following hypothesis is testable, but yet untested: at least the entire type is related to the development of two organs from the same prepatterning site. The most important tendencies distinguishing monocots from eudicots are the more frequent occurrence of common primordia, their presence in some epigynous flowers, the scarcity of polymerous androecia with centrifugal development, the apparent absence of complex polyandry, and polyandry associated with a hypanthium. Some monocots have flowers with multicarpellate gynoecia and at the same time oligostaminate androecia, a pattern that is rare in eudicots.
Fabaceae (Leguminosae) is one of the most species-rich and ecologically important angiosperm families, encompassing extraordinary diversity in growth form, floral architecture, fruit morphology, and symbiotic nitrogen fixation. Despite the central role of MADS-box transcription factors in controlling key developmental processes underlying these traits, their evolutionary history in legumes remains poorly understood. Here, we present a comprehensive phylogenetic and comparative genomic analysis of MIKCc MADS-box genes across Fabaceae, sampling representatives from three of the six subfamilies and spanning major evolutionary lineages using genomic and transcriptomic data. Our analyses reveal that all type II MIKCc MADS-box gene lineages known from angiosperms are represented in Fabaceae, except for TDR8 homologs. However, several clades, including MAF/FLC, AGL16/17/ANR1, ABS, and XAL1, are consistently poorly represented, suggesting lineage-specific constraints or gene loss. While numerous MADS-box genes remain single copy across most legumes, others show duplications prior to the diversification of Fabaceae, including AGL6, AGL24b, PI, SEP, and SOC1. Subfamily-specific expansions were detected in key developmental regulators, with duplications of AGL14/19-like, FUL, TM6, and SOC1 in Caesalpinioideae, and AG, AGL6, AGL79, AP1, FUL, and SEP lineages in Papilionoideae. These patterns coincide with documented whole-genome duplication events in both subfamilies. In addition, pervasive gene duplication in Glycine reflects a genus-specific polyploidization history. Together, these results suggest that differential retention and loss of duplicated MADS-box genes have played a central role in shaping floral and inflorescence diversity, phenological variation, and ecological adaptation in legumes. By integrating phylogenetic patterns with existing functional data, this study provides an evolutionary framework for understanding how MADS-box gene diversification has contributed to the remarkable developmental and adaptive radiation of Fabaceae.
The Caatinga harbors the largest continuous expanse of Seasonally Dry Tropical Forests and Woodlands (SDTFW) in South America, characterized by a highly diverse flora and a significant number of endemic species. In this study, we compiled data on species distribution within the Caatinga by gathering information from 112 peer-reviewed floristic and phytosociological studies published up to December 2020. We characterized this database by identifying woody and non-woody species, checking their International Union for Conservation of Nature (IUCN) Red List status, highlighting the families represented by most species, and analyzing species distribution across Neotropical biomes, biogeographical districts, and Holdridge life zones. Our database includes 1,775 taxa identified at the species level (conservative richness), while the total estimated richness was 2,978 species, including unidentified specimens. However, our analysis revealed that the proportion of unidentified taxa in Caatinga studies decreased from 27.10
Incorporation of evolutionary theory into experimental investigations of natural populations was important to the development of plant ecology. We review the prominent role grasses (Poaceae) have played in this historical development. Beginning in the 1920s, the ecotype concept prompted researchers to investigate genetically based differentiation in agronomically important forage grasses using common gardens, first in relation to climatological and biotic factors (grazing and competition), and later in relation to latitude and elevation at collection sites. Adaptive variation was documented for populations in relation to edaphic factors such as soil nutrients and moisture, salinity, serpentine conditions, and heavy metals. Molecular analyses using allozyme and DNA markers show selection favors specific genetic loci in grass populations from different habitats or under changing climatic conditions. Consistent with theoretical expectations for breeding-system effects on genetic structure, highly outcrossing grass species show lower molecular variation among populations and greater variation within populations. In contrast, highly selfing grasses show more genetic variation partitioned among populations and correspndingly reduced variation within populations. Progress has been made in identifying quantitative trait loci important to genetic differentiation in phenotypic traits. Biotic factors such as herbivory, competition and microbial symbionts can act as agents of natural selection and adaptation in grass species. Despite inconsistencies in usage, “ecotype” persists in the literature, but the term has value as evidenced by recent adaptation studies in the Poaceae. Applications of the ecotype concept include reclamation and phytoremediation of sites polluted by metalliferous wastes, restoration of habitats, evolutionary responses to a changing climate, and adaptation of weedy and invasive species.
Plant organ bending is a fundamental growth response shaped by hormonal regulation, cytoskeletal dynamics, and differential cell expansion. While widely explored in vegetative organs, similar processes drive the movement of reproductive structures, where functional outcomes directly influence pollination and reproductive success. Pistil movement, in particular, plays a central role in promoting outcrossing, regulating pollen deposition, and achieving spatial separation of sexual functions. This review synthesizes current understanding of the mechanisms and ecological significance of pistil bending, drawing on case studies from families such as Malvaceae, Passifloraceae, Zingiberaceae etc. The diversity of pistil movements is shown to correspond with pollinator behavior and habitat predictability, highlighting pistil motility as a finely tuned reproductive strategy. Finally, we outline key knowledge gaps, particularly regarding the cellular drivers of pistil motility and the genetic networks underlying its diversity, and propose future directions that integrate physiology, ecology, and evolutionary biology. Together, these perspectives underscore pistil movement as a model trait at the interface of plant development and reproductive ecology.
