Phylogenetic and ecological correlates of pollen morphological diversity in a Neotropical rainforest

Systematic Implications of Palynomorph Diversity Using Microscopic Trends Among Asteraceous Flora From the Drylands of Baluchistan, Pakistan

Pollen micromorphological traits with taxonomic implications are first reported from the study area for 50 Asteraceous taxa belonging to nine tribes. Cichorieae (21 taxa), Cardueae (11 taxa), Inuleae (six taxa), and Anthemideae (four taxa) are the leading tribes. The research included Cousinia haeckeliae, Himalaiella afghana, Pterachaenia stewartii (endemic to Afghanistan and Pakistan), and Xylanthemum macropodum (endemic to Baluchistan). Light and scanning electron microscopy were employed for the visualization of pollen photomicrographs. The data was analyzed statistically via SPSS, PAST, and Origin. Significant diagnostic qualitative and quantitative palynological traits were explored for discrimination down to the species level within the tribes. All the investigated taxa possessed radial symmetry, isopolarity, and monad form (characters for distinction at the subdivision level). The aperture types were trizonocolporate, tetrazonocolporate, and tricolporate with number position and character (NPC) formulas N3P4C5, N4P4C5, and N3P4C3. Goniotreme, peritreme, and ptychotreme types of amb were recognized. Echinate, echinate lophate, scabrate, and gemmate sculpturing were present with and without perforated surface patterns. Variations in the shapes in polar and equatorial views and lacuna shapes further assisted the separation of taxa. The observed shape classes were perprolate, prolate spheroidal, prolate, subprolate, oblate spheroidal, suboblate, and oblate. Principal component analysis, correlation, standard probability plots, and ridge line paired features plot for quantitative variables determined the positive correlation between the length and width of colpi in equatorial and polar view with polar axis and equatorial diameter and number of spines between colpi with the number of spines per pollen. The number of spines per pollen was negatively correlated with the width and length of colpi in the polar view. Multiple sample analysis of variance (ANOVA) concluded that a high statistically significant difference exists among the means of analyzed traits. The examined qualitative and quantitative palynological traits revealed noticeable variations, thus providing the source for species discrimination in Asteraceous tribes.

Pollen morphology of Acanthoideae species from the Shivalik Foothills in Rajaji National Park (Uttarakhand, India)

Apart from its role in plant taxonomy, the understanding of pollen morphology is considered an essential interdisciplinary tool in diverse applied fields, including plant systematics, melissopalynology, aeropalynology, forensic palynology, paleopalynology, and copropalynology. In palynotaxonomy, it is frequently employed to classify and validate natural groups across a range of hierarchical levels, from higher categories down to the infrageneric level. The subfamily Acanthoideae, within the Acanthaceae family, consists of a diverse group of flowering plants that are distributed globally. The present study attempted a comprehensive analysis of the pollen morphology, employing both light microscopy (LM) and scanning electron microscopy (SEM), for a total of 13 Acanthoideae species from the Shivalik Foothills in Rajaji National Park (located in the northern Indian state of Uttarakhand, Western Himalaya). The findings indicated that the Acanthoideae is characterized by eurypalynous features, and the studied species exhibited pollen grains that were monads, radially symmetrical, and varied in size from small to large. The pollen grains were predominantly tricolporate or heteroaperturate, with porate occurrences being rare. The significant variation in exine sculpturing, including reticulate, coarsely reticulate, and bireticulate patterns, holds substantial taxonomic significance. The detailed presentation encompasses pollen morphological characters described with LM and SEM micrographs, along with a species-level identification key. RESEARCH HIGHLIGHTS: This article provides a thorough analysis of the pollen morphology of Acanthoideae taxa using both light microscopy and scanning electron microscopy, covering 13 species across 10 genera and revealing a broad spectrum of pollen characteristics, including size, shape, aperture type, and exine sculpturing. The microscopic investigation of these Acanthoideae species not only enhances our understanding of their pollen morphology but also aids in species identification through the development of a pollen-based key.

The global pattern of epiphytic liverwort disparity: insights from Frullania

The geographical and ecological patterns of morphological disparity are crucial to understand how species are assembled within communities in the context of the evolutionary history, morphological evolution and ecological interactions. However, with limited exceptions, rather few studies have been conducted on the global pattern of disparity, particularly in early land plants. Here we explored the spatial accumulation of disparity in a morphologically variable and species rich liverwort genus Frullania in order to test the hypothesis of latitude disparity gradient. We compiled a morphological data set consisting of eight continuous traits for 244 currently accepted species, and scored the species distribution into 19 floristic regions worldwide. By reconstructing the morphospace of all defined regions and comparisons, we identified a general Gondwana-Laurasia pattern of disparity in Frullania. This likely results from an increase of ecological opportunities and / or relaxed constraints towards low latitudes. The lowest disparity occurred in arid tropical regions, largely due to a high extinction rate as a consequence of paleoaridification. There was weak correlation between species diversity and disparity at different spatial scales. Furthermore, long-distance dispersal may have partially shaped the present-day distribution of Frullania disparity, given its frequency and the great contribution of widely distributed species to local morphospace. This study not only highlighted the crucial roles of paleoenvironmental changes, ecological opportunities, and efficient dispersal on the global pattern of plant disparity, but also implied its dependence on the ecological and physiological function of traits.

Why does pollen morphology vary? Evolutionary dynamics and morphospace occupation in the largest angiosperm order (Asterales)

Morphological diversity (disparity) is a key component of biodiversity and increasingly a focus of botanical research. Despite the wide range of morphologies represented by pollen grains, to date there are few studies focused on the controls on pollen disparity and morphospace occupation, and fewer still considering these parameters in a phylogenetic framework. Here, we analyse morphospace occupation, disparity and rates of morphological evolution in Asterales pollen, in a phylogenetic context. We use a dataset comprising 113 taxa from across the Asterales phylogeny, with pollen morphology described using 28 discrete characters. The Asterales pollen morphospace is phylogenetically structured around groups of related taxa, consistent with punctuated bursts of morphological evolution at key points in the Asterales phylogeny. There is no substantial difference in disparity among these groups of taxa, despite large differences in species richness and biogeographic range. There is also mixed evidence for whole-genome duplication as a driver of Asterales pollen morphological evolution. Our results highlight the importance of evolutionary history for structuring pollen morphospace. Our study is consistent with others that have shown a decoupling of biodiversity parameters, and reinforces the need to focus on disparity as a key botanical metric in its own right.

Geometric and topological approaches to shape variation in Ginkgo leaves

Leaf shape is a key plant trait that varies enormously. The range of applications for data on this trait requires frequent methodological development so that researchers have an up-to-date toolkit with which to quantify leaf shape. We generated a dataset of 468 leaves produced by Ginkgo biloba, and 24 fossil leaves produced by evolutionary relatives of extant Ginkgo. We quantified the shape of each leaf by developing a geometric method based on elastic curves and a topological method based on persistent homology. Our geometric method indicates that shape variation in modern leaves is dominated by leaf size, furrow depth and the angle of the two lobes at the leaf base that is also related to leaf width. Our topological method indicates that shape variation in modern leaves is dominated by leaf size and furrow depth. We have applied both methods to modern and fossil material: the methods are complementary, identifying similar primary patterns of variation, but also revealing different aspects of morphological variation. Our topological approach distinguishes long-shoot leaves from short-shoot leaves, both methods indicate that leaf shape influences or is at least related to leaf area, and both could be applied in palaeoclimatic and evolutionary studies of leaf shape.