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Leaves with high photosynthetic capacity require high transpiration capacity. Consequently, hydraulic conductance, stomatal conductance, and assimilation capacities should be positively correlated. These traits make independent demands on anatomical space, particularly due to the propensity for veins to have bundle sheath extensions that exclude stomata from the local epidermis. We measured density and area occupation of bundle sheath extensions, density and size of stomata and subsidiary cells, and venation density for a sample of extant angiosperms and fossil and living nonangiosperm tracheophytes. For most nonangiosperms, even modest increases in vein density and stomatal conductance would require substantial reconfigurations of anatomy. One characteristic of the angiosperm syndrome (e.g. small cell sizes, etc.) is hierarchical vein networks that allow expression of bundle sheath extensions in some, but not all veins, contrasting with all-or-nothing alternatives available with the single-order vein networks in most nonangiosperms. Bundle sheath modulation is associated with higher vein densities in three independent groups with hierarchical venation: angiosperms, Gnetum (gymnosperm) and Dipteris (fern). Anatomical and developmental constraints likely contribute to the stability in leaf characteristics – and ecophysiology – seen through time in different lineages and contribute to the uniqueness of angiosperms in achieving the highest vein densities, stomatal densities, and physiological rates.

Premise of the Study Dipteridaceae is a lineage of ferns that has existed from the early Mesozoic and is known for its extensive fossil record. By integrating information from all described extant and extinct genera into a single phylogenetic study, this paper aims to examine the taxonomy of the group on a whole and explore character evolution within the lineage across time. Methods A morphological matrix of 51 characters was developed for 72 species (43 extinct and 29 extant) based on published information. Morphological characters were combined with nucleotide sequences for four chloroplast genes (rbcL, atpA, atpB, and rps4) for extant taxa, and combined parsimony analyses were conducted to infer evolutionary trends in the group. Key Results Dipteridaceae was found to be monophyletic and characterized by highly anastomosing minor veins forming a meshwork of areoles with free‐included veinlets. Based on our analyses, we recognize six previously described genera (i.e., Goeppertella, Thaumatopteris, Clathropteris, Digitopteris, Dipteris, and Cheiropleuria) and one new genus (i.e., Sewardalea). Fossils currently described as Dictyophyllum, Kenderlykia, Hausmannia, and Protorhipis are ambiguously placed on the tree and are recognized as possibly unnatural morphogenera. Conclusions Overall, the evolutionary trend in Dipteridaceae has been toward increasing complexity in the venation pattern and laminal fusion. Only the Hausmannia‐type frond with dichotomizing primary veins and relatively fused lamina persisted in the later part of the Mesozoic to the present. Within the crown group, we see evidence of re‐radiation of frond forms in Dipteris and Cheiropleuria.

Clathropteris was a typical dipterid fern with well documented fossil record and was widely dispersed during the Mesozoic; however, our knowledge of fertile structures including in situ spores for this genus is still very limited. Here we report well-preserved compression specimens of Clathropteris obovata Oishi from the Late Triassic of Guangyuan, Sichuan Province, China. The specimens show round to oval and exindusiate sori, vertical to oblique annuli in sporangia, and in situ trilete spores with verrucate and baculate sculptures, which are comparable to dispersed spore genera of Converrucosisporites and Conbaculatisporites . Comparisons of relevant fossil taxa suggest that specimens of C. obovata from Triassic of China provide for the first time in Asia the detailed fertile structures with in situ spore characters of dipterid fossil Clathropteris . Unlike living Dipteris , Mesozoic fossils of Dipteridaceae show a high diversity and a range of complex morphology of in situ spores, thus are significant for the evolutionary links between Dipteridaceae and other related fern clade, including Gleicheniaceae and Matoniaceae of the Gleicheniales.

Anatomically preserved foliage of a dipteridaceous fern has been identified in both calcareous nodules and fine-grained, carbonate-cemented sandstone from the early Cretaceous (Hauterivian-Barremian) Apple Bay locality from Vancouver Island, British Columbia, Canada. Fronds with attached sporangia containing spores are preserved as both compression/impressions and as permineralizations. Fan-shaped laminar segments display paired teeth along the margin. Major veins dichotomize to the lamina edge, and finer veins reticulate, forming square to polygonal areoles, with freely ending veinlets. Veins are enclosed by sclerenchymatous sheaths, and the abaxial epidermis is recessed, producing concave areas between veins. Adaxial cuticle is thick, and the epidermis contains rectangular cells with undulating walls. Anomocytic scattered stomata occur on the abaxial surface. Sporangia and trichomes are scattered across the abaxial epidermis in the areolar concavities. Sporangial stalks are short, two to three cells long and four to six cells wide throughout their length. Sporangia have a vertical annulus that is interrupted by the stalk, and they contain trilete spores that correspond to Cibotiumspora jurienensis. Leaf morphology is similar to that of extant Dipteris novoguineensis and fossil Hausmannia spp. A unique combination of characters demonstrates that Hausmannia is a distinct genus of fossil dipterids. An examination of leaves from extant Dipteris rhizomes of various ages suggests that the genus Protorhipis may represent juvenile Hausmannia at some localities. The association of Hausmannia with small pieces of delicate moss gametophytes, fern sporelings, and vegetative remains of Lycopodium and Selaginella at Apple Bay reinforces the interpretation that these fossil dipterids were deposited under storm conditions and that Hausmannia may have grown in disturbed habitats. [PUBLICATION ABSTRACT]

Examination of two species of osmundaceous ferns, two species of marattialean, and one dipterid, all representative of ferns with a long fossil history, has shown that the egg cells possess numerous large amyloplasts. The nuclei of these egg cells also produce no vesicular or sheet-like protrusions during maturation. In these respects the egg cells of the ferns examined differ sharply from those of more recent ferns such as Pteridium and Dryopteris. The significance of these findings is discussed.

Description du sujet. Cette étude traite de la végétation et des Diptères Syrphidae au sein de Surfaces de Promotion de la Biodiversité (SPB) de type « prairies extensives » en contexte agricole. Objectifs. L’objectif consiste à tester l’influence des facteurs « taille » et « qualité botanique » des SPB sur la syrphifaune qui s’y développe. Il s’agit également de rechercher les relations entre la végétation et les syrphes, ainsi que de mettre en avant le potentiel de lutte biologique de ces surfaces. Méthode. Douze SPB ont été sélectionnées, sur la base de leur taille (< 3 000 m2 vs > 9 000 m2) et de leur niveau de qualité botanique établi sur la base de la présence d'espèces végétales indicatrices. Des inventaires de végétation ont été réalisés dans chacune des SPB, l’échantillonnage des syrphes a été effectué par la pose de deux pièges à émergence et d’un piège Malaise par site. Résultats. Indépendamment de leur taille ou de leur niveau de qualité botanique, les SPB abritent et attirent une faune syrphidologique majoritairement aphidiphage au stade larvaire. Les fleurs de couleur jaune et blanche ainsi que celles produisant du nectar influencent la richesse et l'abondance en syrphes. Conclusions. Le potentiel des SPB à abriter et attirer des syrphes aphidiphages montre qu'elles sont en mesure d’offrir un service de lutte biologique contre les ravageurs des cultures adjacentes. Functional biodiversity in an agricultural landscape: a floristic and syrphidologic study of Biodiversity Promotion Surfaces (BPSs) Description of the subject. This study focuses on the vegetation and Diptera Syrphidae found in biodiversity promotion surfaces (BPSs) of the “extensive meadows” type, within an agricultural context. Objectives. The objective was to test the influence of the “size” and “botanical quality” factors of BPSs on the syrphifauna that develops there. It also aimed to highlight the relationships between vegetation and hoverflies, and to emphasize the potential for the biological control of these surfaces. Method. Twelve BPSs were selected on the basis of their size (< 3,000 m2 vs > 9,000 m2) and their level of botanical quality, defined on the basis of indicator plant species. Vegetation inventories were conducted in each of the BPSs. Hoverfly sampling was carried out via the two emergence traps and one Malaise trap that were installed on each site. Results. Regardless of their size or level of botanical quality, BPSs are home to and attract mostly aphidiphagous hoverflies in the larval stage. Yellow and white flowers, as well as those producing nectar, influence the richness and abundance of hoverflies. Conclusions. The potential of BPSs to shelter and attract aphidiphagous hoverflies shows that they are able to offer a biological control service against pests in adjacent crops.