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90
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Introduction
My current research tries to understand the pattern of morphological evolution in the seed plants, with a particular focus on modern and fossil cycads.
Current institution
Current position
- Emmy Noether Junior Group Leader
Additional affiliations
April 2022 - March 2024
August 2015 - August 2019
Education
August 2015 - August 2019
March 2010 - March 2012
September 2006 - September 2009
Publications
Publications (90)
The placement of angiosperms and Gnetales in seed plant phylogeny remains one of the most enigmatic problems in plant evolution, with morphological analyses (which have usually included fossils) and molecular analyses pointing to very distinct topologies. Almost all morphology-based phylogenies group angiosperms with Gnetales and certain extinct se...
The pinnately lobed Aptian leaf fossil Mesodescolea plicata was originally described as a cycad, but new evidence from cuticle structure suggests that it is an angiosperm. Here we document the morphology and cuticle anatomy of Mesodescolea and explore its significance for early angiosperm evolution.
We observed macrofossils and cuticles of Mesodesc...
The determinants of biodiversity patterns can be understood using macroevolutionary analyses. The integration of fossils into phylogenies offers a deeper understanding of processes underlying biodiversity patterns in deep time. Cycadales are considered a relict of a once more diverse and globally distributed group but are restricted to low latitude...
Although molecular phylogenetics remains the most widely used method of inferring the evolutionary history of living groups, the last decade has seen a renewed interest in morphological phylogenetics, mostly driven by the promises that integrating the fossil record in phylogenetic trees offers to our understanding of macroevolutionary processes and...
The living fossil metaphor is tightly linked with the cycads. This group of gymnosperms is supposed to be characterised by long-term morphological stasis, particularly after their peak of diversity and disparity in the Jurassic. However, no formal test of this hypothesis exists. Here, we use a recent phylogenetic framework and an improved character...
The Arabidopsis root apical meristem is an excellent model for studying plant organ growth that involves a coordinated process of cell division, elongation, and differentiation, while each tissue type develops on its own schedule. Among these tissues, the protophloem is particularly important, differentiating early to supply nutrients and signallin...
Paleoart is an important tool for paleobotanists when reconstructing fossil plants and ancient ecosystems, and communicating with diverse audiences. Plants are fundamental components of terrestrial ecosystems. us, accurately depicting ancient plants in art is crucial for communicating comprehensive knowledge about ancient life. Here, we brie y revi...
Leaf-associated fungi, the fungi that depend on leaves to sporulate, have a rich Cenozoic record, however their earlier diversity is poorly characterized. Here we describe Harristroma eboracense gen. et sp. nov., a Middle Jurassic leaf-associated fungus colonizing the leaf cuticle of Nilssonia tenuicaulis (cycadophyte). To place our newly described...
OCTOPUS ( OPS ) and OCTOPUS-LIKE 2 ( OPL2 ), two homologous genes, were previously identified as important regulators of phloem differentiation in Arabidopsis roots, impacting root growth when their function is lost. Here, we investigated the roles of the other three OPS homologs in Arabidopsis, OPL1 , OPL3 , and OPL4 . We employed promoter activit...
Leaf venation is a pivotal trait in the success of vascular plants. Whereas gymnosperms have single or sparsely branched parallel veins, angiosperms developed a hierarchical structure of veins that form a complex reticulum. Its physiological consequences are considered to have enabled angiosperms to dominate terrestrial ecosystems in the Late Creta...
Citation: Ulrich, S.; Vieira, M.; Coiro, M.; Bouchal, J.M.; Geier, C.; Jacobs, B.F.; Currano, E.D.; Lenz, O.K.; Wilde, V.; Zetter, R.; et al. Origin and Early Evolution of Hydrocharitaceae and the Ancestral Role of Stratiotes. Plants Abstract: The combined morphological features of Stratiotes (Hydrocharitaceae) pollen, observed with light and elect...
Amber deposits are rare in Jurassic successions, occurring in small quantities, whereas Lower Cretaceous strata host many substantial and commonly fossiliferous amber deposits worldwide. Minor amounts of Early Jurassic amber have been reported from Italy, and small amounts of Late Jurassic amber are known from Lebanon, Jordan and Thailand. Other Ju...
What grows where? Knowledge about where to find particular species in nature must have been key to the survival of humans throughout our evolution. Over time, and as people colonised new land masses and habitats, interactions with the local biota led to a wealth of combined traditional and scientific wisdom about the distributions of species and th...
Previous paleobotanical work concluded that Paleogene elements of the sclerophyllous subhumid vegetation of western Eurasia and western North America were endemic to these disjunct regions, suggesting that the southern areas of the Holarctic flora were isolated at that time. Consequently, molecular studies invoked either parallel adaptation to dry...
The Gnetales are one of the most fascinating groups within seed plants. Although the advent of molecular phylogenetics has generated some confidence in their phylogenetic placement of Gnetales within seed plants, their macroevolutionary history still presents many unknowns. Here, we review the reasons for such unknowns, and we focus the discussion...
Pollen of the rare endemic Australian conifer Wollemia nobilis (Araucariaceae) has been reported to have quite variable features and has been linked to the dispersed fossil pollen Dilwynites. It was suggested that Dilwynites could indicate the presence of Wollemia in the fossil record since the macrofossil record for Wollemia is difficult to distin...
Premise:
Approximately 14% of all fern species have physiologically active chlorophyllous spores that are much more short-lived than the more common and dormant achlorophyllous spores. Most chlorophyllous-spored species (70%) are epiphytes, and these account for almost 37% of all epiphytic ferns. Chlorophyllous-spored ferns are also overrepresente...
Cycads (Cycadales) are among the most ancient lineages of extant seed-bearing plants and are the most threatened plant order on Earth, with circa 75% of the 356 accepted species endangered or threatened with extinction. Zamia is the most species-rich (81 spp.) and widely distributed cycad genus in the Americas, notable for its morphological and eco...
The fossil record of Lythrum is scarce and every new find brings an extra piece of the puzzle to the obscure phytogeographic history of this genus. Lythrum pollen is unique and has the potential to be recognized in palynological assemblages. Therefore, the few pre-Holocene fossil records are all pollen described from North America, Russia, and Euro...
Premise:
Unlike most flowering plants, orchid flowers have under-developed ovules that complete development only after pollination. Classical studies reported variation in the stage in which ovule development is arrested but the extent of this variation and its evolutionary and ecological significance are unclear.
Methods:
Here, we performed lig...
To understand Earth´s climate variability and improve predictions of future climate change, studying past climates is an important avenue to explore. A previously published record of pCO2, across the Triassic–Jurassic boundary (TJB, ~201 Ma) of East Greenland, showed that Bennettitales (Anamozomites and Pterophyllum) responded in parallel to the em...
Background and Aims
The gymnosperm order Cycadales is pivotal for our understanding of seed-plant phylogeny because of its phylogenetic placement close to the root node of extant spermatophytes and its combination of both derived and plesiomorphic character states. Although widely considered a ‘living fossil’ group, extant cycads display a high deg...
Fossil pollen believed to be related to extant Hagenia abyssinica were discovered in the early Miocene (21.73 Ma) Mush Valley paleoflora, Ethiopia, Africa. Both the fossil and extant pollen grains of H. abyssinica were examined with combined light microscopy, scanning electron microscopy, and transmission electron microscopy to compare the pollen a...
The origin of angiosperms is a classic macroevolutionary problem, because of their rapid rise in the Early Cretaceous fossil record, beginning about 139 Ma ago, and the conflict this creates with older crown-group ages based on molecular clock dating. Silvestro et al. use a novel methodology to model past angiosperm diversity based on a Bayesian Br...
The Mediterranean realm, comprising the Mediterranean and Macaronesian regions, has long been recognized as one of the world’s biodiversity hotspots, owing to its remarkable species richness and endemism. Several hypotheses on biotic and abiotic drivers of species diversification in the region have been often proposed but rarely tested in an explic...
Background:
Although pollen morphology has always been an important tool in plant systematics, the possibility of distinguishing between related taxa is still debated. A difficult case is the cycads, where their morphology and small size is very similar. Pollen morphology has been important in plant systematics and determination at the species leve...
Premise of the Research: The morphology of leaves is shaped by both historical and current
selection acting on constrained developmental systems. For this reason, the phylogenetic signal of
these characters is usually overlooked.
Methodology: We investigate morphology of the leaflets of all genera of the Zamiaceae using
multiple microscopical tech...
Background:
β-Amylases (BAMs) are a multigene family of glucan hydrolytic enzymes playing a key role not only for plant biology but also for many industrial applications, such as the malting process in the brewing and distilling industries. BAMs have been extensively studied in Arabidopsis thaliana where they show a surprising level of complexity...
The morphology of the early ontogenetic stages of cycad foliage may help resolve the relationships between extinct to extant cycad lineages. However, prior to this study, fossil evidence of cycad seedlings was not known. We describe a compression fossil of cycad eophylls with co-occurring fully developed leaves of adult specimens from the early Pal...
Calibrating the molecular clock is the most contentious step in every dating analysis, but the emerging total-evidence dating approach promises increased objectivity. It combines molecular and morphological data of extant and fossil taxa in a Bayesian framework. Information about absolute node ages stems from the inferred fossil placements and asso...
The pantropical Picrodendraceae produce mostly spheroidal to slightly oblate, echinate pollen grains equipped with narrow circular to elliptic pori that can be hard to identify to family level in both extant and fossil material using light microscopy only. Fossil pollen of the family have been described from the Paleogene of America, Antarctica, Au...
Premise of research. The genus Zamia L. (Zamiaceae), consisting of 79 species, is the most species-rich and widely distributed cycad genus in the New World and arguably the most morphologically and ecologically diverse genus in the Cycadales. However, a strong phylogenetic framework for this genus is still lacking. Methodology. We used a multilocus...
The timing of the origin of angiosperms is a hotly debated topic in plant evolution. Molecular dating analyses that consistently retrieve pre‐Cretaceous ages for crown‐group angiosperms have eroded confidence in the fossil record, which indicates a radiation and possibly also origin in the Early Cretaceous. Here, we evaluate paleobotanical evidence...
Background and aims:
Heteroblasty is a non-reversible morphological change associated with life stage change and has been linked to predictable environmental variation. It is present in several clades from mediterranean-type climates, such as African Restionaceae (restios). These have heteroblastic shoots: juvenile shoots are thin, branched and st...
The family Nymphaeaceae includes most of the diversity among the ANA‐grade angiosperms. Among the species of this family, floral structures and pollination strategies are quite varied. The genus Victoria, as well as subgenera Lotos and Hydrocallis in Nymphaea, presents night‐blooming, scented flowers pollinated by scarab beetles. Such similar polli...
Background:
In contrast to most animals, plants have an indeterminate body plan, which allows them to add new body parts during their lifetime. A plant's realized modular construction is the result of exogenous constraints and endogenous processes. This review focuses on endogenous processes that shape plant architectures and their evolution.
Sco...
Protophloem and metaphloem sieve tubes are essential for transporting carbohydrates and signalling molecules towards sink tissues. OCTOPUS ( OPS ) was previously identified as an important regulator of protophloem differentiation in Arabidopsis roots. Here, we investigated the role of OCTOPUS ‐ LIKE 2 ( OPL 2 ), a gene homologous to OPS .
OPL 2 exp...
Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angi...
The placement of angiosperms and Gnetales in seed plant phylogeny remains one of the most enigmatic problems in plant evolution, with morphological analyses (which have usually included fossils) and molecular analyses pointing to very distinct topologies. Almost all morphology-based phylogenies group angiosperms with Gnetales and certain extinct se...
Background
Even if they are considered the quintessential “living fossils”, the fossil record of the extant genera of the Cycadales is quite poor, and only extends as far back as the Cenozoic. This lack of data represents a huge hindrance for the reconstruction of the recent history of this important group. Among extant genera, Bowenia (or cuticles...
An improved pseudo-Schiff propidium iodide staining technique well suited for, but not limited to, the visualization of xylem cell walls in whole mount samples is presented. The pseudo-Schiff reaction results in covalent binding of the fluorescent dye propidium iodide to cell walls. This stable linkage permits the use of clearing agents after stain...
To uncover components of the mechanism that adjusts the rate of leaf starch degradation to the length of the night, we devised a screen for mutant Arabidopsis thaliana plants in which starch reserves are prematurely exhausted. The mutation in one such mutant, named early starvation 1 or esv1, eliminates a previously-uncharacterized protein. Starch...
The genus Dioon occupies an important phylogenetic position as sister to the other Zamiaceae. However, its
epidermal morphology is still poorly known. We employed scanning and transmission electron microscopy, confocal
microscopy and light microscopy to examine the epidermal and cuticular morphology of 12 of the 14 currently
recognized species of D...
The domestication of starch crops underpinned the development of human civilisation, yet we still do not fully understand how plants make starch. Starch is composed of glucose polymers that are branched (amylopectin) or linear (amylose). The amount of amylose strongly influences the physico-chemical behaviour of starchy foods during cooking and of...
UV ‐ B radiation damage in leaves is prevented by epidermal UV ‐screening compounds that can be modulated throughout ontogeny. In epiphytic orchids, roots need to be protected against UV ‐ B because they photosynthesize, sometimes even replacing the leaves. How orchid roots, which are covered by a dead tissue called velamen, avoid UV ‐ B radiation...
The evolution of the apertural type in the ANITA-grade family Nymphaeaceae, despite the importance of pollen characters for both palaeobotanical and neobotanical investigations, has not been yet totally understood. To elucidate some unclear aspects regarding the homologies of the apertural condition in basal and core Nymphaeaceae, we examined the p...
The genus Ceratozamia (Cycadales; Zamiaceae) was classically divided into two groups based on gross leaf morphology, but recent molecular phylogenetic analyses has identified three clades. On a larger scale, Ceratozamia appears closely related to Stangeria and to the neotropical genera Microcycas and Zamia. Whole leaf and isolated cuticle specimens...
