A Complete Fossil-Calibrated Phylogeny of Seed Plant Families as a Tool for Comparative Analyses: Testing the 'Time for Speciation' Hypothesis

Tissue succulence in plants: Carrying water for climate change

Tissue succulence in plants involves the storage of water in one or more organs or tissues to assist in maintaining water potentials on daily or seasonal time scales. This drought-avoidance or drought-resistance strategy allows plants to occupy diverse environments including arid regions, regions with rocky soils, epiphytic habitats, and saline soils. Climate-resilient strategies are of increasing interest in the context of the global climate crisis, which is leading to hotter and drier conditions in many regions throughout the globe. Here, we describe a short history of succulent plants, the basic concepts of tissue succulence, the anatomical diversity of succulent morphologies and associated adaptive traits, the evolutionary, phylogenetic, and biogeographical diversity of succulent plants, extinction risks to succulents due to poaching from their natural environments, and the myriad uses and applications of economically important succulent species and the products derived from them. Lastly, we discuss current prospects for engineering tissue succulence to improve salinity and drought tolerance in crops.

Invasive alien plants are phylogenetically distinct from other alien species across spatial and taxonomic scales in China

Introduction

Phylogenetic relatedness is one of the important factors in the community assembly process. Here, we aimed to understand the large-scale phylogenetic relationship between alien plant species at different stages of the invasion process and how these relationships change in response to the environmental filtering process at multiple spatial scales and different phylogenetic extents.

Methods

We identified the alien species in three invasion stages, namely invasive, naturalized, and introduced, in China. The occurrence records of the species were used to quantify two abundance-based phylogenetic metrics [the net relatedness index (NRI) and the nearest taxon index (NTI)] from a highly resolved phylogenetic tree. The metrics were compared between the three categories of alien species. Generalized linear models were used to test the effect of climate on the phylogenetic pattern. All analyses were conducted at four spatial scales and for three major angiosperm families.

Results

We observed significantly higher NRI and NTI values at finer spatial scales, indicating the formation of more clustered assemblages of phylogenetically closely related species in response to the environmental filtering process. Positive NTI values for the invasive and naturalized aliens suggested that the presence of a close relative in the community may help the successful naturalization and invasion of the introduced alien species. In the two-dimensional phylogenetic space, the invasive species communities significantly differed from the naturalized and introduced species, indicating that established alien species need to be phylogenetically different to become invasive. Positive phylogenetic measures for the invasive aliens across the spatial scales suggested that the presence of invasive aliens could facilitate the establishment of other invasive species. Phylogenetic relatedness was more influenced by temperature than precipitation, especially at a finer spatial scale. With decreased temperature, the invasive species showed a more clustered assemblage, indicating conservatism of their phylogenetic niche. The phylogenetic pattern was different at the family level, although there was a consistent tendency across families to form more clustered assemblages.

Discussion

Overall, our study showed that the community assemblage became more clustered with the progression of the invasion process. The phylogenetic measures varied at spatial and taxonomic scales, thereby highlighting the importance of assessing phylogenetic patterns at different gradients of the community assembly process.

Neophytes may promote hybridization and adaptations to a changing planet

Human activities erode geographic barriers, facilitating hybridization among previously isolated taxa. However, limited empirical research exists on the consequences of introduced species (neophytes) for hybridization and subsequent evolutionary outcomes. To address this knowledge gap, we employed a macroecological approach. First, we examined the spatial and phylogenetic overlap between neophytes and hybrids by integrating the Plants of the World Online database with the Global Naturalized Alien Flora database. Second, leveraging the largest dated plant phylogeny available, we compared diversification rates between genera containing hybrids and neophytes versus those without. Third, focusing on the extensively studied hybrid flora of Britain, we studied the spatial distributions of hybrids in relation to neophyte and native parents, assessing potential adaptations to anthropogenic disturbances and impacts on native species. Overall, our findings highlight positive ties between contemporary biodiversity redistribution and hybridization. Spatially (across countries) and phylogenetically (across genera), neophyte incidence was positively associated with hybrid incidence. Genera comprising both hybrids and neophytes displayed significantly higher diversification rates. Neophyte hybrids primarily occupied areas with a higher human footprint, with limited evidence of hybrids threatening native species throughout their range in more natural habitats. These results challenge the notion that species naturalizations and hybridizations exclusively yield negative outcomes for biodiversity. While it is conceivable that anthropogenic hybridization may facilitate recombination of genetic variation and contribute to conserving genetic diversity in disturbed environments, further research is needed to fully understand these processes.

Mass production of unvouchered records fails to represent global biodiversity patterns

The ever-increasing human footprint even in very remote places on Earth has inspired efforts to document biodiversity vigorously in case organisms go extinct. However, the data commonly gathered come from either primary voucher specimens in a natural history collection or from direct field observations that are not traceable to tangible material in a museum or herbarium. Although both datasets are crucial for assessing how anthropogenic drivers affect biodiversity, they have widespread coverage gaps and biases that may render them inefficient in representing patterns of biodiversity. Using a large global dataset of around 1.9 billion occurrence records of terrestrial plants, butterflies, amphibians, birds, reptiles and mammals, we quantify coverage and biases of expected biodiversity patterns by voucher and observation records. We show that the mass production of observation records does not lead to higher coverage of expected biodiversity patterns but is disproportionately biased toward certain regions, clades, functional traits and time periods. Such coverage patterns are driven by the ease of accessibility to air and ground transportation, level of security and extent of human modification at each sampling site. Conversely, voucher records are vastly infrequent in occurrence data but in the few places where they are sampled, showed relative congruence with expected biodiversity patterns for all dimensions. The differences in coverage and bias by voucher and observation records have important implications on the utility of these records for research in ecology, evolution and conservation research.

Next-generation sequencing data show rapid radiation and several long-distance dispersal events in early Costaceae

The monocot family Costaceae Nakai consists of seven genera but their mutual relationships have not been satisfactorily resolved in previous studies employing classical molecular markers. Phylogenomic analyses of 365 nuclear genes and nearly-complete plastome data provide almost fully resolved insights into their diversification. Paracostus is identified as sister to all other taxa, followed by several very short branches leading to discrete lineages, suggesting an ancient rapid radiation of these early lineages and leaving the exact relationships among them unresolved. Relationships among Chamaecostus, Dimerocostus and Monocostus confirmed earlier findings that these genera form a monophyletic group. The Afro-American Costus is also monophyletic. By contrast, Tapeinochilos appeared as a well-supported crown lineage of Cheilocostus rendering it paraphyletic. As these two genera differ morphologically from one another owing to a shift from insect- to bird-pollination, we propose to keep both names. The divergence time within Costaceae was estimated using penalized likelihood utilizing two fossils within Zingiberales, †Spirematospermum chandlerae and †Ensete oregonense, indicated a relatively recent diversification of Costaceae, between 18 and 9 Mya. Based on these data, the current pantropical distribution of the family is hypothesized to be the result of several long-distance intercontinental dispersal events, which do not correlate with global geoclimatic changes.

Comparison of the chloroplast genomes and phylogenomic analysis of Elaeocarpaceae

Background

Elaeocarpaceae is a vital family in tropical and subtropical forests. Compared with the important position of Elaeocarpaceae species in forest ecosystem and the concern of medicinal value, the most research on Elaeocarpaceae are classification and taxonomy. Molecular systematics has corrected the morphological misjudgment, and it belongs to Oxalidales. Phylogenetic and divergence time estimates of Elaeocarpaceae is mostly constructed by using chloroplast gene fragments. At present, although there are reports on the chloroplast structure of Elaeocarpaceae, a comprehensive analysis of the chloroplast structure of Elaeocarpaceae is lacking.

Methods

To understand the variation in chloroplast sequence size and structure in Elaeocarpaceae, the chloroplast genomes of nine species were sequenced using the Illumina HiSeq 2500 platform and further assembled and annotated with Elaeocarpus japonicus and Sloanea sinensis (family Elaeocarpaceae) as references. A phylogenomic tree was constructed based on the complete chloroplast genomes of the 11 species representing five genera of Elaeocarpaceae. Chloroplast genome characteristics were examined by using Circoletto and IRscope software.

Results

The results revealed the following: (a) The 11 sequenced chloroplast genomes ranged in size from 157,546 to 159,400 bp. (b) The chloroplast genomes of Elaeocarpus, Sloanea, Crinodendron and Vallea lacked the rpl32 gene in the small single-copy (SSC) region. The large single-copy (LSC) region of the chloroplast genomes lacked the ndhK gene in Elaeocarpus, Vallea stipularis, and Aristotelia fruticosa. The LSC region of the chloroplast genomes lacked the infA gene in genus Elaeocarpus and Crinodendron patagua. (c) Through inverted repeat (IR) expansion and contraction analysis, a significant difference was found between the LSC/IRB and IRA/LSC boundaries among these species. Rps3 was detected in the neighboring regions of the LSC and IRb regions in Elaeocarpus. (d) Phylogenomic analysis revealed that the genus Elaeocarpus is closely related to Crinodendron patagua on an independent branch and Aristotelia fruticosa is closely related to Vallea stipularis, forming a clade with the genus Sloanea. Structural comparisons showed that Elaeocarpaceae diverged at 60 Mya, the genus Elaeocarpus diverged 53 Mya and that the genus Sloanea diverged 0.44 Mya. These results provide new insight into the evolution of the Elaeocarpaceae.

The evolution of insular woodiness

Insular woodiness (IW)-the evolutionary transition from herbaceousness toward woodiness on islands-is one of the most iconic features of island floras. Since pioneering work by Darwin and Wallace, a number of drivers of IW have been proposed, such as 1) competition for sunlight requiring plants with taller and stronger woody stems and 2) drought favoring woodiness to safeguard root-to-shoot water transport. Alternatively, IW may be the indirect result of increased lifespan related to 3) a favorable aseasonal climate and/or 4) a lack of large native herbivores. However, information on the occurrence of IW is fragmented, hampering tests of these potential drivers. Here, we identify 1,097 insular woody species on 375 islands and infer at least 175 evolutionary transitions on 31 archipelagos, concentrated in six angiosperm families. Structural equation models reveal that the insular woody species richness on oceanic islands correlates with a favorable aseasonal climate, followed by increased drought and island isolation (approximating competition). When continental islands are also included, reduced herbivory pressure by large native mammals, increased drought, and island isolation are most relevant. Our results illustrate different trajectories leading to rampant convergent evolution toward IW and further emphasize archipelagos as natural laboratories of evolution, where similar abiotic or biotic conditions replicated evolution of similar traits.

Parental and Environmental Control of Seed Dormancy in Arabidopsis thaliana

Seed dormancy-the absence of seed germination under favorable germination conditions-is a plant trait that evolved to enhance seedling survival by avoiding germination under unsuitable environmental conditions. In Arabidopsis, dormancy levels are influenced by the seed coat composition, while the endosperm is essential to repress seed germination of dormant seeds upon their imbibition. Recent research has shown that the mother plant modulates its progeny seed dormancy in response to seasonal temperature changes by changing specific aspects of seed coat and endosperm development. This process involves genomic imprinting by means of epigenetic marks deposited in the seed progeny and regulators previously known to regulate flowering time. This review discusses and summarizes these discoveries and provides an update on our present understanding of the role of DOG1 and abscisic acid, two key contributors to dormancy.

A global phylogenetic regionalization of vascular plants reveals a deep split between Gondwanan and Laurasian biotas

Existing global regionalization schemes for plants consider the compositional affinities among biotas, but these have not explicitly considered phylogenetic information. Here, we present for the first time, a phytogeographical delineation of the global vascular flora based on species-level evolutionary relationships. We analysed 8737 820 geographical occurrence records for vascular plants together with a time-calibrated phylogeny including 67 269 species. We constructed a global phylogenetic regionalization by estimating species composition and phylogenetic beta diversity among 200 km × 200 km grid cells across the world. We identified de novo 16 phytogeographical units that are deeply split into two clusters: Laurasian and Gondwanan. Our regionalization broadly matches previous schemes, but also highlights the separation of the Gondwanan biota into an Holotropical cluster and an Australian-Neozealandic-Patagonian cluster. In contrast, no clear split among Laurasian and Gondwanan biotas was retrieved when omitting phylogenetic information. The integration of phylogenetic and geographical information provides new insights into the delineation of phytogeographical areas and their historical relationships, enabling the identification of three large, clearly differentiated biotas, here referred to as kingdoms: Holarctic, Holotropical, and Austral. Our results provide further evidence for delineating transition zones and show a clear latitudinal pattern of increasing evolutionary distinctiveness towards the poles.

Whence Came These Plants Most Foul? Phylogenomics and Biogeography of Lowiaceae (Zingiberales)

Lowiaceae (order Zingiberales) is a small family of forest herbs in Southeast Asia. All species belong to the genus Orchidantha. They are known for possessing orchid-like flowers that are smelly, apparently mimicking dead animals, feces, or mushrooms. Little is known of the biogeographic patterns or character evolution of the family. We sampled the family extensively, including many recently discovered species, and reconstructed the phylogeny of the family using HybSeq with Lowiaceae-specific RNA baits. Our phylogenetic reconstructions confirm that the family is most closely related to Strelitziaceae, and that species with dark, foul-smelling flowers form a grade in which a clade of species with paler flowers are embedded. The pale-flowered species produce a distinct odor, resembling edible mushrooms. Apart from a single species, the species from Borneo form a clade, and the same is true for Indochinese species. The remaining species form a more widespread clade. A biogeographic analysis shows that the distribution of Lowiaceae can explained by vicariance and gradual dispersal from a shared ancestral range of Borneo and Indochina. There is no evidence of long-distance dispersal, only a later extension in distribution to Peninsular Malaysia which coincides with the presence of a land bridge. Different directions of spread are possible, but none require long-distance dispersal. The results are consistent with the geological history of Southeast Asia. In particular, the relatively early isolation between Indochina and Borneo could be explained by the presence of a sea barrier that developed 10–15 MYA, and the continuous movement of plant species between Borneo and Peninsular Malaysia could be explained by a land bridge that existed until c. 5 MYA. The lack of an extensive land bridge with a suitable habitat may explain the absence of this genus from Sumatra and other Indonesian islands aside from Borneo. The strict reliance on a continuous habitat for the range expansion of Lowiaceae can be explained by their fruits and seeds, which lack obvious adaptations for long-distance dispersal. The inability to disperse to new areas may also explain why the extant species have very restricted distributions.

A chromosome-scale genome assembly and annotation of the spring orchid (Cymbidium goeringii)

Cymbidium goeringii, commonly known as the spring orchid, has long been favoured for horticultural purposes in Asian countries. It is a popular orchid with much demand for improvement and development for its valuable varieties. Until now, its reference genome has not been published despite its popularity and conservation efforts. Here, we report the de novo assembly of the C. goeringii genome, which is the largest among the orchids published to date, using a strategy that combines short- and long-read sequencing and chromosome conformation capture (Hi-C) information. The total length of all scaffolds is 3.99 Gb, with an N50 scaffold size of 178.2 Mb. A total of 29,556 protein-coding genes were annotated and 3.55 Gb (88.87% of genome) repetitive sequences were identified. We constructed pseudomolecular chromosomes using Hi-C, incorporating 89.4% of the scaffolds in 20 chromosomes. We identified 220 expanded and 106 contracted genes families in C. goeringii after divergence from its close relative. We also identified new gene families, resistance gene analogues and changes within the MADS-box genes, which control a diverse set of developmental processes during orchid evolution. Our high quality chromosomal-level assembly of C. goeringii can provide a platform for elucidating the genomic evolution of orchids, mining functional genes for agronomic traits and for developing molecular markers for accelerated breeding as well as accelerating conservation efforts.

A dated phylogeny of Lardizabalaceae reveals an unusual long-distance dispersal across the Pacific Ocean and the rapid rise of East Asian subtropical evergreen broadleaved forests in the late Miocene

Temperate South American-Asian disjunct distributions are the most unusual in organisms, and challenging to explain. Here, we address the origin of this unusual disjunction in Lardizabalaceae using explicit models and molecular data. The family (c.40 species distributed in ten genera) also provides an opportunity to explore the historical assembly of East Asian subtropical evergreen broadleaved forests, a typical and luxuriant vegetation in East Asia. DNA sequences of five plastid loci of 42 accessions representing 23 species of Lardizabalaceae (c. 57.5% of estimated species diversity), and 19 species from the six other families of Ranunculales, were used to perform phylogenetic analyses. By dating the branching events and reconstructing ancestral ranges, we infer that extant Lardizabalaceae dated to the Upper Cretaceous of East Asia and that the temperate South American lineage might have split from its East Asian sister group at c. 24.4 Ma. A trans-Pacific dispersal possibly by birds from East Asia to South America is plausible to explain the establishment of the temperate South American-East Asian disjunction in Lardizabalaceae. Diversification rate analyses indicate that net diversification rates of Lardizabalaceae experienced a significant increase around c. 7.5 Ma. Our findings suggest that the rapid rise of East Asian subtropical evergreen broadleaved forests occurred in the late Miocene, associated with the uplift of the Tibetan Plateau and the intensified East Asian monsoon, as well as the higher winter temperature and atmospheric CO₂ levels.

Naked resting bud morphologies and their taxonomic and geographic distributions in temperate, woody floras

Resting bud cataphylls are often assumed to play an essential protective role in winter due to their widespread presence among temperate, woody plants. This view is challenged by our documentation of significant numbers of temperate woody angiosperm taxa with naked buds that overwinter without cataphyll protection. We inventoried temperate, woody angiosperm taxa reported to have resting buds without cataphyll protection in winter and for the first time characterised the morphological and functional diversity of naked buds. Using this new classification of bud types, the taxonomic and geographic distributions of taxa with naked buds were summarised and relationships between plant functional traits and bud type were investigated. Naked buds are not, as long presumed, markedly rare in temperate, woody floras. They occur in at least 87 genera in 42 families throughout the angiosperm phylogeny in various morphologically distinct manifestations. The geographic distribution of species with naked buds in temperate areas was found to be associated with summer precipitation, but not with winter climatic variables. Resting bud structure is not necessarily a trait optimised solely for winter survival. A taxon's bud composition may be influenced by factors such as biogeographic history and ontogenetic pattern of leaf formation over the growing season.

Sowing forests: a synthesis of seed dispersal and predation by agoutis and their influence on plant communities

Granivorous rodents have been traditionally regarded as antagonistic seed predators. Agoutis (Dasyprocta spp.), however, have also been recognized as mutualistic dispersers of plants because of their role as scatter-hoarders of seeds, especially for large-seeded species. A closer look shows that such definitions are too simplistic for these Neotropical animals because agoutis can influence plant communities not only through seed dispersal of large seeds but also through predation of small seeds and seedlings, evidencing their dual role. Herein, we summarize the literature on plant-agouti interactions, decompose agouti seed dispersal into its quantitative and qualitative components, and discuss how environmental factors and plant traits determine whether these interactions result in mutualisms or antagonisms. We also look at the role of agoutis in a community context, assessing their effectiveness as substitutes for extinct megafaunal frugivores and comparing their ecological functions to those of other extant dispersers of large seeds. We also discuss how our conclusions can be extended to the single other genus in the Dasyproctidae family (Myoprocta). Finally, we examine agoutis' contribution to carbon stocks and summarize current conservation threats and efforts. We recorded 164 interactions between agoutis and plants, which were widespread across the plant phylogeny, confirming that agoutis are generalist frugivores. Seed mass was a main factor determining seed hoarding probability of plant species and agoutis were found to disperse larger seeds than other large-bodied frugivores. Agoutis positively contributed to carbon storage by preying upon seeds of plants with lower carbon biomass and by dispersing species with higher biomass. This synthesis of plant-agouti interactions shows that ecological services provided by agoutis to plant populations and communities go beyond seed dispersal and predation, and we identify still unanswered questions. We hope to emphasise the importance of agoutis in Neotropical forests.

The Reference Genome of Tea Plant and Resequencing of 81 Diverse Accessions Provide Insights into Its Genome Evolution and Adaptation

Tea plant is an important economic crop, which is used to produce the world's oldest and most widely consumed tea beverages. Here, we present a high-quality reference genome assembly of the tea plant (Camellia sinensis var. sinensis) consisting of 15 pseudo-chromosomes. LTR retrotransposons (LTR-RTs) account for 70.38% of the genome, and we present evidence that LTR-RTs play critical roles in genome size expansion and the transcriptional diversification of tea plant genes through preferential insertion in promoter regions and introns. Genes, particularly those coding for terpene biosynthesis proteins, associated with tea aroma and stress resistance were significantly amplified through recent tandem duplications and exist as gene clusters in tea plant genome. Phylogenetic analysis of the sequences of 81 tea plant accessions with diverse origins revealed three well-differentiated tea plant populations, supporting the proposition for the southwest origin of the Chinese cultivated tea plant and its later spread to western Asia through introduction. Domestication and modern breeding left significant signatures on hundreds of genes in the tea plant genome, particularly those associated with tea quality and stress resistance. The genomic sequences of the reported reference and resequenced tea plant accessions provide valuable resources for future functional genomics study and molecular breeding of improved cultivars of tea plants.

Pollen Cell Wall Patterns Form from Modulated Phases

The ornately geometric walls of pollen grains have inspired scientists for decades. We show that the evolved diversity of these patterns is entirely recapitulated by a biophysical model in which an initially uniform polysaccharide layer in the extracellular space, mechanically coupled to the cell membrane, phase separates to a spatially modulated state. Experiments reveal this process occurring in living cells. We observe that in ∼10% of extant species, this phase separation reaches equilibrium during development such that individual pollen grains are identical and perfectly reproducible. About 90% of species undergo an arrest of this process prior to equilibrium such that individual grains are similar but inexact copies. Equilibrium patterns have appeared multiple times during the evolution of seed plants, but selection does not favor these states. This framework for pattern development provides a route to rationalizing the surface textures of other secreted structures, such as cell walls and insect cuticle.

Evolutionary trajectories, accessibility and other metaphors: the case of C4 and CAM photosynthesis

Are evolutionary outcomes predictable? Adaptations that show repeated evolutionary convergence across the Tree of Life provide a special opportunity to dissect the context surrounding their origins, and identify any commonalities that may predict why certain traits evolved many times in particular clades and yet never evolved in others. The remarkable convergence of C₄ and Crassulacean Acid Metabolism (CAM) photosynthesis in vascular plants makes them exceptional model systems for understanding the repeated evolution of complex phenotypes. This review highlights what we have learned about the recurring assembly of C₄ and CAM, focusing on the increasingly predictable stepwise evolutionary integration of anatomy and biochemistry. With the caveat that we currently understand C₄ evolution better than we do CAM, I propose a general model that explains and unites C₄ and CAM evolutionary trajectories. Available data suggest that anatomical modifications are the 'rate-limiting step' in each trajectory, which in large part determines the evolutionary accessibility of both syndromes. The idea that organismal structure exerts a primary influence on innovation is discussed in the context of other systems. Whether the rate-limiting step occurs early or late in the evolutionary assembly of a new phenotype may have profound implications for its distribution across the Tree of Life.

Exploring the Concept of Lineage Diversity across North American Forests

Lineage diversity can refer to the number of genetic lineages within species or to the number of deeper evolutionary lineages, such as genera or families, within a community or assemblage of species. Here, we study the latter, which we refer to as assemblage lineage diversity (ALD), focusing in particular on its richness dimension. ALD is of interest to ecologists, evolutionary biologists, biogeographers, and those setting conservation priorities, but despite its relevance, it is not clear how to best quantify it. With North American tree assemblages as an example, we explore and compare different metrics that can quantify ALD. We show that both taxonomic measures (e.g., family richness) and Faith’s phylogenetic diversity (PD) are strongly correlated with the number of lineages in recent evolutionary time, but have weaker correlations with the number of lineages deeper in the evolutionary history of an assemblage. We develop a new metric, time integrated lineage diversity (TILD), which serves as a useful complement to PD, by giving equal weight to old and recent lineage diversity. In mapping different ALD metrics across the contiguous United States, both PD and TILD reveal high ALD across large areas of the eastern United States, but TILD gives greater value to the southeast Coastal Plain, southern Rocky Mountains and Pacific Northwest, while PD gives relatively greater value to the southern Appalachians and Midwest. Our results demonstrate the value of using multiple metrics to quantify ALD, in order to highlight areas of both recent and older evolutionary diversity.

Lateral root formation involving cell division in both pericycle, cortex and endodermis is a common and ancestral trait in seed plants

Studies on the model plant Arabidopsis have led to the common view that lateral roots are exclusively formed from pericycle cells and that the latter are unique in their ability to be reprogrammed into stem cells. By analysing lateral root formation in an evolutionary context, we show that lateral root primordium formation in which cortex, endodermis and pericycle are mitotically activated, is a common and ancestral trait in seed plants, whereas the exclusive involvement of pericycle evolved in the Brassicaceae. Further, also the endodermis can be reprogrammed into stem cells in some species.

Seeds-An evolutionary innovation underlying reproductive success in flowering plants

"Seeds nourish, seeds unite, seeds endure, seeds defend, seeds travel," explains the science writer Thor Hanson in his book The Triumph of Seeds (2015). The seed is an ultimate product of land plant evolution. The nursing and protective organization of the seed enable a unique parental care of the progeny that has fueled seed plant radiation. Seeds promote dispersal and optimize offspring production and thus reproductive fitness through biological adaptations that integrate environmental and developmental cues. The composite structure of seeds, uniting tissues that originate from three distinct organisms, enables the partitioning of tasks during development, maturation, and storage, while a sophisticated interplay between the compartments allows the fine-tuning of embryonic growth, as well as seed maturation, dormancy, and germination. In this review, we will highlight peculiarities in the development and evolution of the different seed compartments and focus on the molecular mechanisms underlying the interactions between them.