Perspectives in Plant Ecology Evolution and Systematics最新文献

Seed and fruit structures are one of the key innovations that allow plants to successfully occupy habitats all around the globe, ensuring dispersal, survival of unfavourable conditions and seedling establishment. While adaptive tracking in the majority of plants resulted in a single most optimal seed and fruit phenotype, some plants produce two or more types of morphologically distinct fruits and/or seeds that differ in their ecological and physiological characteristics. These carpological heteromorphisms are a type of bet-hedging strategy and are believed to have developed as a response to an unpredictable spatiotemporally-changing environment. Although recognized already by Charles Darwin, the true extent of this evolutionary phenomenon, its trade-off characteristics, heritability, evolvability, and its environmental and genetic regulation are still insufficiently investigated. Carpological heteromorphisms have been described from several plant families, however, they are most commonly found in Asteraceae and Amaranthaceae sensu lato (including Chenopodiaceae). The latter is an integral part of vegetation occurring in seasonally highly unpredictable semi-arid and arid zones worldwide. Carpological heteromorphisms in this family are multifold and span from morphologically distinct diaspores with different dispersal potentials and fleshy and non-fleshy fruits with different dispersal agents, to morphologically (in)distinct seeds with different germination behaviours. Heterocarpic and heterospermic taxa in Amaranthaceae sensu lato are predominantly diploid, possess relatively small genomes and have a high number of available genomic resources, which could expedite genomic investigations of these carpological heteromorphisms. Nevertheless, knowledge of the evolutionary seed ecology of Amaranthaceae sensu lato is scarce and disconnected. Here we review the literature on ecological, physiological and (epi)genetic aspects of germination and stress tolerance in early ontogenetic stages of heteromorphic Amaranthaceae sensu lato. Furthermore, we critically address the shortcomings of current studies and provide guidelines for further research. The authors anticipate this review to raise interest in this plant family and this biological phenomenon, which harbours a great potential to answer some very fundamental biological questions on how individual angiosperm lineages managed to conquer the most inhospitable habitats worldwide.

Sympetaly is a notable feature within the mimosoid clade (Leguminosae: Caesalpinioideae), specially as it is uncommon in rosids. The way the petals are organized, forming a tubular corolla by the union of the petals directly affects the perception of pollinators. This study examines whether the petal union leading to a sympetalous corolla in the mimosoid clade is widespread and whether there is variation in type and extent. For this purpose, floral buds and flowers of 16 species from 13 genera were collected, fixed, and processed for analysis by light and scanning electron microscopy. Most species studied display a pentamerous sympetalous corolla with free lobes. The petal primordia are individualized and emerge simultaneously on the floral apex, alternating with the sepal primordia. Petals remain free at the beginning of the intermediate stages of development, and subsequently, the petals curve and approach each other, and their margins touch. Epidermal papillae are found on the petals’ apical margin interconnecting the lobes, which enclose the inner organs of the floral bud. The structure of the sympetalous corolla is variable regarding the type and extent of the union. Four different types of sympetaly were found and classified as follows: 1. full connation - petals fully united along their length; 2. connation-coherence - petals genuinely united in the basal portion and coherent in the median and apical portion; 3. full coherence - petals intertwined with papillae throughout; and 4. partial coherence - free petals at the base and intertwined with papillae in the middle and apical portion. Thus, sympetaly of mimosoid legumes results from postgenital union of the petals at the apical, median, and basal regions during their development by tissue union (connation), intertwining of epidermal papillae (coherence), or both processes. The mucilage cells found along the petals guarantee the stabilization and flexibility of the tubes, in addition to contributing to the protection of the internal organs of the flower. Although more studies on floral development are needed to understand the evolution of this unusual trait, connation appears to be a derived trait within mimosoids.

The species composition and extent of hybridization in Sparganium subgenus Xanthosparganium in North Eurasia reported in different published sources significantly vary. Thus, we aimed to clarify the taxonomy and distribution of aquatic Sparganium in that area. We supplemented the existing fragmentary genetic and morphological data mainly from North America and South Asia with our data from East Europe and North Asia. We combined molecular barcoding of the nuclear phyC and plastid psbJ-petA DNA regions (382 samples) with morphological analysis of herbarium collections (more than 1500 specimens from 16 herbaria) and numerous natural populations with a special focus on hardly accessible Siberian and the Far Eastern regions of Russia. We found that aquatic Sparganium is represented in North Eurasia by nine species and 14 hybrids. Nine previously unknown hybrids are formally described as new nothotaxa. All species and hybrids could be reliably discriminated with barcoding. We refined the distribution of all taxa in North Eurasia, e.g., S. angustifolium, a species avoiding continental areas, where it was confused by many authors with mostly vegetative specimens of other taxa. In the S. emersum complex in addition to recognized earlier widespread S. emersum and eastern North American S. chlorocarpum we proved the existence of one more distinct lineage – Asian Pacific S. rothertii. We discovered different evolutionary lineages within some species (e.g., S. glomeratum and S. hyperboreum) causing additional issues in the taxa identification. Almost all species cross with each other, usually acting both as plastid and pollen donors. Most of the hybrids are widespread and abundant. They originate each time when the ranges of parental species overlap and suitable habitats are available, and rather do not disperse from the centres of origin. Hybridization can be a threat to species with narrow ecological tolerance. Active gene flow is also evident within species when different evolutionary lineages come in contact (e.g., S. emersum, S. rothertii, S. glomeratum, S. hyperboreum, S. natans). We provide a new taxonomic treatment, which solves many long-standing issues in subgenus Xanthosparganium, and a new identification key for both species and hybrids occurring in North Eurasia.

Studies in community genetics have often revealed a relationship between genetic diversity of the focal species and species diversity of the associated biotic communities. This relationship was studied in forest communities dominated by black alder (Alnus glutinosa Gaertn.), one of the few tree species tolerating an anoxic environment of waterlogged soils. It is a dominant species of tree overstory in two types of communities: alder carrs, forest swamps with stagnating water, and riparian forests occurring along smaller waterflows, periodically flooded with a considerable water level fluctuation during the vegetation period. Plant community composition and genetic variation of alder populations were studied in 218 black alder communities of both types distributed along a broad latitudinal transect from the Pannonian lowland to the Western Carpathians (Hungary, Slovakia, Poland). Species diversity was significantly higher in riparian stands than in alder carrs, while no difference was observed in the genetic diversity. The analysis of population structure revealed differentiation between Pannonian and Carpathian populations, which may be attributed to different migration pathways during the Holocene. No correlation was observed between genetic diversity of alder and species diversity of the associated vascular plant communities. On the other hand, using the ddRAD-sequencing approach applied to 96 trees, we identified 19 single-nucleotide polymorphisms significantly associated with climatic and soil variables. However, the hypothesized bioindication function of the plant community composition on the genetic variation of black alder as a focal species was not confirmed.

In parts of Angola, Namibia and South Africa the sparse vegetation at the margin of the Namib Desert is often dotted with roughly circular bare patches. The origin of these “fairy circles” (FC) is subject of an ongoing debate. In a recent article in PPEES, Getzin et al. (2022) provided assessments of grasses and termites combined with soil moisture measurements, in and near to fairy circles in several areas in Namibia. In their interpretation they state that termite herbivory is not causing this grass death as the plants had undamaged roots. Instead they propose that the matrix grasses severely depleted the water in FCs. Here, we use a comprehensive, detailed body of measurements and assessments collated during the last 14 years to propose an alternative interpretation. We structure our interpretation with four statements, each of them based on shown evidence: (1) Long-term soil moisture measurements confirm that the soil beneath the dry topsoil of the bare patch of fairy circles contains an equal or, especially during the biologically active season, higher amount of moisture than the surrounding matrix, at any given time. The grasses of the fairy circles bare patch die during the moist phase of the first weeks after a rain, before even the soil beneath the matrix vegetation gets depleted by transpiration. (2) Within the sandy soils of fairy circle landscapes, there is no sufficiently strong “uptake –diffusion feedback” that could cause a horizontal movement of soil moisture over several meters within a few days. (3) The grasses of the fairy circles bare patch first die at the centre of the bare patch and later towards the margin. (4) The grass in the bare patch of fairy circles dies because of damage to roots due to herbivory by sand termites.

Calyceraceae comprises 46 species mostly endemic to the Andes and Patagonia in Southern South America, and it is the sister family of Asteraceae, one of the largest Angiosperm families. With a robust phylogeny and with an exceptionally good sampling fraction, we performed macroevolution and biogeographic analyses to understand paleodiversity dynamics through time and space, and its potential drivers. We address the impact of the Andean uplift, global temperature, life forms, and biogeography on Calyceraceae diversification through a time-calibrated phylogeny. Calyceraceae diversification was homogeneous through time and followed a low speciation rate for the last 24 Mya, with no lineage differing much in their diversification dynamics. In accordance with the homogeneous speciation rate, we found that neither the Andean uplift, nor the evolution of global average temperature, nor the different life forms have affected its diversification. The Southern Andes is the centre of origin of the family and major clades within it, and most dispersal events occurred from the Andes to Patagonia. Most Calyceraceae species seem to have originated, evolved, and dispersed within the Argentinean Arid Diagonal, indicating that niche conservatism could have played an important role in the evolution of Calyceraceae. Differences in macroevolution dynamics could explain the asymmetry of species richness in the two sister families Asteraceae-Calyceraceae.

One of the fundamental questions in ecology is why species occur in some areas and not in others. Range limits, the boundaries between a species’ presence and absence, reflect the interplay of dispersal and population dynamics driven by biotic and abiotic conditions. As a result, range limits may shift as dispersal barriers are removed, climates change, and local species composition is altered, but the relative importance of these mechanisms is still not well understood. This is particularly true for introduced species, where current range limits may or may not reflect range limits at equilibrium, and is becoming more pressing under the effects of global climate change. To understand the drivers and stability of range limits in introduced Rumex conglomeratus, we used common garden experiments growing plants within, at the edge of and beyond their current range edge. Seeds were sourced from both lowland and upland populations and planted at all three sites. By measuring survival, growth, and the occurrence of reproduction, we tested whether upland populations are locally adapted to high elevation sites and whether plants were capable of surviving and reproducing above the current range edge. However, we found that upland populations were not better adapted to higher elevations, and often were small and performed more poorly than lowland populations across sites. Upland populations appear to be maintained by human-aided seed dispersal from lowland populations, which may constrain the opportunity for local adaptation. Although some plants survived above the current range edge, frost and growing season length restricted plant size and reproduction was infrequent. Therefore, the current range limit seems unlikely to expand as long as regular frost continues at the range edge and dispersal from the lowland continues to prevent local adaptation to upland environments.

Although functional traits are defined based on their impact on demographic parameters, trait-demography relationships are often reported as weak. These weak relationships might be due to disregarding trait interactions and environmental contexts, which should modulate species trait-demography relationships. We applied different models, including boosted regression tree (BRT) models, to investigate changes in the relationship between traits and demographic rates of tropical tree species in plots along an elevational gradient and among time intervals between censuses, analyzing the effect of a strong drought event. Based on a large dataset of 18,000 tree individuals from 133 common species, distributed among twelve 1-ha plots (habitats) in the Atlantic Forest (Brazil), we evaluated how trait interactions and the environmental context influence the demographic rates (growth, mortality, and recruitment). Functional traits, trait-trait, and trait-habitat interactions predicted demography with a good fit through either BRTs or linear mixed-models. Changes in growth rates were best related to size (diameter), and mortality rates to habitats, while changes in recruitment rates were best related to the specific leaf area. Moreover, the influence of traits differed among time intervals, and for demographic parameters, habitat affected growth and mortality by interacting with diameter. Here, we provide evidence that trait-demography relationships can be improved when considering the environmental context (space and time) and trait interactions to cope with the complexity of changes in the demography of tropical tree communities. Thus, to expand predictions of demography based on functional traits, we show that it is useful to fully incorporate the concept of multiple trait-fitness optima, resulting from trait interactions in different habitats and growth conditions.

As global warming progresses, plants may be forced to adapt to drastically changing environmental conditions. Arctic-alpine plants have been among the first to experience the effects of climate change. As a result, cold acclimation and freezing tolerance may become increasingly crucial for the survival as winter warming events and earlier snowmelt will cause increased exposure to occasional frost. The tribe Cochlearieae in the mustard family (Brassicaceae) offers an instructive system for studying cold adaptation in evolutionary terms, as the two sister genera Ionopsidium and Cochlearia are distributed among different ecological habitats throughout the European continent and the far north into circumarctic regions. By applying an electrolyte leakage assay to leaves obtained from plants cultivated under controlled temperature regimes in growth chambers, the freezing tolerance of different Ionopsidium and Cochlearia species was assessed measuring lethal freezing temperature values (LT₅₀ and LT₁₀₀), thereby allowing for a comparison across different species and accessions in their responses to cold. We hypothesized that, owing to varying selection pressures, geographically distant species would differ in freezing tolerance. Despite Ionopsidium occurring under warm and dry Mediterranean conditions and Cochlearia species distributed often at cold habitats, all accessions exhibited similar cold responses. The results may indicate that physiological adaptations of primary metabolic pathways to different stressors, such as salinity and drought, may confer an additional tolerance to cold; this is because all these stressors induce osmotic challenges.