Perspectives in Plant Ecology Evolution and Systematics最新文献

Although over-exploitation and habitat loss limit sustainable management, medicinal and aromatic plants (MAPs) are essential for traditional health practices and as a source of cash income for rural communities around the world. In contrast to a general assumption that harvest negatively affects resource abundance, local knowledge and detailed empirical observations have shown that for some species, some harvest methods maintain or increase abundance. However, many management plans for wild-harvested MAPs lack empirical data on post-harvest recovery of density as well as key demographic measures such as fruit-setting and seed formation. To deepen our understanding of these important social-ecological dynamics across taxa, as well as to offer in-depth empirical data on a key economically important and threatened MAP, we applied controlled simulated-harvest field experiments to Neopicrorhiza scrophulariiflora in eight populations along an elevation gradient (3800–4700 m) in the Nepal Himalayas, including four populations in a restricted-access site and four in an open-access site in north-central and north-western Nepal. Each site with a different conservation regime exhibits distinctive ecological circumstances that enable assessing how environmental factors and the level of exploitation influence the characteristics of the plant populations. We hypothesized that not all levels of harvest would be harmful, and that restoration capacity would permit a sustainable level of harvest, subject to both social and ecological pressures (access and elevation). Experimental harvest treatments included removing 0 % (control), 25 %, 50 %, 75 %, and 100 % of the ramets from the experimental plots. We applied a mixed-effects model for repeated measures ANCOVA to determine if harvest treatments appeared to exert influence on each of the response variables at each site. Density and reproductive output varied significantly among the harvest treatments and covaried with the pre-harvest condition. At low elevations in the restricted-access site, both density and reproductive output recovered within three years after harvest of 50 % of the ramets, and within a single year after a 25 % harvest. To some extent, strong budding potential and re-sprouting from the old rhizomes compensated for negative harvest impacts. However, in the open-access site, recovery to the pre-harvest level was achieved only for a 25 % treatment after one year. Harvest recovery was slower at higher elevations (>4250 m), and plots harvested more intensively (>50 % extraction) recovered very slowly. Our results indicate that spatially and temporally specific harvesting strategies can be used to manage populations sustainably, supporting both wild plant populations and human livelihoods.

Leaves, encountered in the majority of modern tracheophytes, evolved multiple times independently in several lineages. We define leaves as lateral appendages that share a common set of characters: vascularization, determinacy, regular arrangement, bilateral symmetry and, in most cases, adaxial-abaxial (dorsiventral) polarity. In this review we integrate data from developmental genetics and the fossil record to understand how the molecular and cellular mechanisms of leaf development evolved. We show that lycopsid leaves likely evolved once, and earlier, than euphyllophyte leaves, and that euphyllophyte leaves all evolved from lateral branching systems that were produced at regular intervals around the stem. We also show that the mosaic pattern of distribution and tempo of evolution of leaf-defining features (such as bilateral symmetry and dorsiventral polarity) among the different lineages suggests that these features evolved independently. Overall, at the level of the entire tracheophyte clade, integration of developmental, regulatory and fossil data reveals three overarching patterns: (1) the different leaf characters evolved independently throughout tracheophyte phylogeny and their regulatory pathways were assembled independently, only to become tightly integrated with each other later in the evolution of different lineages; (2) bilateral symmetry is a distinct and evolutionarily independent leaf feature from dorsiventral polarity; (3) regular arrangement is the most plesiomorphic and earliest-evolving leaf-defining feature across tracheophytes.

Epiphytes are often characterized by small size, specifically adapted to a relatively dry and nutrient-poor habitat. However, this epiphyte syndrome is derived from studies on species-rich and habitat-dominating groups such as orchids and bromeliads. To better understand general trait syndromes of epiphytes, it is important to analyze plant groups that are more transitional in the evolution of epiphytism e.g., the Australasian vireyas (Rhododendron sect. Schistanthe; Ericaceae). Here, we studied the morphology, ecophysiology, and anatomy of 44 species of Rhododendron section Schistanthe from living collections and obtained data for 288 species related to their "life form" (holoepiphytes [= obligatory epiphytes], facultative epiphytes and terrestrial congeners) from the literature. For phylogeny and time-calibrated tree, we used the nuclear ITS (Internal Transcribed Spacers) region. Using different statistics and phylogenetic comparative methods, our results support the hypothesis that holoepiphytic vireyas are smaller in size than the terrestrial ones. Terrestrial vireyas are found at higher minimum and maximum elevation than either facultative or holoepiphytic congeners. We demonstrate that the diversification of tropical Rhododendron is not related to the evolution of the epiphytic life form. Regarding the evolution of traits that are important for water economy, holoepiphytic vireyas do not differ much from their terrestrial relatives indicating that evolutionary steps for specialization towards an holoepiphytic habit are in their initial stages in Rhododendron. Given the large species diversity of the group conclusions based on the subset used here must be considered preliminary. However, our results provide the basis for more detailed future studies.

A trade-off between growth in high light and survival under shade is widely regarded as the main driver of secondary succession in humid forests. Outside the humid tropics, however, the microclimates of large openings may select for traits other than those that maximize growth rates. We tested for differential filtering of sapling functional traits by four different microenvironments in a south-temperate forest in south-central Chile. We measured light, temperatures, humidity, soil nutrients and sapling densities in each of four phases of a forest dynamic mosaic: shaded understoreys, tree-fall gaps, Chusquea bamboo thickets, and clearings. We then measured leaf, wood and reproductive traits, as potential predictors of species’ regeneration patterns. Clearings were exposed to more than twice as many frost days as any other forest phase, and to much larger vapour pressure deficits in summer. Clearings were compositionally distinct from the other three phases, which were indistinguishable from each other. Saplings of 6 out of 20 common arborescent species were significantly associated with one or other of the four phases. These associations were best predicted by a three-trait model combining seed mass, leaf dry matter content, and % winter leaf retention; though this model explained only 10% of observed variation. No species was significantly associated with bamboo thickets. Community-weighted trait means showed that large seeds were the most distinctive trait of understorey plots, whereas bamboo thicket plots had the highest average wood density, and winter leaf retention was significantly lower in clearings than in any other forest phase. Despite the abundant recruitment of large-leaved (semi)deciduous species in clearings, several evergreens with small leaves (< 3.5 cm²) also established primarily or exclusively in clearings. Although this study confirms the strong environmental filtering imposed by the microclimates of clearings in some temperate forests, it reveals more functionally diverse responses to clearing environments than was reported in a parallel study in New Zealand. Smaller sample sizes may partly explain why overall we found less evidence of regeneration niche differentiation and environmental filtering than in the New Zealand study, although attenuation of filtering by vegetative reproduction may also have contributed.

Organisms can adapt to environmental heterogeneity through two mechanisms: (1) expression of population genetic variation or (2) phenotypic plasticity. In this study we investigated whether patterns of variation in both trait means and phenotypic plasticity along elevational and latitudinal clines in a North American endemic plant, Mimulus laciniatus, were consistent with local adaptation. We grew inbred lines of M. laciniatus from across the species’ range in two common gardens varying in day length to measure mean and plastic trait expression in several traits previously shown to be involved in adaptation to M. laciniatus’s rocky outcrop microhabitat: flowering time, size-related traits, and leaf shape. We tested for phenotypic plasticity and GxE, examined correlations between the mean phenotype and plasticity, and tested for a relationship between trait variation and population elevation and latitude. We did not find a strong correlation between mean and plastic trait expression at the individual genotype level suggesting that they operate under independent genetic controls. We identified multiple traits that show patterns consistent with local adaptation to elevation: critical photoperiod, flowering time, flower size, mean leaf lobing, and leaf lobing plasticity. These trends occur along multiple geographically independent altitudinal clines indicating that selection is a more likely cause of this pattern than gene flow among nearby populations with similar trait values. We also found that population variation in mean leaf lobing is associated with latitude. Our results indicate that both having more highly lobed leaves and greater leaf shape plasticity may be adaptive at high elevation within M. laciniatus. Our data strongly suggest that traits known to be under divergent selection between M. laciniatus and close relative Mimulus guttatus are also under locally varying selection within M. laciniatus.

The Capparis spinosa group is represented in the Mediterranean by a complex of taxa widespread in North Africa, the Middle East, and southern Europe. The taxonomy of this group used to be based on morphological characters with little work on the genetics of the group, and there is still much to be learned about its evolutionary history and diversification. We sampled 431 individuals of two subspecies and five varieties of C. spinosa and analysed them using highly informative EST-SSR markers to evaluate the population genetic diversity, structure and differentiation of the species in the Mediterranean. In addition, comparisons with the genetic profiles of C. spinosa subsp. cartilaginea, the putative ancestral taxon were made to investigate the phylogeographic history and possible gene flow across taxa. Integrated Bayesian approaches showed: i) a high divergence among C. spinosa subsp. spinosa var. canescens, C. spinosa subsp. spinosa var. aegyptia and the three varieties belonging to C. spinosa subsp. rupestris (var. rupestris, var. ovata and var. myrtifolia), with a clear separation between var. aegyptia and var. canescens which allows to consider var. aegyptia as a subspecies of C. spinosa; ii) a significant correlation between genetic divergence and geographic distance between the five varieties studied; iii) that the different varieties in the Mediterranean may have been derived from C. spinosa subsp. cartilaginea. Further genomic investigations are required to confirm our results. However, the findings presented allows us to suggest the genus Capparis can be considered a model for the study of the gene flow and differentiation in species occurring in a wide range of habitats.

Areas where range-restricted species are concentrated are of importance for conservation. However, most of the studies aim at identifying areas rich in endemics for conservation planning, while few studies aim at understanding the causal factors of endemic richness. Here, our goal is to identify the determinants of endemic richness within a centre of endemism, the Southwestern European Alps, by testing four non-mutually exclusive hypotheses that have been proposed to explain patterns of endemic richness. In particular, we examined to what extent temporal and spatial climatic stability and environmental heterogeneity are related to endemic richness. Almost all hypotheses partially support the observed patterns of plant endemics richness within the SW Alps. In general, most of the relationships between environmental variables and endemic richness are statistically significant. However, the highest effect in explaining endemic richness is found for climate change velocity and standard deviation of slope, two factors affecting the possibility of species to disperse. This is in line with the idea that endemics are strongly limited by dispersal and not only by climate. Our results suggest that in regions where the effects of past climate changes were less dramatic endemic richness results from the interaction of species dispersal with regional and specific historical factors.

Current distribution of C₃ and C₄ grasses is often explained by contrasting environmental conditions. Regions where C₃ and C₄ grasses coexist, as the Southeastern South America grasslands (SESA grasslands), provides an excellent opportunity to investigate the evolutionary imprints of grasses through clade distribution patterns. Here, we aimed to understand how ecological and evolutionary processes affect the phylogenetic diversity of grass communities along 666 sites located in a latitudinal gradient ranging from 26°S to 38°S in SESA grasslands (Argentina, Brazil, and Uruguay). We applied generalized linear models (GLM) to understand the role of the different environmental and historical drivers that shape the proportion of C₃ grasses distribution in SESA grasslands. The effect of latitude on phylogenetic beta-diversity patterns among the vegetation surveys was evaluated through principal coordinates of phylogenetic structure. Contribution of C₃ species increased southwards (R² = 0.40, P<0.001). C₃ species are more likely to occur in colder areas with higher historical temperature stability, reflecting lineages that have specialized and radiated in cold environments (GLM results: R² = 0.37, P<0.01). Climatically stable areas are the coldest, while unstable areas include warmer habitats, which enabled colonization by C₄ species. Regarding soil conditions, C₃ grasses are more likely to occur in more fertile soils and with low capacity to retain water (GLM results: pseudo-R² = 0.37, P<0.01). We found that phylogeny has an important role as a structuring agent of grass communities across our study region, indicating turnover of grass lineages along the latitudinal gradient. Grass species found at the northern portion of the gradient belong mostly to the clade which contain both C₄ and C₃ species. At the southern part of the gradient, communities are dominated by grasses belonging to a C₃-exclusive clade. The distribution of grass clades across the SESA grasslands is indicative of the environmental gradients found in this region between temperate and tropical zones, describing a climate space where disturbance driven feedbacks play a major role in maintaining open vegetation. Our results contribute to the understanding of ecological and evolutionary drivers of grass distribution in the region that up to now has been poorly described.

West Asia, with its high mountain ranges and glacial refugia, stands out as a biodiversity hotspot for various plant taxa, including the taxonomically complex Rubus subgen. Rubus. Despite this significance, our understanding of the evolutionary processes shaping this group in the region has been limited. We employed an integrative approach combining flow cytometry, Sanger sequencing of two plastid regions, microsatellite genotyping, and double digest restriction-site associated DNA sequencing to characterize evolutionary and diversity patterns in West Asian brambles. We identified four diploid and two sexual tetraploid species, with the remaining diversity comprising apomictic tetra- and triploids, mostly belonging to R. ser. Discolores, and sexual pentaploid hybrids/hybridogens derived from R. caesius. Rubus dolichocarpus, newly reported here as diploid, emerged as a significant ancestor for many polyploids. Most apomictic genotypes are locally distributed and only three genotypes exhibit extremely large ranges from Armenia to Kyrgyzstan and from Georgia to Iran. These genotypes are probably of an ancient (Pleistocene) European origin and likely laid the foundations for the evolution of apomicts in West Asia, whose diversification was subsequently boosted by the genetic contribution of sexual taxa. DNA markers confirmed the West Asian origin of Rubus armeniacus, a globally significant invasive species, yet rare in its native range. We report on the first indigenous occurrence of this species based on microsatellite genotyping. Our findings contribute to filling existing gaps in understanding the evolution and diversity of Rubus subgen. Rubus in West Asia.