Functional leaf traits indicate phylogenetic signals in forests across an elevational gradient in the central Himalaya

Different sets of traits determine transition of alien species along the invasion continuum

Invasive alien species are currently considered as one of the dominant drivers of global environmental change. Till now, the majority of studies have focused on single or a few traits of alien species that facilitate their invasion. Also inclusion of all the traits which determine the transition of aliens along the different stages of invasion continuum (casual, naturalised and invasive) has remained largely overlooked. In this study, we collected a comprehensive trait dataset on 144 alien plant species of Kashmir Himalaya - a global biodiversity hotspot region. To test which traits of alien species, individually or in combination along with anthropogenic factors, determine their transition along the invasion continuum, we employed chi-square tests, boosted regression trees and phylogenetic methods. We found the perennial life span, longer residence time, greater number of introduced regions, and better seed dispersal mechanism were critical in determining the transition from casual to naturalised. The herbaceous growth form, therophyte Raunkiaer life-form, annual life span, achene fruit, longer residence time and broader introduced range were the species' traits determining transition from naturalised to invasive. Aliens introduced as ornamentals have more propensity to become naturalised; whereas aliens introduced unintentionally show overrepresentation at the invasive stage. Phylogeny alone showed mixed results indicating both clustering and dispersion; however, in combination with other traits, it plays a significant role in determining the stage of invasion. Overall, our study disentangles the individual and interactive roles of multiple traits that determine the transition of alien species' along the invasion continuum. Further, we foresee the potential applicability of our findings in designing robust invasion risk analysis protocols and stage-specific invasion management strategies in this Himalayan region, with learnings for elsewhere in the world.

Intercontinental comparison of phylogenetic relatedness in introduced plants at the transition from naturalization to invasion: A case study on the floras of South Africa and China

Invasive species may pose significant threats to biodiversity and ecosystem structure and functioning. The number of introduced species that have become invasive is substantial and is rapidly increasing. Identifying potentially invasive species and preventing their expansion are of critical importance in invasion ecology. Phylogenetic relatedness between invasive and native species has been used in predicting invasion success. Previous studies on the phylogenetic relatedness of plants at the transition from naturalization to invasion have shown mixed results, which may be because different methods were used in different studies. Here, I use the same method to analyze two comprehensive data sets from South Africa and China, using two phylogenetic metrics reflecting deep and shallow evolutionary histories, to address the question whether the probability of becoming invasive is higher for naturalized species distantly related to the native flora. My study suggests that the probability of becoming invasive is higher for naturalized species closely related to the native flora. The finding of my study is consistent with Darwin's preadaptation hypothesis.

Variation and association of leaf traits for desert plants in the arid area, northwest China

Characterizing variation and association of plant traits is critical for understanding plant adaptation strategies and community assembly mechanisms. However, little is known about the leaf trait variations of desert plants and their association with different life forms. We used principal component analysis, Pearson's correlation, phylogenetic independent contrasts, linear mixed model, and variance decomposition to explore the variation and association of 10 leaf traits in 22 desert plants in the arid area of northwest China. We found that: (1) the contribution of interspecific variation to the overall variation was greater than the intraspecific variation of all the studied leaf traits; (2) intraspecific and interspecific variation in leaf traits differed among life forms. Some leaf traits, such as tissue density of shrubs and specific leaf area of herbs, exhibited greater intraspecific than interspecific variation, while other traits exhibited the inverse; (3) desert shrubs corroborate the leaf economic spectrum hypothesis and had a fast acquisitive resource strategy, but herbs may not conform to this hypothesis; (4) there were trade‐offs between leaf traits, which were mediated by phylogeny. Overall, our results suggest that interspecific variation of leaf traits significantly contributes to the total leaf traits variation in desert plants. However, intraspecific variation should not be overlooked. There are contrasts in the resource acquisition strategies between plants life forms. Our results support understanding of the mechanisms underlying community assembly in arid regions and suggest that future works may focus on the variation and association of plant traits at both intra‐ and interspecific scales.

Patterns of phylogenetic relatedness of non-native plants across the introduction-naturalization-invasion continuum in China

Human activities have caused the exchange of species among different parts of the world. When introduced species become naturalized and invasive, they may cause great negative impacts on the environment and human societies, and pose significant threats to biodiversity and ecosystem structure. Knowledge on phylogenetic relatedness between native and non-native species and among non-native species at different stages of species invasion may help for better understanding the drivers of species invasion. Here, I analyze a comprehensive data set including both native and non-native angiosperm species in China to determine phylogenetic relatedness of introduced species across a full invasion continuum (from introduction through naturalization to invasion). This study found that (1) introduced plants are a phylogenetically clustered subset of overall (i.e. native plus non-native) angiosperm flora, (2) naturalized plants are a phylogenetically clustered subset of introduced plants, and (3) invasive plants are a phylogenetically clustered subset of naturalized plants. These patterns hold regardless of spatial scales examined (i.e. national versus provincial scale) and whether basal- or tip-weighted metric of phylogenetic relatedness is considered. These findings are consistent with Darwin's preadaptation hypothesis.

Evolutionary lability underlies drought adaptation of Australian shrubs along aridity gradients

Leaf drought tolerance traits influence plant survival in water deficit conditions, and these traits are influenced by both the plant's evolutionary history and the environment in which the plant is currently growing. However, due to the substantial phenotypic plasticity in leaf traits, we still do not know to what degree variation in leaf traits is governed by species' phylogenetic history or by their environment. To explore this question, we re-examined a drought tolerance dataset from 37 native Australian shrub species with varying climate origins growing in a common garden located in Melbourne, Australia. We previously measured seven leaf morphophysiological traits, and here, we estimated how phylogenetically conserved these traits are. We quantified phylogeny and the strength of correlation between the morphological traits and physiological traits before and after accounting for shared phylogenetic history. We also evaluated the relationship between species' leaf traits and the climate of their native ranges. We present three main findings: (a) most leaf drought tolerance traits had weak phylogenetic signals, which is consistent with the convergent evolution of these traits. (b) There is weak but consistent coordination between distinct leaf drought tolerance traits, which can be masked due to species' phylogenetic histories. (c) Leaf drought tolerance traits show strong correlations with the climate of species' origins, and this relationship is only weakly impacted by phylogenetic signals. Therefore, the role of phylogeny on the coordination among leaf functional traits and their links to climate were limited. A better understanding of trait-environment relationships might be more pivotal than understanding the evolution of these traits for improving the predictions of species' response to climate change-type drought, especially for shrub species that span substantial aridity gradients.

Abiotic Regulation: Landslide Scale and Altitude Regulate Functional Traits of Regenerating Plant Communities After Earthquakes

Regeneration and assembly of a plant community after a large-scale natural disturbance are affected by many factors. The relative importance of abiotic factors represented by the external environment and the biological factors inside the plant community during this process is still unexplored. This work investigated the regions affected by the Wenchuan earthquake, focusing on areas with the highest intensity (XI degrees) of this earthquake, and the process of community assembly through functional traits on landslides. The aim of this study was to understand the importance of factors influencing community assembly from the perspective of functional traits. The main conclusion is presented as follows: after the regeneration of large earthquake-induced landslides, community-level functional traits covering many plant organs, such as roots, stems, leaves and seeds, are obviously different from those unaffected by landslides. Functional traits do not show strong phylogenetic conservatism. Overall, community traits are divergent or random, and the degree of divergence among the different traits varies. Species composition and alpha diversity have minimal effect on community functional traits during the process of landslide restoration. Landslide scale and altitude significantly affected community-level functional traits in the process of community assembly. All the findings suggested that the functional traits of regenerating vegetation after the earthquake changed significantly and that the functional traits depended more on abiotic regulation than on evolutionary and species-specific factors.