Perspectives in Plant Ecology Evolution and Systematics最新文献

It has been widely accepted that the biological control agents released on invasive Australian Acacia in South Africa, have impacted on the population dynamics of their host plants. However, there are no quantitative data to support these claims and these invasive species remain at similar abundance levels prior to the release of their associated biological control agents and also show evidence of range expansion. The effect of biological control agents, two bud galling wasps (Trichilogaster acaciaelongifoliae and T. signiventris) and one gall-forming rust fungus (Uromycladium morrisii), on the pod production of their respective hosts (Acacia longifolia, A. pycnantha and A. saligna) was assessed by quantifying the reproductive and galled trees per hectare as well as the pods and galls produced per tree and per square meter over a one to two year period. It was shown that invasive Australian Acacia satiate their gall-forming biological control agents, with many pods surviving in their presence. Pod production and loss was placed into perspective using recent findings of seed rain and seed bank studies. It was concluded, based on pod production, seed rain and seed bank data that despite T. acaciaelongifoliae, T. signiventris and U. morrisii reducing pod production, they have had no impact on the population dynamics of their invasive Australian Acacia hosts in South Africa.

The Balkan Peninsula was the primary glacial refugium for many temperate tree species and contributed overproportionally to the postglacial recolonisation of central and eastern Europe. This is also the case for Carpinus betulus, the European hornbeam, whose main glacial refugium was in the Balkans. During our fieldwork in the southern Balkans, we discovered trees with a morphology similar to that of C. betulus, but differing in their rough, highly rigged bark and the shape of their fruit involucre. The aim of this study was to investigate the evolutionary origin and differentiation of these morphologically distinct populations of C. betulus from the North Pindus Mountain range in northern Greece and southern Albania using an integrative approach. Our study combined phylogenetic analyses of plastid and nuclear internal transcribed spacer sequences, amplified fragment length polymorphism fingerprinting, relative genome size estimation, and multivariate morphometric analyses. After establishing the genetic and morphological divergence of the aforementioned populations, we described them as a new species, Carpinus austrobalcanica D.Lakušić, Kuzmanović, Stevanoski, Schönsw. & Frajman, sp. nov. We provide diagnosis, description, geographical distribution, and conservation status of this enigmatic newly described tree species locally endemic to the southern Balkans.

The Australian Camphorosmeae represent a monophyletic lineage that diversified to include ca. 150 spp. across 12 genera, and populate large parts of arid Australia. Tracking the origin and spread of this ancestrally salt and drought tolerant lineage provides additional evidence about the timing of the evolutionary history and phylogenetic assembly of arid habitats in Australia. Using a customized RADseq approach, sequence data for 104 species of the Australian Camphorosmeae representing all 12 genera were generated and included in phylogenetic and dating analyses. Furthermore, habitat type occurrences and preferences of species and clades were recorded. As suspected, the characters used to delimit current Australian Camphorosmeae genera do not support monophyletic groups, as phylogenetic analyses yielded 17 statistically supported clades across a large Maireana grade and crown radiation of Sclerolaena. The diversification of Australian Camphorosmeae is clearly linked to landscape changes and emerging new habitat types in arid Australia since the ancestral element likely arrived from temperate semi-arid to arid parts of continental Eurasia in the Middle Miocene. Migration was likely multidirectional and followed a west-to-east aridification. Crown group diversification was strongest during the Pliocene and likely promoted by the west-to-east expansion of Riverine Desert habitats and subsequent expansion and colonization of newly developing arid habitats. Rapid range expansion, fast habitat saturation, as well as periodic expansion, contraction and replacement of arid habitats, may have caused the rather species-poor clades of the earlier-divergent Maireana grade, compared to the continuously diversifying Sclerolaena clade.

The Euro-Siberian steppes have experienced large-scale range fluctuations due to the climatic changes of the Pleistocene that may have also fuelled reshuffling of past steppe vegetation. These species-rich steppe grasslands were much more widespread during glacials and contracted during interglacials, a dynamic which should also be reflected by the evolutionary history of their biota. Astragalus austriacus is a widespread steppe species with European-western Siberian distribution and an ideal model to study the florogenesis of the Euro-Siberian steppes. Here, we inferred the phylogeography of A. austriacus based on genotyping-by-sequencing (GBS) data from populations sampled from the western edge of the Pannonian region across the Pontic region to the western Siberian region. Additionally, we applied molecular dating using single gene sequence data (ycf1, matK and ITS). We outline an evolutionary scenario in which intraspecific diversification occurred in the eastern part of Europe during the later Pleistocene (0.48–0.24 Ma). From there, the species expanded both eastwards and westwards, likely during a cold period, which is reflected by two main lineages within A. austriacus that today occur in the Pannonian sensu lato and in the Pontic/south-western Siberian regions, respectively. Demographic modelling supported such a scenario and showed that population sizes were larger during the last cold stage and contracted postglacially. Within the Pannonian sensu lato region, strong substructure was detected, likely as a result of repeated disintegration of the continuous cold-stage steppes in Europe. Finally, our results are in line with evolutionary scenarios suggested for other steppe species such as Adonis vernalis.

In the current context of climate changes, which causes strong habitat variation, an understanding of the mechanisms underlying plant community dynamics is crucial to predict species fates. The taking of inter- and intraspecific trait variability into account would aid the identification of these mechanisms. Recently, a method involving the calculation of hypervolumes (n-dimensional spaces of trait values) was developed for the study of plant responses to their environments. Through hypervolume comparison, we examined the effects of interannual variations in abiotic conditions on aquatic plant communities in ponds of the sub-Antarctic Iles Kerguelen. This model system is particularly relevant for the examination of the consequences of climate changes–related habitat variation, as aquatic plant communities are adapted to cold and overall stable habitat conditions and the sub-Antarctic climate is changing rapidly. We conducted field sampling over four years at three sites. For all aquatic species, we measured five foliar, shoot, and clonal traits characterizing individual growth strategies that are likely to respond to variations in abiotic conditions on 1565 ramets over the four years. We measured 10 abiotic variables to characterize the plants’ habitats every three months during the survey period. Hypervolumes were calculated for each site and year to assess variation in aquatic plant strategies at the community level. We demonstrated (i) the importance of spatiotemporal gradients of trophic status, temperature, and pH and dissolved oxygen concentration for the functional structure of aquatic plant communities; (ii) that the shape of the mean response was trait dependent, with traits related to plant metabolism (specific leaf area and specific internode mass) and three-dimensional space exploration (height and internode length) responding to the three spatiotemporal abiotic gradients; (iii) that selection pressures were especially high on aerial traits relative to clonal traits; and (iv) that given the community response to interannual variations of abiotic conditions, environmental changes should impact macrophyte community productivity. Synthesis. We conclude that the examination of interannual abiotic variation over four years is sufficient to detect rapid responses of macrophyte communities, with likely reliance on phenotypic plasticity. Our findings may inform the characterization of future functional changes in aquatic plant communities of the sub-Antarctic region, where similar species are found.

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.