Perspectives in Plant Ecology Evolution and Systematics最新文献

The centres of diversification of the iconic family Proteaceae are in South Africa and southern Australia. Since the ancestors of the family can be traced to NW Africa our task was to explain how all subfamilies (Proteoideae, Grevilleoideae, Persoonioideae) managed to reach Australia and we propose the pathway: (Africa (N South America (S South America (Antarctica (Australia))))). Our dated molecular phylogeny shows that the family arose 132 million years ago (Ma), and by 125 Ma had separated into the three subfamilies that remain dominant today. The age and location of records for 420 fossil pollen with Proteaceae affinities were collated per continent and submitted to curve-fitting analysis. This showed spread of early Proteaceae into N South America from ∼121 Ma that was able to continue for another 20–25 My. These three subfamilies (plus Carnarvonia) travelled south through South America and Antarctica, crossing the Weddellian Isthmus from ∼110 Ma, to reach southern Australia by ∼104 Ma. The history of Proteaceae in South America mimics that of Africa, where Grevilleoideae diversified instead of Proteoideae that died out. Entry to Australia via Antarctica was possible until ∼70 Ma at its SW corner and 45 Ma at its SE (Tasmanian) corner enabling the three subfamilies (and Carnarvonia) restricted entry into Australia over 35–60 million years. The SW Australian sclerophyll flora became the centre of diversification and emigration at the species level of all but the rainforest (mesophyll) Grevilleoid/Proteoid clades within Australia. Close genetic links between clades in South Africa (the centre of diversification of the sclerophyll flora in Africa) and SW Australia are the product of disparate migratory histories from their common ancestor in NW Africa, differential survival among subfamilies and parallel evolution in matched environments. SE Australia became the centre of diversification at the subtribe level. Close genetic links between clades in South America and SE Australia are the product of long-distance dispersal from their common ancestor in N South America, genetic stability in matched environments and eventual vicariance.

A rapidly warming climate with growing frequency of hot droughts urges Central Europe’s forestry sector to adapt to increasing climatic stress. One option is to choose native minor timber species with assumed higher stress tolerance; yet, information on the drought resistance of many species is scarce. We examined the drought resistance of adult trees of Norway maple (Acer platanoides), European hornbeam (Carpinus betulus), Common ash (Fraxinus excelsior) and Little-leaved lime (Tilia cordata) at leaf, branch, stem and root levels, combining studies on leaf water status, branch xylem hydraulics, fine root vitality and radial stem growth, for deriving an evidence-based drought resistance ranking of the species. Results were compared to Sessile oak (Quercus petraea), a fairly drought-resistant major timber species. All species showed constant growth rates despite increasing climatic aridity, indicating low climate vulnerability. Foliage loss after the severe 2018/19 drought increased in the sequence Quercus < Fraxinus < Acer < Tilia < Carpinus. The water potential at leaf turgor loss (P_TLP) was no suitable indicator of the species’ climate-sensitivity of growth or drought-induced foliage loss. The growth performance of Tilia demonstrates that some angiosperm trees can achieve a fairly high degree of drought resistance through plant-internal water storage and high leaf tissue elasticity, despite a small hydraulic safety margin and high P_TLP. Drought resistance as deduced from growth performance and defoliation after severe drought decreased in the sequence Quercus > Fraxinus & Acer > Tilia > Carpinus. We conclude that Acer, Carpinus, and Tilia (and Fraxinus, despite being often Hymenoscyphus-infected) are suitable timber species for Central Europe’s forestry sector in a drier and warmer climate.

Intraspecific trait variability has been identified as a possible reason why the trait-based approach in functional ecology is not as predictive as we would like. However, sources of intraspecific variability are not only largely acknowledged responses to the environmental gradients, but also the intrinsic effects due to seasonal and ontogenetic development. Yet, the effect of seasonal and ontogenetic development on intraspecific trait variability has not been as theoretically predicted or studied so far as it would deserve. In this opinion paper, we follow recent theoretical predictions on the ontogenetic development of a key functional trait capturing plant economics - leaf mass per area (LMA,) and contribute to the debate on whether general predictions based and demonstrated on trees hold true also for herbs. While plant height, the position of leaves in the canopy, and the whole plant leaf area are suggested to be important drivers of LMA in trees, we propose seasonal development, bud preformation, meristem size, and amount of carbohydrate storage to be crucial for intraspecific trait variability in temperate herbs.

Recent climatic changes, such as more frequent droughts and heatwaves, can lead to rapid evolutionary adaptations in plant populations. Such rapid evolution can be investigated using the resurrection approach by comparing plants raised from stored ancestral and contemporary seeds from the same population. This approach has so far only been used in common garden experiments, allowing to reveal genetic differentiation but not adaptation. In this study, we performed a novel approach by testing for evolutionary adaptation in natural plant populations using a resurrection study in combination with in situ transplantations. We cultivated seedlings from ancestors (23–26 years old) and contemporary descendants of three perennial species (Melica ciliata, Leontodon hispidus and Clinopodium vulgare) from calcareous grasslands in the greenhouse and transplanted them back to their collection sites. In addition, we sowed seeds of ancestors and descendants of two species (L. hispidus and C. vulgare) to the collection sites in order to investigate germination rates. In transplanted M. ciliata seedlings, we observed lower mortality and larger plant size in descendants compared to ancestors. This indicates that descendants are better adapted than ancestors to the current environmental conditions, which proved to be exceptionally hot and dry during the study period. Descendants of C. vulgare seedlings tended to be smaller and descendants of L. hispidus seedlings produced fewer leaves compared to their ancestors in their contemporary environmental conditions. In C. vulgare and L. hispidus, we found evolution towards faster germination, and especially descendant seeds of C. vulgare were better adapted to the unfavourable conditions during the experimental period. Concluding, we demonstrate that our novel approach to combine resurrection ecology with transplant experiments is a promising avenue to rigorously test for evolutionary adaptations in changing environments.

Understanding how functional traits affect plant performance and fitness is a key step in unravelling the role of natural selection in shaping the evolutionary trajectory of populations. We examined early-age selection acting on leaf traits via their effects on growth performance and fitness, measured in Eucalyptus ovata trees planted in a common-garden field trial embedded in a reforestation planting in Tasmania, Australia. We focused on two important leaf traits - stomatal length and specific leaf area (SLA) - measured two years after planting, and compared interplanted E. ovata groups originating from dry and wet home-site climates, with the trial site having intermediate long-term mean annual rainfall. Two-year height growth was used as the performance attribute, and the time-averaged tree survival over the subsequent six years as the fitness component. There was evidence for performance-based selection on the leaf traits, with the strength and form of selection depending on the trait and climate group being considered. In this sense, selection in the dry group operated mainly on stomatal length where a combination of directional (favouring longer stomata) and stabilizing selection was detected, whereas selection in the wet group acted only on SLA and was purely stabilizing. Estimates of performance-based correlational selection were not statistically significant. For both climate groups, estimates of fitness-based selection gradients provided evidence for significant directional (but not quadratic) selection on height performance, favouring individuals with faster growth, but did not indicate statistical support for direct effects of the leaf traits on tree survival, conditional on measured performance. These results validated qualitative inferences of selection from the performance-based analysis, and suggested that selection on the leaf traits appeared to be mediated by their effects on early-age height performance, which in turn directly influenced later-age survival. We discuss the mechanisms by which the focal traits may have affected height performance, and likely factors contributing to the different patterns of phenotypic selection observed in the two groups experiencing the same environment. We also provide expressions of analytical derivatives that were developed for the estimation of selection gradients based on a logistic regression model relating a binary fitness response to linear and nonlinear covariate terms for the target regressor variables.

Floral nectar is central to ecology, since it mediates interactions with pollinators, flower-visiting antagonists and microbes through its chemical composition. Here we review how historical assumptions about its ecological meaning were first challenged, then modified and expanded since the discovery of secondary metabolites in nectar. We then explore the origin of specific neuroactive nectar compounds known to act as important insect neurotransmitters, and how advances in the field of bee cognition and plant-microbe-animal interactions challenge such historical views. As all actors involved in the latter interactions are under simultaneous reciprocal selective pressures, their coexistence is characterized by conflicts and trade-offs, the evolutionary interpretation of which suggests exciting new perspectives in one of the longest studied aspects of plant-pollinator interactions.

A central issue in plant ecology is exploring universal rules and the mechanisms under which photosynthetic energies are allocated to different organ parts. Until recently, prevalent studies focused on testing either optimal allocation theory or allometric allocation theory in predicting plant biomass partitioning patterns. However, paying much attention to the stable state prevents the development of new biomass allocation theories in transient time scales. Here, based on theories in transients and the allometric relationships in plant traits, I develop general theoretical models to study the transient perturbations of plant biomass allocated to non-photosynthetic organ parts. With both simulation and empirical approaches, I investigate the effect of plant stem diameter at breast height (DBH) on the variation of biomass allocation patterns during plant ontogeny. Results show that increases in DBH can mitigate the magnitude of the perturbations of plant biomass and biomass fractions allocated to both plant stem and root parts. The findings are robust when either deterministic or stochastic models are conducted. Moreover, empirical analyses from a large forest database in Eurasia consistently support the predictions from the theoretical frameworks. In this paper, I draw attention to the transient allocation pattern of plant biomass for non-photosynthetic organs, and I find the significant role of DBH. This work has important implications in both theoretical breakthroughs and practical applications. It not only provides the foundation to test new biomass allocation hypotheses but also directs agricultural and forest management to achieve stabilized yields.

Climate change is a serious concern around the world, particularly in tropical regions including Bangladesh. Yet, how tree growth and hydraulic behavior of Bangladeshi native tree species changed in response to past climate variability and changes have not been adequately understood. We developed the first ring-width and vessel chronologies of Albizia procera (Roxb.) Benth. from a moist tropical forest of Bangladesh (Rema-Kalenga Wildlife Sanctury, RKWS) to analyze the impact of inter-annual climate variability on tree growth and xylem hydraulic traits. The chronologies contained common environmental signals as shown by the values of expressed population signal (EPS) and other statistical parameters. Climate-growth analysis showed that maximum temperature (T_max) favored tree growth at the end of the wet season (November). Among the vessel and hydraulic trait chronologies, number of vessels (NV) had significant positive relation with May minimum temperature (T_min) and vessel density (VD) had a negative relationship with April T_min. Precipitation had a negative relation with vessel density (VD), and the potential specific hydraulic conductivity (K_S). Relative humidity (RH) and vapour pressure deficit (VPD) had contrasting effects on vessel and hydraulic traits. On a regional scale, the ring-width index and vessel chronologies were correlated with both gridded land surface temperature and precipitation, but during different periods of the year. Linear mixed effect modeling revealed significant positive relationships between VD and T_max implying a good acclimation potential of this tree to rising temperature. However, the absence of the generally expected trade-off between VD and D_H calls for further studies on the hydraulic functions of this species in moist tropical forests.

We compared seasonal leaf gas exchange patterns, photosynthetic pigments, and photosynthetic nutrient use efficiencies in two co-occurring tree species, Nepalese alder (Alnus nepalensis D. Don) and white oak (Quercus leucotrichophora A. Camus), in the central Himalaya. In both species, area-based and mass-based photosynthetic CO₂ assimilation rates, stomatal conductance, leaf nutrient concentration, photosynthetic nutrient use efficiency, and leaf chlorophyll pigments peaked in summer, while water use efficiency peaked in autumn. In spring, summer, and autumn, values for most parameters (specific leaf area, relative water contents, area-based and mass-based photosynthetic CO₂ assimilation rates, leaf nutrient concentration, photosynthetic nutrient use efficiencies, and leaf chlorophyll pigments) were higher in A. nepalensis than in Q. leucotrichophora. In winter, however, values for area-based CO₂ assimilation rates, water use efficiency, leaf calcium, leaf magnesium concentration, and photosynthetic pigments were higher in Q. leucotrichophora than in A. nepalensis. We conclude that A. nepalensis exhibits a more resource-acquisitive strategy, characterized by higher levels of leaf nutrients and nutrient use efficiencies, that supports higher photosynthetic capacity. In contrast, Q. leucotrichophora exhibits a resource-conservative strategy with higher construction cost.

Reproductive barriers and directional geneflow may play a key role in maintaining genetic gradients, thereby allowing ecological differentiation along ecological clines. In Brassicaceae, a sporophytic incompatibility system (SI) contributes to such barriers to geneflow, with the maternal component represented by a large diversity of SRK (stigma-specific S locus receptor kinase) alleles at varying frequencies and levels of dominance. Such clinal genetic gradient along an ecological gradient following a shift towards much drier and warmer conditions and also the bedrock type shifts from calcareous to silicious has been found earlier in an Arabidopsis introgression system involving A. lyrata and A. arenosa. The metapopulation system spans from the northeastern Austrian forealps northward towards the Danube river and the Bohemian massif. Here we explore diversification of population-level SRK gene pools across these hybrid Arabidopsis tetraploid metapopulation system and its putative parental source populations. Since it has been demonstrated that A. lyrata served as the maternal parent and A. arenosa introgressed via pollen constituting a genetic cline with decreasing contribution of A. arenosa genetic background, we test the hypothesis that this cline can be also explained by SRK allelic differentiation. A total of 603 individuals from 45 populations of introgressed and non-introgressed A. lyrata and A. arenosa across a 80 km transect were analysed for SRK allele variation. In total, 22 alleles from all four previously described dominance classes have been documented. Although there is clinal morphological and genetic variation following the introgression zone, SRK alleles do not follow this signature of the paternal taxa. Furthermore, the functional SI system is fully maintained across the transect, and crossing experiments show that there is no decrease in fitness depending on varying distances between populations along the transect studied herein. We conclude that transmission and structure of the SRK allelic gene pool contributes to the postglacial colonization success along such a pronounced ecological gradient maintaining a functional SI system and counteracting genetic depletion.