Perspectives in Plant Ecology Evolution and Systematics最新文献

The distribution of ploidy levels and their ecological associations were studied using the genus Lessingianthus (Vernonieae, Asteraceae) as a model system. This genus is very complex from a cytogenetic point of view, with high cytotype diversity at the interspecific and intraspecific levels and with a continuous distribution throughout South America. So far, no previous studies have summarized chromosome count data for Lessingianthus or addressed the cytogeography of the genus. In this study, the ploidy levels of Lessingianthus species were determined by chromosome counts during mitosis and ecological niche modelling (ENM) was used to compare the environmental associations of the diploid and polyploid cytotypes. In total, 28 chromosome counts and six ploidy levels (2x, 4x, 6x, 8x, 10x, and 11x) were recorded. Among these counts, the chromosome numbers for three hexaploids with 2 n = 96 (L. parvifolius, L. vepretorum and L. “bolivianensis” sp. ined.) and one decaploid taxon with 2 n = 160 (L. roseus) were reported for the first time. In addition, a new cytotype for L. laniferus (2 n = 6x = 96) was also reported. The cytogeographic analysis resulted in detecting two geographic zones with high diversity of cytotypes and species. The ENMs showed that the areas of climatic suitability of diploids and polyploids are similar in extent, as well as the climatic requirements, showing high values of niche overlap within the environmental space. Our findings suggested that polyploidization in Lessingianthus has not caused expansion to novel environmental conditions and phylogenetic niche conservatism (PNC) may explain the lack of niche differentiation between diploids and polyploids.

Phenotypic plasticity (i.e. the ability to express different phenotypes under changing environmental conditions) is thought to play a key role in habitat adaptation, but little is known about how trait plasticity evolves following dispersal into novel island habitats. We hypothesize that shifts from seasonal Mediterranean climates to more stable (subtropical) island conditions would promote a net reduction in trait plasticity over time. To test this hypothesis, we set two common gardens with contrasting environmental (low resource vs. mesic) conditions, where we grew seedlings of wild olive (Olea europaea var. sylvestris) populations that represented two Canary Island lineages with different colonization times (old vs. young) and their Mediterranean ancestral lineage (N = 275 individuals). Plasticity was assessed for 12 morphological, photosynthetic and chemical traits by (i) subjecting half of the seedlings to simulated herbivore browsing (50% of aerial biomass removal) and (ii) comparing phenotypic values between both common garden settings. Simulated herbivore browsing induced few plastic responses, mostly restricted to photosynthetic traits, but these were similarly displayed by all lineages. Comparisons between common gardens revealed a contrasting response between the Mediterranean and both subtropical island lineages in leaf phenotypes. Furthermore, the older island lineage showed an overall lack of plasticity (i.e. environmental canalization) in morphological and chemical traits. These results suggest that, unlike photosynthetic traits that are fundamental for fast acclimation to environmental shifts, some developmental traits may lose plasticity over time as a result of phenotypic adjustment to subtropical insular conditions.

The tempo and mode of colonization of the Iberian Peninsula (IP) by Cannabis sativa, its further internal spreading and the potential cultural and environmental factors involved remain unknown. The available continental-wide European meta-analyses using pollen and archeological evidence account for only a few IP sites, insufficient for a sound assessment. This paper presents a nearly comprehensive database of almost 60 IP sites with palynological evidence of Cannabis and analyzes the corresponding spatiotemporal patterns. The first scattered records of this pollen type date from the Middle and Upper Paleolithic (150–12 kyr BP) and would have entered the IP by maritime Mediterranean or terrestrial continental pathways, or both. A first burst of introductions, probably in a cultivated form, would have occurred during the Neolithic (7–5 kyr BP) using similar paths. Human participation in these Neolithic introductions remains unclear but cannot be dismissed. A period of reduced Cannabis arrivals (mostly via maritime pathway) occurred between the Chalcolithic and the Roman Epoch (4.5–2 kyr BP), when the innermost parts of the IP were colonized (Late Bronze). A second, likely anthropogenic, introduction acceleration took place in the Middle Ages (1.5 kyr BP onward) using the Mediterranean and the continental pathways. Maximum cultivation and hemp retting activity was recorded during the Modern Ages (16th-19th centuries), coinciding with the increased demand of hemp fiber to supply the Spanish royal navy for imperial expansion and commerce. A potential link between Cannabis colonization/introduction bursts and climatic warmings has been observed that should be tested with future studies. Regional moisture variations seem to be less influential. Further efforts to enhance and improve the database used in this study are encouraged. The results of this paper should be compared with archeological and historical evidence to clarify the role of human migrations and cultural changes in the historical biogeography of Cannabis in the IP.

The semi-domesticated nature of the reindeer (Rangifer tarandus L.) makes it a distinct case among the world’s herbivores. Here, we review the literature on how reindeer shape vegetation and soil carbon and nitrogen cycles in northernmost Fennoscandia. We first describe main historical events that shaped the present-day grazing patterns in the different countries, then discuss the methodological considerations needed for interpreting evidence from grazer exclosures in ecological and environmental contexts. We argue that it is critical to be aware that these experiments do not measure the effect of grazing per se, but rather, they measure the responses of existing ecosystem structure and function to the sudden cessation of grazing in an environment, which was to a large degree shaped by it. Studies show that the direction and the magnitude of the effects of reindeer on vegetation and soil processes vary across habitats and depend on both the current land-uses and the historically formed grazing regimes; knowledge of the history is thus a key prerequisite for understanding the role of reindeer in ecosystems. As a general trend, reindeer affect soil nutrient cycles to a stronger extent in subarctic than in boreal ecosystems. In sites where reindeer have changed soil nutrient availability, they indirectly modify vegetation and productivity even after the cessation of grazing. We reason that the concepts of cultural and natural landscapes are not mutually exclusive in the case of reindeer ranges. Understanding how the intensity and seasonal timing of both past and present grazing direct ecosystem changes under climate warming is crucial for predicting future ecosystem structures and functioning in northern Fennoscandia as well as ecosystems in general.

Capparis is the largest genus of the family Capparaceae, represented by 142 species in the tropics and subtropics of the Old World. Despite being one of the medicinally and economically important genera with its unique distribution pattern, the evolutionary history of Capparis remained unexplored. Moreover, the phylogenetic relationships, origin, dispersal, and character evolution of the genus were poorly understood. With the objectives to (i) test the congruence between the molecular and morphological datasets, (ii) validate Jacobs' hypothesis on the origin, dispersal, and speciation pattern of Capparis using new fossil data, and (iii) understand the possible evolutionary role of some key morphological characters, we sampled across the five speciation centres of Capparis. The results derived from three plastidial markers (matK, trnL-F and rbcL) revealed incongruence with the morphology based delimitations and suggested a new sectional classification in Capparis. Divergence dating analysis revealed that Capparaceae originated in Africa at 47.25 MYA and Capparis in Peninsular India at about 29.32 MYA. Capparis followed multiple forward and backward dispersal, supporting the “into and out of India” hypothesis. These dispersal events were consistent with the various land bridges in different parts of the Old World during the Eocene to Miocene. The only long-distance dispersal event was observed in the case of the New World Capparaceae, corroborating the earlier findings. Our results suggest West Asia to the North African region as another centre of speciation for Capparis and present a robust age estimate for the genus. The character state reconstruction of Capparis revealed a unique evolutionary adaptation due to exposure to various climatic conditions and the acquisition of suitable pollination strategies. We hypothesize that the gynophore length, sepal shape, and blotches on petals contribute substantially to the pollination success.

The invasive herb Lupinus polyphyllus has been focus of a number of fact sheets worldwide but a comprehensive summary of the species’ taxonomy and morphology, distribution, habitat requirements, and biology has been lacking. This paper gives a thorough account of the species’ systematic position and taxonomy, highlighting the difficulties to delimit taxa, which is related to interbreeding among members of this genus. However, L. polyphyllus var. polyphyllus is apparently the taxon that has naturalized and is regionally invasive in temperate-humid climates worldwide. We also present an updated distribution map of L. polyphyllus in the native and invaded ranges, which highlights seven regions in the world where the species has been established. We show that the climatic niche of L. polyphyllus in the invaded range shifts towards higher summer precipitation and lower isothermality, probably because the invaded range includes subcontinental regions of eastern Europe and western Siberia. The habitats of L. polyphyllus range from rather dry to wet, have moderately acidic to strongly acidic soils, and the species’ indicator values across Europe suggest that it occurs along a gradient from very nutrient poor sites to intermediate to rich sites from northern to southern Europe. The species shows high resistance to both drought and frost. In Central Europe, the species has a stronghold in alpic mountain hay meadows, abandoned meadows and pastures, low and medium altitude hay meadows, anthropogenic herb stands and temperate thickets and scrubs. In northern Europe, the species occurs in anthropogenic herb stands along roads and railroads as well as in abandoned pastures and fields. We also found some doubtful information about L. polyphyllus in the literature. This refers to its description as “rhizomatous perennial” although it lacks rhizomes; an apparently very high longevity of its seeds, which may only be true under artificial conditions in an ex situ seed repository; and a very deep rooting depth, which may not represent the average rooting depth but rather an extreme value. Knowledge about the interrelationships between the species’ future population dynamics and spread and ongoing climate warming is lacking. Finally, our review points out that there is currently no evidence-based strategy for a cost-efficient management of L. polyphyllus although it is among the most problematic non-native plant species in Europe due to its environmental and socio-economic impacts.

The fairy circles of Namibia form a remarkable gap pattern in arid grassland along the Namib Desert. The origin of the fairy circles is subject to an ongoing debate. Solving the mystery of the fairy circles (FCs) requires the right timing in fieldwork after rainfall, as the newly appearing grasses complete their life cycle within only a few weeks. Here we followed the rains along the Namib between 2020 and 2022 and assessed the cause of the grass death within FCs at different time intervals after grass-triggering rainfall. To assess whether termite herbivory was the cause, we used grass excavations and observations on the roots and shoots. To test if edaphic differences may explain the grass death in FCs, we undertook infiltration measurements in 10 FC-hotspot regions. Finally, we used continuous soil-moisture measurements from the dry into the rainy seasons to examine how the newly emerging grasses affect the soil-water content in space and time. Generally, in study plots that received grass-triggering rainfall most recently, the roots of the dead grasses in FCs were in 100 % of the cases undamaged, root-shoot ratios were significantly greater, and the roots were as long or even longer as those of the surrounding matrix grasses outside of the FCs. This indicates that drought stress caused grasses in the FCs to invest resources into roots to reach the percolating water. The results also show that the cause of the grass death in fairy circles was not induced by termite herbivory. Also, we found no systematic differences in the rate of water infiltration between FCs and the matrix, hence the plant wilting cannot result from quicker percolation within FCs. However, the soil-moisture measurements indicate that the matrix grasses strongly depleted the upper soil water of the FCs after rainfall, which explains why most grasses cannot establish and quickly die in the FCs. The research shows that grass death in fairy circles occurs immediately after rainfall due to plant water stress but not due to termite activity. Our results conform with previous fieldwork, pattern analysis and theoretical modeling, suggesting that Namibia’s fairy circles are a self-organized vegetation phenomenon induced by ecohydrological feedbacks.

The preference of certain plant species for gypsum soils with a patchy distribution leads to disjunct population structures that are thought to generate island-like dynamics potentially influencing biogeographic patterns at multiple evolutionary scales. Here, we study the evolutionary and biogeographic history of Nepeta hispanica, a western Mediterranean plant associated with gypsum soils and displaying a patchy distribution with populations very distant from each other. Three approaches were used: (a) interspecific phylogenetic analyses based on nuclear DNA sequences of the ITS region to unveil the relationships and times of divergence between N. hispanica and its closest relatives; (b) phylogeographic analyses using plastid DNA regions trnS-trnG and psbJ-petA to evaluate the degree of genetic isolation between populations of N. hispanica, their relationships and their genetic diversity; and (c) ecological niche modelling to evaluate historical distributional changes. Results reveal that N. hispanica belongs to an eastern Mediterranean and Asian (Irano-Turanian) clade diversified in arid environments since the Miocene-Pliocene. This species represents the only lineage of this clade that colonised the western Mediterranean, probably through the northern Mediterranean coast (southern Europe). Present Iberian populations display a high plastid genetic diversity and, even if geographically distant from each other, they are highly connected according to the distribution of plastid haplotypes and lineages. This can be explained by a scenario involving a complex history of back-and-forth colonisation events, facilitated by a relative stability of suitable conditions for the species across the western Mediterranean throughout the Quaternary.

Nonmonotonic changes in species richness along ecological gradients are frequently observed in nature. While theories support both symmetric and skewed unimodal relationships, related studies usually fit second-order polynomials, which assume symmetric relationships. These studies often apply various transformations of the predictor variable to reduce the effects of outliers or to meet assumptions of normality. We studied whether predictor transformation affects the shape of the fitted curves. To test the effect of predictor transformation on the shape of the fitted curves, we re-analyzed the dataset of a highly-cited global analysis on the productivity–species richness relationship without performing any data transformations and contrasted the results with those of the original analyses that used log-transformed productivity data. We found that predictor variable transformation, which was used in the original paper, changed the shape of fitted curves in 32 % of the sites as well as the shape of the global relationship compared to the use of untransformed data. Therefore, we propose the reconsideration of predictor transformation and suggest an alternative approach: the piecewise regression. We found that piecewise regression is robust against predictor variable transformation. It resulted in much fewer inconsistent shape categories between the transformed and untransformed cases compared to the original analyses (2 instead of 9). We suggest that studies applying untransformed and transformed predictors when studying the shape of species richness curves along gradients are not directly comparable. Using piecewise regression models may contribute toward resolving the ongoing debate on the change in species richness along ecological gradients in general, and the productivity-species richness relationship in particular.