The Chapada Diamantina (CD) clade (Asteraceae, Eupatorieae) comprises 26 species distributed among six genera (Agrianthus, Arrojadocharis, Bishopiella, Lasiolaena, Semiria, and Stylotrichium) endemic to the high elevations of the Espinha & ccedil;o Range in Brazil. We aimed to clarify phylogenetic relationships within the CD clade, which shows low genetic differentiation, high morphological variation, and unclear species delimitation. The DNA sequences of four plastid (psbA-trnH, trnC-petN, trnY-rpoB, and trnL-trnF with trnL intron) and three nuclear markers (ITS and low-copy regions gsh1 and shmt) allowed the construction of a dataset with 96% of the species described for the clade. Our results confirm that the CD clade is monophyletic and originated during the Pliocene (5.1 Mya), with subsequent diversification in the Pleistocene (2.5 Mya). Phylogenetic analysis also confirmed Bishopiella and Semiria as monotypic genera, a broader circumscription of Agrianthus including Arrojadocharis and two species of Lasiolaena, and that Lasiolaena and Stylotrichium are sister groups. In addition, four potential hybrids were detected, possibly providing evidence that reticulate evolution has occurred in the CD clade. Further studies with endemic and sympatric species with recent radiation could benefit from approaches combining phylogenetic trees and non-tree-like results, as well as nuclear markers, to propose improved explanations for the underlying evolutionary mechanisms generating diversity.
To conserve threatened species effectively, it is necessary to integrate ecological and population genetic data, identify drivers of population decline, and define protection priorities. We studied the rare and endangered annual plant species Omphalodes scorpioides at its northwestern range margin in central Germany. Genetic diversity, germination ecology, and environmental associations were assessed across multiple populations and years. We found strong genetic variation among populations (39.7%), and significant isolation by distance, yet consistently moderate within-population genetic diversity (mean uHe = 0.23, mean FIS =-0.23). Low variation in genetic diversity between years suggests genetic stability despite annual fluctuations in population size. In the laboratory, seed germination was low (5.6%), with seed viability declining rapidly during storage. No germination occurred in the soil seed bank samples over two years, indicating that recruitment may require specific or disturbed environmental conditions. Population size was not related to genetic diversity or environmental factors. Larger populations showed a higher reproductive performance but produced smaller seeds, whereas vegetative performance was associated with environmental conditions. An assessment of herbarium specimens revealed a phenological deceleration over the last 200 years, accompanied by a reduction in leaf area, both of which may result from increasing environmental stress over time. Our results highlight the ecological vulnerability of O. scorpioides, whose survival is closely linked to narrow environmental niches. Successful conservation measures require maintaining habitat quality and conditions that promote recruitment to ensure the long-term survival of peripheral populations.
Positive plant-plant interactions are important drivers of community assembly in environmentally stressful ecosystems, yet the ecological role of bromeliads as potential nurse plants in semi-arid rocky outcrops remains poorly understood. We investigated patterns of vascular plant richness associated with clumps of Encholirium spectabile, a rupicolous bromeliad endemic to the Brazilian Caatinga. Specifically, we evaluated how bromeliad clump size, plant growth form, seasonality, and cacti presence were associated with variation in plant assemblages occurring within bromeliad clumps. We sampled 155 bromeliad clumps distributed across 22 semi-arid rocky outcrops in northeastern Brazil during dry and rainy seasons. Generalized linear models and hierarchical partitioning analyses were used to evaluate the relative importance of ecological predictors associated with vascular plant richness. Associated plant richness increased consistently with bromeliad clump size, indicating that structural complexity strongly influenced plant assemblages within bromeliad microsites. Climbing and woody species exhibited higher richness than herbaceous taxa, suggesting functionally structured associations linked to bromeliad architecture. Cacti presence contributed to richness variation in isolated analyses but showed no independent conditional effect in the full multivariate model. Seasonal variation exerted comparatively little influence on total richness, although growth-form composition differed between dry and rainy periods. Our findings are consistent with the interpretation that Encholirium spectabile may contribute to the formation of structurally buffered microsites capable of supporting diverse vascular plant assemblages in environmentally restrictive rocky outcrop ecosystems. Given the increasing anthropogenic pressures affecting semi-arid rocky outcrops, preserving structurally complex bromeliad clumps may contribute to biodiversity maintenance and ecological resilience in these threatened landscapes.
The structure of meadow communities is determined by the abiotic environment and biotic interactions (mostly competition). Yet, both the environment and species identity affect the final balance (symmetry) and strength of competition. Here, we aimed to disentangle the mutual competitive effects and the symmetry of competition between a potential grass dominant and four closely related sedges (Carex). We asked whether the dominant experienced competition effects from subordinates (and vice versa), and how the magnitude and dynamics of these interactions are shaped by contrasting water regimes. We experimentally planted four sedge species, all with a grass competitor or alone, and under low or high water regimes. Both the dominant and subordinate species exerted significant competitive effects. The grass affected the final biomass of all sedges similarly, while their growth dynamics differed among species. Nevertheless, the strength of competitive effects exerted on the grass depended largely on the identity of the neighbouring sedge. The magnitude of competitive interaction was unequal resulting often in asymmetric competition favouring the grass. However, in several species, the interaction strength was context-dependent as sedges exhibited mostly symmetric competition with the grass dominant under the high water regime. The overall competitive strength of sedge species corresponded to their soil moisture requirements, with drought-tolerant species being weaker competitors, while more water-demanding species being stronger competitors, and the effects were even more pronounced under high water regime. Our results shed light on the abiotic and biotic drivers of plant-plant interactions, and the mechanisms maintaining balance precluding competitive exclusion in meadows.
Environmental filtering is widely associated with plant community structure in harsh ecosystems, such as Neotropical inselbergs. In these systems, leaf functional traits provide insights into patterns of community assembly and variation in ecological strategies. Here, we investigated how fine-scale edaphic and topographic heterogeneity is associated with variation in plant functional strategies across vegetation patches on eight Brazilian inselbergs. We measured key leaf economic traits and classified species strategies using the Competitive, Stress-tolerant and Ruderal (CSR) framework. Community-weighted means (CWMs) of traits and CSR components were calculated for each vegetation plot. Associations between environmental variables (soil depth, patch area, slope, and soil properties summarized by PCA) and CWM traits were assessed using linear mixed-effects models. Plant communities were predominantly characterized by conservative trait syndromes and stress-tolerant strategies, with several functional traits and CSR components showing significant associations with fine-scale environmental variation. Soil depth was positively associated with higher leaf dry matter content and greater expression of stress-tolerant strategies, while showing negative associations with leaf area and competitive strategy components. In contrast, patch area was positively associated with plant height and competitive strategies, and negatively associated with specific leaf area and ruderal strategies. Together, these results indicate a consistent functional trade-off between patch area and soil depth across inselberg vegetation islands, with contrasting associations along the CSR spectrum. Fine-scale habitat heterogeneity was associated with the coexistence of conservative and acquisitive strategies, contributing to functional differentiation in resource-poor environments. Our findings highlight the importance of maintaining microhabitat heterogeneity for understanding and conserving the functional structure of inselberg plant communities, while emphasizing the need for experimental approaches to disentangle correlation from causation in future studies.
