Morphological and molecular identification of new records and new host plants of powdery mildews (Erysiphaceae) from Mexico

Powdery mildew is one of the most severe diseases affecting Cucurbitaceae. We identify the members of Erysiphaceae infecting cucurbits in three producing regions in Mexico. We determined that Golovinomyces ambrosiae, Neoerysiphe sechii, and Podosphaera xanthii infected cultivated and wild cucurbits species or subspecies. Leaf samples showing symptoms and signs of powdery mildew were collected from the northwestern, central western, and eastern regions of Mexico between 2017 and 2020. Species associated with the disease were identified based on morphology and ITS rDNA sequences. All powdery mildew specimens presented only the anamorph. Podosphaera xanthii was the predominant species; it was found in 85.7 % of the samples and in 13 out of 14 species or subspecies of cucurbits. Neoerysiphe sechii was found in 15.23 % of the samples and in only four cucurbit species from the central western and eastern regions of Mexico. Golovinomyces ambrosiae was documented for the first time in a Cucurbitaceae species (Sicyos deppei) from Central West Mexico. Three new hosts were registered for Neoerysiphe sechii (Cucurbita ficifolia, Echinopepon milleflorus, and Sicyos laciniatus) and eight for Podosphaera xanthii (Cucurbita argyrosperma, C. argyrosperma subsp. sororia, C. ficifolia, C. okeechobeensis subsp. martinezii, C. radicans, Sechium edule, Sicyos laciniatus, and S. deppei).

Origin of Symphyotrichum anticostense (Asteraceae: Astereae), an endemic, high polyploid species of the Gulf of St. Lawrence region, based on morphological and nrDNA evidence

Symphyotrichum anticostense (Fernald) G.L.Nesom (Asteraceae: Astereae), a rare endemic of the Gulf of St. Lawrence region is a high allopolyploid (2n=10x=80). It has been hypothesized to be derived from the hybrid between tetraploid (2n=4x=32) individuals of S. boreale (Torr. & A.Gray) Löve & Löve and the hexaploid (2n=6x=48) S. novi-belgii (L.) G.L.Nesom. We investigated this hypothesis using morphological and molecular ITS-sequence data, and we tried to determine the potentially geographic origins of the taxon. Univariate morphological analyses show that 67.5% of the S. anticostense characters are parent-like, 43.5% from S. novi-belgii and 13% from S. boreale, the remainder not differing statistically from either parent; 23.5% are intermediate; and 9% transgressive. Multivariate analyses show that S. anticostense is intermediate between its putative parents. The molecular results support the morphological data, but due to the insufficient resolution among ribotypes on the tree, a more rapidly evolving marker will be needed to ascertain more reliably the origin of S. anticostense. Besides the hypothesis of genetic drift and allele fixation following long-distance dispersals, at least three independent geographic origins may be suggested for S. anticostense; Anticosti Island, Lake St. John, and Gaspé Peninsula-New Brunswick-Maine.

Plant exposure to glyphosate-based herbicides and how this might alter plant physiological and structural processes

Chemical weed control is essential to ensure high levels of productivity in agricultural areas, and glyphosate-based herbicides (GBHs) are the most widely used herbicides at a global scale. GBHs inhibit the 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) enzyme, which impairs the shikimate pathway and often leads to plant death. However, indirect effects of GBHs on plant physiology can also lead to plant death. The objectives of this review are to discuss the biochemical, physiological and structural changes GBH application produces in plant species, in addition to inhibiting EPSPS (EC 2.5.1.19), and to reveal how these changes contribute to plant death. We conclude that GBHs promote plant death not only because of EPSPS inhibition but also due to biochemical, physiological and structural changes. Some changes are recurrent and can be used as biomarkers of GBH sensitivity, which can contribute to future works that monitor the presence of these herbicides in plant communities near agricultural areas.

Reproductive phenological shifts and other phylogenetic trait changes in the Arbutoideae (Ericaceae) in the context of drought, seed predation, and fire.

Phenology is an ecologically critical attribute that commonly is coordinated with other plant traits. Phenological shifts may be the result of evolutionary adjustments to persistently new conditions, or transitory, varying with annual flux in abiotic conditions. In summer-dry, fire-prone Mediterranean-climates, for example, many plant lineages have historically migrated from forests to more arid shrublands resulting in adaptive trait changes. These shifts in habitat abiotic conditions and biotic interactions influence morphology of flowers and fruits and will interact with phenological timing. The Arbutoideae (Ericaceae) is one lineage that illustrates such modifications, with fruit characters evolving among genera from fleshy to dry fruit, thin to stony endocarps, and bird to rodent dispersal, among other changes. We scored herbarium collections and used ancestral trait analysis to determine phenological shifts among the five Arbutoid genera found in semi-arid climates. Our objective was to determine if phenology shifts with the phylogenetic transition to different reproductive characters. Our results indicate that phenological shifts began with some traits, like the development of a stony endocarp or dry fruits, but not with all significant trait changes. We conclude that early phenological shifts correlating with some reproductive traits were permissive for the transition to other later character changes.

Leaf structural traits of two Restinga plant species with different resistance pattern to iron toxicity

Iron mining activities are a source of particulate iron, which contaminates soil and plants of Restinga biome (Brazil). To investigate the possible effects of iron toxicity to Ipomoea pes-caprae and Canavalia rosea leaves, plants were submitted to different exposure times (12, 36, 108 and 228 hours) and iron concentrations (0.5 or 150 mg L-1, Fe2+ as FeSO4.7H2O). After 108 hours C. rosea leaves were chlorotic while I. pes-caprae leaves presented venal chlorosis and bronzing after 228 hours, both from iron excess treatment. The anatomical alterations in I. pes-caprae were more intense and appeared earlier than in C. rosea, after 36 hours exposed to iron excess. The leaf epidermal cells of I. pes-caprae presented alterations in organization, size and shape and for both species the epicuticular wax was altered and wax rupture occurred close to the stomata. The positive staining for the presence of iron in leaf tissues matches with damaged areas in I. pes-caprae leaves, indicating direct iron toxicity. I. pes-caprae was the species with the most severe symptoms while C. rosea was the most resistant one. The results support that over time, the emission of particulate matter may negatively impact the ecological succession and biodiversity of Restinga.

A preliminary investigation of the lichen biota associated with recently deglaciated terrain in southeastern Alaska

Glaciers worldwide are currently retreating at unprecedented rates, revealing large tracts of newly exposed rock and till. We present the results of a preliminary, qualitative investigation of the lichen diversity of transient habitats near three glaciers in southeastern Alaska: Muir Glacier within Glacier Bay National Park, and Baird and Patterson Glaciers in the Tongass National Forest. This work is noteworthy as it (i) documents previously undescribed lichen species and communities within rapidly changing glacier habitats, (ii) illustrates the importance of cryptogams (lichens, bryophytes, algae, and cyanobacteria) in the primary colonization of recently deglaciated terrain, (iii) sets apart the lichen biota of recently deglaciated terrain in southeastern Alaska from that of other glacial regions worldwide (e.g., the European Alps, Svalbard, and southern South America) and even other parts of Alaska (e.g., Brooks Range), and (iv) emphasizes the importance of more lichen studies that focus on this rapidly changing habitat. The lichen biotas found at different successional stages near these glaciers are described and compared. The role of lichens and other cryptogams in post-glacial vegetation initiation, the threats to the lichen biota, and suggestions for the possible origins of the lichen propagules that colonize these newly exposed surfaces are also discussed.

Post-fire peatland vegetation recovery: A case study in open rich fens of the Canadian boreal forest

Fire plays a major role in structuring and the functioning of boreal ecosystems. As peatlands are important components of boreal forests, the impact of fire upon these wetter ecosystems is increasingly studied, but with the main focus on treed peatlands and Sphagnum-dominated bogs so far. Important fires occurring more frequently in the past decade in southern Northwest Territories (Canada) provide the opportunity to assess early post-fire vegetation regeneration in open rich fens (1, 2 and 5-years post-fire) and to better understand early recovery succession. We aimed to 1) evaluate whether and how open rich fens are affected by fire 2) describe short-term vegetation regeneration, for both bryophytes and vascular species. A shift was observed between pioneer bryophytes and brown mosses between the second and fifth-year post-fire. Vascular plants, especially slow-growing species and the ones reproducing mainly by seeds, recovered partially. The first bryophyte species recovering were pioneer species adapted to colonize burned environment such as Marchantia polymorpha or Ceratodon purpureus. For vascular plant species, the ones previously present and capable to regrowth rapidly from unburned plant structures (base of tussocks, rhizomes, roots) were represented by species like Betula glandulosa or Carex aquatilis. The wetter conditions and lower fuel availability of fen depressional biotopes were important factors controlling the resistance and regeneration of species associated with them.

Leaf ontogenesis of Trembleya phlogiformis DC. (Microlicieae, Melastomataceae): functional aspects and indumentum characterization

Leaf ontogenesis is determinant for the establishment and regulation of its structural and functional properties, in addition to being an excellent tool for assignment to different groups of angiosperms. Even though the importance of leaf morphology and anatomy for taxonomic use is well known, few studies have addressed the processes of leaf ontogeny in Melastomataceae. Herein, we sought to define the ontogenetic steps of leaf of Trembleya phlogiformis, highlighting the indumentum, to understand the main functional traits. Shoot apex, young and fully expanded leaves were processed by usual light microscopy procedures. At the first node, leaf primordia are densely covered with trichomes and emergences. The adaxial layer of ground meristem gives rise to the palisade parenchyma, the procambium originates from median layers of ground meristem and the spongy parenchyma develops from abaxial layers of ground meristem. The differentiation of isobilateral mesophyll on leaves of T. phlogiformis, a common feature in Microlicieae, comes from ground meristem stratification. However, T. phlogiformis stands out by showing in the leaf mature spongy parenchyma cells with irregular shapes. The leaf ontogeny reveals distinct mechanisms of cell differentiation and may be important for the establishment of functional adaptive traits.

Nunatsiavut, ‘Our beautiful land’: Inuit landscape ethnoecology in Labrador, Canada

For Inuit in the subarctic transition zone of northeastern Canada, an intimate knowledge of the environment and local biodiversity is crucial for successful traditional activities. This study examines what kinds of landscape features and habitats Inuit of Nunatsiavut recognize and name. During interviews, community members (mostly Elders) were shown photographs from the region, and were asked to describe and name salient types of places in Labrador Inuttitut. The most frequently reported geographical units dealt with the region’s topography (e.g., ‘mountain’, ‘island’, ‘flat-place’), hydrology (e.g., ‘river’, ‘bay’), and superficial characteristics (e.g., ‘bedrock’, ‘permanent snow patch’). Ecological considerations were also prominent, such as plant associations and animal habitats (e.g., ‘shrubby-place’, wetland’, ‘caribou-return-to-place’). Areas were often characterized by a dominant species or substrate type, being named using the plural form of the species/substrate (e.g., napâttuk ‘tree’/ napâttuit ‘forest’, siugak ‘sand’/siugalak ‘sandy-area’). Some types of places reported by Inuit were significant mainly for traditional activities (e.g., ‘berry-patch’, ‘seal-place’, ‘dry-wood-place’, ‘danger-place’), aiding navigation and resource finding. Integrating Inuit conceptions of ecosystems and their component landscape units with those of contemporary science can improve our understanding of subarctic ecology, benefit climate change adaptation strategies and Inuit language/culture conservation initiatives.