Phenology of competitive interactions and implications for management of the invasive wetland plant Alternanthera philoxeroides

Phenological differences between invading plants and members of recipient communities may increase the success of invaders because of priority effects. Thus, the application of management when the invader has a phenological advantage (for example, early in the year) can benefit other species by increasing resource availability. This technical note summarizes results from a combination of field observations and a mesocosm experiment to explore whether phenological differences between the invasive wetland plant, alligatorweed (Alternanthera philoxeroides [Mart.] Grseb.), and resident species contribute to alligatorweed success. We documented over two years the early-season growth of alligatorweed and other species at 12 sites in Louisiana, USA. We then conducted a subsequent mesocosm competition experiment between alligatorweed and a common wetland emergent species, spotted lady’s thumb (Persicaria maculosa [L.] Small), over a full year to detect differences in timing of growth and competitive interactions under two fertilizer levels.

High ecological resilience of the sea fan Gorgonia ventalina during two severe hurricanes

Since about the turn of the millennium, octocorals have been increasing in abundance on Caribbean reefs. The mechanisms underlying this trend have not been resolved, but the emergent species assemblage appears to be more resilient than the scleractinians they are replacing. The sea fan Gorgonia ventalina is an iconic species in the contemporary octocoral fauna, and here its population dynamics are described from St. John, US Virgin Islands, from 2013 to 2019. Mean densities of G. ventalina at Yawzi Point (9-m depth) varied from 1.4–1.5 colonies m−2, and their mean heights from 24–30 cm; nearby at Tektite (14-m depth), they varied from 0.6–0.8 colonies m−2 and from 25–33 cm. These reefs were impacted by two Category 5 hurricanes in 2017, but neither the density of G. ventalina, the density of their recruits (< 5-cm tall), nor the height of colonies, differed among years, although growth was depressed after the hurricanes. Nevertheless, at Tektite, colony height trended upwards over time, in part because colonies 10.1–20 cm tall were reduced in abundance after the hurricanes. These trends were sustained without density-associated effects mediating recruitment or self-thinning of adults. The dynamics of G. ventalina over seven years reveals the high resilience of this species that will contribute to the persistence of octocorals as a dominant state on Caribbean reefs.

Primate tool use and the socio-ecology of thinging: how non-humans think through tools

While ecological psychology and embodied approaches to cognition have gained traction within the literature on non-human primate tool use, a fear of making assumptions on behalf of animal minds means that their application has been conservative, often retaining the methodological individualism of the cognitivist approach. As a result, primate models for technical and cognitive evolution, rooted in the teleological functionalism of the Neo-Darwinist approach, reduce tool use to the unit of the individual, conflating technology with technique and physical cognition with problem-solving computations of energetic efficiency. This article attempts, through the application of material engagement theory, to explore non-human primate technology as a non-individualistic phenomenon in which technique is co-constructed through the ontogenetic development of skill within a dynamic system of structured action affordances and material interactions which constitute an emergent, species-specific mode of technical cognition.

Distribution of aquatic macrophytes along depth gradients in Lajeado Reservoir, Tocantins River, Brazil

Aim The present study investigated the diversity of aquatic macrophytes in the littoral zone of Lajeado Reservoir, Tocantins River. We characterized spatial variations in species richness, composition and abundance along depth gradients. Methods Macrophyte sampling occurred at the end of the dry season (September and October 2014) in four sites of the reservoir. We established transects perpendicular to the shoreline, each 25 m long, divided in 3 sections (plots of 5 x 5 m). Results In total, we recorded 18 taxa of aquatic macrophytes, belonging to nine families and four life forms. Najas microcarpa, Echinodorus tenellus. and Chara sp. were the more frequent and abundant taxa. Considering depth gradients, we recorded 18 taxa in the section closer to the shoreline, 13 in the middle section and 10 in the section more distant to the shoreline. Submerged and emergent species were more frequent and abundant, especially in the section close to the shoreline; epiphytes and free-floating species were rare. Plot species richness (total, emergent and submerged) decreased along the gradient, and a Non-Metric Multidimensional Scaling (NMDS) revealed that the plot close to the shoreline had different composition when compared to adjacent sections. Individual species showed particular behaviors, but most tended to decline in abundance and occurrence along the gradient. Conclusions The present study revealed that small-scale environmental gradients affect the distribution of aquatic plants in Lajeado Reservoir, with greater diversity in habitats close to the shoreline.

An update on the knowledge of aquatic macrophytes in Northeast Brazil

We updated the first checklist of aquatic macrophytes from Northeast Brazil (First Flora), which included data collected up to 2010, with a new checklist based on data from works published between 2011 and 2017 (New Flora). Together, these checklists record 637 species of 89 families, with an emphasis on strictly amphibious or emergent species, with 392 and 115 species, respectively. We found differences in observed richness between New Flora and First Flora, with an increase of 106 species in the New Flora. The rarefaction curve shows that a considerable increase in collection effort is necessary to determine the aquatic flora of the studied region. From the compiled data, we suggest new perspectives for floristic inventories of aquatic macrophytes, highlighting the prioritization of poorly studied areas; the exploration of ecological information of the species (e.g., endemism, rarity, threat of extinction or invasive potential); and the promotion of projects on a regional scale.

Potential of Submerged Vegetation to Remove Nutrients from Eutrophic Fishponds

The possibility to remove nutrients from two eutrophic fishponds in the Czech Republic through harvesting the dominant submerged species, Ceratophyllum demersum and Stuckenia pectinata, was evaluated. Both plants were sampled in three locations within the fishpond in two-week intervals from late June to late September 2016. In the biomass of both plants nitrogen and phosphorus concentrations were measured and, subsequently, standing stocks of both elements were calculated. The results revealed that the maximum biomass occurred at different times, in June for S. pectinata and in July for C. demersum. The maximum standing stocks were 3.61 and 7.44 g N m−2 and 0.13 and 0.53 g P m−2, respectively.. These values are within the range reported in the literature for the studied species, but they are about one order of magnitude lower when compared to tall emergent species. The total amount of removable nutrients in the monitored fishponds varied between 448 and 842 kg N and between 30.5 and 31.9 kg P.

Provenance of invaders has scale-dependent impacts in a changing wetland ecosystem

Exotic species are associated with a variety of impacts on biodiversity, but it is unclear whether impacts of exotic species differ from those of native species with similar growth forms or native species invading disturbed sites. We compared presence and abundance of native and exotic invaders with changes in wetland plant species diversity over a 28-year period by re-surveying 22 ponds to identify factors correlated with observed changes. We also compared communities found within dense patches of native and exotic emergent species with similar habits. Within patches, we found no categorical diversity differences between areas dominated by native or exotic emergent species. At the pond scale, the cover of the exotic grass Phragmitesaustralis best predicted change in diversity and evenness over time, likely owing to its significant increase in coverage over the study period. These changes in diversity and evenness were strongest in younger, less successionally-advanced ponds. Changes associated with cover of P.australis in these ponds were not consistent with expected diversity decreases, but instead with a dampening of diversity gains, such that the least-invaded ponds increased in diversity the most over the study period. There were more mixed effects on evenness, ranging from a reduction in evenness gains to actual losses of evenness in the ponds with highest invader cover. In this wetland complex, the habit, origin and invasiveness of species contribute to diversity responses in a scale- and context-dependent fashion. Future efforts to preserve diversity should focus on preventing the arrival and spread of invaders that have the potential to cover large areas at high densities, regardless of their origin. Future studies should also investigate more thoroughly how changes in diversity associated with species invasions are impacted by other ongoing ecosystem changes.

Architecture of four tree species from different strata of a semideciduous forest in southern Brazil

The present study was conducted in a semideciduous Brazilian forest to verify whether there were architectural differences during development among tree species that differ in adult stature, such that understorey species maximise light interception and canopy and emergent species maximise height gain to rapidly reach high light environments. The crown illumination index and light interception index of individual trees as well as the variation in form among the understorey species were also analysed. Two understorey, one canopy and one emergent species were chosen, and the individuals were divided into height classes. Architectural comparisons among individuals were evaluated using allometry; crown illumination and light interception indices were compared among species. All comparisons were made within each height class. The two understorey species presented some differences in growth form, but both exhibited greater investment in the crown than did the canopy and emergent species. The crown illumination index did not differ among species, but the light interception index was higher for the understorey species. The results indicated that architectural differences between the studied species arise predominantly because species belong to different strata of the forest. Comparison within height classes was important because it allowed us to evaluate species architectural characteristics throughout plant development that cannot be detected using a single height-class comparison or that can be neglected if individuals of different heights are compared.

Wetland Plants and their Local Uses: Observations from Rampur Ghol, Chitwan, Nepal

This paper is based on the study of wetland plant resources of Rampur Ghol conducted from 2012 to 2014. This paper documents 117 plant species belonging to 39 families and 92 genera in the area. Dicot species (60 spp.) dominated over the monocots (53 spp.) and pteridophytes (4 spp.). The dominant family was the Poaceae (21 spp.) followed by Cyperaceae (14 spp.), Asteraceae (10 spp.), Scrophulariaceae (8 spp.), Polygonaceae (5 spp.)and Acanthaceae (4 spp.). By life form, emergent species were highest (86%) compared to submerged (6%), rooted floating leaved plants (6%) and free floating plants (2%). These plants had use value of medicine, food (for human, domestic animals, and fish), fuel energy, artifacts, etc. Realizing its contribution along with useful plants, Rampur Ghol area should be conserved for learning and recreation purposes.J. Nat. Hist. Mus. Vol. 28, 2014: 142-159