Population Dynamic of the Annual Halophyte Salicornia ramosissima in Salt Pans: Towards a Sustainable Exploitation of Its Wild Populations.

Halophyte species growing under stressful conditions, such as the annual species of the Salicornia genus, have been recognized as a source of metabolites of pharmacological and nutraceutical interest. Therefore, planning the extraction of individual plants from wild populations in a sustainable way is especially important in the case of annual species. We studied the environmental matrix and population dynamic of four Salicornia ramosissima populations growing at two elevations in salt pans under a Mediterranean climate. In elevated areas, S. ramosissima populations presented maximum plant densities of between 628-6288 plants m-2 that remained almost constant until fruiting. In contrast, populations in depressed zones presented five-times greater soil-seed-bank densities and maximum plant densities than populations in elevated zones. In this context, populations in depressed zones lost c. 60% of their maximum plant densities from the end of spring and through summer. In whatever way the environmental matrix seemed to control the population dynamic of S. ramosissima in depressed zones, the effects of a stressful environment would interact with plant densities. In this sense, we recorded the density-dependent mortality for the densest population (max. 51,558 plants m-2). Our results are useful for planning a sustainable harvesting of natural populations of S. ramosissima.

Metal effects on germination and seedling development in closely-related halophyte species inhabiting different elevations along the intertidal gradient.

Seed germination and seedling establishment are very sensitive plant stages to metal pollution. Many halophyte species colonizing salt marshes are able to germinate and establish in highly contaminated habitats and low marsh halophyte species seem to show higher tolerance to metals than high marsh species. We analyzed the effects of copper, zinc and nickel in concentrations up to 2000 µM on seed germination and seedling growth in two closely related species of Sarcocornia, S. perennis, a low marsh species, and S. fruticosa, a high marsh species. Germination of both halophytes was not affected by any metal concentration, and their seedling growth, mainly radicle length, was reduced by increasing metal concentrations. Seedlings of S. perennis showed higher tolerance to the three metals than those of S. fruticosa. Our results are useful for designing ecotoxicological bioassays and planning phytoremediation projects in salt marshes.

Seed bank persistence of a South American cordgrass in invaded northern Atlantic and Pacific Coast estuaries.

Invasive alien plant species impart considerable impacts that contribute to the decline of biodiversity worldwide. The ability of an invasive species to overcome barriers to establish and spread in new environments, and the long-term effects of plant invasions supporting their persistence are keys to invasion success. The capacity of introduced species to form soil seed banks can contribute to their invasiveness, yet few studies of invaders have addressed seed bank dynamics. Improved knowledge of this recruitment process can improve conservation management. We studied temporal and spatial changes in soil seed bank characteristics of the cordgrass Spartina densiflora from two continental invaded ranges. In the Odiel Marshes (Southwest Iberian Peninsula), S. densiflora formed transient seed banks (<1 year). At Humboldt Bay Estuary (California), viable seeds persisted for at least 4 years though the germination percentage fell abruptly after the first year from 29 % to less than 5 % of remaining viable seeds. Total soil seed bank density increased with S. densiflora above-ground cover in both estuaries, pointing to the transient component of the seed bank as a critical component of vegetation dynamics during S. densiflora invasion. Even so, seed densities as high as c. 750 seeds m-2 in Odiel Marshes and c. 12 400 seeds m-2 in Humboldt Bay were recorded in some plots without fruiting S. densiflora plants. S. densiflora spikelet (dispersal unit) density was more than double close to the sediment surface than deeper within soil. Our study shows the importance of evaluating seed banks during the design of invasive species management since seed bank persistence may vary among invaded sites, and can affect the timing and duration required for desired management outcomes.

Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses.

Seed germination and seedling establishment are the stages most sensitive to abiotic stress in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 µM). However, the increase in metal concentration had negative effects on S. densiflora seedlings. The primary effect was on radicle development, representing initial seedling emergence. Spartina densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, showed higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Comparing our results to metal concentrations in the field, we expect S. densiflora seedling development would be negatively impacted in the most metal-polluted areas in Odiel and Tinto Estuaries.

Differential Effects of Increasing Salinity on Germination and Seedling Growth of Native and Exotic Invasive Cordgrasses.

Soil salinity is a key environmental factor influencing germination and seedling establishment in salt marshes. Global warming and sea level rise are changing estuarine salinity, and may modify the colonization ability of halophytes. We evaluated the effects of increasing salinity on germination and seedling growth of native Spartina maritima and invasive S. densiflora from wetlands of the Odiel-Tinto Estuary. Responses were assessed following salinity exposure from fresh water to hypersaline conditions and germination recovery of non-germinated seeds when transferred to fresh water. The germination of both species was inhibited and delayed at high salinities, while pre-exposure to salinity accelerated the speed of germination in recovery assays compared to non-pre-exposed seeds. S. densiflora was more tolerant of salinity at germination than S. maritima. S. densiflora was able to germinate at hypersalinity and its germination percentage decreased at higher salinities compared to S. maritima. In contrast, S. maritima showed higher salinity tolerance in relation to seedling growth. Contrasting results were observed with differences in the tidal elevation of populations. Our results suggest S. maritima is a specialist species with respect to salinity, while S. densiflora is a generalist capable of germination of growth under suboptimal conditions. Invasive S. densiflora has greater capacity than native S. maritima to establish from seed with continued climate change and sea level rise.

Supporting Spartina: Interdisciplinary perspective shows Spartina as a distinct solid genus.

In 2014, a DNA-based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, biological invasions, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 yr. We do not agree with the subjective arguments underlying the proposal to change Spartina to Sporobolus. We understand the importance of both the objective phylogenetic insights and of the subjective formalized nomenclature and hope that by opening this debate we will encourage positive feedback that will strengthen taxonomic decisions with an interdisciplinary perspective. We consider that the strongly distinct, monophyletic clade Spartina should simply and efficiently be treated as the genus Spartina.

Some Like It Hot: Maternal-Switching With Climate Change Modifies Formation of Invasive Spartina Hybrids.

Climate change can induce temporary, spatial or behavioral changes in species, so that only some species can adapt to the new climatic conditions. In the case of invasive species, it is expected that they will be promoted in a context of global change, given their high tolerance to environmental factors and phenotypic plasticity. Once in the invaded range, these species can hybridize with native species thus introducing their genotype in the native biota. However, the effects that climate change will have on this process of invasion by hybridization remain unclear. We evaluated the historical establishment of the reciprocal hybrids between the native Spartina maritima and the invasive S. densiflora in the Gulf of Cadiz (SW Iberian Peninsula) and we related it to climatic changes during the period 1955-2017. Our results showed that, according to their dating based on their rate of lateral expansion rates, the establishment of S. maritima × densiflora and S. densiflora × maritima in the Gulf of Cadiz has occurred in the last two centuries and has been related to changes in air temperature and rainfall during the flowering periods of their parental species, with antagonist impacts on both hybrids. Thus, the hybrid S. densiflora × maritima has been established in years with mild ends of spring and beginning of summer when the flowering of S. maritima lengthened and its pollen production was higher, and it coincided with the beginning of the flowering period of S. densiflora. Moreover, the establishment of this hybrid was related to higher spring/summer rainfalls, probably due to the reduction in salinity in middle marshes. However, the hybrid S. maritima × densiflora, was established mainly in warmer spring/summers in which the proportion of pollen:ovule of S. maritima was reduced favoring its pollination by S. densiflora. As a consequence of the promotion of S. maritima × densiflora with climate change, the native and endangered species S. maritima would be threatened, as both taxa share the same habitat and the hybrid shows a remarkably higher competitive potential.

Airborne spores of Basidiomycetes in Mérida (SW Spain).

The aim of this work was to detect the presence of Basidiomycetes spores (basidiospores, teliospores, uredospores and aeciospores) in Mérida (SW Spain) and assess the influence of weather parameters. Air was sampled continuously with a volumetric seven-day Burkard spore trap for two years. Fungi spores were identified and counted at x1,000 microscope resolution. Daily and weekly meteorological data and airborne spore concentration were analysed. Twenty-three spores types were identified, including basidiospores (Amanita, Agrocybe, Cortinarius, Coprinus -2 types-, Boletus, Bovista, Calvatia, Entoloma, Ganoderma, Inocybe, Russula, Scleroderma, Telephora), teliospores (Phragmidium, Tilletia, Ustillago -4 types-), uredospores, and aeciospores (2 types), all of these types of spores included different taxa. Average concentration was of 616 spores/m(3), with maximum concentration in autumn (October), and a second concentration in spring (May-June); however, some spore types were more frequent in summer (Bovista, Ganoderma) or even in winter (Entoloma, Calvatia). The Amanita type was the most frequent (white-hyaline basidiospores); the second were teliospores of Ustilago, the third spore type was basidiospores of Coprinus (blackish basidiospores) and Agrocybe type (smoothed light to dark coloured basidiospores). Basidiospore concentration was positively correlated with temperature and negatively with relative humidity in most cases, and Ustilago teliospores concentration was positively correlated with wind speed. Differences in monthly rain were probably the origin between years. Airborne spores of Basidiomycetes may be separated into more than 20 types, and their seasonal concentration depended on meteorology as well as whether they were saprotrophic or parasitic.

Reproductive phenology and pre-dispersal fruit predation in Atriplex halimus L. (Chenopodiaceae).

BACKGROUND: The flowering phenology pattern of Atriplex halimus was studied in a Mediterranean habitat in order to analyze protandry effectiveness. Fruit set evolution was recorded over two years and the impact of pre-dispersal predation by insects was also evaluated. RESULTS: The flowering phenology coincided in 2006 and 2007, starting in mid-July and reaching full flowering at the end of August in both years. Inflorescences are composed of glomerules with 8.78 ± 2.79 male flowers and 4.57 ± 2.58 female flowers, with no significant differences in position on the inflorescence. The peaks of male and female flower anthesis were reached in mid-August, but the male maximum occurred one week before the female. Plants at the start of flowering only bear male flowers, but female flowers soon appear. Fruit set starts at the end of August; all the flowers were transformed into fruit by mid-September and their development continued to the beginning of October, when fruit structures had matured and began to drop. Fruit predation started at the end of September and reached maximum intensity in mid-October. CONCLUSIONS: At population level, male and female flowers seemed to open in the same weeks, but at plant and glomerule level male flowers opened one week before the females. Fruit predation levels were 62.42 and 43.14% in 2006 and 2007 respectively, with no significant differences between different parts of the inflorescence. And larvae of Coleophoridae were the most abundant predators.

Influence of meteorological parameters in hourly patterns of grass (Poaceae) pollen concentrations.

Hourly grass pollen concentrations were recorded over a 10-year study period at an aerobiological station of Badajoz (SW Spain). The record was carried out by means of a Burkard spore trap. Meteorological data were used to find correlation with the hourly patterns in the months of principal concentration. The observed variations were found to be due to independent contributions of patterns corresponding to different groups of species within the family of grasses. Three pollen concentrations peaks were recognized. Peak A, at around 10:00 h, of great importance in April and May, although maintained until July; peak B, at around 15:00 h, important in April, May and June; and peak C, towards the end of the day, dominant in July. Differences with respect to the pollen sources responsible for these peaks are suggested by the influence of the meteorological parameters before and during flowering. The results are directly applicable to the epidemiology of allergies in the zone, since the thresholds of grass pollen concentrations capable of triggering allergic processes shift from the central hours of the day in April and May to the night hours in July. Also, considering the observed patterns of hourly grass pollen concentrations as the result of combining different models could explain the annual and geographical variations found at other locations.