Recovery of Germination from Different Osmotic Conditions by Four Halophytes from Southeastern Spain

Seeds of four halophytes from southeastern Spain (the perennialsHalocnemum strobilaceum,Arthrocnemum macrostachyum and Sarcocorniafruticosa, and the annual Salicornia ramosissima) were exposedto iso-osmotic stress with NaCl, MgCl₂, MgSO₄and Na₂SO₄. Theosmotic potential that enforced dormancy in the majority ofseeds was determined. The percentage of ungerminated seeds thatrecovered when they were transferred to distilled water didnot differ significantly from the percentage germination ofseeds in distilled water controls, irrespective of the saltused to impose the stress. Therefore, the factor responsiblefor the dormancy of seeds seems to be the decrease in osmoticpotential. Such osmotic pretreatments promoted an increase inthe rate of recovery germination which, inArthrocnemum macrostachyumand Sarcocornia fruticosa, doubled their rates of germinationcompared to distilled water controls. The osmotic potentialsof the soils where the four species occur naturally were morenegative than those allowing seeds to germinate after osmoticstress. Copyright 2000 Annals of Botany Company Arthrocnemum macrostachyum, Halocnemum strobilaceum, halophytes, osmotic stimulation, recovery of seed germination, Salicornia ramosissima, Sarcocornia fruticosa.     

Influence of season on leaf litter ant (Hymenoptera: Formicidae) diversity in the locality of Minko'o (Southern,Cameroon)

Seasonality is known to influence ant activity in many tropical rain forests in the world such as South America and Africa. We surveyed ant fauna in the leaf litter in the locality of Minko'o. The work aimed to evaluate the effect of seasonal variation on the diversity and composition of litter ants. Ants were sampled from November 2015 to June 2017, using four sampling methods: visual capture, bait, pitfall trap and extraction. Species richness, Shannon diversity index and analysis of similarities were used to characterise diversity of ant communities between seasons. We collected 306 ant species, shared out between 56 genera and 11 subfamilies. Subfamilies Myrmicinae, Ponerinae, Dolichoderinae, Formicinae, Dorylinae, Cerapachyinae and Pseudomyrmecinae occurred in all the seasons. Species richness was highest in major dry season with 243 species followed by minor rainy season with 188, major rainy season with 177 species and finally minor dry season that recorded the lowest with 155 species. Kruskal–Wallis test showed that ant species richness did not differ between seasons (p > 0.05). Species diversity index indicated that diversity was the highest during minor dry season (H′ = 4.24), followed by the major dry season (H′ = 4.23), minor rainy season (H′ = 4.21) and lowest during major rainy season (H′ = 4.06). Eight most frequents ants have been recorded: Axinidris sp.1, Camponotus flavomarginatus, Monomorium guineense, Myrmicaria opaciventris, Odontomachus troglodytes, Carebara perpusilla, Paltothyreus tarsatus and Pheidole megacephala. Assessment of the seasonal effect on diversity reveals that dry season is richer and more diverse than rainy season and the season significantly influence the diversity of litter ants.     

Vegetation analysis of Burullus Wetland: a RAMSAR site in Egypt

We analyzed the vegetation of Lake Burullus at the deltaic Mediterranean coast of Egypt, the sand bar between its northern shore and Mediterranean Sea, the water courses that drain into the lake and the wetland around it. Our ultimate aim was to identify threatened species and communities and the environmental factors that affect their distribution in order to formulate a plan for their conservation. The total number of the recorded species was 197 (100 annuals and 97 perennials), including 12 floating and submerged hydrophytes. Three species are endemic to Egypt: two annuals (Sinapis arvensis subsp. allionii and Sonchus macrocarpus) and one perennial (Zygophyllum album var. album). Thirty-four species are rare allover Egypt (15 annuals and 19 perennials). The lake area included 10 types of habitat (sand formations, salt marshes, lake cuts, terraces, slopes, water edges and open water of the drains, islets, shores and lake). The vegetation was classified into 13 groups (i.e., plant communities). Six groups were dominated or co-dominated by the common reed (Phragmites australis); these groups occupied a wide environmental gradient from xeric to hydric habitats. Five other groups were dominated by halophytic species (Arthrocnemum macrostachyum, Suaeda vera, Sarcocornia fruticosa, Halocnemum strobilaceum and Salsola Kali). The remaining two groups were dominated by the emergent Typha domingensis and the submerged Potamogeton pectinatus. Moisture, salinity and sedimentation were the main factors that governed the plant succession in this wetland.     

Cambial growth dynamics and climatic control of different tree life forms in tropical mountain forest in Ethiopia

Munessa Forest is a mountain forest in south-eastern Ethiopia experiencing seasonal rainfall variation. We investigated seasonal cambial activity and dormancy from increment rates of four different tree species belonging to varying life forms, namely, evergreen native conifer (Podocarpus falcatus), evergreen introduced conifer (Pinus patula), evergreen broadleaved tree (Prunus africana) and deciduous broadleaved tree (Celtis africana). Measurements of stem radius fluctuations were registered with the help of high-resolution electronic dendrometers. Daily amplitudes of stem diameter variations and daily and monthly net growth rates were determined and related to climatic variables measured at local climate stations. Thin sections of wood collected with a microcorer every 3–6 weeks allowed a visual control of newly formed wood cells during consecutive time intervals. Lack of water availability during the long dry season induced cambial dormancy of 5–7 months depending on life forms. After the onset of the short rainy season, stem swelling started quite synchronously with a variation of only single days in all studied species. Evergreen tree species were able to initiate wood formation during the short rainy season, whereas growth in the deciduous broadleaved species started in the long rainy season. The acquired data provide a basis for delineating the species-specific growth boundaries and the duration of the cambial growing season.     

New insights into seminal and stomatal morphology and their contribution to the taxonomy of the Old World succulent perennial Salicornioideae

Seminal and stomatal morphology of three succulent halophyte genera (Sarcocornia, Halocnemum and Arthrocnemum) around the Mediterranean basin and surroundings areas were investigated. Scanning electron microscopy (SEM) investigations showed well-different seminal coat ornamentations among the studied taxa. Both Arthrocnemum macrostachyum and Halocnemum strobilaceum do not show trichomes. Conversely, the species Sarcocornia perennis and S. fruticosa can be easily identified by the presence of long curved hairs against papillae or short conic hairs, respectively. Because most of the herbarium vouchers of Sarcocornia lack seeds, and thus the permanency of seeds on plants is quite short, an alternative vegetative character as stomata was also studied using SEM and light microscope. The detailed stomatal morphological features were analysed for the first time to infer taxonomic relationships among these perennial halophytes. Stomata are constantly paracytic for the four studied species, but two morphotypes were identified related to the level arrangement of guard cells, named as sunken and prominent stomata, respectively. Sunken stomata are found in A. macrostachyum, H. strobilaceum and S. fruticosa, whereas prominent stomata are only characteristic for S. perennis. Besides, we have found somehow relationships among the ecology of these plants based on the frequency of floodings and the observed morphology and density of stomata. Nonetheless, each observed morphotype is a stable character, without any influence of climate or environmental conditions. As a result, seminal coat ornamentation and stomata morphology are the two most reliable characteristics for discriminating Mediterranean halophytes taxa, especially related to Sarcocornia taxa.     

Seasonality affects the parasitism levels in two fish species in the eastern Amazon region

Fish parasite communities have strong interactions with the environment, the host fish, and the aquatic invertebrate communities. Thus, factors directly involving their different life cycles, such as different host populations and environments, as well as seasonal fluctuations in water levels can cause different responses. The main factors structuring parasite communities may be the hydrodynamic variations, together with seasonal variations in the availability of infectious stages of parasites in the environment. The purpose of this study was therefore to investigate the influence of the rainy and dry seasons on parasite infracommunities in fish species in the Amazon River System of Brazil. Between October 2009 and April 2011, specimens of Colossoma macropomum and Colossoma macropomum × Piaractus brachypomus hybrids (tambatinga) were examined for the presence of parasites. The parasite communities were similar in these two species that both showed aggregate dispersion, although the hybrid specimens were less parasitized. For both hosts, the Brillouin diversity, species richness, evenness and Berger‐Parker dominance indices were similar in the rainy season and dry season, except that the Berger‐Parker dominance index for the C. macropomum × P. brachypomus hybrid was higher during the dry season. Ichthyophthirius multifiliis was the dominant parasite, followed by Piscinoodinium pillulare, in both hosts. However, C. macropomum had a higher prevalence and abundance in the dry season, while in the C. macropomum × P. brachypomus hybrid, only the I. multifiliis prevalence increased. The abundance of monogenean species (Anacanthorus spathulatus, Linguadactyloides brinkmanni, Mymarothecium and Notozothecium janauachensis) was higher during the dry season in the gills of C. macropomum. Despite overdispersion of the lernaeid Perulernaea gamitanae, a seasonal pattern was seen only in the C. macropomum × P. brachypomus hybrid, with higher prevalence in the rainy season. The low prevalence and abundance of the ectoparasites Tetrahymena sp., Trichodina sp. and Braga patagonica, as well as of the endoparasites Procamallalus (Spirocamallanus) inopinatus and Neoechinorhynchus buttnerae, were not affected by seasonality. This information is applicable in farming practice for these economically important fish, as it indicates the best time for prophylactic management and treatment against parasites, in order to prevent economic losses in fish farms.     

Diversity of parasites in Cichlasoma amazonarum Kullander, 1983 during rainy and dry seasons in eastern Amazon (Brazil)

This study investigated the influence of the rainy and dry seasons on the parasite communities of Cichlasoma amazonarum (Kullander, 1983) in a tributary of the Amazon River system, northern Brazil. Of 112 fish examined, 95.5% were parasitized by Ichthyophthirius multifiliis, Piscinoodinium pillulare, Gussevia disparoides, Posthodiplostomum sp., Procamallanus (Spirocamallanus) inopinatus, and Echinorhynchus paranensis, as well as by the Glossiphoniidae leech. Ichthyophthirius multifiliis and P. pillulare were the dominant parasite species, with I. multifiliis the most prevalent and abundant; the leech (Glossiphoniidae) was the least prevalent and least abundant. Parasites presented an aggregate dispersion pattern and seasonal variations in infestation levels, influenced by the environmental conditions in the rainy season. Variation in the parasite dynamics created overall changes in the parasite communities, characterized by greater diversity, species richness and evenness during the rainy season. However, there was a high similarity (99.8%) in the parasite community structure between the rainy and dry seasons. During the dry season the hosts had predominantly 1–3 parasite species compared to 3–4 parasites in the rainy season. Some parasites in the eastern Amazon undergo population changes relating to seasonality. These results thus indicate the correct season to apply adequate prophylactic measures to reduce negative impacts of parasites in this wild ornamental fish when captured.     

Seasonal variation in abundance and diversity of eavesdropping frog‐biting midges (Diptera,Corethrellidae) in a neotropical rainforest

1. In the tropics, precipitation patterns result in seasonal fluctuations in the abundance and distribution of plant and animal species. Tropical predators and parasites are therefore faced with seasonal changes in prey and host availability. 2. This study investigates the seasonal interaction among a specialised ectoparasite, eavesdropping frog‐biting midges (Corethrella spp.), and their anuran hosts, examining how the abundance and diversity of the frog‐biting midge community fluctuate between the rainy (host abundant) and dry (host sparse) seasons. 3. Midges were captured in both the rainy and dry seasons using acoustic playbacks of calls from a common frog species that breeds during the rainy season, the túngara frog (Engystomops, Physalaemus, pustulosus). During the dry season túngara frog choruses are absent. To explore seasonal shifts in host preference or changes in the midge community due to host specificity, midges were also captured using playbacks of calls from a frog that breeds during the dry season, the pug‐nosed tree frog (Smilisca sila). 4. While the overall abundance of midges decreased in the dry season, only slight differences in the relative abundance between midge species were found. These results suggest that midge populations can shift between hosts as they become available across seasons, allowing adult populations of frog‐biting midges to persist year‐round. To overcome the challenge of detecting and localising different host species, it is proposed that frog‐biting midges have evolved a generalised acoustic template, allowing them to respond to a broad range of available hosts, regardless of seasonal host composition.     

Phenology and floral synchrony of Rhizophora mangle along a natural salinity gradient

Rhizophora mangle is the most common species of mangrove within its range and a major component of coastal ecosystems in the tropics and subtropics. Its phenology is affected by seasonal variations in temperature, salinity, and precipitation, all of which may be altered by impending climate change. In this work, the monthly leaf, flower, and fruit phenology of R. mangle was assessed at three sites, along a natural salinity gradient for 12 months. We assessed phenological states using litter traps installed in mangrove stands, and by direct observation of leaf production at two sites, and flower, and fruit production at a single site. Phenological events were compared with seasonal climatic variations (in wind, rain, and temperature) to explore potential abiotic controls on the phenology of this species. Leaf shedding was lowest at the low salinity site. Leaf and stipule production showed a seasonal trend, decreasing during the cool and dry winter months. Flowering was highly seasonal and synchronous and peaked during the rainy season. Flowering was correlated with average temperature (r = 0.82; p < 0.05) at all three study sites, but was not correlated with precipitation. At the high‐salinity site, flowering was restricted to the rainy season. Fruit abortion was associated with wind speed (r = 0.79; p < 0.05). Flowering of R. mangle is induced by increasing temperatures and the onset of rains. Rising temperatures, drier summers, and more frequent and intense storms, due to climate change, may influence mangrove productivity, population dynamics, and floral synchrony.     

Extreme trophic segregation between sympatric fish species: the case of small sized body <Emphasis Type="Italic">Aphyocharax</Emphasis> in the Brazilian Pantanal

Interspecific differences in diet of the two sympatric fish species of the subfamily Aphyocharacinae were investigated. Both were sampled monthly (March 2000 to February 2001) during the rainy and dry season in North region of the Pantanal. Aphyocharax anisitsi was an invertivorous/insectivorous species, feeding mainly on aquatic insects during the rainy season and terrestrial insects in the dry season. Aphyocharax dentatus remained a piscivorous regardless of the hydrological season. Low feeding-overlap values, 0.079 in the dry season and no overlap in the rainy season were observed. The diet-breadth values for each species were low (less than 0.1) except for A. anisitsi in the lake during the dry season (0.4). A detrended correspondence analysis (DCA) summarized the diet similarity patterns: in DCA 1, it was observed that fish prey grouped A. dentatus in the lower scores, and insect prey grouped A. anisitsi in the higher scores. A two-way ANOVA showed that the diets differed significantly between the species. Our results show a clear trophic segregation between these species, supporting the niche concept that presumes that differences between sympatric species must exist, to allow their coexistence. Besides extreme segregation, it was clear that A. dentatus is a piscivorous fish, despite its low size (until 72 mm). This finding counteracts the current view about food web structure that poses a direct and positive relationship between body size and trophic position.     

Seasonal decline of the tomato leafminer,Tuta absoluta,in the shifting landscape of a vegetable‐growing area

Insect pest populations exhibit seasonal dynamics in response to changes in resource availability or other environmental factors such as climatic conditions, natural enemies, and intra‐ or interspecific competition. Understanding such dynamics is critical for developing effective integrated pest management strategies. The objective of the present study was to identify factors driving the seasonal decline of the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in the shifting landscape of a vegetable‐growing area in Senegal. A set of 42 tomato fields was monitored for the number of T. absoluta adults caught in pheromone traps and for the incidence of larvae, during 5 months from June to November 2016 in the Niayes area (Senegal). The surface of solanaceous host crops, climatic conditions, and abundance of natural enemies were also monitored. A drastic decline in T. absoluta abundance was observed during the rainy season. The decrease in resource availability, especially tomato crops, in the surrounding landscape of monitored fields was the main factor affecting the population dynamics during the rainy season. However, alternative host crops such as eggplant and Ethiopian eggplant, can provide ‘reservoirs’ for residual populations of the pest. For applied purpose, it would be interesting to focus the management efforts on residual populations during the rainy season, to make more difficult the reconstitution of populations during the dry season.     

Seasonal home range dynamics and sex differences in habitat use in a threatened,coastal marsh bird

A comprehensive understanding of spatiotemporal ecology is needed to develop conservation strategies for declining species. The king rail (Rallus elegans) is a secretive marsh bird whose range historically extended across the eastern United States. Inland migratory populations have been greatly reduced with most remaining populations inhabiting the coastal margins. Our objectives were to determine the migratory status of breeding king rails on the mid‐Atlantic coast and to characterize home range size, seasonal patterns of movement, and habitat use. Using radiotelemetry, we tracked individual king rails among seasons, and established that at least a segment of this breeding population is resident. Mean (±SE) home range size was 19.8 ± 5.0 ha (95% kernel density) or 2.5 ± 0.9 (50% kernel density). We detected seasonal variation and sex differences in home range size and habitat use. In the nonbreeding season, resident male home ranges coincided essentially with their breeding territories. Overwintering males were more likely than females to be found in natural emergent marsh with a greater area of open water. Females tended to have larger home ranges than males during the nonbreeding season. We report for the first time the use of wooded natural marsh by overwintering females. Brood‐rearing king rails led their young considerable distances away from their nests (average maximum distance: ~600 ± 200 m) and used both wooded natural and impounded marsh. King rails moved between natural marsh and managed impoundments during all life stages, but the proximity of these habitat types particularly benefitted brood‐rearing parents seeking foraging areas with shallower water in proximity to cover. Our results demonstrate the importance of interspersion of habitat types to support resident breeders. Summer draining of impounded wetlands that are seasonally flooded for wintering waterfowl allows regrowth of vegetation and provides additional habitat at a critical time for wading birds.     

Small-scale resource heterogeneity among halophytic plant species in an upper salt marsh community

The focus of the present study was to determine whether spatial and temporal variation, in soil and plant factors of upper salt marsh areas, exists among microsites of three coexisting halophytic plant species, Grindelia humilis, Jaumea carnosa and Limonium californicum, on the Pacific coasts of California. Low frequencies in tidal inundations coupled with variation in temperature and rainfall patterns often result in wide seasonal salinity variations in these upper salt marsh zones. The study was carried out to evaluate (1) variation in soil osmolalities and soil water contents for the three species; (2) differences in chemical soil factors associated with the three species; (3) variation in leaf succulence associated with saline stress; and (4) levels of plant nutrients present in each of the three species. The results indicated that soil osmolalities associated with Limonium, a salt excreting halophyte were markedly different from those recorded for the other two species. Nitrogen levels in soils associated with Jaumea as well as levels in composite plant samples were significantly lower than those of the other two species. Also noted were variations in nutrient ions in plants as well as soil environments.     

Seasonal variation in food availability and relative importance of dietary items in the Gambian epauletted fruit bat (Epomophorus gambianus)

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Dormancy cycles in buried seeds of three perennial Xyris (Xyridaceae) species from the Brazilian campo rupestre

• Dormancy cycles are an important mechanism for avoiding seed germination under unfavourable periods for seedling establishment. This mechanism has been scarcely studied in tropical species. Here, we studied three tropical and perennial species of Xyris, X. asperula, X. subsetigera and X. trachyphylla, to investigate in situ longevity and the existence of seasonal seed dormancy cycles.
• Seeds of three species of Xyris were buried in their natural habitat, with samples exhumed bimonthly for 18 months. Germination of exhumed seeds was assessed under a 12‐h photoperiod over a broad range of temperatures. Seeds of X. trachyphylla were also subjected to treatments to overcome secondary dormancy.
• Seeds of all species are able to form a persistent seed bank and exhibit seasonal changes in germinability. Secondary dormancy was acquired during the rainy summer and was overcome during the subsequent dry season (autumn/winter). Desiccation partially overcomes secondary dormancy in X. trachyphylla seeds.
• Soil seed bank persistence and synchronisation of seed germination under favourable conditions for seedling establishment contribute to the persistence and regeneration of X. asperula, X. subsetigera and X. trachyphylla in their natural environment.

     

Photosynthetic responses to light intensity of <Emphasis Type="Italic">Sarcocornia</Emphasis> taxa (Chenopodiaceae)

Salt marshes show a characteristic zonation of species distribution, which is correlated with marsh elevation. Radiation intensity and photoperiod change throughout the tidal frame. Photosynthetic response to light regime, 90–2450 μmol/(m² s), was determined in the laboratory for four closely related halophytic taxa of the genus Sarcocornia (Chenopodiaceae), which inhabit different positions in the tidal frame. Sarcocornia fruticosa, which germinates below vegetation cover and is found at high levels in the tidal frame, had the lowest maximum net photosynthetic rate and stomata conductance values. The two S. perennis subspecies demonstrated intermediate maximum net photosynthetic rates but S. perennis ssp. alpini reached light saturation point at higher light intensities. S. perennis ssp. perennis, found in the lowest elevations of the marshes, spends a significant proportion of its time submerged and therefore needs to take full advantage of available light. S. perennis ssp. alpini is exposed to very high light intensities in open salt pans at high elevations. The hybrid, S. perennis x fruticosa, which is currently found at intermediate elevations with less frequent inundation, had the highest net photosynthetic rate and chlorophyll a content. The ability to cope with high light levels may help to explain one of the environmental parameters, which affects distribution of four taxa throughout the tidal frame and also raise intriguing questions about the future role of the hybrid in the successive development of these marsh systems.     

Hydrodynamics and seed dispersal in the lower Amazon

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Habitat segregation in a salt marsh among adult sticklebacks (Gasterosteidae)

Synopsis The spatial distribution, seasonal abundance and diel activity of four sticklebacks,Gasterosteus aculeatus, G. wheatlandi, Pungitius pungitius, andApeltes quadracus. coexisting in a St. Lawrence salt marsh were examined to see how these closely related species share their habitat. While all four species breed in the Riviè des Vases, a tidal creek, only three species are found in the adjacent salt marsh pools,A. quadracus being absent. Results are interpreted in terms of avoidance of interspecific competition for space during the relatively short breeding season at this latitude.     

Halo-nitrophilous scrub species and their relationship to the atmospheric concentration of allergenic pollen: case study of the Mediterranean saltbush (Atriplex halimus L., Amaranthaceae)

Halo-nitrophilous scrubs are characterised by their floristic richness in species of the family Amaranthaceae (include Chenopodiaceae) and the Mediterranean saltbush (Atriplex halimus L.) is one of the most characteristic species in the Mediterranean region. Pollen from Amaranthaceae is the main cause of pollinosis at the end of summer and autumn. In this study, the floral phenology of the species Atriplex halimus L., was studied relating it to the atmospheric concentration of Amaranthaceae pollen with the aim to know if it can serve as an indicator of the maximum pollen concentrations. Observations of the male floral phenology of Atriplex halimus were performed over the course of three years in the central Iberian Peninsula (Spain) and the aerobiological pollen data of Amaranthaceae were obtained using a Hirst-type volumetric trap. The results demonstrated that the flowering period of Atriplex halimus closely coincided with the peak pollen levels. Besides, the prevailing movements of air masses in relation to the distribution and abundance of the halo-nitrophilous scrub during the flowering period of Atriplex halimus were studied using a back-trajectory analysis. The results showed that distinct predominant wind patterns led to differences in the quantity of pollen recorded during the pollen season and in the behaviour of the evolution of airborne pollen concentrations.     

Reproductive phenology of two Mimusops species in relation to climate,tree diameter and canopy position in Benin (West Africa)

Assessing species phenology provides useful understanding about their autecology, to contribute to management strategies. We monitored reproductive phenology of Mimusops andongensis and Mimusops kummel, and its relationship with climate, tree diameter and canopy position. We sampled trees in six diameter classes and noted their canopy position. For both species flowering began in the dry season through to the rainy season, but peaked in the dry season, whilst fruiting occurred in the rainy season and peaked during the most humid period. Flowering was positively correlated with temperature. Conversely, fruiting was negatively correlated with temperature and positively with rainfall, only in the Guineo‐Sudanian zone. For M. andongensis, flowering and fruiting prevalences were positively linked to stem diameter, while only flowering was significantly related to canopy position. For M. kummel, the relationship with stem diameter was significant for flowering prevalence only and in the Guineo‐Sudanian zone. Results suggest that phylogenetic membership is an important factor restricting Mimusops species phenology. Flowering and fruiting of both species are influenced by climate, and consequently climate change might shift their phenological patterns. Long‐term investigations, considering flowering and fruiting abortion, will help to better understand the species phenology and perhaps predict demographic dynamics.