Role Of Abiotic Factors Research Articles

Establishment of Cryptostegia madagascariensis in the semiarid: what is the role of abiotic factors in germination and initial growth?

Studies on seed germination and seedling development in different environmental conditions help to understand the ability of exotic species to colonize new environments. Cryptostegia madagascariensis is an exotic invasive species in the semiarid Caatinga Phytogeographical Domain, in the northeastern region of Brazil. In this study, was evaluate how the abiotic factors interfere in germination and the impacts of a water deficit in the initial growth of seedlings. During germination, the seeds were exposed to different temperatures (constant and alternating) combined with two light conditions (white and dark light). In germination, we also evaluated the effects of water and saline stress. In initial growth, the seedlings were submitted to four levels of water availability (100%, 70%, 40% and 10% of field capacity). The milder (20 at 30°C) and alternate temperatures studied provided greater germination four days after sowing, independent of light. High temperatures (35°C) are a limiting factor for germination, as well as water and saline stress (>2 MPa). The water deficit reduces the growth of the seedlings, but these showed morphological adaptations to the different treatments. However, lower levels of water reduced its invading potential. Therefore, factors such as high temperature (> 30° C), saline and water stress, reduce its germination potential and the reduction of water availability affects its growth, but not its survival.

Role of abiotic factors in Nothofagus pumilio forest mortality: The sensitivity of ecotones

The world's forests are being affected by a changing climate. Recently, patches of dead trees have been found in forests of the Patagonian endemic species Nothofagus pumilio, which could not be related to insects or pathogenic fungi acting as primary agents. This study aimed to analyze environmental variables associated with N. pumilio mortality at a landscape scale. Dead patches were recorded from satellite image analysis and field trips throughout the distribution of N. pumilio forests in Chubut province (Argentina). The relation between forest mortality and environmental variables, including elevation, slope, aspect, recent volcanic ash deposits, precipitation, and temperature, was analyzed by contingency tables and chi-square analysis, and a risk model was developed using the Maximum Entropy (MaxEnt) algorithm. One hundred and seven dead patches were recorded only in the northern region of the study area (ca. −42.5°S to −44.5°S), where forests develop at higher elevations, slopes, precipitations, and temperatures than in the southern region. In the northern region, elevation, followed by precipitation, was the environmental variable most related to forest mortality. Nothofagus pumilio mortality was related to two ecotones: an altitudinal one, associated with middle-high mountainsides (1200 and 1400 m asl), and a longitudinal one, associated with intermediate values of mean annual precipitation within the west-east rainfall gradient. These results highlight the sensitivity of these transitional environments. According to the risk model based on abiotic features, more than 100,000 ha of forest (ca. 30%) are located under environmental variables favorable for decline and death. In the context of climate change and in the light of the results, abiotic factors seem to be the main predisposing factors of N. pumilio mortality.

Habitat heterogeneity, temperature, and primary productivity drive elevational gradients in avian species diversity.

AimAnticipating and mitigating the impacts of climate change on species diversity in montane ecosystems requires a mechanistic understanding of drivers of current patterns of diversity. We documented the shape of elevational gradients in avian species richness in North America and tested a suite of a priori predictions for each of five mechanistic hypotheses to explain those patterns.LocationUnited StatesMethodsWe used predicted occupancy maps generated from species distribution models for each of 646 breeding birds to document elevational patterns in avian species richness across the six largest U.S. mountain ranges. We used spatially explicit biotic and abiotic data to test five mechanistic hypotheses proposed to explain geographic variation in species richness.ResultsElevational gradients in avian species richness followed a consistent pattern of low elevation plateau‐mid‐elevation peak (as per McCain, 2009). We found support for three of the five hypotheses to explain the underlying cause of this pattern: the habitat heterogeneity, temperature, and primary productivity hypotheses.Main ConclusionsSpecies richness typically decreases with elevation, but the primary cause and precise shape of the relationship remain topics of debate. We used a novel approach to study the richness‐elevation relationship and our results are unique in that they show a consistent relationship between species richness and elevation among 6 mountain ranges, and universal support for three hypotheses proposed to explain the underlying cause of the observed relationship. Taken together, these results suggest that elevational variation in food availability may be the ecological process that best explains elevational gradients in avian species richness in North America. Although much attention has focused on the role of abiotic factors, particularly temperature, in limiting species’ ranges, our results offer compelling evidence that other processes also influence (and may better explain) elevational gradients in species richness.

Phytoplankton diversity of a de-mineralized subtropical reservoir of Meghalaya state, northeast India

This study monitors the spa-tio-temporal variations of phytoplankton of a soft-water and de-mineralized reservoir of Meghalaya state of northeast India. Phyto-plankton assemblages of the littoral and limnetic regions reveal total 36 species and diverse desmids, and con-tribute dominantly to net plankton abundance. Our results record the quantita-tive importance of Charo-phyta > Bacillariophyta > Dinophyta and Charophyta > Dinophyta, and the ‘spe-cialist’ nature of 11 and six species at the littoral and limnetic regions, respective-ly. Staurastrum spp. and Cosmarium spp. are notable taxa. Phytoplankton indi-cates moderate species di-versity and depicts domi-nance and evenness varia-tions. The individual abiotic factors exert differential in-fluence on various taxa at the two regions and the ca-nonical correspondence analysis registers 73.02 and 71.14% cumulative influ-ence of 10 abiotic factors on the littoral and limnetic as-semblages, respectively. The spatial differences of phytoplankton composition, richness, abundance, im-portant groups and taxa, specialist species, diversity indices and the influence of individual abiotic factors are hypothesised to habitat heterogeneity amongst the sampled regions. This study records notable temporal differences of phytoplank-ton richness, abundance, di-versity and the role of abiot-ic factors vis-a-vis the lim-ited survey of November 1990–October 1991.

Role of abiotic factors on the incidence of major insect pests of pigeonpea, Cajanus cajan (L.) Millsp

During present studies incidence of pod fly; Melanagromyza obtusa Malloch (Diptera: Agromyzidae), thrips; Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae), pod bug; Clavigralla gibbosa (Spinola) (Hemiptera: Coreidae), Kudzu bug; Megacopta cribraria Fabricius (Hemiptera: Plataspidae) and cow bug; Otinotus oneratus (Walker) (Hemiptera: Membracidae) was found negatively correlated with temperature (both maximum and minimum) and rainfall whereas positively correlated with morning relative humidity except thrips. It was also found that Leaf webber; Grapholita critica (Meyr.) (Lepidoptera: Tortricidae) incidence was positively correlated with temperature and morning relative humidity. Regression analysis showed that minimum temperature significantly contributed more than 49% variation to the high population buildup of the C. gibbosa, M. cribraria and O. oneratus insects. The present study also report first time the effects of different abiotic factors on the incidence of Kudzu bug; M. cribraria.

Disentangling the ecological basis of floral trait variation in NeotropicalPiperspecies

AbstractIn generalist pollination systems, it has been assumed that pollinators play a minor role in the diversification of floral traits, but recent studies have pointed to a different scenario. Although pollination in Piper is considered generalist, there are flower and inflorescence variations among subclades that may be associated with different pollinator functional groups. Based on this, we aimed to test whether pollinators influenced the evolution of floral traits in a clade of generalist plants, by studying 17 co-occurring Piper spp. Sixteen species were insect-pollinated (46 species: bees, beetles and flies). We found no evidence of anemophily. Eight species were dependent on pollen vectors for sexual reproduction, but no correlation between floral and pollinator traits was recorded. None of the floral traits presented phylogenetic signal, and the evolution of these traits was not correlated. Nine species were independent of pollen vectors for sexual reproduction. We did not find any evidence of pollinator-driven floral diversification of Piper spp.; we suggest a possible role of abiotic factors as agents of selection on floral diversification. As self-pollination seems to be a common feature in the genus, the flexibility of mating systems could be another important factor related to the maintenance of floral phenotypic variation.

Stable C and N Isotope Composition of Suspended Particulate Organic Matter in the Neva Estuary: The Role of Abiotic Factors, Productivity, and Phytoplankton Taxonomic Composition

Knowledge of carbon and nitrogen isotopic ratios in organic matter and their changes is important when studying nutrient cycles in aquatic ecosystems. Relationships between δ13C and δ15N values of suspended particulate organic matter (POM), water temperature, salinity, pH, redox potential, chlorophyll a concentration, primary production, and biomasses of different taxonomic groups of phytoplankton in the Neva Estuary were statistically analyzed. We tested the hypothesis that the studied physicochemical and biogeochemical characteristics, as well as the species composition of phytoplankton and its productivity, can be significant predictors of changes in the isotopic ratios of suspended particulate organic matter in estuaries. In the Neva Estuary, δ13CPOM (−16.8–−27.6‰) and δ15NPOM (2.3–7.3‰) changed synchronously. Statistical analysis showed that for both isotopes, the photosynthetic activity and taxonomic composition of phytoplankton are important. For 13CPOM, the second most important factor was water salinity, which was apparently associated with the transition of algae from CO2 to HCO3 consumption during photosynthesis in estuarine waters. For 15NPOM changes, the most important abiotic factor was pH. The study showed that the dependences of POM isotopic ratios on environmental variables obtained for continental and oceanic waters are also valid in transitional zones such as the Neva Estuary.

How do large river zooplankton communities respond to abiotic and biotic drivers over time? A complex and spatially dependent example

Abstract Recent evidence shows that in lotic, physically‐dominated ecosystems like large rivers, zooplankton can develop spatially structured assemblages and fulfill functionally important roles. While refuting the long‐standing notion that riverine zooplankton communities are numerically depauperate and spatially homogeneous, this also shows that the importance of abiotic and biotic drivers and the consistency of ecological patterns are still poorly understood for these communities. We collected zooplankton along 300 km of the Illinois River for 5 years to test the influence of a suite of biotic and abiotic variables on zooplankton density, biomass, and diversity. We hypothesized abiotic variables such as temperature, turbidity, and velocity would be predominant predictors, with biotic variables like planktivory becoming important when physical factors do not constrain them. Results showed basin‐wide declines in zooplankton taxonomic richness as planktivory from the invading silver carp (Hypophthalmichthys molitrix) increased. In contrast, density and biomass were explained by abiotic factors at the basin scale, with velocity, turbidity, and pH driving biomass and velocity driving density. We also found that both the driving factors and the plankton responses varied among the upper, middle, and lower sections of the Illinois River. We conclude that while zooplankton communities of the Illinois River are highly structured in space, the driving forces behind their distribution patterns are not simple. Instead, there is a complex spatio‐temporal template of biological, chemical, and hydraulic factors shaping these communities in the Illinois River. Along with emphasizing the importance of spatial heterogeneity in large river ecosystems, these results also support a growing view that invasive species interactions can supersede the well‐established role of abiotic factors in explaining global freshwater diversity losses. This also highlights the importance of including long‐term zooplankton sampling in ecological monitoring programs in diverse and productive large river systems like the Illinois.

Deciphering of antibiotic resistance genes (ARGs) and potential abiotic indicators for the emergence of ARGs in an interconnected lake-river-reservoir system

This study aimed to decipher the patterns of antibiotic resistance genes (ARGs) and linkages of key abiotic indicators with ARGs in an interconnected lake-river-reservoir system. The results showed that seasonal variations in the relative abundance of ARGs and mobile gene elements (MGEs) were significant (KW, p < 0.05). ARGs representative of fecal pollution and natural environment were primarily distributed in the river and reservoir, respectively. The lake, river, and reservoir shared 54.5% of ARGs subtypes, most of which are multidrug resistance genes encoding for efflux pumps. Network results showed that ARGs conferring resistance to aminoglycoside frequently co-occurred with class 1 integrons and Limnohabitans. The resistance risks were low and associated with non-corresponding ARGs, and the highest resistance risk was caused by enrofloxacin in the Dianshan Lake. Fluorescence indices derived from two methods exhibited consistent positive correlations with abundance of individual genes (i.e. aada1 and aadA2-03) as well as total aminoglycoside resistance genes (Pearson, p < 0.05). Moreover, ARGs indicators of human and animal fecal pollution showed linkages with humic-like and fulvic-like indices (Pearson, p < 0.05). The results provide novel insights into the roles of abiotic factors on indicating dynamics of ARGs in aquatic environment impacted by anthropogenic activities.

The involvement of α-proteobacteria Phenylobacterium in maintaining the dominance of toxic Microcystis blooms in Lake Taihu, China.

Lake Taihu in China has suffered serious harmful cyanobacterial blooms for decades. The algal blooms threaten the ecological sustainability, drinking water safety, and human health. Although the roles of abiotic factors (such as water temperature and nutrient loading) in promoting Microcystis blooms have been well studied, the importance of biotic factors (e.g. bacterial community) in promoting and meditating Microcystis blooms remains unclear. In this study, we investigated the ecological dynamics of bacterial community, the ratio of toxic Microcystis, as well as microcystin in Lake Taihu. High-throughput 16S rRNA sequencing and principal component analysis (PCA) revealed that the bacteria community compositions (BCCs) clustered into three groups, the partitioning of which corresponded to that of groups according to the toxic profiles (the ratio of toxic Microcystis to total Microcystis, and the microcystin concentrations) of the samples. Further Spearman's correlation network showed that the α-proteobacteria Phenylobacterium strongly positively correlated with the toxic profiles. Subsequent laboratory chemostats experiments demonstrated that three Phenylobacterium strains promoted the dominance of the toxic Microcystis aeruginosa PCC7806 when co-culturing with the non-toxic PCC7806 mcyB- mutant. Taken together, our data suggested that the α-proteobacteria Phenylobacterium may play a vital role in the maintenance of toxic Microcystis dominance in Lake Taihu.

Pharmaceutical disposal facilitates the mobilization of resistance determinants among microbiota of polluted environment

The emergence of resistance on exposure to pharmaceuticals among microorganisms has raised serious concern in the therapeutic approach against infectious diseases. Effluents discharge from hospitals, industries, and urban settlements containing pharmaceuticals and other toxic compounds into the aquatic ecosystem selects bacterial population against them; thereby promotes acquisition and dissemination of resistant traits among the inhabitant microbiota. The present study was aimed to determine the prevalence and multidrug resistance pattern of Extended Spectrum β-lactamase (ESBL) producing and non-producing bacterial isolates from the heavily polluted Delhi stretch of river Yamuna, India. Additionally, the role of abiotic factors in the dissemination of conjugative plasmids harbouring resistance genes was also studied using E. coli J53 as recipient and resistant E. coli isolates as donor strains. Of the 227 non-duplicate bacterial isolates, 60% (136) were identified as ESBL+ and 40% (91) as ESBL. ESBL+ isolates were found highly resistant to β-lactam and non-β-lactam classes of antibiotics compared with the ESBL− isolates. 68% of ESBL+ and 24% of ESBL− isolates showed an MAR index of ≥0.5. Surprisingly, multidrug resistance (MDR), extensively drug resistance (XDR), and pandrug resistance (PDR) phenotype were observed for 78.6%, 16.9%, and 0.7% of ESBL+ and 90%, 3%, and none for PDR among ESBL− isolates. Conjugation under different conditions showed a higher mobilization rate at neutral pH (7–7.5) for ESBL+ isolates. Conjugation frequency was maximum at 40 °C for the isolate E. coli MRB6 (4.1 × 10−5) and E. coli MRE32 (4.89 × 10−4) and at 35 °C for E. coli MRA11 (4.89 × 10−5). The transconjugants obtained were found tolerating different concentrations of mercuric chloride (0.0002–0.2 mg/L). Increased biofilm formation for ESBL+ isolates was observed on supplementing media with HgCl2 (2 μg/mL) either singly or in combination with CTX (10 μg/mL). The present study demonstrates that anthropogenically influenced aquatic environments act as a reservoir of MDR, XDR, and even PDR strains; thereby posing a potent public health risk.

Role of abiotic factors on disease progression of Spot blotch of Wheat

Spot blotch of wheat caused by Bipolaris sorokiniana appears at all growth stages, though susceptibility increases with increase in plant age. Every year disease causes high yield losses even up to 60% depending on the wheat variety and weather factors. The cultivation of wheat in North Eastern Plains Zone (NEPZ) of India is increasing, but the crop yield is low due to warm and humid climate which increase diseases like spot blotch. Considering significant impact of the spot blotch on crop yield, an experiment was conducted during rabi seasons of 2015–2016 and 2016–2017 to evaluate the effect of different abiotic factors on spread of the disease, as well as development of a predictive model to predict the disease severity in a set of 12 wheat varieties. Statistical analysis proved that all the thermic variables like temperature (maximum and minimum) and soil temperature are significantly correlated with diseases initiation across growth stages of the crop. Step-wise regression showed high R2 values like, 0.99, 0.97, 0.96, 0.96, 0.98, 0.96, 0.99, 0.98, 0.96, 0.98, 0.98, 0.98 for the predicative model of spot blotch in PBW 343, HD 2733, PBW154, Raj4015, KALYAN SONA, SONALIKA, LERMA RAJO, DBW39, UP301, HD2009, NP114, NP718 respectively.

Macroalgal vegetation on a north European artificial reef (Loch Linnhe, Scotland): biodiversity, community types and role of abiotic factors

Very little is known about the marine macroalgae of artificial reefs—especially in the North Atlantic—despite the growing number and extent of man-made structures in the sea, and even though seaweed communities have paramount importance as primary producers, but also as feeding, reproductive and nursery grounds in coastal ecosystems. This paper explores the macroalgal diversity of a large system of artificial reefs in Loch Linnhe, on the west coast of Scotland, in a quantitative and qualitative study based on diving surveys and correlates the observations with the prevalent abiotic factors. The study was conducted in order to test the hypothesis that artificial reefs can enhance seaweed habitats—in particular, for kelps—and that there is a clear correlation with substrate type. While the reef is home to a large range of biota and abundance of early-successional species of turf and bushy macroalgae, totalling 56 taxa and with Delesseria sanguinea as the dominant species, canopy-forming perennial kelp species are conspicuously relatively rare. Macroalgal vegetation is explored in correlation with reef geometry/geography and depth. Statistical analysis shows benthic communities were strongly affected by substrate type, with turf algae and invertebrates dominating the artificial reefs, while bushy algae dominate the natural ones. Common macroinvertebrates associated with the phytobenthic communities are assessed qualitatively.

Assessment of plasticity and stability of grain sorghum varieties on the basis of their grain yield

Assessment of adaptability, environmental plasticity and stability of crop varieties in different climatic conditions is an important direction of the selection process. The purpose of the research was to assess the ecological plasticity and stability of 5 varieties (Premiera, Slavyanka, Ros, Kinelskoye 63, Dershavnoe) and 3 lines (L-28/14, L-141/14, L 34/14) of grain sorghum, to identify the role of abiotic factors in the dynamics of its grain yield at the final stages of selection in the competitive testing of varieties. The studies were carried out in the forest-steppe of the Samara region in experimental fields and in the laboratories of the Volga Research Institute of Breeding and Seed Production in 2015-2018 according to the dispersion methods of A.V. Kilchevsky and L.V. Khotyleva, S.A. Eberhart and W.A. Russel. According to the ecological plasticity variety Ros and line L-34/14 were of intensive type. Varieties Derzhavhoe, Kinelskoye 63, Slavyanka and line L-28/14 belonged to the semi-intensive type. Variety Premiera and line L-141/14 were of extensive type. The combination of high productivity and stability was observed in varities Kinelskoye 63, Derzhavnoe, L-28/14 with high parameters of breeding value of genotype. Promising sample L-28/14 with high productivity and environmental stability is recommended for transfer to the state variety testing.

Effects of life‐history traits on stream fish abundances across spatial scales

AbstractIdentifying cross‐scale patterns of ecological processes is imperative, especially in hierarchically structured riverine ecosystems. The role of abiotic factors in determining cross‐scale spatial structure of stream fish populations and communities is well studied, but less is known about how species traits drive cross‐scale patterns. We investigated the role of species traits for explaining autocorrelation of stream fish abundance at spatial scales ranging from local stream reaches to major basins. We calculated intraclass correlation coefficients (ICCs) representing abundance autocorrelation within species (N = 47) at each of five spatial scales. A hierarchical Bayesian regression then modelled ICCs against spatial scale with the resulting regression coefficients modelled as functions of species traits. Finally, we ordinated the scale‐by‐species ICC matrix to calculate an overall metric describing species whose abundances were autocorrelated along a gradient of large to small scales, and modelled this metric as a function of species traits. Abundances of most species were autocorrelated at smaller spatial scales. Maximum fecundity had a significant positive relationship with abundance patterns across spatial scales. Species habitat affinities and body forms were significantly associated with overall abundance patterns across spatial scales: populations of upland/lotic‐affiliated species adapted to streams with high flow correlated at small (≤10 km2) spatial scales. Lowland/lacustrine species with laterally compressed bodies showed little correlation across scales. The appropriate spatial scale for modelling abundance is determined not only by exogenous (e.g. environmental) factors, but also endogenous factors, like traits. Careful consideration of traits and life history will aid researchers in designing more effective and efficient surveys and analyses.

Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park: no counter-effect of biotic resistance

Biotic resistance by native communities could have a role in the spread of invasive species. This seems to be the case in the invasion of the Argentine ant, Linepithema humile, but only when the environment is unfavorable for the survival of the invader. We studied the progress of Argentine ant invasion through favorable and unfavorable habitats of Donana National Park across three temporal snapshots covering three decades (1992, 2000, 2016). We assessed biotic resistance of the native community using species richness, as well as dominance and community structure. We also explored the role of abiotic factors (quality of surrounding habitat and spatial variables) and of potential vectors of Argentine ant dispersal across unfavorable areas. We found no evidence of biotic resistance after examining native ant species richness, proportion of native dominant ants, or community structure. On the contrary, invasion proceeded from trees with higher ant species richness, probably because those trees are larger and provide more resources and better protection from aridity. Furthermore, we found evidence that the invasion of new trees across a matrix of unfavorable habitat could be influenced not only by humans, but also by scavenging avian predators, which could act as vectors of ant dispersal through transport of carrion also exploited by the ants. Such leapfrog expansion through mobile predators could represent an overlooked mechanism that would enrich our understanding of invasion dynamics and provide potential opportunities for management of invasive species.

Presence of an invasive species reverses latitudinal clines of multiple traits in a native species

Understanding the processes driving formation and maintenance of latitudinal clines has become increasingly important in light of accelerating global change. Many studies have focused on the role of abiotic factors, especially temperature, in generating clines, but biotic factors, including the introduction of non-native species, may also drive clinal variation. We assessed the impact of invasion by predatory fire ants on latitudinal clines in multiple fitness-relevant traits-morphology, physiological stress responsiveness, and antipredator behavior-in a native fence lizard. In areas invaded by fire ants, a latitudinal cline in morphology is opposite both the cline found in museum specimens from historical populations across the species' full latitudinal range and that found in current populations uninvaded by fire ants. Similarly, clines in stress-relevant hormone response to a stressor and in antipredator behavior differ significantly between the portions of the fence lizard range invaded and uninvaded by fire ants. Changes in these traits within fire ant-invaded areas are adaptive and together support increased and more effective antipredator behavior that allows escape from attacks by this invasive predator. However, these changes may mismatch lizards to the environments under which they historically evolved. This research shows that novel biotic pressures can alter latitudinal clines in multiple traits within a single species on ecological timescales. As global change intensifies, a greater understanding of novel abiotic and biotic pressures and how affected organisms adapt to them across space and time will be central to predicting and managing our changing environment.

Can we generate robust species distribution models at the scale of the Southern Ocean?

AbstractAimSpecies distribution modelling (SDM) represents a valuable alternative to predict species distribution over vast and remote areas of the ocean. We tested whether reliableSDMs can be generated for benthic marine organisms at the scale of the Southern Ocean. We aimed at identifying the main large‐scale factors that determine the distribution of the selected species. The robustness ofSDMs was tested with regards to sampling effort, species niche width and biogeography.LocationSouthern Ocean.MethodsThe impact of sampling effort was tested using two sets of data: one set with all presence‐only data available until 2005, and a second set using all data available until 2015 including recent records from campaigns carried out during the Census of Antarctic Marine Life (CAML) and the International Polar Year (IPY) period (2005–2010). The accuracy ofSDMs was tested using a ground‐truthing approach by comparing recent presence/absence data collected during theCAMLandIPYperiod to pre‐CAMLmodel predictions.ResultsOur results show the significance of theSDMapproach and the role of abiotic factors as important drivers of species distribution at broad spatial scale. The addition of recent data to the models significantly improved the prediction ofSDMand changed the respective contributions of environmental predictors. However, the intensity of change varied between models depending on sampling tools, species ecological niche width and biogeographic barriers to dispersal.Main conclusionsWe highlight the need for new data and the significance of the ground‐truthing approach to test the accuracy ofSDMs. We show the importance of data collected through international initiatives, su ch as theCAMLandIPYto the improvement of species distribution modelling at broad spatial scales. Finally, we discussed the relevance ofSDMas a relevant marine conservation tool particularly in the context of climate change and the definition of Marine Protected Areas.

The role of abiotic factors in the pupation of Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) in the soil

Abstract A key focus area of the South African citrus industry is the improved control of the phytosanitary citrus pest Thaumatotibia leucotreta (Lepidoptera: Tortricidae). New methods of control for this pest are continually being sought and the use of entomopathogens as biological control agents of the soil-dwelling life stages of T. leucotreta has shown great promise. Current understanding of T. leucotreta pupation biology, behaviour and survival is limited; thus, improving upon this knowledge would be useful for the biological control of this life stage. Abiotic factors, namely soil texture class, ground cover, soil compaction and soil moisture, were investigated in the laboratory, aiming to determine the effects of these on T. leucotreta pupation variables. The investigations consisted of an examination of the wandering behaviour of larvae prior to pupation site selection, the pupation behaviour after selecting a pupation site, and eclosion biology and success. These abiotic factors often had a limited influence on T. leucotreta pupation. Interesting consistencies included limited wandering behaviour, the shallowness of T. leucotreta pupation and a high eclosion success in sandy loam soils in certain cases. These factors are likely to have both positive and negative implications for entomopathogenic biological control programmes.

The role of abiotic factors on both mango infestation and Sternochetus mangiferae abundances in mango agroecosystems in Benin

AbstractTo develop management strategies for the mango seed weevil (Sternochetus mangiferae), we surveyed infestation levels of the pest in three agroecological zones of Benin and determined the influences of abiotic factors on mango infestation levels and population dynamics in mango orchards at IITA-Benin from 2009 to 2011. We collected immature and mature fruits from the canopy and fallen fruits from under the canopy from three randomly selected trees per cultivar, per orchard. Samples were examined to determine the number of the mango seed weevil eggs to adults during the rainy seasons of three years of the study. Our results show that the highest abundance of both the weevil and its eggs was from March to May of each year. In the first year of sampling, the cultivar Eldon was more infested than the other two cultivars, while during the second and third years, the cultivar Alphonse was most infested. The occurrence of the weevil was almost nil in the hot agroecological zones, while for the mango cultivars of IITA-Benin the percentage of infested fruit increased or decreased according to the studied variables, such as temperature, rainfall, and relative humidity. We found that the period from March to May with low temperatures and high rainfall was favourable to the population increase of mango seed weevils. We discuss possible implications of our findings for the management of the pest.