Hydric Conditions Research Articles

Drought conditions, aridity and forest structure control the responses of Iberian holm oak woodlands to extreme droughts: A large-scale remote-sensing exploration in eastern Spain

Understanding how Mediterranean forests respond to the increasing frequency of extreme droughts and forest densification is crucial for effective land management in the present context of climate change and land abandonment. We study the responses of Iberian holm oak (Quercus ilex L.) woodlands to recent extreme droughts during 2000–2019 along broad gradients of climate aridity and forest structure. To this purpose, we apply large-scale remote-sensing using MODIS EVI as a primary production proxy in 5274 Q. ilex sites distributed within a 100,000 km2 region in eastern Spain. These woodlands were extensively affected by two extreme drought events in 2005 and 2012. Resistance, assessed as the capacity of the ecosystems to maintain primary production during drought, was significantly lower for semi-arid than for sub-humid and dry-transition conditions. Holm oak woodlands located in semi-arid areas of the region showed also poorer resilience to drought, characterized by low capacity to fully recover to their pre-drought production levels. Further, drought intensity and both pre- and post-drought hydric conditions controlled the variations of resistance, recovery and resilience between the two analyzed extreme drought events. Drought effects were particularly negative for dense Q. ilex stands under semi-arid climate conditions, where strong competition for scarce water resources reduced drought resistance. The observed drought vulnerability of semi-arid holm oak woodlands may affect the long-term stability of these dry forests. Adaptive management strategies, such as selective forest thinning, may be useful for improving drought responses in these more vulnerable semi-arid woodlands. Conversely, natural rewilding may more appropriately guide management actions for more humid areas, where densely developed Q. ilex woodlands show in general a high ability to maintain ecosystem primary production during drought.

Can nesting behaviour allow reptiles to adapt to climate change?

A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

Humidity stress and its consequences for male pre‐ and post‐copulatory fitness traits in an insect

AbstractGlobal declines in insect abundance are of significant concern. While there is evidence that climate change is contributing to insect declines, we know little of the direct mechanisms responsible for these declines. Male fertility is compromised by increasing temperatures, and the thermal limit to fertility has been implicated as an important factor in the response of insects to climate change. However, climate change is affecting both temperature and hydric conditions, and the effects of water availability on male fertility have rarely been considered. Here we exposed male crickets Teleogryllus oceanicus to either low or high‐humidity environments while holding temperature constant. We measured water loss and the expression of both pre‐ and postmating reproductive traits. Males exposed to a low‐humidity environment lost more water than males exposed to a high‐humidity environment. A male's cuticular hydrocarbon profile (CHC) did not affect the amount of water lost, and males did not adjust the composition of their CHC profiles in response to hydric conditions. Males exposed to a low‐humidity environment were less likely to produce courtship song or produced songs of low quality. Their spermatophores failed to evacuate and their ejaculates contained sperm of reduced viability. The detrimental effects of low‐humidity on male reproductive traits will compromise male fertility and population persistence. We argue that limits to insect fertility based on temperature alone are likely to underestimate the true effects of climate change on insect persistence and that the explicit incorporation of water regulation into our modeling will yield more accurate predictions of the effects of climate change on insect declines.

Sets of infiltration models for water infiltration in sustainable urban drainage systems

Infiltration is a crucial process in various fields such as hydrology, agriculture, urban soils, and particularly for Sustainable Urban Drainage Systems (SUDS) operation. Over the past century, the physics of infiltration has been extensively studied by developing models that estimate the dynamics of infiltration. In this study, three physically-based infiltration models (CH1, CH2, and CH3) have been developed as part of the Canoe Hydrobox (CH) platform, designed to simulate and evaluate the performance of SUDS. The three models rely on similar approaches to the Green-Ampt (GA) model by describing the water flux as the product of the equivalent hydraulic gradient and the equivalent hydraulic conductivity. The models differ in their ways of defining the hydraulic gradient and conductivity from the hydric conditions, soil parameters, and geometric features. The two first models (CH1 and CH2) consider an increase in the hydraulic conductivity with infiltrated water amount, whereas the last model (CH3) considers only the saturated hydraulic conductivity. For the hydraulic gradient, the first model considers the difference between the surface water pressure head and the height of infiltrated water. The other two models consider the difference between the surface water pressure head and the isostatic water pressure head at the surface in equilibrium with the height of infiltrated water. These models were applied to simulate water infiltration processes into dry, wet, and intermediate-wet soils. We compared these results with the numerical solution of the Richards equation using HYDRUS software. The comparison allowed the assessment of the capability of CH models to satisfy the critical principles of soil water infiltration. Subsequently we used the three models to invert six real experimental infiltration data to test their capability to work in inverse mode. The two models (CH1 and CH2) produced specific time-evolution of infiltration rates in disagreement with the physics of water infiltration under regular conditions (e.g., no water repellence). The third model (CH3) performed the best for both direct and indirect modes and is therefore considered as the best candidate. The CH3 model will be implemented in the new version of Canoe Hydrobox (CH) platform. This study provides a basis for further research into hydrological models for SUDS and their hydraulic performance.

Effect of moisture, temperature, and maternal influence on the hatching, phenotype, and performance of hawksbill turtles Eretmochelys imbricata

Hawksbill turtles are considered Critically Endangered. An understanding of how nest microenvironment (moisture and temperature) and maternal characteristics can influence embryonic development, hatching success, phenotype, and hatchling performance is needed to ensure effective conservation management. We undertook controlled egg incubations at different temperatures and relative humidities. Additionally, we sampled temperatures at natural nests with data loggers, and relative humidity of the sand at nest depth, to determine the conditions that eggs experienced naturally. We varied relative sand humidity (RSH) percentages (30, 50, 75, and 100%) at a constant incubation temperature of 29.5°C. We also assessed constant temperature incubations at 25, 29.5, and 34°C with 75% RSH. Incubation at 29.5°C resulted in successful hatching (73.3%), whereas temperatures of 25 and 34°C prevented hatching. However, hatching in natural nests occurred even between 34 and 36°C, provided that eggs were exposed to these temperatures <20% of the entire period of incubation, and only towards the end of incubation. Controlled incubation at 30% RSH prevented hatching. RSH linearly affected hatching success, phenotype, and performance of hatchlings: eggs incubated at 100% RSH had the greatest hatching success and produced the heaviest, largest, and fastest hatchlings. RSH correlated positively with sand depth on the beach, so that ≥75% RSH is ensured at the average depth of natural nests (~39.2 cm), resulting in successful hatching (74.3 ± 34.7%). The controlled incubation showed that temperature and hydric conditions had the most significant impact on hatching success, hatchling phenotype (size and weight), and hatchling performance. Maternal characteristics, however, were slightly less important. These results suggest that the impact of moisture should be taken into consideration in hawksbill turtle conservation projects. The thermal and hydric environments experienced by developing embryos should also be considered when evaluating how climate change affects marine turtles.

Inferred Impacts of Extreme Environments on Hawksbill Turtle (Eretmochelys imbricata) Body Size and Reproductive Output

This study presents the first published data on the morphometrics of nesting hawksbill turtles (Eretmochelys imbricata) and their eggs and counts of yolked and yolkless eggs per clutch from Iranian Islands in the northern Persian Gulf. We found significant variation in some variables among 4 main nesting islands (e.g., weight of yolked eggs, p = 0.000; number of yolkless eggs per clutch, p = 0.017), but effect size was moderate or less (r < 0.5 or d < 0.8). The diameter (p = 0.039), weight (p = 0.028), and number of yolked eggs (p = 0.000) per clutch increased significantly with curved carapace length (CCL), but the effect size was only large for the number of yolked eggs (f2 = 0.152). The number of yolkless eggs did not vary with CCL (p = 0.453) or with the number of yolked eggs (p = 0.523). A meta-analysis of global hawksbill turtle morphometrics and reproductive output revealed significant variation in CCL (p = 0.000) and number of yolked eggs (p < 0.001), with nesting region having a very large effect size on both variables (g2 = 0.880 and 0.616, respectively). Hawksbill turtles from the Gulf were smaller than populations from the Gulf of Oman (p < 0.001), Arabian Sea (p = 0.000), Caribbean (p = 0.000), West Atlantic (p = 0.000), and Southwest Pacific (p = 0.000) but not the Red Sea (p = 0.104), and laid fewer yolked eggs than populations in the Caribbean (p < 0.001) and West Atlantic (p = 0.001) but not the Red Sea (p = 0.636). This may be due to hawksbill turtles nesting in the Gulf remaining within its waters postnesting so adult body size is restricted by the relatively poor foraging habitat and/or success and/or the extreme environments, subsequently limiting clutch size. More information on home range and foraging habitat is required to draw similar conclusions about hawksbill turtles nesting in the Red Sea. Hawksbill turtles nesting in the Gulf, Red Sea, and Arabian Sea also appear to lay larger number of yolkless eggs per clutch than other populations worldwide (mean = 17.6 ± 10.8 SD [range = 0–59]). The functional role of yolkless eggs, potentially in the maintenance of thermal and hydric conditions within tolerable conditions in shallow nests laid in extreme environments, requires further investigation. Similarly, the potential for yolkless eggs to be an adaptation to extreme nest environments in other sea turtle species also nesting in the northern Indian Ocean also warrants examination.

Alterations in Kidney Structures Caused by Age Vary According to Sex and Dehydration Condition

Aging is a complex biological process, resulting in gradual and progressive decline in structure and function in many organ systems. Our objective is to determine if structural changes produced by aging vary with sex in a stressful situation such as dehydration. The expression of Slc12a3 mRNA in the renal cortex, α-smooth muscle actin (α-SMA), and fibronectin was evaluated in male and female rats, aged 3 and 18 months, submitted and not submitted to water deprivation (WD) for 48 h, respectively. When comparing ages, 18-month-old males showed a lower expression of Slc12a3 mRNA than 3-month-old males, and control and WD 18-month-old male and female rats exhibited a higher expression of α-SMA than the respective 3-month-old rats. Fibronectin was higher in both control and WD 18-month-old males than the respective 3-month-old males. In females, only the control 18-month-old rats showed higher fibronectin than the control 3-month-old rats. When we compared sex, control and WD 3-month-old female rats had a lower expression of Slc12a3 mRNA than the respective males. The WD 18-month-old male rats presented a higher expression of fibronectin and α-SMA than the WD 18-month-old female rats. When we compared hydric conditions, the WD 18-month-old males displayed a lower relative expression of Slc12a3 mRNA and higher α-SMA expression than the control 18-month-old males. Aging, sex, and dehydration lead to alterations in kidney structure.

A general framework for jointly modelling thermal and hydric constraints on developing eggs

Abstract Eggs are a vulnerable stage because they are sensitive to thermal and hydric conditions and yet cannot behaviourally avoid stressful environments. A general mechanistic model of egg development in natural nests requires microclimatic predictions of temperature, humidity, radiation (if above ground) and water potential (if buried in soil) to be integrated with models of heat and water exchange of the egg and the metabolism of the developmental process. Although all the required pieces for such a model now exist, they have not been integrated into a general modelling framework. We developed such an integration using NicheMapR package for mechanistic niche modelling. Specifically, we took an existing general model of egg water exchange and connected it with the microclimate model in NicheMapR to simulate nest thermal and hydric environments, including the effects of soil water potential on liquid and vapour exchange and moisture‐mediated soil thermal conductivity on heat exchange. We then used the Dynamic Energy Budget model within the ectotherm model of NicheMapR as the mechanistic engine for the developmental process, allowing the explicit computation of the dynamics of metabolic heat production and all aspects of mass exchange. We illustrate the modelling framework using existing laboratory and field data on reptiles, insects, and birds. We show that it can capture laboratory observations of water exchange and metabolic heat production and how it can be used to map potential development and water uptake under natural conditions at the continental scale. The modelling framework can be used to interpret laboratory experiments and allows strong inferences to be made about the abiotic constraints on egg development in natural nests under past, present, and future environmental change.

Climate aridity and habitat drive geographical variation in morphology and thermo-hydroregulation strategies of a widespread lizard species

Abstract Thermo-hydroregulation strategies involve concurrent changes in functional traits related to energy, water balance and thermoregulation and play a key role in determining life-history traits and population demography of terrestrial ectotherms. Local thermal and hydric conditions should be important drivers of the geographical variation of thermo-hydroregulation strategies, but we lack studies that examine these changes across climatic gradients in different habitat types. Here, we investigated intraspecific variation of morphology and thermo-hydroregulation traits in the widespread European common lizard (Zootoca vivipara louislantzi) across a multidimensional environmental gradient involving independent variation in air temperature and rainfall and differences in habitat features (access to free-standing water and forest cover). We sampled adult males for morphology, resting metabolic rate, total and cutaneous evaporative water loss and thermal preferences in 15 populations from the rear to the leading edge of the distribution across an elevational gradient ranging from sea level to 1750 m. Besides a decrease in adult body size with increasing environmental temperatures, we found little effect of thermal conditions on thermo-hydroregulation strategies. In particular, relict lowland populations from the warm rear edge showed no specific ecophysiological adaptations. Instead, body mass, body condition and resting metabolic rate were positively associated with a rainfall gradient, while forest cover and water access in the habitat throughout the season also influenced cutaneous evaporative water loss. Our study emphasizes the importance of rainfall and habitat features rather than thermal conditions for geographical variation in lizard morphology and physiology.

Physiological response and yield components under greenhouse drought stress conditions in potato

Due to the effects of climate change, conditions tend to be increasingly extreme, with water availability being one of the main limiting factors in potato production. The objective of this study was to analyze the differential response of physiological and yield components in six potato varieties under water deficit conditions. For this purpose, a greenhouse trial was carried out with the varieties Agata, Agria, Kennebec, Monalisa, Sante and Zorba. The drought stress was applied in stressed plants 36 days after planting (DAP) by withholding water for 25 days. All measurements were taken at four different times: before stress (T0), 17 days (T1) and 24 days (T2) after stress and five days after re-watering. The physiological parameters evaluated were chlorophyll content and fluorescence, relative leaf water content, stomatal conductance, electrolytic leakage and water potential. After the drought period, the aerial part of half of the plants was cut to evaluate the produced biomass. At the end of the cycle yield components were determined. Stomatal conductance and water potential were the parameters that showed the highest differences between the two hydric conditions, and Monalisa was the variety with the best response in tuber production under stress conditions. Indirect selection based on parameters associated with water stress can be a useful tool in potato breeding programs for the identification of more tolerant varieties.

Patterns in climate and seedling establishment at a dry tropical treeline

In some internal valleys of the northern Andes, precipitation at treeline elevation is seasonal, with one or two dry periods that could exert a strong control on tree seedling survival. However, little is known about (1) the severity of the dry periods, due to a lack of climate data, or (2) the effect of drought on tree seedling demographic dynamics and how this is modulated by local plant interactions in these tropical-alpine ecosystems. We studied annual precipitation variation and seedling demography and ecophysiology in relation to microclimate and neighboring plants in a dry treeline ecotone at 3100 m a.s.l in the Venezuelan Andes. We selected seedlings of the dominant tree species Cybianthus marginatus and Clusia multiflora at three sites, each with three adjacent 10 × 10-m plots within the forest, forest border, and páramo. For both species, seedling density was zero in the páramo and did not differ between border and forest. Growth rates were low for both species, but higher for Cybianthus in the border than in the forest. Survival rates were high in both environments. Low assimilation and transpiration rates were found in both species regardless of the environment. The spatial association of seedlings with moisture-regulating elements such as mosses, ferns and basal rosettes may indicate a benefit of better hydric conditions in their neighborhood. Our study shows a strong limitation for tree establishment in the páramo, but high rates of survival at the edge of the forest. This suggests a scenario of slow potential forest expansion at this tropical treeline, tree cover advancing in a closed front by the successive formation of forest-edge vegetation allowing tree seedling establishment outside of the forest.

Plant communities of the maquis on ultramafic rocks of New Caledonia

ABSTRACT The soils derived from ultramafic rocks in New Caledonia support a rich and unique sclerophyllous shrubby vegetation: the maquis. A phytosociolgical analysis was carried out to identify the different plant communities of this maquis. We surveyed areas of Plaine des Lacs, Mont Dore, Montagne des Sources, Mount Dzumac and Mount Humboldt (Great South region), and along a broad elevation gradient on Mount Boulinda (central-west region). Multivariate analyses revealed 17 plant associations grouped in 5 alliances and 3 orders. The distribution of these associations appears determined by several parameters, including elevation, precipitation, topography, and the local edaphic, physicochemical and hydric conditions. The diversity of plant associations observed in New Caledonia is one of the most remarkable among vegetations on ultramafic rocks globally.This article is a translation of the chapter « Les groupements végétaux des maquis »(pp 69–120) of Jaffré (1980), with minor updates.

The dependence of thermophysical and hygroscopic properties of macro-porous geopolymers on Si/Al

Aerated geopolymers are low calcium alkali-activated materials with induced porosity. These materials are reported to have huge potential to modulate the thermal and hydric conditions within buildings. The performance of these materials as a passive hygrothermal controller depends on various factors. However, studies in this area are limited. This study investigates how Si/Al ratio impacts the thermal and hydric features of foamed geopolymers. The thermal conductivity of the samples increased as the Si/Al ratio increased. While the vapor permeability of the materials decreases with rising silicon content. This is because the pore network declines with Si/Al. The vapor permeability of the samples has values ranging between 7.55 to 6.37(10−11)(Kg/m.s.Pa). The moisture buffer capacity also follows a similar trend with values from 4.17 to 6.81(g/m2%RH). The moisture absorption capacity also reduces when the Si/Al increases. Therefore, Si/Al ratio is a key factor that needs to be controlled to engineer aerated geopolymers for passive house applications.

Differential Response of Rhizobium Leguminosarum Inoculation for Inducing Water Deficit Tolerance in Triticum Durum

Limited soil water availability is a major threat to agricultural productivity because it inhibits plant growth and yields. Soil microorganisms having the ability to alleviate abiotic stress and promoting plant development would be highly valuable tools in sustainable agriculture. To this purpose, two Rhizobium leguminosarum strains were tested for their potential to induce tolerance against water deficits in Triticum durum grown under two hydric conditions in greenhouse experiments. For this, physiological and biochemical parameters were measured as criteria to assess the effect of R. leguminosarum inoculation on T. durum under water deficiency. In the presence of rhizobia, wheat plants were able to withstand water stress more effectively than un-inoculated plant, as indicated by the recorded increases in relative water content of inoculated plants compared to un-inoculated plants, higher accumulation of osmoprotectant (soluble sugar), lower MDA and H2O2 accumulation, and increased in antioxidant responses (peroxidase). Under water-limited condition, co-inoculation of selected rhizobia was better than single application for one of studied genotype, which let us hypothesize that this variation in responsiveness indicates a possible genotype effect. As a result, rhizobia from various legumes have a huge potential for enhancing the water deficiency stress tolerance of cereals.

Leaf Morpho-Colorimetric Characterization of Different Grapevine Varieties through Changes on Plant Water Status

(1) Background: Currently, some ampelographic methods are developing in order to identify grapevine varieties. For this purpose, morpho-colorimetric parameters in leaves have been analyzed by digital imagen analysis, but some environmental conditions may affect their determinations. (2) Methods: A research study was conducted to characterize leaf morpho-colorimetric parameters in five grapevine varieties growing under different plant water status and to discriminate them under these conditions. Leaves were collected in vines, and twelve leaf morpho-colorimetric and fractal dimension variables were assessed. (3) Results: Merlot presented the highest values of perimeter and area to perimeter ratio in leaves and higher leaf area than Chardonnay in both plant water conditions. Most of the leaf morpho-colorimetric variables allowed discriminating the grapevine varieties under the contrasted hydric conditions. Under non-water stress, Carmenère was not related to any measured parameters. Merlot was positively related to most of the leaf morphometric parameters, whereas Chardonnay presented the opposite behavior. RGB color system variables allowed discriminating the grapevine varieties under water stress conditions, and Sauvignon Blanc was not related to any measured parameter. Chardonnay and Pinot Noir were positively related to green color and negatively related to most of the leaf morphometric parameters, whereas Merlot showed the opposite behavior. (4) Conclusions: Leaf morpho-colorimetric and fractal dimension parameters were affected by plant water stress and more variables should be incorporated into the new ampelographic methods in order to characterize leaf morpho-colorimetric parameters of the different grapevine varieties more clearly.

Accelerated soil development due to seasonal water-saturation under hydric conditions

Pedogenesis is considered a long-term environmental process; however, it can be accelerated by periodic water saturation (hydric conditions). The exact nature and effectiveness of hydric conditions in the intensification of soil development are not clear yet. Our understanding of the timescales of the mineralogical changes occurring in soils is limited; however, the timeframe of soil organic matter accumulation is broadly known. Here, we described soil development over a period of 50 years.The studied soils Calcaric Mollic Gleysol (Endoarenic, Epiloamic, Hyperhumic) and a Calcaric Calcic Histic Gleysol (Endoarenic, Epiloamic) are located in a swampy area in Hungary, Central Europe. The start of the soil formation process is well documented here; the parent material was deposited during a major flood event in 1963. Therefore, the examined soil profile represents development over the last 50 years. We also studied the parent material of an adjacent dune as a reference. We used a CN elemental analyser to determine soil organic carbon and total bound nitrogen content. Selective extractions were also used to determine amorphous and crystalline Fe and Mn content alongside X-ray phase analysis (XRD) and transmission electron microscopy (TEM) for mineralogical analysis, X-ray fluorescence spectroscopy (XRF) for elemental analysis, and laser diffraction for particle size analysis of the bulk soil samples. Simple chemical tests were also performed in the field. Redox potential (Eh) and pH were measured by a field monitoring station.Fifty years under hydric conditions resulted in rapid vertical differentiation within the soil profile including remarkable soil organic matter enrichment in the topsoil, and the formation of smectite and Fe accumulation in the zone of groundwater fluctuation. A high proportion of amorphous and colloidal phases indicated that very intense processes had taken place in the zone of the most intensive redox oscillation. The presence of more crystalline goethite in the bulk soil reflects frequent Eh changes, associated with chemical or microbial processes, while the presence of amorphous ferrihydrite indicates the effect of plant roots. Permanently reductive subsoil conditions also facilitated intense carbonate precipitation. These findings demonstrate that soil formation can proceed faster than previously assumed under hydric conditions.

Repeated use of high risk nesting areas in the European whip snake, Hierophis viridiflavus

Oviparous snakes deposit their egg clutches in sites sheltered from predation and from strong thermal and hydric fluctuations. Appropriate laying sites with optimum thermal and hydric conditions are generally scarce and are not necessarily localised in the home range. Thus, many gravid females undertake extensive trips for oviposition, and many may converge at the best egg laying sites. Dispersal mortality of neonates post-hatchling is also a critical factor. Assessing the parameters involved in this intergenerational trade-off is difficult however, and no study has succeeded in embracing all of them. Here we report data indicating that gravid females of the highly mobile European whip snake, Hierophis viridiflavus exhibit nest site fidelity whereby they repeatedly deposit their eggs in cavities under sealed roads over many decades. These anthropogenic structures provide benefits of relative safety and suitable incubation conditions (due to the protective asphalted layer?), but they expose both females and neonates to high risk of road mortality. Artificial laying sites constructed at appropriate distances from busy roads, along with artificial continuous well protected pathways (e.g. dense hedges) that connect risky laying sites to safer areas, should be constructed.

Germination response to water availability in populations of Festuca pallescens along a Patagonian rainfall gradient based on hydrotime model parameters

Sensitivity to water availability is a key physiological trait for grassland species located in arid and semiarid environments, where successful germination is closely related to rainfall dynamics. Festuca pallescens inhabits diverse environments along a steep precipitation gradient in North Patagonia, thus offering a suitable model for the study of germination behavior in response to water availability. By analyzing germination in nine populations using a hydrotime model approach, we aimed to find within-species variation. Seed population behavior was analyzed under different hydric conditions using hydrotime model parameters (hydrotime, mean base water potential and its standard deviation). We estimated the mean base water potential for F. pallescens (ψb(50) = − 2.79 ± 0.45 MPa), which did not differ significantly between populations. However, the hydrotime parameter (θH) varied markedly, suggesting physiological adaptation to local environments. Higher values of θH were found in populations located at the extremes of the distribution gradient, indicating that germination may be prevented or delayed in conditions that are suboptimal for the species. Since the variation in hydrotime model parameters did not follow a cline, micro-environmental cues may have the greatest influence on the physiological behavior of the species, rather than the macroscale rainfall gradient.

Population origin, maternal effects, and hydric conditions during incubation determine embryonic and offspring survival in a desert-dwelling lizard.

While the effects of incubation environment on embryonic development and offspring traits have been extensively studied in oviparous vertebrates, studies into how genetic inheritance (population origin), maternal effects, and incubation environment interact to produce varying phenotypes, are rare. To elucidate the interactive role of those three factors during incubation in shaping offspring phenotypes through hydric conditions, we conducted a fully factorial experiment [arid and semiarid populations × maternal dry and wet treatments (MDT and MWT) × embryonic dry and wet treatments (EDT and EWT)] with a desert-dwelling lacertid lizard (Eremias argus). Female lizards in dry conditions produced larger clutch sizes but smaller eggs. The incubation period and hatching success were significantly affected by embryonic but not by maternal moisture treatments. Eggs in the EDT hatched later than those in the EWT in both arid and semiarid populations. Hatching success was lower in EDT than in EWT in the semiarid population, but not in the arid population. Hatchlings from the EDT had a slower post-hatch increase in body mass than those from the EWT. EDT would decrease the survival rates of hatchlings in the semiarid population only. In addition, structural equation models revealed that population had a stronger effect on embryonic and offspring survival than maternal and embryonic moisture. Our study demonstrates locally adaptive strategies of drought resistance at multiple life-history stages in lizard populations from diverse hydric habitats and highlights the importance of genetic factors in determining embryonic drought resistance in oviparous lizards.

Living between land and water \u2013 structural and functional adaptations in vegetative organs of bladderworts

AimsThe carnivorous Utricularia (Lentibulariaceae) has an anatomically simple and seemingly rootless vegetative body. It occupies a variety of wetlands and inland waters and shows a broad range of life forms. Here, we aimed to elucidate structural and functional traits in various hydric conditions. Furthermore, we intended to evaluate morpho-anatomical adaptations in correlation with life forms.MethodsMorpho-anatomical characteristics typical for hydrophytes of all life forms were investigated by light microscopy on 13 Utricularia taxa, compared to one Pinguicula and two Genlisea taxa, and assessed by multivariate analyses.ResultsVegetative structures of Utricularia and Genlisea showed reduced cortical, supporting, and vascular tissues. With increasing water table, leaves were thinner, and narrower or dissected, and submerged organs tended to contain chloroplasts in parenchymatic and epidermal cells. In some main stolons, an endodermis with Casparian strips was visible. Large gas chambers, including a novel ‘crescent’ and a special ‘hollow’ aerenchyma pattern, were found in amphibious to free-floating taxa.ConclusionsThe evolutionary transfer of carnivory from aerial to subterranean organs in Genlisea, and even more in Utricularia, coincides with a highly simplified anatomy, which is adapted to a broad variety of hydric conditions and compensates for structural innovations in the uptake of nutrients.