Effect Of Latitude Research Articles

From spermatogenesis to fertilisation: the role of melatonin on ram spermatozoa.

This review presents recent findings on the effect of melatonin on ram spermatozoa. This hormone regulates seasonal reproduction in the ovine species through the hypothalamic-pituitary-gonadal axis, but it also exerts direct effects on spermatogenesis, seminal quality and fertility. In the testis, melatonin stimulates blood flow to this organ, but it also appears to be involved in the differentiation of spermatogonial stem cells and the secretion of testosterone through the MT1 and MT2 receptors. In the epididymis, this hormone modulates sperm maturation and the secretory activity of epidydimal epithelial cells. In addition, the antioxidant activity of melatonin may protect spermatozoa from oxidative damage during their formation in the testis and their maturation in the epididymis. After ejaculation, the melatonin present in seminal plasma may also protect sperm from oxidative damage and premature capacitation and may improve seminal quality. Finally, once the sperm begins its transit through the female genital tract, melatonin may modulate sperm capacitation. Thus, melatonin could have a bimodal activity in ram sperm capacitation, so high concentrations, such as those in seminal plasma, have a decapacitating effect. In contrast, low concentrations, such as those present in the female reproductive tract, may promote it, likely through interaction with MT2 receptors. In addition, melatonin could also be involved in chemotaxis and fertilisation, although further studies are needed to elucidate the specific role of melatonin in these processes. Finally, the effect of latitude and melatonin receptor gene polymorphisms in ram reproduction is also discussed.

Climatic versus biotic drivers' effect on fitness varies with range size but not position within range in terrestrial plants

AbstractAll populations are affected by multiple environmental drivers, including climatic drivers such as temperature or precipitation and biotic drivers such as herbivory or mutualisms. The relative response of a population to each driver is critical to prioritizing threat mitigation for conservation and to understanding whether climatic or biotic drivers most strongly affect fitness. However, the importance of different drivers can vary dramatically across species and across populations of the same species. Theory suggests that the response to climatic versus biotic drivers can be affected by both the species' fundamental niche breadth and the latitude of the population at which the response is measured. However, we have few tests of how these two factors affect relative response to drivers separately, let alone tests of how niche breadth and latitude together influence responses. Here, we use a meta‐analysis of published studies on population response to climatic and biotic drivers in terrestrial plants, combined with estimates of climatic niche breadth and position within climatic niche derived from herbarium records, to show that species' niche breadth is the primary determinant of response to climatic versus biotic drivers. Namely, we find that response to climatic drivers changes only minimally with increasing niche breadth, while response to biotic drivers increases with niche breadth. We see similar relationships when considering range size instead of niche breadth. Surprisingly, we find no effects of latitude on the relative effect of climatic versus biotic drivers. Our work suggests that populations of species with small and large ranges experience similar extirpation risks due to the negative impacts of climate change. By contrast, populations of species with large (but not small) ranges may be highly susceptible to changes in densities or distributions of interacting species.

Human identification via digital palatal scans: a machine learning validation pilot study

BackgroundThis study aims to validate a machine learning algorithm previously developed in a training population on a different randomly chosen population (i.e., test set). The discrimination potential of the palatal intraoral scan-based geometric and superimposition methods was evaluated.MethodsA total of 23 participants (16 females and seven males) from different countries underwent palatal scans using the Emerald intraoral scanner. Geometric-based identification involved measuring the height, width, and depth of the palatal vault in each scan. These parameters were then input into Fisher’s linear discriminant equations with coefficients determined previously on a training set. Sensitivity and specificity were calculated. For the superimposition method, scan repeatability was compared to between-subjects differences, calculating mean absolute differences (MAD) between aligned scans. Multiple linear regression analysis determined the effects of sex, longitude, and latitude of country of origin on concordance.ResultsThe geometric-based method achieved 91.2% sensitivity and 97.1% specificity, consistent with the results from the training set, showing no significant difference. Latitude and longitude did not significantly affect geometric-based matches. In the superimposition method, the between-subjects MAD range (1.068–0.214 mm) and the repeatability range (0.011–0.093 mm) did not overlap. MAD was minimally affected by longitude and not influenced by latitude. The sex determination function recognized females over males with 69.0% sensitivity, similar to the training set. However, the specificity (62.5%) decreased.ConclusionsThe assessment of geometric and superimposition discrimination has unequivocally demonstrated its robust reliability, remaining impervious to population. In contrast, the distinction between sexes carries only moderate reliability. The significant correlation observed among longitude, latitude, and palatal height suggests the feasibility of a comprehensive large-scale study to determine one’s country of origin.Clinical significancePortable intraoral scanners can aid forensic investigations as adjunct identification methods by applying the proposed discriminant function to palatal geometry without population restrictions.Trial registrationThe Clinicatrial.gov registration number is NCT05349942 (27/04/2022).

Characteristics of tritium, stable isotopes and chemical components in monthly precipitation at Hiroshima, Japan.

This article mainly discusses tritium concentrations in monthly precipitation at Hiroshima City during 2021. The tritium concentrations, which were measured with a low background liquid scintillation counter, fluctuated from 0.16 to 0.78BqL-1. Additionally, hydrogen and oxygen stable isotopes and ionic species were measured in order to characterize precipitation, and their trends including tritium concentrations were compared with data collected in other regions of Japan in previous studies. Although the results showed the characteristics of precipitation were similar to those observed in the other regions, the tritium concentrations were found to be contrary to behavior expected from the latitude effect and some of the observed ionic components were suggested to be continental in origin. Since these results are not common at other sites in Japan, the tritium concentration in the westernmost region of Honshu, including Hiroshima City, may be influenced by Asian continental influences.

Tritium concentration in monthly precipitation in Okinawa and Kagoshima, southern Japan.

This study aimed at understanding the background concentration level of tritium in precipitation in southern Japan, where precipitation samples were collected monthly in 2022 in Okinawa and Kagoshima. Tritium concentration in monthly precipitation collected in Okinawa since 2014 ranged from 0.05 to 0.39Bq per L with the mean value (2015-2022) of 0.15±0.06Bq per L. That of Kagoshima since 2022 ranged from < 0.11 to 0.58Bq per L with the mean value of 0.30±0.13Bq per L. Our observed values were summarized with reported values, from which a clear latitude effect for tritium concentration was found in precipitation of southern Japan.

Physiological and morphological traits affect contemporary range expansion and implications for species distribution modelling in an amphibian species.

Species range shifts due to climate alterations have been increasingly well-documented. Although amphibians are one of the most sensitive groups of animals to environmental perturbations due to climate change, almost no studies have offered evidence of poleward distribution shifts in this taxon in response to climate warming. Range shifts would be facilitated by variation in traits associated with the ability of species to persist and/or shift their range in the face of climate change, but the extent and consequences of intraspecific variation in these traits is unclear. We studied the role of intraspecific variation in the ongoing range shift of green treefrogs (Hyla cinerea) in response to climate change. We explored factors that are often associated with range shifts to test the hypothesis that there are differences in these traits between recently range-expanded and nearby historical populations. We then tested the consequences of intraspecific variation for modelling climate-induced range shifts by comparing species distribution models (SDMs) that used as input either data from the entire species range or separate inputs from 'subpopulations' corresponding to the historical range or the recently expanded range. We expected that building a separate SDM for each population would more accurately characterize the species range if historical and expanded populations differed in traits related to their response to climate. We found that critical thermal minimum decreased and thermal breadth increased with latitude, but the effect of latitude was significantly stronger for expanded populations compared to historical populations. Additionally, we found that individuals from expanded populations had longer leg lengths when compared to their historical counterparts. Finally, we found higher model accuracy for one of the population-level SDMs than the species-level SDM. Our results suggest that thermal tolerance and dispersal morphologies are associated with amphibian distributional shifts as these characteristics appear to facilitate rapid range expansion of a native anuran. Additionally, our modelling results emphasize that SDM accuracy could be improved by dividing a species range to consider potential differences in traits associated with climate responses. Future research should identify the mechanisms underlying intraspecific variation along climate gradients to continue improving SDM prediction of range shifts under climate change.

Thermal Tolerance and Species Distributions: Interactions Between Latitude, Elevation and Arboreality in Ants

ABSTRACTAimGlobal warming has highlighted the importance of understanding the role of thermal tolerance as a driver of species distributions, especially for ectotherms. Here we analyse interactions between latitude, elevation and arboreality as predictors of geographic patterns of thermal tolerance in ants.LocationThe collected data are distributed globally.MethodsWe first tested the effect of latitude, elevation and its interactive effect on ant CTmax and CTmin. Second, we tested whether CTmax and CTmin are phylogenetic clustering. Finally, we tested whether CTmax and CTmin can be explained by nesting microhabitat (ground vs. tree‐nesting species) and whether the probability of occurrence of tree‐nesting species along thermal gradients helps explain the global pattern in ant CTmax.ResultsCTmax and CTmin displayed high and low phylogenetic signals respectively and therefore showed different responses to geographic gradients. Notably, we found that CTmax was higher in higher latitudes. This was explained by a lack of elevational turnover at high latitudes among tree‐nesting species, which are exposed to warmer microclimates and have higher CTmax compared with ground‐nesting species. CTmin decreased with elevation at low latitudes, but did not vary with elevation at higher latitudes.Main ConclusionsOur findings highlight the important influence of arboreality on the macroecology of thermal tolerance, substantially modifying traditional notions of variation along latitudinal and elevation gradients.

Variations on the chemical compositions of chestnut fruits collected at different locations

Chestnut is an essential food source in many countries. Nutritional quality and potential health benefits of Anatolian chestnut trees (Castanea sativa Mill.) have led to increased concern and interest in chestnut production. However, knowledge of the factors that influence the chemical content of chestnut fruits still needs to be improved. Thus, the chemical compositions were evaluated for Anatolian chestnut fruits collected at 14 different locations in northern Türkiye, which is one of the biggest chestnut producers in the world. The effects of latitude, longitude, altitude, aspect, mean annual temperature (°C) (TMA), and mean annual precipitation (mm) (PMA) of the study locations on the chemical compositions of chestnut fruits were monitored. The effects of these parameters on several chestnut characteristics were examined using a mixed-effects multiple regression model. Latitude, longitude, TMA, and PMA were correlated with the mean concentrations of sucrose, free amino acid, glycine betaine, nitrogen (N) (%), and total carbon (C) (%) of the chestnut samples. The moisture content of the fruits was affected by longitude. The antioxidant and mineral content of the chestnut samples also varied by location. These findings may be helpful in site selection, production, and conservation of chestnut cultivars.

Untangling island biogeography of terrestrial vertebrates in protected areas of America

Island Biogeography Theory (IBT) is a foundational framework in conservation science, yet its application to large-scale protected area (PA) design remains relatively understudied. This research investigates the influence of IBT-derived variables on terrestrial vertebrate richness and threatened species abundance within 4990 PAs across continental America. By examining the effects of area, shape, isolation, elevation, latitude, and human influence, we assessed the relative importance of these factors in shaping vertebrate diversity patterns. Our findings reveal that while IBT principles, such as the positive relationship between area and species richness, are evident, the influence of human activities is pervasive. Specifically, latitude and elevation significantly influenced species richness for most taxonomic groups, while area positively affected amphibians, birds, reptiles, and threatened mammals and reptiles. Shape and isolation exhibited varying degrees of impact across different taxa. Critically, human influence emerged as a dominant factor, particularly for birds, including threatened species. These results underscore the complex interplay between natural and anthropogenic processes in shaping biodiversity patterns. To effectively conserve terrestrial vertebrates, and overall biodiversity, PA managers and policy-makers must integrate IBT principles with strategies that address the impacts of human activities, such as habitat loss, fragmentation, and climate change.

Internal Tides at the Coast: Energy Flux of Baroclinic Tides Propagating into the Deep Ocean in the Presence of Supercritical Shelf Topography

Abstract The generation of internal tides at coastal margins is an important mechanism for the loss of energy from the barotropic tide. Although some previous studies attempted to quantify energy loss from the barotropic tides into the deep ocean, global estimates are complicated by the coastal geometry and spatially and temporally variable stratification. Here, we explore the effects of supercritical, finite amplitude bottom topography, which is difficult to solve analytically. We conduct a suite of 2D linear numerical simulations of the barotropic tide interacting with a uniform alongshore coastal shelf, representing the tidal forcing by a body force derived from the vertical displacement of the isopycnals by the gravest coastal trapped wave (of which a Kelvin wave is a close approximation). We explore the effects of latitude, topographic parameters, and nonuniform stratification on the baroclinic tidal energy flux propagating into the deep ocean away from the shelf. By varying the pycnocline depth and thickness, we extend previous studies of shallow and infinitesimally thin pycnoclines to include deep permanent pycnoclines. We find that scaling laws previously derived in terms of continental shelf width and depth for shallow and thin pycnoclines generally hold for the deeper and thicker pycnoclines considered in this study. We also find that baroclinic tidal energy flux is more sensitive to topographic than stratification parameters. Interestingly, we find that the slope of the shelf itself is an important parameter but not the width of the continental slope in the case of these steep topographies. Significance Statement The objective of this study is to better understand how vertical density stratification, which can vary seasonally in the ocean, affects the interaction of tides with steep coastal topography and the generation of waves that travel away from the coast in the ocean interior. These waves in the interior can travel over long distances, carrying energy offshore into the deep ocean. Our results suggest that the amount of energy in these internal waves is more sensitive to changes in topography and latitude than to the vertical density profile. The scaling laws found in this study suggest which parameters are important for calculating global estimates of the energy lost from the tide to the ocean interior at the coastal margins.

Eco-geographic and sexual variation of the ribcage in Homo sapiens.

Up to now, Allen and Bergmann's rules have been studied in modern humans by analyzing differences in limb length, height, or body mass. However, there are no publications studying the effects of latitude in the 3D configuration of the ribcage. To assess this issue, we digitally reconstructed the ribcages of a balanced sample of 109 adult individuals of global distribution. Shape and size of the ribcage was quantified using geometric morphometrics. Our results show that the ribcage belonging to tropical individuals is smaller and slenderer compared to others living in higher latitudes, which is in line with Allen and Bergmann's rules and suggests an allometric relationship between size and shape. Although sexual dimorphism was observed in the whole sample, significant differences were only found in tropical populations. Our proposal is that, apart from potential sexual selection, avoiding heat loss might be the limiting factor for sexual dimorphism in cold-adapted populations.

Effects of extrinsic and intrinsic factors on parturition and reproductive output in wolverines

AbstractOne of the selective advantages of delayed implantation in carnivores is the flexibility to decouple the time between mating and parturition, allowing both to occur when conditions are most favorable. Terrestrial carnivores with delayed implantation have evolved reduced maternal energy expenditure through shorter gestation length, smaller neonates, and smaller litters, with a possible linkage between maternal body condition and time of birth or litter size. Using data on wolverine (Gulo gulo) females and cubs from management removals covering the entire latitudinal gradient of the Scandinavian population in 2001‐2022, I assessed the effect of extrinsic and intrinsic factors on variation in parturition date and litter size. Timing of parturition varied over 2 months, where 90% of the litters were born between 5 February and 11 March, with a birth peak on 23 February. Females living in winter grazing pastures of semi‐domestic reindeer (Rangifer tarandus) gave birth earlier than those outside, and along an elevation gradient parturition date was delayed at higher altitudes. I did not find evidence of an effect of latitude on parturition date. Furthermore, older females had greater odds than younger females of having litters with 3 cubs rather than 1 cub. To minimize the risk of harvesting lactating females, management regulations should implement harvest seasons that extend no longer than the end of January.

Caught out in the cold: Anas platyrhynchos (Mallard) survival decreased during an extreme climatic event

Abstract Extreme climatic events (ECEs) can have profound impacts on individual fitness, affecting survival directly or indirectly. Late winter ECEs may be especially detrimental to fitness due to limited food resources and increased energetic requirements during this time. A polar vortex disruption ECE descended upon the mid-continental United States during February 7–20, 2021 with temperatures as low as −29°C in areas concurrent with ongoing research on Anas platyrhynchos (Mallard) movement ecology and survival in Arkansas, Louisiana, and Tennessee, United States spanning winters 2019–2022. Therefore, we opportunistically evaluated the effects of individual characteristics and latitude on daily survival during the ECE. We extended the survival analysis to March to test for lasting effects of the ECE on survival. We tracked 181 Global Positioning System (GPS)-marked A. platyrhynchos during February 2020, 256 in February 2021, and 324 in February 2022. We documented 22 mortalities during the February 2021 ECE (i.e., 9%), but only 6 mortalities during February 2020 (i.e., 2%) and 2022 (i.e., 1%) when conditions were average. February survival (e.g., 28-day survival) during the ECE was 0.908 (85% CI: 0.879–0.937) but was 0.982 (85% CI: 0.973–0.991) during the 2 non-ECE Februaries. The ECE effect on survival was isolated to February and did not affect March survival. Anas platyrhynchos was 5.4 times more likely to die during the ECE in 2021 compared to non-ECE Februaries. Although large-bodied waterfowl appear cold-tolerant and less sensitive to polar vortex disruptions compared to smaller-bodied passerines, direct mortalities can occur if conditions are severe enough and persist, highlighting the need to consider the influence of ECEs on common, seemingly robust species in future global climate change scenarios.

Longitudinal multisite study of the chronobiological control of chronic pain: the CircaHealth CircaPain study protocol

IntroductionOne in five Canadians lives with chronic pain. Evidence shows that some individuals experience pain that fluctuates in intensity following a circadian (24-hour) rhythm. Endogenous molecular rhythms regulate the function...

The effect of elevation, latitude, and plant richness on robustness of pollination networks at a global scale

The effect of elevation, latitude, and plant richness on robustness of pollination networks at a global scale

Comparison of the Ionospheric Dynamo Current of Mars Above InSight and Zhurong Landing Sites: A Modeling Study

AbstractPrevious observational studies suggest that the surface time‐varying magnetic field of Mars originates in large part from the dynamo currents in the Martian ionosphere. However, whether there are significant differences in the strength, configuration, diurnal, and seasonal variations of the dynamo currents above different regions need to be further studied. In this study, using the ionospheric parameters from Mars Climate Database version 5.3 (MCD v5.3) and 7 years of MAVEN magnetic field measurements, we compare the ionospheric dynamo currents above the landing sites of InSight (4.50°N, 135.62°E) and Zhurong (25.07°N, 109.90°E) and the resulting surface magnetic variations at the two landing sites by conducting a modeling study. We find that the average dynamo current as well as its diurnal magnetic field amplitude on the Martian surface is significantly stronger at InSight than that at Zhurong due to the stronger background magnetic field strength and more perpendicular angle between magnetic field and neutral wind vectors in the dynamo region, though the conductivities is always weaker over InSight landing site. The seasonal variation of the current intensity (represented by differences between northern winter and summer solstices) is prominent over InSight than that over Zhurong because the heliospheric distance effect‐resulted conductivity difference is the dominate factor for the seasonal variations over InSight while both the heliospheric distance and solar zenith angle (SZA) contribute to the current intensity at different Ls over Zhurong. The two factors partially offset each other and lead to a smaller seasonal variation. The role of crustal field, as well as the latitude effects on dynamo currents is also discussed. This study provides an attempt to promote the understanding of the solar wind‐induced magnetosphere‐ionosphere‐surface coupling process.

Mottled ducks, feral mallards, and their hybrids in Florida

AbstractThe nonmigratory and endemic Florida mottled duck (Anas fulvigula fulvigula) is facing conservation threats from the combined effects of urbanization and introgressive hybridization with feral mallards (Anas platyrhynchos) and mallard x mottled duck hybrids. In the past, the status of the Florida mottled duck population was assessed during annual aerial surveys and most brown ducks (mottled ducks, mallards, and hybrids of them) detected during the survey would have been mottled ducks. But the release of domesticated mallards for aesthetic purposes has led to increases in the prevalence of mallards‐hybrids (mallards or mallard x mottled duck hybrids) throughout peninsular Florida, USA, and because it is impossible to differentiate among mottled ducks, female mallards, and hybrids during aerial surveys, helicopter surveys were halted in 2009 until state researchers could conduct a range‐wide study to determine what proportion of brown ducks are mottled ducks versus mallards‐hybrids. We used plumage keys and high‐resolution photography to categorize brown ducks from 557 wetland grid points as either mottled ducks or mallards‐hybrids. Of the 5,179 brown ducks categorized, 40.1% were mottled ducks and 59.9% were mallards‐hybrids. We used logistic regression analysis to model the interactive effect of a site's latitude and level of urbanization (urban gradient value within a 2‐km buffer) to generate a predictive raster surface (1‐km resolution) of the study area with values corresponding to the probability that a brown duck observed within a cell is a pure mottled duck. Predicted values will be used as correction factors when estimating final mottled duck population abundance from brown‐duck survey data. Additionally, the predictive raster surface will be used to identify wetlands where mottled ducks remain predominant so that these sites can be targeted for preservation. Overall, mallards‐hybrids outnumbered mottled ducks throughout most of peninsular Florida, especially in more urbanized regions, and their current prevalence rate presents a serious conservation threat, via hybridization, to extant mottled duck populations.

Latitudinal variation in survival and immature development of Ceratitis capitata populations reared in two key overwintering hosts

Ceratitis capitata, a major agricultural pest, is currently expanding its geographic distribution to northern, temperate areas of Europe. Its seasonal biology and invasion success depend on temperature, humidity and host availability. In coastal warmer Mediterranean regions and cooler temperature areas, bitter oranges and apples serve as overwintering hosts during the larval stage. We assessed the overwintering capacity of C. capitata populations obtained from different areas of the northern hemisphere by studying the survival and development rates of immature stages in both fruits under laboratory conditions. Eggs from each population were artificially inserted in the flesh of the two hosts and kept at 15, 20, or 25 °C until pupation and adult emergence. Climatic analysis of the area of the population origin showed combined effects of latitude, host and macroclimatic variables on immature survival and development rates. Egg to adult survival rates and developmental duration were longer in apples than in bitter oranges. For populations originated from southern-warmer areas, egg to adult developmental duration was prolonged and adult emergence reduced at 15 °C compared to those populations obtained from northern regions. Our findings reveal varying plastic responses of medfly populations to different overwintering hosts and temperatures highlighting the differential overwintering potential as larvae within fruits. This study contributes towards better understanding the medfly invasion dynamics in temperate areas of Northern Europe and other parts of the globe with similar climates.

Summary of the Groundwater Recharge from the South West African Monsoon: A Transect from the Guinea Coast to the Hombori Mountains in Mali

There is an increasing demand on water supplies in semi-arid regions. There is an urgent need to better understand the recharge process of groundwater in these areas, but there an underrepresentatity of long-term data in these regions ay a global scale. we present the seasonal variations of groundwater over a two-three-year period over a 1500 km transect from the Gulf of Guinea coast to inland Mount Hombori in Mali. The results show a strong seasonal and interannual variability, with important evaporation processes for surface and shallow groundwater with rapid infiltration processes. The continental /latitude effect is low along the first 500 km in Guinea, and decrease slowly with the reduction of rainfall and air moisture in direction of Sahel.

A New Brightness Temperature Mapping Method for Weakening Latitude Effect With Chang’e-2 MRM Data and Its Geologic Significances

A New Brightness Temperature Mapping Method for Weakening Latitude Effect With Chang’e-2 MRM Data and Its Geologic Significances