Anisotropic expansion of plant cells requires organized arrays of cortical microtubules. Mutations in microtubule-associated proteins and a particular mutation in α-tubulins were reported to cause ...abnormal microtubule arrays and result in helical growth in Arabidopsis thaliana. However, the way in which these mutations affect the organization of microtubules remains unknown. We here identified 32 Arabidopsis twisting mutants that have either missense or amino acid deletion mutations in α- or β-tubulins. Mutations were mapped to the GTPase-activating region in α-tubulin, intra- and interdimer interfaces of tubulin heterodimers, and lateral contact regions among adjacent protofilaments. These dominant-negative tubulin mutants were incorporated into the microtubule polymer and formed shallow helical arrays of distinct handedness along the long axis of the root epidermal cells. A striking correlation exists between the direction in which cortical helical arrays are skewed and the growth direction of elongating roots. The GTPase-activating-region mutant had left-handed helical arrays composed of highly stabilized microtubules, which could be decorated along the entire microtubule lattices with the otherwise tip-localized End Binding 1 protein. A mutation at the intradimer interface, on the other hand, generated highly dynamic microtubules and right-handed helical arrays. Cortical microtubules in wild type and these two tubulin mutants were composed mainly of 13 protofilaments. This comprehensive analysis of tubulin mutations provides insights into the mechanism by which tubulin structures influence microtubule dynamics and organization.
We conducted dietary analysis on 140 raccoon dog fecal samples, collected between March 2019 and February 2020 in a satoyama area in Tokyo, to see if any effects from competition with invasive ...raccoons were evident. Raccoon dogs mainly consumed fruits, seeds, and cultivated plants (frequency of occurrence 90.7%), earthworms (60.7%), and insects (48.6%). Dominant food types included summer tangerines (Citrus natsudaidai), and berries (e.g., Vaccinium spp.), with earthworms (Oligochaeta spp.) providing their primary source of protein. These raccoon dogs consumed more fruits but less insects than reported by other studies from Japan. We then compared our results with a previous study (2004–2005) in the same area, prior to the arrival of invasive raccoons. We detected minimal effects of raccoon arrival on raccoon dog summer or autumn diet, thus allowing raccoon dogs to find sufficient food to accumulate body-fat for over-wintering; however, their restricted winter diet diversity, with fewer animal species consumed, suggests that they may experience some protein limitation prior to the cub rearing season. The co-existence of raccoon dogs alongside invasive raccoons currently appears viable in this satoyama area, apparently enabled by the ability of raccoon dogs to shift their diet to include more fruit. Published online 4 December, 2023; Print publication 31 January, 2024
We reviewed dietary data in the literature for Japanese martens Martes melampus from 21 study sites covering the entire geographic range of the species, tested for differences in the diets of martens ...in evergreen and deciduous forests, and described variation in main diets and dietary diversity in relation to geographical and environmental variables.
Fruits, mammals, and insects occurred at the highest frequencies in faeces throughout the species’ range. Mammal prey items and non‐fruits were detected less frequently in scats collected in evergreen forests than in deciduous forests, while non‐fruits were detected more frequently in evergreen forests.
Three environmental variables (mean temperature, variation in the normalised difference vegetation index NDVI, and snow depth) had significant effects on variation in dietary composition, but the relative contribution of each variable varied among food items. Geographical variables, on the other hand, had no significant effects on variation in dietary composition.
Mean temperature explained the variation in insect feeding, which increased in forests with moderate temperature. Snow depth explained the variation in feeding on non‐insects and other vertebrates; the former increased in forests with lower snow depth, while the latter increased in forests with higher snow depth. Variation in NDVI, on the other hand, had no effect on variation in feeding on a specific dietary category.
The snow depth had a significant effect on the variation in dietary diversity, which became lower in forests with moderate snow depth. The high plasticity in the dietary composition and dietary diversity might represent a behavioural trait acquired by Japanese martens to allow them to expand their range into various forests with different food availabilities.
When studying the variation in feeding behaviour of omnivorous carnivores, multiple environmental variables need to be considered equally.
•We examined niche partitioning among sympatric mesocarnivores using camera traps.•Smaller species adjusted their hunting activity to avoid larger competitors.•Species specialising on hunting rodents ...avoided each other spatially.•Spatio-temporal partitioning reduced interference and enabled intra-guild sympatry.
The top trophic level in many terrestrial food webs is typically occupied by mammalian carnivores (Order Carnivora) that broadly affect and shape ecosystems through trophic cascades. Their inter-specific interactions can further complicate effects on community dynamics as a consequence of intra-guild competition. The capacity for competitive mammalian carnivores to segregate their hunting and activity regimes is in major part a function of their similarity, in terms of body-size and dietary niche; termed the ‘niche variation hypothesis’. In this study, we used camera-trapping to investigate intra-guild interactions and spatio-temporal partitioning among five mesocarnivores, the golden jackal (Canis aureus), European badger (Meles meles), red fox (Vulpes vulpes), European wildcat (Felis sylvestris) and stone marten (Martes foina), in the Stara Planina Mountains, Bulgaria. We collected a total of 444 images of golden jackals, 236 images of European badgers, 200 images of red foxes, 171 images of stone martens, and 145 images of European wildcats, from 6612 camera-days across fifteen camera-trapping stations. With respect to body size, the three smaller species (fox, wildcat and marten) were active in different time periods than the two larger competitors (jackal and badger) through both the warm and cold season. The more similar the trophic niche between species pairs (particularly relating to rodent consumption), the greater the spatio-temporal partitioning we observed within the pair; however, this adapted to seasonal dietary shifts. In conclusion, spatial and temporal (fine-scale and seasonal) niche partitioning appeared to reduce encounter probabilities and competition and may act to facilitate sympatric coexistence among this regional mesocarnivore guild.
Illumination at night is determined by moon phase, naturally affecting the reproductive activities of nocturnal animals. The European badger (
Meles meles
Linnaeus, 1758) is a large-sized mustelid ...that lives throughout Bulgaria. Since information on its reproductive activity is scarce for the country, a two-year camera trap survey was conducted at five main setts. It aimed to establish the mating period of the badger, as well as some behavioral activities of the observed individuals in a semi-mountainous area in Central Bulgaria (Sarnena Sredna gora Mts). In the present study, badger mating behavior was only observed in winter. Winter is the main breeding period for badgers from Central Bulgaria, which corresponds to greater activity in front of the setts. Darker lunar phases (i.e., new moon) significantly increased the badger's reproductive activities at their setts. Further research is needed to elucidate the underlying mechanism responsible for the nocturnality and preferences to darkness of reproductive badgers.
•We report the effects of tourist trail on mammals in a developing Protected Area (PA).•Mammal signs along transects adjacent to less used, unpaved trails were affected less.•Species and guilds ...exhibited different sign score responses to Trail Type and Use.•Paucity of larger mammal signs was associated with greater Trail Use.•However, smaller mammals were associated with human-modified forest types.
Despite economic benefits, particularly in developing countries, ecotourism can have unintended negative consequences for wildlife conservation in protected areas (PAs). We report the effects of tourist Trail-Type and -Use on the incidence of mammal fieldsigns in a PA in central China. Surveys conducted adjacent to five categories of trail-type and fieldsigns were scored for three duplicates of four 0.5km transects (=60 transects). Higher Trail Use along more major Trail Types were associated with significantly fewer fieldsigns along transects close to trails, compared with more distant transects. Fieldsign scores along transects adjacent to less used, unpaved trails were far less affected. In multiple-regression models, species and guilds exhibited different fieldsign score responses to Trail Type and Use. In general, a paucity of larger mammal (>15kg) fieldsigns was associated primarily with greater Trail Use, whereas fieldsign scores for smaller mammals were associated more strongly with human-modified forest types. As international demand for nature-based tourism continues to grow it is important to evaluate openly the consequences of providing public access to protected areas while conserving biodiversity.
The raccoon dog (Nyctereutes procyonoides viverrinus) has recently become common in urban environments in Japan. We predicted that, like other carnivores adapted to urban environments, raccoon dogs ...in urban areas should have smaller home ranges than those in rural areas. We investigated the size of home ranges of raccoon dogs in the Akasaka Imperial Grounds, a 51-ha green area in central Tokyo. Between August 2012 and August 2014, 7 adult males and 4 adult females were radiotracked. Mean (± SD) home range size of these 11 raccoon dogs (100% minimum convex polygon = 17.6 ± 13.0 ha; 95% fixed kernel = 8.3 ± 5.7 ha) was smaller than that of raccoon dogs in rural areas obtained in previous studies, and core areas (75% local convex hull) averaged 3.7 ± 4.1 (SD) ha. We detected no seasonal changes in home range size. These results were consistent with the notion that urban carnivores typically have small home ranges. The small home range size seems to be explained by abundance of food resources, restricted environment, and the high population density of raccoon dogs in the urban green area.
We compared the reliability of visual diagnostic criteria to DNA diagnostic techniques, including newly designed primers, to discriminate Japanese marten (Martes melampus) feces from those of other ...sympatric carnivore species. Visual criteria proved > 95% reliable for fresh, odoriferous scats in good condition. Based upon this verification, we then examined if and how Japanese marten diet differs among seasons at high elevation study site (1500-2026 m). We also considered how intra-specific competition with the Japanese red fox (Vulpes vulpes japonica) may shape marten feeding ecology. From 120 Japanese marten fecal samples, high elevation diet comprised (frequency of occurrence) 30.6-66.0% mammals, 41.0-72.2% insects and 10.6-46.2% fruits, subject to seasonal variation, with a Shannon-Weaver index value of 2.77. These findings contrast substantially to seasonal marten diet reported in adjacent lowland regions (700-900 m), particularly in terms of fruit consumption, showing the trophic adaptability of the Japanese marten. We also noted a substantial dietary overlap with the red fox (n = 26 scats) with a Shannon-Weaver index of 2.61, inferring little trophic niche mutual exclusion (trophic niche overlap: 0.95), although some specific seasonal prey selection differences were likely related to relative differences in body size between foxes and martens. This additional information on the feeding ecology of the Japanese marten enables a better assessment of the specific risks populations face in mountainous regions.
Aim Studies comparing feeding habits across a genus in different geographical regions or habitats can identify factors associated with adaptive feeding behaviour, linking key ecological traits ...between consumers and their environment. We investigated biogeographical patterns in dietary composition and trophic diversity across the genus Martes in relation to geographical range and environmental variables. We hypothesized that widely distributed opportunistic Martes species should demonstrate adaptive variations in dietary composition and trophic diversity relative to regional geographical location (e.g. latitude, elevation), environmental variation (e.g. temperature, rainfall, snow cover and primary productivity) and concomitant variation in food supply. Location Europe, Asia and North America. Methods We examined the dietary habits of martens (Martes spp.) using original data expressed as relative frequency of occurrence, and using principal components analysis to extract the main gradients in diet composition. These were then used as response variables in regression analyses, predicted from latitude or elevation. Multiple regression analyses were performed to assess the influence of food types and environmental variables on the trophic diversity index. Results A clear latitudinal gradient in dietary composition was observed. Small mammals were the primary food type, but were less abundant in the diet of martens at lower latitude and elevation. Vegetable matter and insects were consumed more frequently in southerly and/or lower‐elevation localities. Trophic diversity was lower at higher elevation, and increased with a decline in consumption of the dominant food types, i.e. rodents, fruits and insects. Trophic diversity also increased with increasing mean temperature. Main conclusions Biogeographical variations in feeding habits across the genus Martes proved to be associated with latitude, local climate (especially temperature regime) and the availability of alternative potential foods. On an extensive geographical scale, martens respond to varying food availability by adjusting their foraging strategy and thus should be considered facultative generalists. At the species level, however, different climatic variables emerged as differentially important, indicative of adaptations to local conditions. Martes species are opportunistic and flexible feeders, and thus their conservation requires informed management, mindful of how changes in environmental conditions might influence their varied food supply.
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