Ecological Research最新文献

Few studies have evaluated the structure and dynamics of forests in Madagascar with high levels of endemism. Ankarafantsika National Park holds the largest of the remaining primary dry forests in northwestern Madagascar, where most of the forests have been lost or degraded by fire and other human activities. In this primary forest, we established a 15-ha forest dynamics monitoring plot and mapped and identified all woody stems with a diameter at breast height (DBH) ≥5 cm. The forest stand was characterized by small-sized individuals (75% of stems with DBH <10 cm, with 99% of trees with height <15 m), encompassing 35,758 tree and 513 liana individuals belonging to 160 species in 53 families (including 20 species of lianas accounting for 1.4% of the stems). Most species-rich families were Rubiaceae, Fabaceae, Lamiaceae, and Malvaceae, which together encompassed 43 tree species and 23% of all tree individuals. The plot was located on a hill consisting of white sand at elevations from 150 to 200 m, with a gentle slope down from southwest to northeast. Over this elevation gradient, stem density and species diversity increased with elevation, while tree height and diameter decreased. The most abundant two species, Drypetes perrieri (Putranjivaceae) and Noronhia alleizettei (Oleaceae) are evergreen, suggesting the importance of a nutrient conservation strategy. These results provide the foundational knowledge necessary for the conservation and restoration of natural semi-deciduous dry forests that used to cover large areas in northwestern Madagascar until recently.

The overabundance of sika deer has become a significant threat to plant communities across Japan. As a result of the deer overgrazing, rare plants are undergoing a demographic bottleneck, leading to a loss of genetic diversity. Genetic diversity is crucial for the reproductive success of self-incompatible plants, and it also provides evolutionary potential, which increases their long-term population viability. Therefore, it is essential to appropriately manage the remaining genotypes to conserve local genetic resources. In this study, we exemplify this, via a conservation genetic analysis of Parasenecio peltifolius populations impacted by deer. Genetic data revealed that the small populations confined to isolated refugial sites consisted of effectively single genets. Recent reproductive failures in these populations may be attributed to the loss of genotypic diversity. Despite the bottlenecks, the remaining genets exhibited high individual heterozygosity, which is a good indicator that they have not been affected by severe inbreeding. Hybrid simulations suggested that interpopulation outbreeding between the unique genotypes can be a viable option to promote sexual reproduction and re-establish genetic diversity within the local populations. Establishing artificial progenies in botanical gardens can serve as a vital genetic resource for the long-term viability of threatened P. peltifolius populations.

In Europe, the largest and most floristically diverse ultramafic (serpentine) outcrops are located on the Balkan Peninsula. In Greece, the Northern Pindus mountain range is characterized as a floristic diversity hotspot, due to the presence of large ultramafic outcrops that harbor a large number of nickel (Ni) hyperaccumulators with potential use in agromining. The work presented here is part of a more in-depth study of floristic composition and ecology of plant communities in ultramafic grasslands of the Northern Pindus mountain range. In 2021–2022, 120 relevés in three subareas (sA1, sA2, and sA3) were sampled according to the Braun-Blanquet method. We identified 493 plant taxa belonging to 61 families. The most abundant families were Asteraceae, Poaceae, Fabaceae, Lamiaceae, and Caryophyllaceae. A total of 22 plant taxa are endemic to Greece. Ninety-five taxa are of Balkan origin while 158 taxa are distributed to the broader Mediterranean region. The highest number of plant life-forms are hemicryptophytes (56.39%) and therophytes (23.33%). Eight Ni hyperaccumulators including Centaurea thracica, Bornmuellera baldaccii, Bornmuellera emarginata, Bornmuellera tymphaea, Noccaea boeotica, Noccaea tymphaea, Odontarrhena chalcidica, and Odontarrhena smolikana were recorded.

Minerals are among the important nutritional components that are indispensable for animals. In particular, the acquisition of sodium is important for plant-feeding animals because sodium may be deficient for these animals as plants do not need sodium. This study compiled data on the mineral contents of leaves in 28 forests in Japan, with special emphasis on the effect of distance from the sea and bedrock type. The aim of this study was to provide basic data on mineral availability for forest-dwelling folivores, which provide important baseline data for understanding the mineral acquisition strategy of plant-feeding animals. Sodium and phosphorus contents of live leaves were lower than the levels required for folivores (captive non-human primates and ungulates). The effect of the distance from the sea was evident only for magnesium and sodium. The sodium content of live leaves was high enough to satisfy folivores' requirements at only a few hundred meters from the sea. The live leaves in forests growing on sedimentary bedrocks contained more minerals than those on granite/rhyolite. Seasonality was also evident based on repeated sampling at three study sites. The mineral contents of dead leaves at the three study sites showed similar inter-site and inter-season variations to those of live leaves. Phosphorus and potassium contents in dead leaves were consistently lower and iron content was consistently higher than in live leaves.

Multicontamination of soils by various organic and inorganic pollutants is considered as an obstacle for the development of hyperaccumulator plants and phytoextraction of metals. The aim of this study was to investigate the effect of polycyclic aromatic hydrocarbons (PAHs) in combination with trace elements on the antioxidant response and phytoextraction efficiency of two populations of the hyperaccumulator Noccaea caerulescens from either a metalliferous (Ganges) or a nonmetalliferous (Chavignée) site. Plants were grown for 17 days in soil containing moderate concentrations of trace elements and under the effect of phenanthrene (PHE), a PAH stress model. In general, exposure to PHE resulted in a reduction of growth parameters, together with the upregulation of antioxidant enzymes and compounds and limitations in nutrient uptake and heavy metal extraction in N. caerulescens. Variations were observed in the extent of enzymatic activities and the amount of metals extracted between the two populations studied. Plants from Chavignée exhibited a slightly more tolerant response to PHE stress than those from Ganges. The presence of PHE in the soil proved highly toxic to N. caerulescens, resulting in low numbers of survivors. Nevertheless, the differences observed between the two populations with regard to growth, metal extraction, and antioxidant defense responses suggest that the difference in defense capacity may ensure different tolerance. This difference may be linked to adaptations acquired by each population according to the soil type from which it originates. However, these results need to be confirmed by further experiments.

The striped hyena is one of the most secretive and enigmatic mammal species. Despite some success in describing their distribution and analyzing population trends, further understanding of the factors affecting reproductive success is needed. Therefore, we present the first analysis of the reproductive success of this species in the wild. We measured the reproductive success of female striped hyenas in at least one litter over 15 breeding seasons. We inspected 33 dens with 67 breeding events during this time and recorded 151 young hyenas. The dens were inhabited for an average of 2 years, with litter sizes ranging from 1 to 4 per reproductive female and most young born between January and June. We also found that litter size was positively associated with lowland areas and shrubs near the den. Despite methodological limitations that we could not overcome given the enigmatic nature of this species, our discovery is crucial because we have shown that reproductive success depends on the habitat in which dens are located, thus ensuring consistent reproductive success over the long-term cycle.

Root foraging may allow hyperaccumulator plants to enhance element accumulation. This study compared root proliferation of two annual serpentine endemics: Streptanthus polygaloides (Ni hyperaccumulator) and Streptanthus insignis (nonhyperaccumulator). In a greenhouse experiment, pots were divided by a sealed partition, Ni-amended soil (800 mg kg ⁻¹) in one half, unamended soil in the other. Seeds were germinated over the partition, allowing roots to explore both soils. After 5 months, roots from each side of each pot were harvested, washed, dried, and weighed. Streptanthus polygaloides root biomass was significantly (twofold) greater in Ni-amended soil whereas S. insignis root biomass was similar in the two soils. In a lab experiment, seedlings were grown in vertical agar-filled petri dishes to determine if Ni affected seedling root growth. Seedlings were placed on either side of a central filter paper strip soaked in either NiCl₂ solution or deionized water. Growth direction of the primary root (toward, away, neutral) and lateral root numbers and lengths were recorded. For seedlings, primary root direction and lateral root numbers/lengths were significantly increased toward Ni-soaked filter paper only for S. polygaloides. We conclude that S. polygaloides exhibited positive root foraging responses. These may enhance Ni uptake and we suggest the term “nickelophilic root foraging” be applied to this behavior.

Japanese walnuts (Juglans mandshurica) are known to be seed-dispersed by the hoarding of two species of rodents, Japanese squirrels (Sciurus lis) and large Japanese field mice (Apodemus speciosus). The previous study showed that the squirrel transported and stored larger walnut seeds farther, whereas the mice transported smaller seeds farther. Divergent selection by different seed dispersers may play an important role in differentiation between local walnut populations, in which understanding seed size heritability is crucial. This study aims to determine how the seed size selected by rodents affects the initial growth of walnuts and to what extent walnut seed size is genetically determined. Sixty walnut seeds were collected from a small seed-producing tree, and 50 walnut seeds from a large seed-producing tree were sown and grown for 18 years. The seed size produced from each tree showed that the heritability of seed size was high (h² = 0.52). When 50 smaller and 50 larger walnut seeds were planted under the same conditions, the dry weight of shoots and roots of the larger seeds was significantly greater than that of the smaller seeds, and root length was also significantly longer in the larger seeds. Seed size is heritable, so if squirrels are inhabiting, larger seeds, which are advantageous for regeneration, will be selected, and walnut trees producing larger seeds will be passed on to the next generation. Because selective hoarding has implications for seed establishment success, inhabiting a suitable seed disperser, the squirrel, is more critical for walnut regeneration than previously assumed.

The two-spotted spider mite, Tetranychus urticae Koch (Acarina, Tetranychidae), is a notorious agricultural pest known for its high dispersal ability. Understanding the dispersal patterns of T. urticae is crucial for studying its population dynamics and assessing the risk of gene dispersal related to acaricide resistance. We investigated the impact of surrounding landscapes on T. urticae occurrence and detected gene flow between nearby apple orchards. Land use data within 0.2–2 km radius buffers of the orchards were extracted and summarized using principal component analysis. The effects of landscape composition on the occurrence of T. urticae in apple orchards were analyzed using a hierarchical Bayesian model that considers spatial autocorrelation. In addition, we conducted a population genetic analysis on samples collected from five orchards. The results indicate that the best model was one at a 200-m scale, revealing a positive correlation between forest area ratio and T. urticae occurrence. The population genetic analysis demonstrated distinct genetic structures within T. urticae populations across different orchards. However, we estimated gene flow among some orchards that were geographically close. These findings suggest that T. urticae may migrate from surrounding landscapes, particularly forests, and nearby orchards to apple orchards. These findings have substantial implications for developing control units based on the gene flow range of the two-spotted spider mite, as well as for assessing the risk of infestation in each orchard.