Conspecific thistle plant selection by a herbivorous ladybird beetle, Epilachna pustulosa

Host selection by Epilachna pustulosa Kôno (Coleoptera: Coccinellidae) was surveyed in an area of about 130 ares, focusing on the role of the spatial distribution pattern of the host plant, thistle Cirsium kamtschaticum Ledeb. (Asteraceae) and the environmental conditions of habitats where thistle plants were growing. A total of 198 thistle clones were found in the area studied, and approximately 40% showed some degree of E. pustulosa infestation by July. Eggs were only oviposited on thistle clones that were fed on by adults. Adult beetles and egg masses of E. pustulosa showed an aggregated distribution in the earlier season (June) among thistle clones. The distribution of adults became more random (but still aggregated) by the later season (July), along with an increase in the number of infested clones. Multiple logistic regression analyses revealed that clone size and soil moisture were consistently important for the beetle's choice of clones to feed on. The other logistic regression analyses indicated that thistle‐clone size and sunlight condition influenced egg distribution. Thistle clone selection by E. pustulosa changed with season from a rather strict selection in June to a more obscure one in July, expanding the range of thistle clones used as feeding and oviposition substrate.     

Field-cage experiments on host fidelity in a pair of sympatric phytophagous ladybird beetles

Using field cages, we tested the hypothesis that two phytophagous ladybird beetles, Henosepilachna niponica (Lewis) and Henosepilachna yasutomii Katakura (Coleoptera: Coccinellidae: Epilachninae), are reproductively isolated from each other by their host fidelity alone. We planted host plants of the two species [the thistle Cirsium alpicola Nakai (Asteraceae) for H. niponica and the blue cohosh, Caulophyllum robustum Maxim. (Berberidaceae), for H. yasutomii] in 7 × 7 m cages (BT cages), and planted the two host plants and the beetles’ common food plant, the Japanese nightshade, Solanum japonense Nakai (Solanaceae), in other cages (BJT cages). We then released overwintered reproducing beetles into these cages and recorded their dispersal, the distribution of egg masses, and the incidence of copulations. In BT cages, the beetles moved almost exclusively between their own host plants, and all females laid eggs exclusively on their own host plants. In BJT cages, the beetles moved between their own host plants and the Japanese nightshade, resulting in occasional interspecific mating on the same nightshade plant. Females of both species laid eggs on their own host plants as well as on the Japanese nightshade. These results indicate that host fidelity functions as a strong barrier against gene flow between H. niponica and H. yasutomii. However, this barrier can easily be broken down if a third plant species bridges the beetle populations.     

Adaptive change and conservatism in host specificity in two local populations of the thistle-feeding ladybird beetle Epilachna niponica

We investigated geographic differences in the host specificity of Epilachna niponica Lewis (Coleoptera: Coccinellidae). The Yuwaku population feeds mainly on Cirsium matsumurae Nakai (Asteraceae) and secondarily on Cirsrium kagamontanum Nakai. The Asiu population, located 150 km away from the Yuwaku, feeds exclusively on C. ashiuense Yokoyama et T. Shimizu. Under laboratory conditions, we examined the differences between the two populations in adult feeding acceptance, adult feeding preference, and larval performance, using several closely related thistle species and varieties, including their native hosts. In the Asiu population, adult beetles clearly avoided the host of the Yuwaku population, C. kagamontanum, and no larvae were able to complete their development, whereas in the Yuwaku population, adults accepted and even preferred it to some other thistle species, and about 10% of first instar larvae became adults. This indicates that the Yuwaku population evolved its feeding preference and physiological adaptation to C. kagamontanum through a utilization of this low‐ranked host under natural conditions. Apart from C. kagamontanum, the two populations showed a similar host susceptibility pattern, indicating that this ladybird beetle has a conserved hierarchy in feeding preference and growth performance. We also observed adult leaf choice behavior when given different thistle species, and found that difference in biting rate after palpation determined the leaf areas consumed, implying that factors on the leaf surface played an important role in the choice.     

Consequences of adult size for survival and reproductive performance in a herbivorous ladybird beetle

Abstract.

• 1 A univoltine herbivorous ladybird beetle Epilachna niponica (Coleoptera: Coccinellidae) shows a large variation in adult size within a population.
• 2 Large adults had higher survival from emergence to the reproductive season, and the size-dependent adult survival was most apparent during hibernation. On the other hand, adult survival during pre-hibernation contributed little to size-dependent overall survival.
• 3 Neither reproductive lifespan nor lifetime fecundity were a function of adult size, though large females produced larger size of egg batches.
• 4 Size of adult beetles was significantly reduced by leaf damage to plants on which they grew up on larval stage. Since leaf herbivory increases through the season, late emerged adults that were subjected to food deterioration during the larval period were smaller than early-emerged individuals.

     

Host plant suitability of a recently naturalized thistle Cirsium vulgare (Asteraceae) for a phytophagous ladybird beetle,Epilachna pustulosa (Coleoptera: Coccinellidae)

The phytophagous ladybird beetle, Epilachna pustulosa Kôno occurs mainly on the thistle Cirsium kamtschaticum Ledeb. In recent years, we have confirmed feeding and oviposition by E.pustulosa, and some degree of larval development of this beetle, on a naturalized congeneric thistle, Cirsium vulgare (Savi) Tenore. In this study, we assessed the host suitability of C.vulgare for E.pustulosa, using larval rearing and simple food choice tests, by comparing the performance on, and preference for, their legitimate host C.kamtschaticum. All experiments were initiated in July, when the utilization of C.vulgare by E.pustulosa became obvious. For larval performance, E.pustulosa showed a lower eclosion rate, shorter developmental duration and smaller body size when reared on C.vulgare than on C.kamtschaticum. Cirsium vulgare appeared to be a less adequate larval food than C.kamtschaticum. Adult feeding preference was altered seasonally; females preferred C.kamtschaticum to C.vulgare in a food choice test conducted in early July, whereas they showed the opposite preference in tests conducted in mid and late July. The utilization of C.vulgare by E.pustulosa appeared to be induced by qualitative deterioration of C.kamtschaticum leaves in July, which resulted in increased dispersion of adult beetles.     

Detection of ecological hybrid inviability in a pair of sympatric phytophagous ladybird beetles (Henosepilachna spp.)

Ecological speciation is a process by which reproductive isolation evolves as the result of divergent natural selection between populations inhabiting distinct environments or exploiting alternative resources. Ecological hybrid inviability provides direct evidence for ecological speciation. To detect ecological hybrid inviability, we examined survival rates to the second instar of F1 hybrids and backcross hybrids in a pair of sympatric phytophagous ladybird beetles, Henosepilachna niponica Lewis and Henosepilachna yasutomii Katakura (Coleoptera: Coccinellidae: Epilachninae), reared on their respective host plants, thistle [Cirsium alpicola Nakai (Asteraceae)] and blue cohosh [Caulophyllum robustum Maxim. (Berberidaceae)], and on a common food plant, Japanese nightshade [Solanum japonense Nakai (Solanaceae)]. Hybrid larvae reared on leaves of the Japanese nightshade always had high rates of survival, irrespective of the crossing type of their parents, suggesting a lack of intrinsic hybrid inviability between the two species. In contrast, survival rates on thistle and blue cohosh varied greatly. On blue cohosh, the survival rate of F1 hybrids was nearly as high as that of H. yasutomii, but on thistle, survival was significantly lower than of H. niponica. Survival rates of backcross hybrids on the two host plants were intermediate between those of the parents, showing a reversed rank order of different types of backcross hybrids on the two food plant species. These results suggest that ecological hybrid inviability exists between H. niponica and H. yasutomii, although the two species do not show intrinsic hybrid inviability. Thus, our study supports the hypothesis that H. niponica and H. yasutomii underwent ecological speciation by divergent selection.     

Variable correspondence of female host preference and larval performance in a phytophagous ladybird beetle Epilachna pustulosa (Coleoptera: Coccinellidae)

Genetic and environmental factors causing intraspecific variation of the thistle Cirsium kamtschaticum Ledeb. as a host plant of the phytophagous ladybird Epilachna pustulosa Kôno were investigated through simple food-choice tests and rearing of larvae. Two thistle clones (T1U₁ and T4H₂) were used, originally growing approximately 12 km apart. A previous study showed that adult female ladybirds preferred T1U₁ to T4H₂, and that larval performance was better on T1U₁, when leaves from the clones in situ were examined. The two clones retained their characteristics with respect to beetle preference after transplantation into a common garden. However, the difference between T1U₁ and T4H₂ with respect to larval performance was reduced after the transplantation. When leaves from shoots of T1U₁ exposed to different sunlight intensities were offered, adult female ladybirds did not show obvious preferences. Larval eclosion rates increased significantly with the increase in leaf sunlight intensity exposure. These results suggest strongly that both genetic and environmental factors are involved in interclonal variation of thistle quality in beetle preference and/or performance. It is suggested that the quality of thistle leaves for larval performance is largely affected by environmental factors, while leaf quality for beetle preference may be determined strictly by genetic factors. Under certain conditions, E. pustulosa females may behave maladaptively, preferring plants not appropriate for larval growth, or not choosing plants appropriate for the larval growth.     

Individual variation in two host plants of the ladybird beetle,Epilachna pustulosa (Coleoptera: Coccinellidae)

Individual variation in two species of host plants (thistle,Cirsium kamtschaticum, and blue cohosh,Caulophyllum robustum) of the herbivorous ladybird beetleEpilachna pustulosa was examined under laboratory conditions for their acceptability to adult beetles as a food resource, for adult preference and for larval performance. When clones of these plants were subjected to non-choice tests using posthibernating female beetles, there was found to be significant intraspecific variation among clones in terms of their acceptability, but interspecific variation was not detected. Significant intraspecific as well as interspecific variation were frequently detected in the two host plants when clones of these plants were subjected to choice tests using posthibernating female beetles; the magnitude of interspecific plant variation for beetle preference is not necessarily larger than that of intraspecific plant variation. Individual variation across plant species with respect to beetle larval performance was also significant. A positive correlation between adult preference and larval performance is suggested across the two taxonomically remote host plant species, thistle and blue cohosh, although this needs further investigation.     

Distribution and host specificity of the thistle‐feeding tortoise beetle Cassida vibex (Coleoptera: Chrysomelidae) in southwestern Hokkaido,northern Japan

The thistle‐feeding tortoise beetle Cassida vibex (Coleoptera: Chrysomelidae) is widespread in the Palearctic region. In Japan, this species has been recorded only from the largest island, Honshu. Here we report the occurrence of this species on Hokkaido, the most northern main island of Japan, along with detailed distributional records from the southwestern part of the island (southern Oshima Peninsula) and information on host plants. We also present the results of laboratory experiments on adult feeding preference and larval developmental performance to determine the specificity of C. vibex for four thistle species (Cirsium grayanum, Cir. alpicola, Cir. yezoense and Cir. aomorense; Asteraceae) common in southwestern Hokkaido. Cassida vibex was detected at only four sites among 97 sites investigated on the Oshima Peninsula, in strong contrast to the common occurrence of the congeneric thistle feeder C. rubiginosa (74 of 97 sites). Cassida vibex was found mainly on Cir. alpicola in the wild, but adult beetles showed no feeding preference for this or three other thistle species when given a choice in the laboratory. Larval performance of C. vibex was similar on Cir. alpicola, Cir. yezoense and Cir. aomorense but significantly lower on Cir. grayanum. Since Cir. alpicola often forms large clumps of individual plants, whereas Cir. yezoense and Cir. aomorense are scattered in their habitats, and C. vibex was collected only at sites where there were dense patches of Cir. alpicola, we postulate that the persistence of C. vibex is possible only where a substantial amount of suitable host plants is available.     

小叶、中间和柠条三种锦鸡儿的分布式样及其生态适应

确定了小叶锦鸡儿、中间锦鸡儿和柠条锦鸡儿3种植物的分布式样:小叶锦鸡儿为蒙古高原东部-F松辽平原西部-华北山地分布种,中间锦鸡儿为东戈壁-鄂尔多斯高原-黄土高原北部分布种,柠条锦鸡儿为南阿拉善-西鄂尔多斯分布种。小叶锦鸡儿适应分布于蒙古高原典型草原带和森林草原带以及华北山地落叶阔叶林带,在草原带高平原上可形成灌丛化草原的景观,在草原带的沙地上可形成以小叶锦鸡儿为建群种的沙地灌丛植被;中间锦鸡儿适应分布于蒙古高原的荒漠化草原及草原化荒漠带、鄂尔多斯高原的典型草原和荒漠化草原带的沙地及梁地上、黄土高原北部的黄土丘坡上,常形成以中间锦鸡儿为建群种的沙地灌丛植被;柠条锦鸡儿则适应分布于草原化荒漠和典型荒漠带的固定和半固定沙地上。近缘的3种锦鸡儿的地带性分布从东至西或从北向南形成明显的有规律的地理替代分布格局。     

中国外来入侵植物的等级划分与地理分布格局分析

基于文献报道、野外调查、标本记录和必要的分类学考证, 整理出我国外来入侵植物72科285属515种。根据外来入侵种的生物学与生态学特性、自然地理分布、入侵范围以及所产生的危害, 将其划分为5类: 即恶性入侵类(34种)、严重入侵类(69种)、局部入侵类(85种)、一般入侵类(80种)和有待观察类(247种)。通过地理分布格局分析, 中国外来入侵植物主要分布在我国西南及东部沿海地区, 并进一步扩散到内陆各省。中国外来入侵等级划分和地理分布格局可以作为外来入侵植物风险防范和管理的依据。本工作提供我国外来入侵植物的本底资料的同时, 还对主要外来入侵植物的管理提出了具体建议。     

Modeling impacts of climate change on the geographic distribution of medicinal plant Fritillaria cirrhosa D. Don

Fritillaria cirrhosa D. Don is a renowned traditional Chinese medicine plant that is mainly distributed in the southeastern margin of the Qinghai–Tibet Plateau. The overexploitation in the recent years has led to a sharp decline of this undomesticated resource. Analyzing the impact of climate change on the geographic distribution of F. cirrhosa is meaningful for its conservation and domestication. In this study, the maximum entropy model (Maxent) was used to simulate the distribution of F. cirrhosa in relation to the current and future climatic conditions. The maximum temperature of the warmest month (Bio 5) and the precipitation of the warmest quarter (Bio 18) were the two most important bioclimatic variables determining the distribution of F. cirrhosa. Based on the predicted level of climatic warming, a further reduction of the geographic distribution of F. cirrhosa is to be expected. This study demonstrated the necessity and urgency of establishing more effective ways to protect the natural F. cirrhosa resources and developing artificial cultivation methodology.     

中国亚热带地区4种极危冷杉属植物的地理分布特征及其与气候的关系

通过野外实地调查和文献调研, 分析4种极危冷杉属(Abies)植物的地理分布现状和特征, 构建其分布区的气候数据库, 采用国际上常用的研究植被与气候关系的指标和方法, 定量分析冷杉属地理分布与水热条件的关系, 并通过因子分析方法确定影响冷杉属地理分布的限制性气候因子。结果表明: 1)百山祖冷杉(Abies beshanzuensis)、梵净山冷杉(A. fanjingshanensis)、元宝山冷杉(A. yuanbaoshanensis)和资源冷杉(A. beshanzuensis var. ziyuanensis)零星分布于我国亚热带地区, 水平分布范围为25°25′-27°55′ N, 108°42′-119°12′ E , 分布范围狭窄; 垂直分布范围为1363-2390 m, 均分布于山体上部。海拔上限高度随着经度的减小而增加。2)整个分布区的气温较低, 年平均气温为7.4-11.2 ℃; 降水较为充沛, 年降水量为1265.4-1945.7 mm, 其中生长季降水量占74.78%; 湿度较大, 年相对湿度为77%-86%。气候指标范围狭窄, 表明对水热条件要求很高。分布区寒冷指数较低, 限制其垂直向下扩散, 呈现局限分布于山体上部的现状。3) 4种冷杉各分布区的气候条件基本相近, 梵净山冷杉分布区气温相对偏低, 元宝山冷杉分布区湿度相对偏大。4) 3个气候因子对这4种冷杉的地理分布影响较大, 其作用排序为: 低温因子>极端低温因子>湿度因子。在全球气候变暖的大背景下, 这4种冷杉自然分布区的适宜生境将进一步缩小, 直至物种灭绝, 急需开展迁地保护工作。     

Occurrence of apomictic conspecifics and ecological preferences rather than colonization history govern the geographic distribution of sexual Potentilla puberula

The geographic distribution of sexual‐apomictic taxa (i.e., comprising individuals usually reproducing either sexually or asexually via seeds) is traditionally thought to be driven by their ecological preferences and colonization histories. Where sexuals and apomicts get into contact with each other, competitive and reproductive interactions can interfere with these factors, an aspect which hitherto received little attention in biogeographic studies. We disentangled and quantified the relative effects of the three factors on the distribution of tetraploid sexuals in Potentilla puberula in a latitudinal transect through the Eastern European Alps, in which they are codistributed with penta‐, hepta‐, and octoploid apomictic conspecifics. Effects were explored by means of binomial generalized linear regression models combining a single with a multiple predictor approach. Postglacial colonization history was inferred from population genetic variation (AFLPs and cpDNA) and quantified using a cost distance metric. The study was based on 235 populations, which were purely sexual, purely apomictic, or of mixed reproductive mode. The occurrence of apomicts explained most of the variation in the distribution of sexuals (31%). Specifically, the presence of sexual tetraploids was negatively related to the presence of each of the three apomictic cytotypes. Effects of ecological preferences were substantial too (7% and 12% of the total variation explained by ecological preferences alone, or jointly with apomicts’ occurrence, respectively). In contrast, colonization history had negligible effects on the occurrence of sexuals. Taken together, our results highlight the potentially high impact of reproductive interactions on the geographic distribution of sexual and apomictic conspecifics and that resultant mutual exclusion interrelates to ecological differentiation, a situation potentially promoting their local coexistence.     

皖南凹耳臭蛙地理分布格局与生境选择

凹耳臭蛙(Odorrana tormota)是一种小型山溪蛙类,由于叫声独特,种内具有超声通讯功能而引起国内外相关专家的广泛关注。首次针对皖南凹耳臭蛙地理分布、生境选择以及人为干扰强度对种群密度的影响进行了研究。共调查了9县1区32条不同的山溪,发现其中的16个有凹耳臭蛙分布,除黄山区的香溪和浮溪具文献记录外,其余14个分布点均为首次报道。基于现存凹耳臭蛙分布点的水系关系,推测该物种在皖南的分布呈现出以青弋江、新安江和水阳江三大水系为纽带、间断分布的格局。对其中10个分布点222只凹耳臭蛙生境选择的统计结果表明,在夜晚活动周期内,该物种对乔木、灌木丛、草本植物、岩石、沙滩和倒伏朽木等不同生境的选择具有显著差异(F5,54=25.75,P0.001),栖息在草本植物和灌丛中蛙的数量明显多于栖息在其它几种生境类型中的蛙类。暗示溪流沿岸的草本植物和灌丛对该物种的生存和繁衍具有重要意义,乔木对其非活动周期的隐蔽可能具有不可替代的作用。根据人类活动对其栖息地破坏程度,将人为干扰程度划分为强、中和弱3种不同强度,对不同干扰强度下种群相对密度进行单因素方差分析。结果表明,中等干扰强度下的种群密度显著高于其它两种强度下的种群密度(F2,13=8.155,P=0.005)。推测适度的人为干扰可能增加了栖息地内昆虫的种类和数量,对蛙类的生存和繁衍更为有利。但随着人为干扰强度的增强,对溪流沿岸植被的破坏更为剧烈,种群密度显著下降。     

濒危植物长苞铁杉的地理分布和资源现状及致危因素分析

根据野外调查的结果,对福建天宝岩国家级自然保护区马石坑、广东南岭国家级自然保护区老蓬顶、湖南莽山国家级自然保护区泽子坪和鬼子寨、广西猫儿山国家级自然保护区小老山、贵州梵净山国家级自然保护区鱼坳、湖南黄桑国家级自然保护区源头山、湖南城步县奇山和江西大余县石溪的长苞铁杉〔Nothotsuga longibracteata(W.C.Cheng)Hu ex C.N.Page〕居群的生境和生存现状进行了比较分析。结果表明:长苞铁杉的地理分布相对狭窄,多呈零星或小片分布;该种正面临分布区缩小和居群规模下降,甚至濒临灭绝的危险。在长苞铁杉集中分布的这些区域,大多数居群面临生存威胁;各居群的个体数量有较大差异,其中,天宝岩居群最大,长苞铁杉数量达几千株;石溪居群和源头山居群最小,长苞铁杉数量只有几十株。全球气候变化、人类活动影响和本身更新困难是导致长苞铁杉濒危的原因,其中,人类活动影响是长苞铁杉致危的直接原因。根据长苞铁杉生存状况,建议对其伴生的阔叶树进行疏伐,适当开辟林窗,有利于长苞铁杉的更新;自然保护区的建立对长苞铁杉的保护发挥了重要的作用,而在其他非保护区的分布区,也应加大宣传力度并采取相应保护措施;实施迁地保护可以有效保护长苞铁杉这一珍稀树种。     

Physiological synecology of tree species in relation to geographic distribution and ecophysiological parameters at the Atlantic forest periphery in Brazil: an overview

This paper provides a synthesis of the three papers published in the series Ecophysiology of selected tree species in different plant communities at the periphery of the Atlantic forest of SE – Brazil (Trees, this issue). We reviewed data obtained for seven tree species, belonging to the legume family and the genus Clusia of the Clusiaceae. These groups were chosen because legumes are the most abundant tree species in the Atlantic forest complex (except in the open restingas), and the genus Clusia is reportedly of utmost ecological importance as nurse plants in several habitats of the complex. These species were surveyed along one or more of several forest and open habitats at the margin of the Atlantic rain forest (open restingas, restinga dry forest, inselberg, semideciduous dry forest) and indicated the following general patterns: (1) at the intraspecific level, ecophysiological performance often (but not always) varied largely in both time and space; (2) at the interspecific level, ecophysiological performance was often (but not always) related positively to species dominance in the community; and (3) at both levels, ecophysiological performance was not related to the geographic distribution patterns, i.e., generalists and specialists did not form groups of similarly behaving plants in regard to ecophysiology. We discuss the implications of these findings, compare them with earlier studies, and suggest that ecophysiological research in the Atlantic rain forest complex could enhance its explanatory power by increasing spatial and temporal scales of observation.     

A new look at geographic and phylogenetic relationships within the species group surrounding Octopus vulgaris (Mollusca, Cephalopoda): indications of very wide distribution from mitochondrial DNA sequences

The distribution of Octopus vulgaris has not yet been completely clarified. For a long time, a cosmopolitan distribution with unknown distribution limits had been assumed. This assumption has recently been questioned and it has been postulated that the distribution is restricted to the Mediterranean and the northeastern Atlantic. However, as our previous studies show, the existence of O. vulgaris can be confirmed for the Mediterranean and the whole eastern Atlantic, and evidence is provided for its occurrence in the western Atlantic. The aim of the present work is to extend our previous data matrix and to clarify whether O. vulgaris exists in the northwestern Pacific. Therefore, the sequence variation in ostensible O. vulgaris from 13 localities in the Mediterranean (France), the Atlantic Ocean [Lanzarote, Senegal, South Africa (Atlantic, Indian Ocean), Tristan da Cunha, north, middle and south Brazil], the Caribbean Sea (Venezuela) and the Pacific Ocean (Taiwan, Japan and Costa Rica) was examined using the mitochondrial genes coding for the 16S rRNA and cytochrome oxidase subunit III (COIII). Sequence divergence was relatively low between populations of O. vulgaris from the Mediterranean, the eastern and western Atlantic (except north Brazil), Venezuela, Taiwan and Japan compared with other species of the genus Octopus . Trees constructed by using maximum likelihood, neighbour joining and maximum parsimony algorithms (PAUP) show the above-mentioned populations from the Mediterranean, the western and eastern Atlantic, Venezuela and the northwestern Pacific (Japan and Taiwan) as a monophyletic cluster. Thus, even if the Octopus vulgaris -like octopus from north Brazil should turn out a cryptic species, the data of this work not only support our hypothesis of the distribution of O. vulgaris in the Mediterranean, the eastern and western Atlantic but also show that O. vulgaris is present in the northwestern Pacific, namely in the waters of Taiwan and Japan.     

Spatial heterogeneity distribution of soil total nitrogen and total phosphorus in the Yaoxiang watershed in a hilly area of northern China based on geographic information system and geostatistics

Soil total nitrogen (STN) and total phosphorus (STP) are important indicators of soil nutrients and the important indexes of soil fertility and soil quality evaluation. Using geographic information system (GIS) and geostatistics, the spatial heterogeneity distribution of STN and STP in the Yaoxiang watershed in a hilly area of northern China was studied. The results showed that: (1) The STN and STP contents showed a declining trend with the increase in soil depth; the variation coefficients (C_v) of STN and STP in the 0‐ to 10‐cm soil layer (42.25% and 14.77%, respectively) were higher than in the 10‐ to 30‐cm soil layer (28.77% and 11.60%, respectively). Moreover, the C_v of STN was higher than that of STP. (2) The maximum C₀/(C₀ + C₁) of STN and STP in the soil layers was less than 25%, this indicated that a strong spatial distribution autocorrelation existed for STN and STP; and the STP showed higher intensity and more stable variation than the STN. (3) From the correlation analysis, we concluded that the topographic indexes such as elevation and slope direction all influenced the spatial distribution of STN and STP (correlation coefficients were 0.688 and 0.518, respectively). (4) The overall distribution of STN and STP in the Yaoxiang watershed decreased from the northwest to the southeast. This variation trend was similar to the watershed DEM trend and was significantly influenced by vegetation and topographic factors. These results revealed the spatial heterogeneity distribution of STN and STP, and addressed the influences of forest vegetation coverage, elevation, and other topographic factors on the spatial distribution of STN and STP at the watershed scale.