Inferring demographic processes from the genetic structure of a metapopulation of <Emphasis Type="Italic">Boltonia decurrens</Emphasis>(Asteraceae)

Boltonia decurrens(Asteraceae), a federally listed, threatened floodplain species, requires regular flooding for suitable habitat and seed dispersal. Flood suppression and habitat destruction have resulted in fewer than 25 populations remaining throughout its 400 km range. Because individual populations are widely interspaced (>10 km) and subject to frequent extinction and colonization, seed dispersal along the river, not pollen flow, is likely the primary determinant of population genetic structure. We used neutral genetic markers (isozymes) assayed for fourteen populations to determine which demographic processes contribute to the genetic structure of B. decurrens. Significant genetic differentiation was detected among populations (F _ST=0.098, P< 0.05) but not among regions (F _RT=0.013, P> 0.05), suggesting that long-distance dispersal events occur and involve seed from a small number of populations. Correspondingly, we found no evidence of isolation by distance, and admixture analyses indicate that colonization events involve seed from 3 to 5 source populations. Individual populations exhibited high levels of fixation (mean F _IS=0.192, P< 0.05), yet mean population outcrossing rates were high (t _m=0.87–0.95) and spatial autocorrelation analyses revealed no fine-scale within population structure, indicating that inbreeding alone cannot explain the observed fixation. Rather, genetic bottlenecks, detected for 12 of 14 populations, and admixture at population founding may be important sources of fixation. These observations are consistent with a metapopulation model and confirm the importance of regular flooding events, capable of producing suitable habitat and dispersing seed long distances, to the long-term persistence of B. decurrens.     

CONTRIBUTIONS TO THE MORPHOLOGY OF LEPTOCHILUS AND PARALEPTOCHILUS

Nayar , B. K. (Natl. Bat. Gard., Lucknow, India.) Contributions to the morphology of Leptochilus and Paraleptochilus. Amer. Jour. Bot. 50(4): 301–308. lllus. 1963.—Morphology of L. axillaris and P. decurrens is described; L. axillaris is epiphytic, possessing a wide creeping, soft, parenchymatous rhizome, covered sparsely by peltate paleae, while P. decurrens is rupicaulous, with a short, brittle rhizome having slender sclerenchyma strands and densely covered by basally attached paleae. The vascular cylinder of the rhizome is dictyostelic and composed of a large number of closely placed, thick, vascular bundles with characteristic, thickened, endodermal cells in L. axillaris; it is dictyostelic and composed of a few, slender, distantly placed vascular strands in P. decurrens. Leaf traces are multiple strands which in P. decurrens originate in alternate succession from either side of the dorsal median vascular bundle of the rhizome, but in L. axillaris, from the lateral vascular bundles of the rhizome. The branch traces are paired strands which are lateral in the former and medianly placed in the latter. Scattered sclerenchyma strands occur in the stipe of P. decurrens. Paraphyses are absent in P. decurrens, but filamentous paraphyses occur in L. axillaris. The spores are bilateral and smooth-walled in both, and the prothalli are of the branched, ribbonlike type developing as in Colysis. Prothalli are naked in L. axillaris, but bear sparse mammillate marginal hairs in P. decurrens.     

The effects of nutrient pulsing on the threatened,floodplain species,Boltonia decurrens

Prior to anthropogenic disturbance, the floodplains of the Illinois River (USA) experienced moderate, cyclical flooding; a phenomenon termed a 'flood pulse'. Significant changes in the hydrology of the Illinois River caused by human alteration of the river channel resulted in a decline in populations of Boltonia decurrens, a native, herbaceous floodplain species of the Illinois River Valley and the demography of the species and underlying mechanisms causing the severe decline of B. decurrens are currently being studied. One component of the river flood pulse is the increased availability of nutrients in floodplain soils. We studied the effects of increased nutrient availability on growth and reproduction of B. decurrens and Aster pilosus, a species replacing B. decurrens in the floodplain. In this study, we examined the effects of a spring nutrient pulse and a late summer nutrient pulse, as compared to a control treatment, on rosettes of B. decurrens and A. pilosus grown in three soil types: sandy loam, silty loam and clay. Biomass, plant height, inflorescences per plant, seed production, and seed mass were measured and compared. Individuals of B. decurrens grown in sandy loam, the predominant soil type of the Illinois River Valley, had thegreatest increase in growth and fecundity in response to nutrient pulsing. Total biomass and inflorescences per plant were significantly greater than the control regardless of the timing of the nutrient pulse. Aster pilosus did not exhibit a clear pattern of increased growth and fecundity in a specific soil type or pulse treatment. The early pulse treatment appeared to have a greater effect across the range of soil types than the late pulse treatment; however, it did not seem to influence any particular variable(s) that we measured. A pulse of nutrients benefits B. decurrens more than A. pilosus, particularly in sandy loam. The increased vigor and fecundity of B. decurrens with a nutrient pulse could be a factor contributing to population survival during the period between disturbance events.     

Impact of land use on the ecology of uncultivated plant species in the Rwenzori mountain range,mid western Uganda

Rwenzori mountain range is important for its high diversity of unique species and as a water catchment area and yet very fragile to human interference. The study documented the impact of land use on ecology of uncultivated plant species in the Rwenzori mountain range using Bugoye sub‐county as a reference site. The ecological aspects of the plants studied included distribution, abundance and diversity of the plant species in and around the various land uses as well as in degraded, disturbed and undisturbed areas. Land uses identified were; agriculture, built up area and land with other activities (conservation and abandoned fields). The study revealed that agriculture was the main land use category taking up 69.7% of land use area. Plants distributed in and around the land uses were mainly trees with species diversity of 34.5%. Generally, there was no relationship in the distribution of plant species in degraded, undisturbed and disturbed areas (a = 0.01). In disturbed areas, there was vegetation cover especially of plant species that occur as secondary re‐growth, and in degraded areas, the ground was sparsely covered by primary succession species while in the undisturbed areas, plant species growing in a ‘natural. habitat dominated and most of them were climax species.     

DENSITY-DEPENDENT GROWTH,ECOLOGICAL STRATEGIES,AND EFFECTS OF NUTRIENTS AND SHADING ON BENTHIC DIATOM SUCCESSION IN STREAMS1

The importance of immigration, growth, and competition for nutrients and light in benthic diatom succession was studied in experimental channels in a low-nutrient stream. Diatom accumulation was greater in channels enriched with nitrate and phosphate (NP) than in control channels, reaching about 5 × 10⁶ and 2 × 10⁶ cells-cm^?2, respectively, after 30 d. Shading during late stages of community development reduced algal standing crop. Synedra ulna (Nitz.) Ehr. and Achnanthes minutissima Kütz. were codominant during early stages of community development in both habitats, but succession to an A. minutissima-dominated community was much faster in NP-enriched than in control conditions. Species dominating early stages tended to immigrate quickly, whereas species that increased in relative abundance during community development had either fast growth rates or fast immigration and average growth rates. Decreases in growth rates indicated resource supply became limiting during community development in control and enriched channels. Density-dependent competition was indicated because nutrient concentrations in the water column and light did not decrease during the 30-d study. Species autecologies were defined by effects of nutrient enrichment, shading, and community development on species growth rates. Differing autecologies of early and late succession species indicated that competition for nutrients was more important than competition for light. Species autecologies also indicated ecological strategies. The species most stimulated by nutrient enrichment were least able to maintain growth rates as algal abundances on substrata increased. In addition, these species that best sustained their growth rates during succession tended to have the highest immigration rates, indicating that drift and immigration may have been an important mechanism of persistence for some populations when resources become limiting within thick benthic mats.     

Spontaneous vegetation succession in human‐disturbed habitats: A pattern across seres

Abstract. Vegetation samples from 15 successional seres in various disturbed habitats in the western part of the Czech Republic were analysed to detect possible trends. For particular seres, data on species cover were available from the onset to 10–76 yr of succession. All seres started on bare ground. Species which attained at least 1% cover in any sere in any year were used as input data for Canonical Correspondence Analysis, assessing the effect of time as the environmental variable, for Detrended Correspondence Analysis and TWINSPAN classification. Two distinct groups ofseres were distinguished: ‘ruderal’, occurring in agricultural, industrial or urban landscapes altered by men, usually on fertile sites; and ‘non‐ruderul’, occurring in less altered, mostly forested landscapes, usually on acid, nutrient‐poor and wetter soils. The former type of succession starts with ruderal annuals, being followed by ruderal perennials. In the latter case non‐ruderal clonal perennials prevail from the onset of succession. The landscape frame is emphasized, beside site environmental conditions, as influencing the type of succession. The character of species attaining dominance in succession, participation of dominant woody plants and the character of late successional stages, i.e. features important from the point of view of potential restoration of human‐disturbed habitats, are discussed.     

长白山温带森林生态系统关键要素耦合及演替过程动态模拟

认识生态系统内和生态系统间耦合机制,揭示复合生态系统功能规律,对促进我国山水林田湖草沙项目一体化修复和保护实践具有重要的意义。针对目前修复和保护工程中出现的缺乏系统性、连续性等问题,以拥有丰富生态资源的长白山温带森林生态系统为研究区域,对其关键要素"水土气生"进行耦合建模。通过分析模型的运行机理,探究重要子模块之间的相互作用以及子模块内部生态关键要素的耦合机制,并以长白山温带落叶阔叶林的组成树种和环境因素为对象构建模型参数,通过运行林窗模型1000次,得出长白山温带森林的动态演替过程。结果表明:在森林生态系统的演替过程中,"水土气生"体现为模型中有效积温、干旱天数(低于土壤凋萎点的天数)、土壤可利用氮以及可利用光,这些关键要素之间相互影响,综合决定着每棵树木的更新、生长、死亡过程。模拟结果显示在长白山温带针阔混交林的动态演替过程中0-70 a,70-170 a,170-280 a,280-400 a四个阶段分别有不同的树种组成特征,与真实演替过程比较发现模拟林具有明显的阶段性。白桦、山杨为演替先锋树种,0-70 a期间生物量共占比为55%,70 a后生物量减少最后消失;紫椴、蒙古栎、水曲柳等为过渡树种,这些树种进一步改变了生长环境。红松在170 a前生物量占比仅为3%左右,随演替的发展生物量持续增加,170-280 a期间生物量占比15%,280 a之后红松生物量占总林分的50%。该结果模拟森林动态过程符合演替规律,充分说明多关键要素"水土气生"耦合机制的合理性,对于促进生态系统尺度上多生态要素耦合的相关研究提供了科学理论基础以及方法技术。     

Effect of legume species introduction to early abandoned field on vegetation development

One of the most important areas in ecology is to elucidate the factors that drive succession in ecosystems. The purpose of our study was to assess the effects of legume species (Medicago sativa, Melilotus suaveolens and Astragalus adsurgens) introduction to abandoned arable land on vegetation development in the Loess Plateau, China. Results from our study showed that addition of legume species strongly affected the composition of recently abandoned-field vegetation. Legume species were effective at reducing the number and dominance of natural colonizers (mainly weeds from the seed bank). The introduction of legume species into newly abandoned fields maintained high total cover and above-ground biomass and could improve soil organic carbon and total nitrogen. However, the effects of the treatments were species-specific. Melilotus suaveolens turned out to be severely suppressive to natural colonizers (weed species). Also, Melilotus suaveolens-adding maintained the highest cover and above-ground biomass and was helpful to improve later succession species, e.g. Stipa breviflora and Astragalus polycladus, to invade and establish. Medicago sativa-adding was superior in enhancing the soil organic carbon and total nitrogen. The present results suggested that addition of legume species with greater cover and biomass strongly suppressed the dominance of the weedy species in early succession and the course of old-field succession may be accelerated by introduction of legume species at least temporarily. However, the experimental period was too short to assess to what extent succession may be affected in the longer term.     

An analysis,by bioassay,of the factors which limit algal growth in the P. K. le Roux Impoundment,Orange River,South Africa

Factors which limit algal growth in a turbid man-made impoundment were investigated using natural phytoplankton populations. Results indicate that light was the primary limiting factor with nutrients possibly limiting growth in the event of an increase in water transparency. These results differ from another study which used Selenastrum capricornutum bioassays of water from other areas of the Orange River. The value of natural phytoplankton bioassay techniques is supported.     

Maintaining diversity through intermediate disturbances: evidence from rodents colonizing rehabilitating coastal dunes

Rodents inhabit the coastal dune forests of KwaZulu‐Natal, South Africa. Here habitat rehabilitation following mining of dunes has resulted in coastal dune forest succession similar to that recorded in nonmined forests. We investigated the colonization of rehabilitating stands and evaluate the role of disturbance in maintaining rodent diversity. A trapping programme was established between July 1993 and February 1995 during which rodent colonization, local extinction and species richness were recorded for rehabilitating stands of different ages. Trends in these variables were closely associated with one of three possible outcomes for a disturbed patch over time, with no intervening disturbances following the initial disturbance. Colonization was initially high which led to an increase in species richness. Extinction was lower than colonization, but became higher when the habitat was 3 years old, which led to a decline in richness. We extrapolate this result assuming negligibly small disturbances after the initiation of rehabilitation and suggest that intermediate levels of disturbance maintain rodent species richness in coastal dune forests. Furthermore, our results illustrated species turnover, a prediction of the recorded outcome, with young stands dominated by Mastomys natalensis and older stands by Saccostomus campestris or Aethomys chrysophilus.     

ALLELOPATHIC EFFECTS OF ANDROPOGON VIRGINICUS AND ITS PERSISTENCE IN OLD FIELDS

Aqueous extracts of fresh roots and shoots of Andropogon virginicus (broomsedge) were found to be inhibitory to the growth of seedlings of Amaranthus palmeri, Bromus japonicus, Aristida oligantha, and Andropogon scoparius. The first two species are often important in the pioneer stage of old-field succession in eastern Oklahoma, Aristida is prominent in the second stage, and Andropogon scoparius is important later in succession including the climax Quercus stellata–Quercus marilandica savanna. Sterile dilute extracts of roots and shoots of broomsedge were inhibitory to two test species of Azotobacter, a free living nitrogen fixer, and to two species of Rhizobium, a symbiotic nitrogen fixer. Small amounts of decaying shoots of broomsedge (1 g per 454 g of soil) were very inhibitory to the growth of the four test species listed above and to Amaranthus retroflexus, another species often important in the first stage of succession. Similar amounts of decaying material in soil also significantly inhibited growth and nodulation of the two most important species of legumes in old-field succession in eastern Oklahoma, Lespedeza stipulacea and Trifolium repens. Broomsedge is known to compete vigorously and grow well on soils of low fertility, so the inhibition of nodulation of legumes could help keep the nitrogen supply low and give broomsedge a selective advantage in competition over species that have higher nitrogen requirements. The combined interference of broomsedge against other species resulting from competition and allelopathy could help explain why it invades old fields in 3–5 yr after abandonment from cultivation and remains so long in almost pure stands.     

Recent status and life history traits of endangered soft‐mouth trout,Salmo obtusirostris in the River Neretva catchment (Bosnia and Herzegovina) as a consequence of river alteration

Soft‐mouth trout, Salmo obtusirostris has disappeared from most of its historical distribution range in the River Neretva catchment. Remnant groups are highly fragmented and distribution of the species is restricted to only 15% of it's historical area. The most abundant length range of remnant individuals is between 20 and 40 cm; with a significant decrease of the bigger individuals. Age population structure is dominated by younger fish aged 2, 3 and 4 years, however, age class 4⁺ and 6⁺ predominated in the lower river part. Specimens older than 8 years were not observed, and estimated fishing mortality (F) was high, particularly in the upper part of the river (0.786). The River Neretva soft‐mouth trout population is under heavy pressure including anthropogenic habitat changes and illegal fishery, leading to disappearance in number of formerly inhabited areas. The Upper and Lower Neretva are the only areas where the species is still abundant. However, the collapse of the number of old individuals increases the risk of extinction of the remaining wild subpopulations.     

基于Vortex模型分析金沙江水电开发对圆口铜鱼种群生存力的影响

圆口铜鱼(Coreius guichenoti)是长江上游特有鱼类,研究金沙江梯级水电开发背景下圆口铜鱼种群生存力变化对该物种的保护具有重要意义。Vortex模型在传统种群评估方法的基础上,引入种群年龄结构、繁殖体制、性比等因素,并考虑了环境、灾害、遗传等随机性对种群的影响,可模拟种群数量和生存力变化特征,是一种应用广泛的种群生存力分析模型。基于1981-2021年金沙江圆口铜鱼资源调查数据,采用Vortex模型构建了金沙江中下游干流大规模水电开发前、后两个时期圆口铜鱼种群生存力分析模型,考虑了水电开发下,水温、流速等环境变化对圆口铜鱼种群的影响,对比了两个时期圆口铜鱼种群数量、结构及生存力等。结果表明:水电开发前,严重过度捕捞对圆口铜鱼种群产生了显著威胁,10年内种群数量下降了12.5%,百年内种群内禀增长率为0.085,种群的生存和繁殖能力较稳定,灭绝概率为1%;水电开发后,10年内种群数量下降了42%,百年内种群内禀增长率降至-0.087,灭绝概率增大至36.1%,种群平均灭绝时间为83.7年,圆口铜鱼抵抗环境干扰的种群恢复能力降低,种群生存力受到影响。     

群落演替对夏蜡梅种群分布和数量的影响

对夏蜡梅(Sinocalycanthus chinensis(Cheng et S.Y.Chang)Cheng et S.Y.Chang)所有分布地(浙江临安、天台和安徽绩溪)进行了详细调查,分析夏蜡梅种群面积、密度、结构和群落特征等,并与前人调查结果对比,阐明群落演替对夏蜡梅种群的影响。10余年来,由于国家相关政策的实施(退耕还林、天然林保护以及自然保护区的建立等)以及夏蜡梅分布地林地经营模式的改变,不同夏蜡梅群落呈现发展演替的不同状态,从而对夏蜡梅种群产生了显著影响。从群落类型来看,较为稳定的种群为大明山、西坑、白水坞、捣臼孔种群,种群结构为增长型或稳定型,群落处于乔木或顶级乔木阶段,原生植被保存较好,生境相对稳定,各物种在长期竞争中趋于稳定;直源种群为严重衰退的种群,群落经历了从灌丛阶段向灌乔阶段演化,原来同层次的常绿乔木逐渐形成密集的乔木层,郁闭度高,造成夏蜡梅生长不良甚至死亡,幼苗缺少或数量少,更新困难,此区域的夏蜡梅呈逐渐退化消亡趋势;而溪古坪、龙塘山种群所处群落正是属于这种群落演替的早期阶段,处于衰退过程中种群,不加人工干预也会逐渐退化;而双石边、经过坪等种群虽目前数量多,分布集中,更新良好,但变数最大,一旦人工干扰加剧或消除,则种群结构将快速发生变化,走向消亡的几率极大。该研究结果可为夏蜡梅保护提供科学依据。     

A spatial simulation model for forest succession in the Upper Mississippi River floodplain

A Markov-chain transition model (FORSUM) and Monte Carlo simulations were used to simulate the succession patterns and predict a long-term impact of flood on the forest structure and growth in the floodplain of the Upper Mississippi River and Illinois River. Model variables, probabilities, functions, and parameters were derived from the analysis of two comprehensive field surveys conducted in this floodplain. This modeling approach describes the establishment, growth, competition, and death of individual trees for modeled species on a 10,000-ha landscape with spatial resolution of 1 ha. The succession characteristics of each Monte Carlo simulation are summed up to describe forest development and dynamics on a landscape level. FORSUM simulated the impacts of flood intensity and frequency on species composition and dynamics in the Upper Mississippi River floodplain ecosystem. The model provides a useful tool for testing hypotheses about forest succession and enables ecologists and managers to evaluate the impacts of flood disturbances and ecosystem restoration on forest succession. The simulation results suggest that the Markov-chain Monte Carlo method is an efficient tool to help organize the existing data and knowledge of forest succession into a system of quantitative predictions for the Upper Mississippi River floodplain ecosystem.     

Early spring leaf out enhances growth and survival of saplings in a temperate deciduous forest

Saplings of many canopy tree species in winter deciduous forests receive the major portion of their light budget for their growing season prior to canopy closure in the spring. This period of high light may be critical for achieving a positive carbon (C) gain, thus contributing strongly to their growth and survival. This study of saplings of Aesculus glabra and Acer saccharum in Trelease Woods, Illinois, USA, tested this hypothesis experimentally by placing tents of shade cloth over saplings during their spring period of high light prior to canopy closure in three consecutive years. Leaf senescence began 16 days (year 0) and 60 days (year 1) earlier for shaded A. glabra saplings than control saplings. No change in senescence occurred for A. saccharum. The annual absolute growth in stem diameter of both species was negligible or negative for shaded saplings, but positive for control saplings. Only 7% of the shaded A. glabra saplings were alive after 2 years, while all control saplings survived for 3 years; only 20% of the shaded A. saccharum saplings survived for 3 years, while 73% of control saplings were alive after the same period. Early spring leaf out is a critical mechanism that allows the long-term persistence of saplings of these species in this winter deciduous forest. Studies and models of C gain, growth, and survival of saplings in deciduous forests may need to take into account their spring phenology because saplings of many species are actually “sun” individuals in the spring prior to their longer period in the summer shade.     

下延叉蕨和芽胞叉蕨配子体发育的研究

利用光学显微镜详细观察了叉蕨属(Tectaria)下延叉蕨(Tectaria decurrens)和芽胞叉蕨(T.fauriei)的配子体发育过程,记录了配子体各发育阶段的特征。结果表明:(1)下延叉蕨和芽胞叉蕨的孢子均为单裂缝,具周壁,由周壁形成纹饰,孢子极面观椭圆形,赤道面观豆形或肾形。(2)孢子萌发方式为向心型。(3)原叶体发育方式为三叉蕨型。(4)成熟原叶体心脏形,两翼向斜上方扩展。(5)均具单细胞和多细胞毛状体,在丝状体或片状体阶段出现。研究认为,从配子体发育角度看,叉蕨属是较进化的陆生真蕨类;毛状体的类型、位置和出现时间等特征在叉蕨属种间存在差异,可作为该属种间分类的特征。     

Population extinction risks of three Neotropical small mammal species

The population persistence and extinction probabilities of three small mammal species were analyzed by estimating growth and extinction properties obtained from 10 years of live-trapping data at two different habitat types in semiarid Chile. We used a stochastic formulation with an exponential growth model known as a Wiener-drift process, out of which growth and extinction quantities were estimated. The rodent Phyllotis darwini showed the lowest rates of growth, and the lowest infinitesimal variances, whereas the opposite trend was found for the rodent Akodonolivaceus. The marsupial Thylamys elegans showed intermediate values for growth rates and infinitesimal variances. The rodent P. darwini showed the lowest extinction risk in the study site. We also detected spatial differences between mesic and xeric habitats in the growth rates of P. darwini and T. elegans, and in the extinction risks of the three species studied. Although the population growth of these three species can be approximated by purely stochastic processes, the introduction of density dependence through autoregressive log-linear models reduced the extinction times of all species analyzed. Received: 16 May 1997 / Accepted: 22 January 1998     

Influence of spoil type on afforestation success and natural vegetative recolonization on a surface coal mine in Appalachia,United States

Surface mining has altered a vast land area in the Appalachian Region, threatening highly biodiverse native forest, contributing to habitat fragmentation, and generating severely disturbed sites that are unsuitable for succession to native ecosystems. Although there are many factors that influence species colonization and establishment on these sites, selection of topsoil substitutes suitable for native species is of particular concern. A series of experimental plots was installed in 2005 on a reclaimed mine site in eastern Kentucky, United States, to examine the suitability of three spoil types (unweathered GRAY sandstone, weathered BROWN sandstone, and MIXED sandstone/shale) as topsoil substitutes. Bareroot 1:0 seedlings of four native hardwood species (Fraxinus pennsylvanica, Quercus rubra, Q. alba, and Liriodendron tulipifera) were planted in the spoil. Seed required for ground cover was not applied so that natural colonization could be evaluated. Two years after installation, researchers concluded that tree growth was highest on BROWN; in addition, species richness and ground cover of volunteer vegetation were higher on BROWN. In 2013, tree volume was over 50 times higher in BROWN than GRAY. In addition to planted hardwoods, naturally colonizing vegetation provided nearly 100% cover on BROWN compared to 20% on MIXED and less than 10% on GRAY plots. Species richness of volunteer vegetation continued to be higher on BROWN (41) than GRAY (30) or MIXED (30), with native species comprising 65–70% of total species richness on all plots. Findings suggest that when topsoil substitutes are used, weathered spoils are more favorable to reforestation than unweathered spoil.     

Diversity and composition of Arctiidae moth ensembles along a successional gradient in the Ecuadorian Andes

Andean montane rain forests are among the most species‐rich terrestrial habitats. Little is known about their insect communities and how these respond to anthropogenic habitat alteration. We investigated exceptionally speciose ensembles of nocturnal tiger moths (Arctiidae) at 15 anthropogenically disturbed sites, which together depict a gradient of forest recovery and six closed‐forest understorey sites in southern Ecuador. At weak light traps we sampled 9211 arctiids, representing 287 species. Arctiid abundance and diversity were highest at advanced succession sites, where secondary scrub or young forest had re‐established, followed by early succession sites, and were lowest, but still high, in mature forest understorey. The proportion of rare species showed the reverse pattern. We ordinated moth samples by non‐metric multidimensional scaling using the chord‐normalized expected species shared index (CNESS) index at various levels of the sample size parameter m. A distinct segregation of arctiid ensembles at succession sites from those in mature forest consistently emerged only at high m‐values. Segregation between ensembles of early vs. late succession stages was also clear at high m values only, and was rather weak. Rare species were responsible for much of the faunal difference along the succession gradient, whereas many common arctiid species occurred in all sites. Matrix correlation tests as well as exploration of relationships between ordination axes and environmental variables revealed the degree of habitat openness, and to a lesser extent, elevation, as best predictors of faunal dissimilarity. Faunal differences were not related to geographical distances between sampling sites. Our results suggest that many of the more common tiger moths of Neotropical montane forests have a substantial recolonization potential at the small spatial scale of our study and accordingly occur also in landscape mosaics surrounding nature reserves. These species contribute to the unexpectedly high diversity of arctiid ensembles at disturbed sites, whereas the proportion of rare species declines outside mature forest.