Keystone predators (eastern newts, Notophthalmus viridescens) reduce the impacts of an aquatic invasive species

Predation, competition, and their interaction are known to be important factors that influence the structure of ecological communities. In particular, in those cases where a competitive hierarchy exists among prey species, the presence of certain keystone predators can result in enhanced diversity in the prey community. However, little is known regarding the influence of keystone predator presence on invaded prey communities. Given the widespread occurrence of invasive species and substantial concern regarding their ecological impacts, studies on this topic are needed. In this study I used naturalistic replications of an experimental tadpole assemblage to assess the influence of predatory eastern newts, Notophthalmus viridescens, on the outcome of interspecific competition among native and nonindigenous tadpoles. When newts were absent, the presence of the tadpoles of one invasive species, the Cuban treefrog, Osteopilus septentrionalis, resulted in decreased survival and growth rate of the dominant native species, Bufo terrestris, and dominance of the tadpole assemblage by O. septentrionalis. However, the presence of one adult newt generally reduced or eliminated the negative impacts of O. septentrionalis tadpoles, resulting in comparable survival and performance of native species in invaded and noninvaded treatments. Differential mortality among the tadpole species suggests that newts preyed selectively on O. septentrionalis tadpoles, supporting the hypothesis that newts acted as keystone predators in the invaded assemblage. The presence of nonindigenous larval cane toads, Bufo marinus, did not significantly affect native species, and this species was not negatively affected by the presence of newts. Collectively, these results suggest that eastern newts significantly modified the competitive hierarchy of the invaded tadpole assemblage and reduced the impacts of a competitively superior invasive species. If general, these results suggest that the presence of certain species may be an essential factor regulating the ecological impacts of biological invasions.     

Characterization of diatom assemblages in mid-altitude streams of NW Italy

Following the European Water Framework Directive, this study aims to be the first step to (i) identify diatom type assemblages in unpolluted streams in NW Italy, and (ii) find which ecological factors explain most of the variation. To achieve this, we collected physical, chemical and benthic community data from four streams in NW Italy from 2001 to 2004, for a total of 72 samples. All sampling sites were between 200 m a.s.l. and 800 m a.s.l., but differed in the dominant lithological substrate, i.e. alluvial or siliceous. Relationships between diatom communities and environmental factors were examined using canonical correspondence analysis (CCA), while Indicator Species Analysis was used to define characterizing species and accompanying species of three environmental groups identified by CCA: (1) high water quality and medium saline content, (2) high water quality and low saline content, (3) poor water quality. The diatom assemblages of the three groups of sites differed significantly, as shown by the Multi-Response Permutation Procedure. There were strong correlations between diatoms and environmental factors, especially chlorides (also highly correlated with sulphates and carbonate hardness), nitrate concentration and conductivity. The group 1 assemblage was typical of the alluvial Alpine streams with medium saline content and was characterized by mostly oligosaprobic/β-mesosaprobic taxa such as Cymbella affinis, Diatoma ehrenbergii and Staurosira pinnata. The species assemblage found in the siliceous Alpine rivers with good water quality make them suitable reference sites for a benthic diatom community. Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users Handling editor: K. Martens     

Diversity and composition of estuarine and lagoonal fish assemblages of Socotra Island,Yemen

Estuarine and lagoonal surveys of Socotra Island and selected sites on the Hadhramout coast of Yemen were conducted with the objective of documenting and analysing fish diversity and assemblage structure. A total of 74 species in 35 families were recorded, among which 65 species in 32 families were from Socotra and 20 species in 17 families were from mainland Yemen. Twenty‐one species represent new faunal records for Socotra. Including historic records re‐examined in this study, the total fish species richness of estuaries and lagoons of Socotra Island reaches 76, which is relatively high compared to species inventories of well‐researched coastal estuaries in southern Africa. Five species dominate the occurrence and abundance frequencies: Terapon jarbua, Hyporhamphus sindensis, Aphanius dispar, Ambassis gymnocephala and Chelon macrolepis. Rarefaction and extrapolation analyses suggest that the actual number of fish species inhabiting some of those estuaries might be higher than the one observed. Thus, additional sampling at specific sites should be conducted to record other less conspicuous species. Ordination and multivariate analyses identified four main distinct assemblage clusters. Two groups are geographically well structured and represent northern Socotra and mainland Yemen, respectively. The other two assemblage groups tend to be determined to a greater extent by the synchrony between physical (e.g. estuary opening periods) and biological (e.g. spawning and recruitment periods) variables than by geographical location. Finally, the single intertidal lagoon of Socotra represents by itself a specific fish assemblage. The high proportion of economically important fish species (38) recorded underscores the paramount importance of these coastal water bodies as nursery sites, and for sustaining vital provisioning ecosystem services.     

Species traits and catchment‐scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

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Isozyme evidence for host races of the fungus Atkinsonella hypoxylon (Clavicipitaceae) infecting the Danthonia (Poaceae) complex in the southern Appalachians

On granite outcrops around Highlands, North Carolina four sympatric Danthonia grass species are infected by the fungus Atkinsonella hypoxylon (Clavicipitaceae). Danthonia epilis and D. sericea (rare hosts) are infected only in this small region, although they range more widely, while D. compressa and D. spicata (widespread hosts) are infected throughout their ranges in eastern North America. To test the hypothesis that infection of the rare hosts has recently spread from the widespread hosts, the genetic structure of fungal populations on different Danthonia hosts was investigated by isozyme electrophoresis. Two hundred isolates were collected from 46 sites and analyzed for ten polymorphic isozyme loci to examine levels of variation, genetic differentiation, and gene flow among fungal populations infecting different hosts. Genetic identities (I) indicated that isolates from within each of the widespread and rare host species pairs were homogeneous (I > 0.99), but the pairs were highly differentiated (0.66 < I < 0.69). With one exception there was no overlap in fungal genotypes isolated from the widespread hosts (12 genotypes) vs. the rare hosts (seven genotypes). Two plants of D. compressa growing sympatrically with infected D. epilis at one site were infected with a genotype characteristic of the latter species. Estimates of gene flow suggest a high degree of host-mediated reproductive isolation in A. hypoxylon, indicating that the fungus forms distinct, long-standing host races or sibling species in the southern Appalachians.     

Spatiotemporal Variation in Fish Assemblage Structure in Tropical Floodplain Creeks

Biotic assemblages of aquatic floodplain systems have great potential to randomly reshuffle during annual flood periods, and have been described both as stochastically and deterministically assembled. However, only a limited number of studies have been conducted in relatively few habitat types. To evaluate large-bodied fish assemblage structure of floodplain creeks, we used experimental gill nets to sample fishes at sites spaced at even intervals within three creeks in consecutive dry seasons. A total of 60 species were collected, 41 of which were collected both years. The most frequently collected species were piscivores and algivores/detritivores. Multivariate analysis suggested non-random patterns of assemblage structure in both years. Correspondence analysis (CA) of the species abundance-by-site matrix for 2001 suggests species assemblages were most similar among sites within the same creek regardless of depth or longitudinal position. Discriminant function analysis (DFA) correctly predicted 100% of samples based on creek identity, and species ordination scores revealed creek-specific species subsets. In 2002, CA and DFA did not distinguish creeks based on species assemblages. Instead, we observed a significant positive relationship between assemblage composition and site depth and position along the creek longitudinal gradient. Assemblages were most similar among sites of comparable depth and longitudinal position, regardless of creek identity. Predators occurred almost exclusively at mouth and mid-reach sites. Flood duration prior to our 2002 sampling period was prolonged due to abnormally heavy rainfall in November and December 2001 (typically the falling-water period), and may account for the observed inter-annual variation in fish assemblage structure.     

Diversity and ecology of algae from the Nahal Qishon river,northern Israel

In 59 samples of periphyton and phytoplankton collected in 2002 - 2003 from the Nahal Qishon (Qishon River), northern Israel, we found 178 species from seven divisions of algae and cyanoprocaryotes. Diatoms, clorophytes, and cyanoprocaryotes prevail. Nitzschia and Navicula (Bacillariophyta) are the most abundant. Most of the species are cosmopolitan or widespread, except Lagynion janei (Chrysophyta), which is endemic for the Mediterranean Realm. About 17% of species (26) are new for Israel and five of them represent the first recorded genera: Crinalium endophyticum Crow, Actinocyclus normanii (Gregory) Hustedt, Rhizoclonium hieroglyphicum (Agardh) Kütz (Chlorophyta), Lagynion janei Bourelly, and Stylococcus aureus Chodat. Most of them come from a rare riverine assemblage with red alga Audouinella pygmea, as well as from the estuarine assemblage. Alkaliphiles predominate among the indicators of acidity, with few acidophiles confined to the communities under the impact of industrial wastes. Among the indicators of salinity, most numerous are the oligohalobien-indifferents and species adapted to a moderate salinity level. The relative species richness of ecological groups and the indices of saprobity are correlated with changes in conductivity, pH, and N-nitrate concentration. Indicators of organic pollution fall in the range of betameso- to alfamesosaprobic self-purification grades. Our studies show ecological significance of the Nahal Qishon as a model for a strongly disturbed aquatic ecosystem in the coastal zone of eastern Mediterranean.     

Fluctuations and patterns of desert rodent communities under human disturbance: fluctuating tendency and sensitive response of their population

The four kinds of sites under different kinds of human disturbances, i.e. a farmland area, a rotational-grazing area, an over-grazing area and a prohibited-grazing area, were selected in the typical region of the Alashan Desert of Inner Mongolia from April to October in 2002, 2003 and 2004 respectively. The fluctuating tendency of rodent communities and the sensitive response of their populations were studied using mark-recapture and trap-day methods. The four kinds of mark-recapture samples and line samples were taken in different human disturbance areas. The area of the mark-recapturing sample was 0.95 hm² and that of the line sample was 10 km². The samples were collected every month in the mark-recapturing sites for four consecutive days and in line sites in April, July and October every year. The variable matrix was composed of the numbers of captured rodents of the rodent communities. The sensitive response of the populations in the communities was analyzed with principal component analysis (PCA). Results showed that there were different types of rodent communities under different kinds of human disturbance on two scales in three years. In each scale, there were large differences in both the number of species and the number of main population in the rodent communities under different kinds of human disturbance on the farmland area and over-grazing area especially. The results of PCA showed that the sensitive response of the populations of the commu nities was significantly different under different kinds of human disturbance on the two scales in the three years. Cricetulus barabensis was the most sensitive on the farmland area, there were no differences in sensitive response of the various rodents on the rotational-grazing area, and Dipus sagitta and Phodopus roborovskii were the most sensitive in the over-grazing area. __________ Translated from Acta Ecologica Sinica, 2006, 26(3): 849–861 [译自:生态学报]     

Perennial grassland dynamics on fertile plains: Is coexistence mediated by disturbance?

Abstract The response of grasslands to disturbance varies with the nature of the disturbance and the productivity of the landscape. In highly productive grasslands, competitive exclusion often results in decreased species richness and grazing may allow more species to coexist. Once widespread, grasslands dominated by Dichanthium sericeum (Queensland bluegrass) and Astrebla spp. (Mitchell grass) occur on fertile plains but have been reduced in extent by cultivation. We tested the effects of exclusion of livestock grazing on these grasslands by comparing the floristic composition of sites in a nature reserve with an adjacent stock reserve. In addition, sites that had been cultivated within the nature reserve were compared with those where grazing but no cultivation had occurred. To partition the effects of temporal variation from spatial variation we sampled sites in three different years (1998, 2002 and 2004). Some 194 taxa were recorded at the nature reserve and surrounding stock routes. Sampling time, the occurrence of past cultivation and livestock grazing all influenced species composition. Species richness varied greatly between sampling periods relating to highly variable rainfall and water availability on heavy clay soils. Native species richness was significantly lower at previously cultivated sites (13–22 years after cultivation), but was not significantly influenced by grazing exclusion. After 8 years it appears that reintroducing disturbance in the form of livestock grazing is not necessary to maintain plant species richness in the reserve. The highly variable climate (e.g. droughts) probably plays an important role in the coexistence of species by negating competitive exclusion and allowing interstitial species to persist.     

Altitude affects the distribution and abundance of two non‐native insect pests of the common walnut

The leaf miner Coptodisca lucifluella and the carpophagous Rhagoletis completa, of American origin, are two non‐native walnut (Juglans spp.) pests in Italy. For the Friuli Venezia Giulia region (FVG) (N‐E Italy), C. lucifluella is not yet listed, while R. completa has been present for over 25 years. During 2015, samples of leaves and fruits were collected from 219 single old common walnut trees (Juglans regia) placed at different altitudes (0–1,073 m a.s.l.) in FVG to detect the distribution and abundance of both pests. Samples of leaf miner larvae and their parasitoids were subjected to mitochondrial DNA analysis for identification. C. lucifluella has been found in 55 out of 219 sites. The species has been identified by typical leaf symptoms and by its DNA barcode. This is the first report of the species for FVG. The leaf miner distribution was negatively correlated with altitude. The species has not been observed at sites over 600 m a.s.l. Larvae were parasitized by native parasitoids identified as belonging to the genus Chrysocharis by morphological features and by DNA barcode. R. completa has been found in 89 out of 165 sites on walnut trees with fruits. The infestation level was very high in lowland localities. At sites over 700 m a.s.l., no infestation was found. Both species are widespread in the region, and their occurrence is significantly affected by altitude. Data suggest that walnut trees could be cultivated in some mountain areas without the need to control R. completa with insecticides.     

Spatial variation in abundance of the junin virus hosts in endemic and nonendemic Argentine haemorrhagic fever zones

Abstract Argentine haemorrhagic fever (AHF) is caused by Junin (JUN) virus, which is hosted by the drylands vesper mouse (Calomys musculinus). In this work we monitored population abundance of C. musculinus and rodent assemblages for 3 years in and outside the AHF endemic zones (northern Buenos Aires, southern Córdoba and Santa Fe Provinces, Argentina). The study area was divided into endemic and nonendemic zones. In the endemic zone epidemic sites were recognized, characterized by recent emergence and maintenance of AHF cases, and also historical sites, characterized by decreased incidence or disappearance of AHF human cases. In the nonendemic zone AHF has never been recognized. Although differences were statistically significant only during some periods, population abundance of C. musculinus was usually lower in the nonendemic sites. The pattern and magnitude of seasonal fluctuations in C. musculinus populations were also distinct in the nonendemic sites as compared to endemic sites. The relative abundance of C. musculinus in rodent assemblage was lower in nonendemic sites than in the endemic sites. The lower population densities and dampened seasonal dynamics may be at least partly responsible for the absence of AHF cases in the nonendemic zone. It is suggested that the balance between intra and interspecific interactions might be the cause of the pattern of incidence and prevalence of pathogens in the host species.     

不同干扰下阿拉善荒漠啮齿动物优势种对气候变化的响应

气候变化已对物种分布范围和丰富度产生了极大的影响。荒漠生态系统对气候变化的反应可能更加敏感。作为荒漠生态系统的重要组成者,了解荒漠啮齿动物特别是优势鼠种将对气候变化如何响应,对于荒漠地区生物多样性的维持将具有重要意义。2002—2010年,采用标志重捕法对阿拉善荒漠4种不同生境下啮齿动物优势种群进行了研究,分别利用Spearman相关分析以及典范对应分析(Canonical Correspondence analysis,CCA)对啮齿动物优势种群动态与年平均温度和年降水量的相关性进行了分析。结果表明,不同啮齿动物优势种对温度和降雨的响应不同,尤其以子午沙鼠表现最为显著。跳鼠对温度的适宜性要高于仓鼠科的子午沙鼠和黑线仓鼠,而仓鼠科啮齿动物对降雨的适宜性高于跳鼠。较小尺度上的人为干扰更可能从改变食性和生境的途径上加剧或缓冲降雨对荒漠啮齿动物优势种的影响,而不是改变温度对啮齿动物的作用。     

Fish assemblages of the Casiquiare River, a corridor and zoogeographical filter for dispersal between the Orinoco and Amazon basins

Aim The aim of this study was to determine whether the Casiquiare River functions as a free dispersal corridor or as a partial barrier (i.e. filter) for the interchange of fish species of the Orinoco and Negro/Amazon basins using species assemblage patterns according to geographical location and environmental features. Location The Casiquiare, Upper Orinoco and Upper Negro rivers in southern Venezuela, South America. Methods Our study was based on an analysis of species presence/absence data and environmental information (11 habitat characteristics) collected by the authors and colleagues between the years 1984 and 1999. The data set consisted of 269 sampled sites and 452 fish species (> 50,000 specimens). A wide range of habitat types was included in the samples, and the collection sites were located at various points along the entire length of the Casiquiare main channel, at multiple sites on its tributary streams, as well as at various nearby sites outside the Casiquiare drainage, within the Upper Orinoco and Upper Rio Negro river systems. Most specimens and field data used in this analysis are archived in the Museo de Ciencias Naturales in Guanare, Venezuela. We performed canonical correspondence analysis (CCA) based on species presence/absence using two versions of the data set: one that eliminated sites having < 5 species and species occurring at < 5 sites; and another that eliminated sites having < 10 species and species occurring at < 10 sites. Cluster analysis was performed on sites based on species assemblage similarity, and a separate analysis was performed on species based on CCA loadings. Results The CCA results for the two versions of the data set were qualitatively the same. The dominant environmental axis contrasted assemblages and sites associated with blackwater vs. clearwater conditions. Longitudinal position on the Casiquiare River was correlated (r² = 0.33) with CCA axis‐1 scores, reflecting clearwater conditions nearer to its origin (bifurcation of the Orinoco) and blackwater conditions nearer to its mouth (junction with the Rio Negro). The second CCA axis was most strongly associated with habitat size and structural complexity. Species associations derived from the unweighted pair‐group average clustering method and pair‐wise squared Euclidean distances calculated from species loadings on CCA axes 1 and 2 showed seven ecological groupings. Cluster analysis of species assemblages according to watershed revealed a stronger influence of local environmental conditions than of geographical proximity. Main conclusions Fish assemblage composition is more consistently associated with local environmental conditions than with geographical position within the river drainages. Nonetheless, the results support the hypothesis that the mainstem Casiquiare represents a hydrochemical gradient between clearwaters at its origin and blackwaters at its mouth, and as such appears to function as a semi‐permeable barrier (environmental filter) to dispersal and faunal exchanges between the partially vicariant fish faunas of the Upper Orinoco and Upper Negro rivers.     

149 Distribution and Invasion of Bangia Atropurpurea (Rhodophyta) in the Laurentian Great Lakes

Müller et al. (1998) noted that freshwater collections of the genus Bangia formed a distinct group separate from marine entities in gene sequence analyses. Recently, the species epithet B. atropurpurea has been resurrected to represent this freshwater lineage. This taxon is one of many invasive species within the Laurentian Great Lakes. B. atropurpurea was first observed in Lake Erie in 1964 and by 1982 was observed in all of the Great lakes except Lake Superior. The present study was initiated to examine the further spread of B. atropurpurea and determine the origin of these populations. Hence, a survey of all the Great Lakes was conducted in 1995 (86 sites) and again in 2002 (104 sites). Bangia was observed at 43 sites in 1995 and 39 sites in 2002. For the first time, this alga has been observed to be present in the St. Lawrence River (1995), Georgian Bay on Lake Huron (2002) and Lake Simcoe (eastern shore, 2002) and hence this alga appears to be spreading into new locations. Cluster analyses of morphological data reveal three distinct groupings that do not separate according to location or lake basin. Preliminary analyses of ITS 1 and 2 sequences show differences among samples within Lake Ontario and among all Lakes; however, collections from Lake Simcoe are very similar in sequence. We are continuing to examine the relationship of Great Lakes populations with freshwater collections from Europe.     

A preliminary assessment of the response of a native reptile assemblage to spot‐spraying invasive Bitou Bush with glyphosate herbicide

During recent work examining the effects of Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) invasion on native reptile assemblages in coastal heathland vegetation in Eastern Australia, unplanned spot‐spraying of glyphosate occurred at some of our experimental sites invaded by Bitou Bush. We used this unexpected herbicide application as an opportunity to provide a preliminary assessment of the short‐term impacts on reptiles of glyphosate spot‐spraying of Bitou Bush. Using an M‐BARCI design, we compared reptile assemblages among uninvaded (reference) sites, invaded (control) sites and invaded and sprayed (impact) sites before and after spraying. We found no significant short‐term (7 – 10 months) differences in reptile abundance, species richness or assemblage composition among invaded, uninvaded and sprayed sites before and after glyphosate application. We cautiously interpret our results to generate a preliminary finding that spot‐spraying of Bitou Bush with glyphosate appears not to have a deleterious effect on reptile assemblages at seven and ten months following herbicide application. While we would not recommend basing management decisions on the outcomes of our study alone, we suggest that our findings can be used to assist in the development of strategic analyses of glyphosate impacts on native flora and fauna.     

Population dynamics of Mus minutoides and Steatomys pratensis (Muridae: Rodentia) in a subtropical grasslandin Swaziland

The population dynamics of Mus minutoides and Steatomys pratensis are virtually unknown. These two species were live-trapped over a 12-month period in a subtropical grassland in Swaziland. Numbers of M. minutoides were relatively high in winter, declined in spring and the population disappeared in summer and autumn. By contrast, numbers of S. pratensis increased gradually from winter to summer and reached a peak in autumn. There were no differences between the mean weights of male and female M. minutoides and S. pratensis. There were, however, seasonal differences in the mean weight of male S. pratensis, with highest weights recorded in summer. Individuals of both species came into breeding condition in spring (October–November). Reproduction had ceased by the end of autumn (April–May). Monthly survival rates of M. minutoides were highest in winter, but did not vary seasonally in S. pratensis. Burning had a pronounced effect on the distribution of S. pratensis. Steatomys pratensis individuals selected recently burnt but revegetated areas over unburnt areas. The effect of burning on the M. minutoides population is difficult to assess, as this species disappeared shortly after the fire.     

Rating the rat: global patterns and research priorities in impacts and management of rodent pests

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The Occurrence of Multidrug-Resistant Pseudomonas aeruginosa on Hydrocarbon-Contaminated Sites

The main aim of this paper was the comprehensive estimation of the occurrence rate and the antibiotic-resistance conditions of opportunistic pathogen Pseudomonas aeruginosa in hydrocarbon-contaminated environments. From 2002 to 2007, 26 hydrocarbon-contaminated sites of Hungary were screened for the detection of environmental isolates. Altogether, 156 samples were collected and examined for the determination of appearance, representative cell counts, and antibiotic-resistance features of P. aeruginosa. The detected levels of minimal inhibitory concentrations of ten different drugs against 36 environmental strains were compared to the results of a widely used reference strain ATCC 27853 and four other clinical isolates of P. aeruginosa. Based on our long-term experiment, it can be established that species P. aeruginosa was detectable in case of 61.5% of the investigated hydrocarbon-contaminated sites and 35.2% of the examined samples that shows its widespread occurrence in polluted soil–groundwater systems. In the course of the antibiotic-resistance assay, our results determined that 11 of the examined 36 environmental strains had multiple drug-resistance against several clinically effective antimicrobial classes: cephalosporins, wide spectrum penicillins, carbapenems, fluoroquinolones, and aminoglycosides. The fact that these multiresistant strains were isolated from 8 different hydrocarbon-contaminated sites, mainly from outskirts, confirms that multiple drug-resistance of P. aeruginosa is widespread not only in clinical, but also in natural surroundings as well.     

Plague studies in California: a review of long‐term disease activity,flea‐host relationships and plague ecology in the coniferous forests of the Southern Cascades and northern Sierra Nevada mountains

We review 28 years of long‐term surveillance (1970–1997) for plague activity among wild rodents from ten locations within three coniferous forest habitat types in the northern Sierra Nevada and the Southern Cascade mountains of northeastern California. We identify rodent hosts and their fleas and document long‐term plague activity in each habitat type. The highest seroprevalence for Yersinia pestis occurred in the chipmunks, Tamias senex and T. quadrimaculatus, and the pine squirrel, Tamiasciurus douglasii. The most commonly infected fleas were Ceratophyllus ciliatus and Eumolpianus eumolpi from chipmunks and Oropsylla montana and O. idahoensis from ground squirrels. Serological surveillance demonstrated that populations of T. senex, T. quadrimaculatus and T. douglasii are moderately resistant to plague, survive infection, and are, therefore, good sentinels for plague activity. Recaptured T. senex and T. quadrimaculatus showed persistence of plague antibodies and evidence of re‐infection over a two year period. These rodent species, their fleas, and the ecological factors common to the coniferous forest habitats likely promote the maintenance of plague foci in northeastern California.     

Fingerprints of environmental change on the rare mediterranean flora: a 115-year study

We empirically assessed the long‐term changes in the rare species assemblage of a Mediterranean flora, in terms of species life history traits, niche and biogeographic features, and taxonomic groups. We used a 115‐year historical record of ca. 2100 plant species occurrences in a 6250 km² region in Mediterranean France. Species were assigned to two classes of regional abundance for the years 1886 and 2001 (rare species, i.e. exhibiting one or two occurrences vs. nonrare species), and to three classes of abundance changes during 1886–2001 (decreasing/extinct, stable, increasing/immigrant). Then, we tested whether species regional abundance and species abundance change were related to their morphological and life‐history traits (life form, perenniality, height, dispersal agent, pollination mode), niche and biogeographic features (habitat specialization, level of endemism, biogeographic origin) and taxonomic group. The regional assemblage of rare species was not biologically random and significantly changed between 1886 and 2001. Species classified as rare in 1886 had a significantly higher rate of extinction in the study region during 1886–2001. The highest rate of regression/extinction was found among hydrophyte and/or water‐dispersed rare species, and among annual rare species. However, herbaceous perennial, tree and wind‐dispersed rare species significantly increased in abundance during 1886–2001. Rare species with Eurosiberian distributions, occurring at the southern margin of their range in the study region, dramatically declined or went extinct in the region during 1886–2001; whereas rare species with Mediterranean affinities remained significantly stable. We also found strong evidence for taxonomic patterns in species abundance and abundance changes from 1886 to 2001. The long‐term biological changes documented here in the rare species assemblage of a Mediterranean flora are consistent with the predicted consequences of climate and land use changes currently occurring in the Mediterranean Basin. With the potential decline or even extinction of entire taxa and the loss of southern ecotypes of widespread Eurosiberian species, both evolutionary history and speciation potential of the Mediterranean Region could be strongly altered in future decades.