The results of long-term monitoring of the abundance of the raven (Corvus corax L., 1758) in the forest parks of Moscow and the Moscow region

Generalizations about rare and endangered species are important for the development of conservation management policy and for understanding of the nature of rarity. Therefore, we sought such generalizations by statistically comparing eight life history and reproductive traits of rare and common plant species in two better-studied but climatically and geographically distinct Holarctic floras-those of California and the British Isles. Trends were often similar in both floras. Rare and common species differ significantly for a number of characters. In both floras, a woody habit was significantly more frequent for the rare species than the common species. Also, in both floras, monocarpy was less frequent in the rare species, significantly so in California. The rare species of both floras were, on average, significantly shorter in stature than the common species. This trend in stature remained significant when nonwoody species were compared but did not do so for woody species. Rare and common species differed with regard to their frequency of inflorescence structure types, but these differences were not concordant for both floras. The rare species of the British Isles had significantly higher proportions of mixed and polymorphic flower colors; the trend was not significant in California. In both floras, rare species had a higher frequency of many-seeded fruits, significantly so in California. California's rare species had a significantly higher frequency of dehiscent fruits than common species; the trend was reversed and not significant for the British Isles. We found no significant differences for characters associated with fruit dispersal. Finally, in California, the median altitude of the range of the common species was significantly greater than that of the rare species. At present, these correlates cannot be assigned as possible causes or consequences of rarity. Nonetheless, they may represent "high-risk" traits that could be used to identify other species already at risk or potentially at risk of becoming rarer.

AimOur primary aim is to understand how assemblages of rare (restricted range) and common (widespread) species are correlated with each other among different taxa. We tested the proposition that marine species richness patterns of rare and common species differ, both within a taxon in their contribution to the richness pattern of the full assemblage and among taxa in the strength of their correlations with each other.LocationThe UK intertidal zone.MethodsWe used high‐resolution marine datasets for UK intertidal macroalgae, molluscs and crustaceans each with more than 400 species. We estimated the relative contribution of rare and common species, treating rarity and commonness as a continuous spectrum, to spatial patterns in richness using spatial cross‐correlations. Correlation strength and significance was estimated both within and between taxa.ResultsCommon species drove richness patterns within taxa, but rare species contributed more when species were placed on an equal footing via scaling by binomial variance. Between taxa, relatively small sub‐assemblages (fewer than 60 species) of common species produced the maximum correlation with each other, regardless of taxon pairing. Cross‐correlations between rare species were generally weak, with maximum correlation occurring between small sub‐assemblages in only one case. Cross‐correlations between common and rare species of different taxa were consistently weak or absent.Main conclusionsCommon species in the three marine assemblages were congruent in their richness patterns, but rare species were generally not. The contrast between the stronger correlations among common species and the weak or absent correlations among rare species indicates a decoupling of the processes driving common and rare species richness patterns. The internal structure of richness patterns of these marine taxa is similar to that observed for terrestrial taxa.

We investigated relationships between richness patterns of rare and common grassland species and environmental factors, focussing on comparing the degree to which the richness patterns of rare and common species are determined by simple environmental variables. Using data collected in the Machair grassland of the Outer Hebrides of Scotland, we fitted spatial regression models using a suite of grazing, soil physicochemical and microtopographic covariates, to nested sub‐assemblages of vascular and non‐vascular species ranked according to rarity. As expected, we found that common species drive richness patterns, but rare vascular species had significantly stronger affinity for high richness areas. After correcting for the prevalence of individual species distributions, we found differences between common and rare species in 1) the amount of variation explained: richness patterns of common species were better summarised by simple environmental variables, 2) the associations of environmental variables with richness showed systematic trends between common and rare species with coefficient sign reversal for several factors, and 3) richness associations with rare environments: richness patterns of rare vascular species significantly matched rare environments but those of non‐vascular species did not. Richness patterns of rare species, at least in this system, may be intrinsically less predictable than those of common species.

Rare and common species contribute disproportionately to the functional variation within tropical forests

Rare species contribute greater to ecosystem multifunctionality in a subtropical forest than common species due to their functional diversity

AimWhether richness patterns and determinants are consistent between common and rare species remains controversial, and the answer is fundamental for the conservation of species in vulnerable habitats. Although effects of climate and geological history on species richness have been widely explored, their relative contribution among common and rare species is poorly understood. Here, using a valuable ornamental plant family Gesneriaceae, we evaluated how contemporary climate, habitat heterogeneity and long‐term climate change affect the distribution of rare and common species. Additionally, we identified hotspots of Gesneriaceae diversity and evaluated its protection gap in China.LocationChina.MethodsDistribution of Gesneriaceae was compiled at a spatial resolution of 50 × 50 km. Species were grouped as rare and common based on the number of grid cells they occupied, and their richness patterns and hotspots were estimated separately. Generalized linear models and Random Forest were used to compare effects of different factors on species richness.ResultsRichness of Gesneriaceae peaked in south‐western China. The Yunnan–Guizhou Plateau and Hengduan Mountains were identified as hotspots for overall and common species, while only the former was hotspot for rare species. Temperature seasonality, winter coldness and temperature change since the Last Glacial Maximum (LGM) dominated species richness patterns, but their relative effects differed between species range size. Temperature seasonality had strongest effects on richness of common species, whereas temperature change since the LGM was strongest for rare species. Neither current nor past precipitation affects richness patterns significantly.Main conclusionsGesneriaceae species richness is strongly influenced by temperature changes. Specifically, rare and common species are primarily dominated by long‐ and short‐term temperature changes, respectively. These findings suggest that most Gesneriaceae species may face high risk under future climate changes, and hence, more conservation efforts are urgently needed, especially in Yunnan–Guizhou Plateau, which is hotspot of rare species.

Identification of valuable biotopes was carried out on the example of a small territory —the “Gagarka” forest park, located on the Northern coast of the Gulf of Finland within the borders of St. Petersburg (Fig. 1). Field data on landscapes, vegetation, flora and fauna were collected in 2018 to proof the need to create a specially protected natural territory of regional significance. The study area of 58.7 ha is an accumulative sea terrace with absolute elevations not exceeding 2.5 m above sea level. Despite of small area size, the vegetation is quite diverse and it is represented by the coniferous (spruce and pine) forests, several types of black alder forests, tree and shrub fens, littoral meadows, coastal and aquatic vegetation. Rare species of herbaceous plants and shrubs listed in the Red books of the Russian Federation (Krasnaya…, 2008) and St. Petersburg (Krasnaya…, 2018) are recorded and they often dominate in the plant communities. The preservation of biological diversity may be successful only if the landscapes and the biotopes hosting plant and animal species, including rare ones, are protected. Objects of protection can be both rare and typical ones for the regional biotopes. The environmental value of biotopes of the “Gagarka” forest park was assessed according to the following criteria: ecotopic (areas with rare and specific landforms, soils, hydrochemical regime), geobotanical (the presence of primary plant communities, rare plant communities; widespread, but with a tendency to reduce the area as a result of natural or anthropogenic impacts), floristic (the presence of rare species and species located on the border of their ranges), faunistic (the pre­sence of rare animal species, the species richness of fauna, the presence of permanent habitats of animals and birds, as well as biotopes used in certain seasons: during breeding, nesting, molting and migration). In addition, the compliance of biotopes with the European habitat classification EUNIS (European Nature Information System) was taken into account (Davies et al., 2004, EUNIS, 2018). Plant communities are the main indicator of habitats, and their borders mark the boundaries of habitats. In this regard, the geobotanical map (Fig. 2) is the basis for creating a map of biotopes. In addition to the geobotanical map, the map of actual landscapes, the map of the locations of rare plant species, and faunistic materials were used to create a map of valuable biotopes (Materialy…, 2018). It shows 6 types of habitats, that are particularly important for the conservation of biological and biotopic diversity (Fig. 3). All valuable habitats of the “Gagarka” forest park are located in the littoral zone of the Gulf of Finland and near its coast. They are grouped into 4 categories: black alder forests as a model of natural tree communities of the Littorina terrace and habitats of rare plant and animal species, coastal fens as rare plant communities on the territory of St. Petersburg and habitats of rare plant species, littoral meadows as rare plant communities on the territory of St. Petersburg and habitats of rare plant and animal species, shallow waters of the Gulf of Finland as habitats with highly productive communities of macrophytes, rare plant species, with a large species diversity and a high number of birds, including rare ones. The creation of new protected area “Gagarka” is necessary to preserve the habitats and rare species that grow and live here.

Summary During the last century, many plant species typical of heathland and nutrient‐poor acidic grasslands have become rare whereas others have remained common. Habitat restoration often fails to enhance the rare species, which may in part be caused by the failure to restore the biogeochemical conditions suited to these species. Many soil variables have been shown to affect plant fitness but it is unknown what their relative importance is and whether any biogeochemical variable acts as a key factor constraining the persistence of rare heathland species. We compiled a data set consisting of 300 vegetation samples and the associated soil chemical properties from a range of studies carried out across the Netherlands. We asked whether growth sites of rare and common species typical of heathland and acidic grasslands differed in their biogeochemical properties, and whether growth sites of rare species displayed less variation in soil biogeochemical variables (e.g. had narrower ecological amplitude). Regardless of rarity, the species’ growth sites were most accurately described by a curvilinear relationship between pH and Al/Ca ratios. Other soil characteristics did not vary systematically with changing acidity of the soil or the patterns were less pronounced. Acidification will therefore most rapidly and predictably result in an increase in Al/Ca ratio whereas this is not necessarily the case for the other soil variables affecting plant fitness. The soil ammonium (NH4) concentration and ammonium/nitrate (NH4/NO3) ratio were 3·5 and 3 times higher, respectively, in growth sites of common species compared with those of rare species. No other measured variable differed significantly between rare and common plant species. On average rare species had a significantly narrower ecological amplitude than common species for soil biogeochemical parameters. Synthesis and applications. A greater sensitivity to high NH4 concentrations in combination with a narrower ecological tolerance zone for a range of soil biogeochemical factors may explain the demise of rare species adapted to nutrient‐poor acidic habitats in recent decades. Conservation management should aim to restore low NH4 concentrations and NH4/NO3 ratios. Experimental studies indicate that the most effective way to do this is through removal of the topsoil in combination with liming.

Habitat type and grazing are key factors controlling benthic diatom communities. Nonetheless, the strength of grazing may depend on the habitat complexity at fine (substratum roughness) and meso scales (mesohabitat type). The interaction between grazers and physical conditions may thus be an important factor shaping benthic diatom communities. Several investigations have evaluated how habitat type, grazing and substratum roughness separately affect the biomass, species richness and community structure of algal communities. However, how these factors act together remains poorly understood, particularly for sets of common and rare species. The latter is important for understanding whether common and rare species are affected differently by environmental filters at the local scale.We investigated the effects of mesohabitat type, grazer occurrence and substratum roughness as well as their interactions on benthic diatom communities in a split‐split‐plot field experiment consisting of hierarchical treatments: (i) mesohabitat (pools and riffles); (ii) grazer occurrence (presence or absence of grazers >1 cm in size); and (iii) substratum roughness (smooth and rough substrata). We analysed the entire community and also datasets of common and rare species. Here, we define common and rare species based on their abundance–occupancy relationships, with rare species presenting low mean abundance per experimental unit (between 0.025 and 8.2) and low occupancy (between 2.5% and 25%).Substratum roughness was the main factor explaining differences in species richness, with higher species richness found on rough than on smooth substrata for both the complete dataset and for common and rare species. There was evidence that the interactions between mesohabitat and grazer occurrence and between mesohabitat and substratum roughness affected community structure (relative abundances) for the complete dataset and for common species, whereas the three‐way interaction between mesohabitat, grazer and substratum roughness affected community structure of rare species.Our findings emphasise that crevices are important microhabitats that allow the establishment of both common and rare species. Furthermore, our results suggest that physical differences between mesohabitats influenced the effect of grazers on the community structure of common and rare species. For common species, the effects of this interaction were difficult to depict, but we found a change in the second‐most‐common species between mesohabitats and depending on the occurrence of grazers. For rare species, grazers more clearly affected community structure on smooth substrata in riffles than in pools.Our results demonstrate that local patterns of common and rare diatom species resulted from distinct combinations of the evaluated environmental filters. Together, our results highlight how multifactorial field experiments are key to understanding the main environmental filters driving the species richness and community structure of benthic diatom communities.

The contribution of common and rare species to species abundance patterns in alpine meadows: The effect of elevation gradients

Common species determine richness patterns in biodiversity indicator taxa

How do biodiversity patterns of river animals emerge from the distributions of common and rare species?

Understanding how overall patterns of spatial variation in species richness are affected by species distributional is one of the key questions in species diversity research. In the present study, we investigated the relative contributions of common and rare species to overall plant species richness in the Liaodong oak (Quercus wutaishanica) forest, which is located in the Ziwu Mountains of Loess Plateau, northwestern China. Based on species frequency distribution, we developed rank sequences of the most common to the most rare and the most rare to the most common species. We then correlated the rank sequences with cumulative species distributions. Our results showed that common species had a higher correlation with the cumulative species distribution in comparison with rare species. Moreover, common species had stronger effects on species α diversity and species β diversity as compared with rare species. Although the number of rare species was greater than that of common species, the overall species richness pattern was better predicted by common species than rare species. Therefore, common species were confirmed to be good indicators of species richness pattern and need to be protected priority.

Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. 1) Are sets of common and rare species affected by similar niche and spatial processes? 2) How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine‐grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.

AimCommon species contribute more to species richness patterns (SRPs) than rare species in most studies. Our aim was to test this hypothesis using a novel model system, species living exclusively in subterranean habitats. They consist of mainly rare species (small ranges), only a few of them being common (large ranges), and challenge whether rare species are less important for the development of SRPs in this environment. We separately analyzed aquatic and terrestrial species.LocationWestern Balkans in southeastern Europe.MethodsWe assembled two datasets comprising 431 beetle and 145 amphipod species, representing the model groups of subterranean terrestrial and aquatic diversity, respectively. We assessed the importance of rare and common species using the stepwise reconstruction of SRPs and subsequent correlation analyses, corrected also for the cumulative information content of the subsets based on species prevalence. We applied generalized linear regression models to evaluate the importance of rare and common species in forming SRPs. Additionally, we analyzed the contribution of rare and common species in species‐rich cells.ResultsPatterns of subterranean aquatic and terrestrial species richness overlapped only weakly, with aquatic species having larger ranges than terrestrial ones. Our analyses supported higher importance of common species for forming overall SRPs in both beetles and amphipods. However, in stepwise analysis corrected for information content, results were ambiguous. Common species presented a higher proportion of species than rare species in species‐rich cells.Main ConclusionWe have shown that even in habitats with the domination of rare species, it is still common species that drive SRPs. This may be due to an even spatial distribution of rare species or spatial mismatch in hotspots of rare and common species. SRPs of aquatic and terrestrial subterranean organisms overlap very little, so the conservation approaches need to be habitat specific.