Is orchid species richness and abundance related to the conservation status of oak forest?

The response of organisms to anthropogenic or natural modification of the environment is one of the most important questions in conservation biology and ecological theory. In spite of the fact that orchids are one of the most studied groups of plants, little information exists regarding their response to habitat alteration. The few existing studies are biased toward European orchid species and no consensus exists with regard to the response of orchids to human and natural disturbance. In this study, we sampled 30 transects (0.1 ha each) of oak forest located in Morelos, Central Mexico, and measured 13 variables related to forest aging and stump abundance, and six variables of orchid species richness and abundance. Neither abundance nor the richness and specific abundance of orchid genus or species were related to timber extraction. The abundance of dead standing trees in the forest, a surrogate variable of forest age, was positively related to abundance of orchids of the genus Malaxis, orchid richness and orchid abundance. This finding suggests that the conservation of all facets of the studied forest orchid community is dependent on natural processes (such as self-thinning) and the maintenance of older areas of the forest, and concurs with previous studies that suggest that natural disturbance is a key process for orchid survival.     

Environmental filtering and taxonomic relatedness underlie the species richness–evenness relationship

We examined the relationship between species richness (S) and evenness (J) within a novel, community assembly framework. We hypothesized that environmental stress leads to filtering (increasing the proportional abundance of tolerant species) and taxonomic dispersion (decreasing the number of species within genera and families). Environmental filtering would cause a decline in S by eliminating some stress-sensitive species and a reduction of J by allowing only tolerant species to maintain large populations. Taxonomic relatedness may influence both S and J by controlling the nature of interspecific interactions—positive under taxonomic dispersion versus negative under taxonomic clustering. Therefore, the S–J relationship may be a product of environmental filtering and taxonomic relatedness. We tested this framework with redundancy analyses and structural equation models using continental stream diatom and fish data. We confirmed that (i) environmental stress, defined by watershed forest cover, slope, and temperature, caused filtering (lower sensitive:tolerant species abundance ratios) and taxonomic dispersion (elevated genus:species richness and family:species richness ratios); (ii) S and J, which declined with filtering and taxonomic dispersion, exhibited a positive relationship; and (iii) the role of filtering on J was pronounced only under stressful conditions, while taxonomic dispersion remained an important predictor of J across stressful and favorable environments.     

Are richness patterns of common and rare species equally well explained by environmental variables?

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.     

The effects of reindeer grazing on the composition and species richness of vegetation in forest–tundra ecotone

We conducted an 8-year exclosure experiment (1999–2006) in a forest–tundra ecotonal area in northwestern Finnish Lapland to study the effects of reindeer grazing on vegetation in habitats of variable productivity and microhabitat structure. The experimental sites included tundra heath, frost heath and riparian habitats, and the two latter habitats were characterized by hummock-hollow ground forms. The total cover of vegetation, cover of willow (Salix spp.), dwarf birch (Betula nana), dwarf shrubs, forbs and grasses (Poaceae spp.) increased in exclosures in all habitats. The increase in the total cover of vegetation and in the covers of willow and dwarf birch tended to be greatest in the least productive tundra heath. Opposing to the increase in the dominant vascular plant groups, the cover and species number of bryophytes decreased in exclosures. We conclude that the effects of reindeer grazing on vegetation composition depend on environmental heterogeneity and the responses vary among plant groups. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Morphological variability in the ecotone — an important factor for the conservation of fish species richness in Swiss rivers

Data from a survey on the distribution of fish species in Switzerland were used to test the hypothesis that species richness of the fish fauna is closely related with the structure, heterogeneity and complexity of the ecotonal zone in rivers. Species richness increased with increasing structural heterogeneity and variability of the ecotone in rivers wider than 2.5 m at altitudes below 500 m. In lowland brooks and in rivers at higher altitudes other factors seemed to be more important than morphological variability: alpine rivers are more often left natural than lowland rivers and salmonid stocking is more important in these naturally species poor fish communities. The proportion of threatened species was higher if riverbed and -banks were natural, the slope was flat, the variability in depths and sediment composition was high and if the ecotonal zone was well structured. Specialized species such as nase and riffle minnow only occurred in larger rivers, whereas in small and medium-sized rivers with low morphological variability these threatened species were missing. On the other hand, ubiquitous species such as chub, roach and perch, occurred in all sizes of rivers, even if morphological variability was small. Low morphological variability and its impact on the composition of the fish community is mainly a consequence of past human interventions. Therefore river management has to take into account the ecological requirements of specialized species and increasing the variability of riverbed and banks would considerably contribute to the conservation of endangered fish species.     

Fish abundance and species richness across an estuarine–freshwater ecosystem in the Neotropics

We investigated the distributional patterns of shallow-water fish and their environmental correlates along a broad spatial scale encompassing estuarine and freshwater ecosystems. Marine-vagrant species were restricted to the sites under the influence of salinity intrusion, whereas estuarine-related and freshwater guilds were found along the entire estuarine–freshwater gradient. Primary- and secondary-freshwater fish guilds had the most widespread spatial distribution and comprised a major fraction of the total abundance and species richness. Abiotic factors correlated with fish abundance and composition along two main environmental axes, one related with variation in salinity, water transparency, and sediment granulometry and the other with the slope gradient. Species richness was significantly higher at the natural channel linking the estuarine- and freshwater-ecosystem, which probably was due to: (a) a steeper slope that favored the confluence of fish from the littoral (<2 m) and limnetic (>2 m) zones and (b) the sporadic inflow of saltwater that carried into this region several marine-related species. Although estuarine–freshwater ecotones are known to support few species, mainly salinity tolerant, our results suggest that habitat features and seasonal fish movement associated with salinity intrusion could lead to more diverse fish assemblages in this transitional zone.     

Are rare species useful species? Obstacles to the conservation of tree diversity in the dry forest zone agro‐ecosystems of Mesoamerica

Aim To test the potential to conserve rare dry forest tree and shrub species circa situm. Location Oaxaca, Mexico and Southern Honduras. Methods Local uses (timber, posts and firewood) of species were determined principally through semistructured interviews with 20 rural householders in each of four communities in Honduras and four in Oaxaca. Tree and shrub diversity inventories were carried out in a total of 227 forest patches and parcels of farmland in those eight communities. Species’ conservation priorities were determined using the star system of Hawthorne (1996) and IUCN listings. Results Despite a large number of useful species, remarkably few were also conservation priorities. Useful species were found to be substitutable as is illustrated by Bombacopsis quinata, Cordia alliodora, Guaiacum sanctum and G. coulteri. Conclusions In these areas, circa situm conservation is inhibited by the lack of species that are both rare and useful. Usefulness must be interpreted as a function of substitutability. Natural regeneration provides an abundance of diversity, farmers are unlikely to invest in the management of a species when suitable substitutes are freely available. The key to conserving rare species may be in maintaining or enhancing the value of the landscape elements in which they are found.     

Length conversions and mass–length relationships of five forage-fish species in the California current ecosystem

Length-measurement conversions and seasonal mass–length relationships (MLR) for Pacific herring Clupea pallasii, northern anchovy Engraulis mordax, Pacific sardine Sardinops sagax, Pacific mackerel Scomber japonicus and jack mackerel Trachurus symmetricus in the California Current are presented. The conversions between total (L_T), fork (L_F,) and standard lengths (L_S) should facilitate comparisons of data across disciplines and institutions. These equations resulted from an analysis of measurements spanning 14 years and the western seaboard of North America, from the north end of Vancouver Island to the USA–Mexico border. Major-axis regressions were used to calculate reciprocal length-measurement conversions (e.g., L_T to L_S and L_S to L_T) and generalised linear models and ordinary least-squares models were used to create MLRs that account for seasonal variations. The MLR models indicated seasonal differences for all species except C. pallasii, for which there was no multi-season data. Discrepancies between these and published models were examined, along with the suitability and benefit of the various types of models used for length-measurement conversion and MLRs.     

Is phenotypic canalization involved in the decline of the endemic Aquilegia thalictrifolia? Rethinking relationships between fluctuating asymmetry and species conservation status

Fluctuating asymmetry (FA), the deviation from the normal symmetrical condition of a morphological trait having specific morphological symmetry, increases in response to environmental and genetic stress, is related to phenotypic plasticity and is considered a tool for monitoring a species conservation status. However, FA–stress relations are dependent on measured traits or species‐specific characteristics such as mating system and habitat. This study investigates the relationships between FA, genetic diversity, population size, density and individual fitness traits (plant height, fruit and seed set), in the endemic Aquilegia thalictrifolia, a mixed breeder that is declining, but maintaining high levels of heterozygosity. Leaf and flower FA and other traits were investigated in 10 populations of A. thalictrifolia, the whole species range. As a result, we found similar patterns of FA in leaves and flowers between populations, indicating a homogenous level of stress between populations that differed for other traits. FA and the other traits were not related, including heterozygosity. Heterozygosity was not related to individual fitness traits with the exception of plant height. In accordance with other studies, we found that the role of FA as a tool for assessing the conservation status of a species or population should be reconsidered. However, we conclude that a low level of FA should not automatically be considered an indicator of good conservation status or low level of stress, because in species that evolved in highly stable environments it may indicate a scarce ability to plastically respond to environmental changes, as a consequence of environmental and genetic canalization. Further investigation of this point is needed.     

Does restoration help the conservation of the threatened forest of Robinson Crusoe Island? The impact of forest gap attributes on endemic plant species richness and exotic invasions

Invasive plant species are major drivers of biodiversity losses, especially on islands which are prone to invasions and extinctions. In the “endemic montane forest” of Robinson Crusoe Island (Pacific Ocean, Chile) invasive exotic plant species threaten conservation efforts by establishing in gaps and outcompeting native tree species regeneration. We compared gap attributes and ground vegetation cover in three gap types: those dominated by native species (<5 % cover of invasive species), invaded gaps (>30 % cover by invasive species), and treated gaps (invasive species removed). We examined (a) which gap attributes favored native and exotic species, (b) the relationship between gap size and species richness, and (c) species responses to invasion and treatment. Gaps ranged in size from 46 to 777 m² caused mainly by uprooted and snapped trees. Multi response permutation procedures showed a different floristic composition between natural, invaded and treated gaps. The presence of Myrceugenia fernandeziana (native species) and Aristotelia chilensis (invasive species) as gap border trees was positively and negatively correlated with native species richness, respectively. New gaps had more native species than old gaps, and smaller gaps contained relatively more native species than larger ones. An increase in invasive species cover was related to a decline in native species cover and richness. 1–6 years after treatment gaps tended to recover their native floristic composition. Highly effective conservation management programs will concentrate on monitoring gap creation, early control of invasive species, and by treating smaller gaps first.     

Preventing extinction and improving conservation status of Vanilla borneensis Rolfe—A rare,endemic and threatened orchid of Assam,India

Vanilla borneensis Rolfe is considered as a rare, endemic and threatened terrestrial climbing orchid of Assam, India. The plant is restricted to only two pockets of Assam with a poor population size. Therefore, conservation of this plant through proper scientific investigation is urgently needed. The present study has as its objectives to study the distribution, standardization of suitable macropropagation methods for reinforcement and reintroduction in suitable wild habitat, as determined by ecological niche modelling (ENM) for the purposes of conservation. For improving the conservation status of the species, potential area and habitat for reintroduction was determined using maximum entropy (MaxEnt) distribution modelling algorithm. Seed germination under natural conditions was found to be very poor for which a macropropagation protocol was standardized; plantlets were raised and reinforced to locations where the population size is very small i.e., mean density, frequency of occurrence and abundance in relation to other associated species was 17.77, 14.16 and 0.82 respectively. Macropropagation method standardized here through cutting was found to be more efficient in terms of time and cost. Application of 100 ppm indole −3- butyric acid (IBA) and 40 ppm naphthalene acetic acid (NAA) significantly improved rooting traits. Further, survival rate was measured significantly very high at 73% while 1000 numbers of V. borneensis plantlets were transferred to the field. Present study has improved the population and conservation status of V. borneensis.     

Wild bee species abundance and richness across an urban–rural gradient

Long-term and widespread monitoring programs are essential to understanding the role of human-dominated landscapes in supporting wild bee populations. Urbanization results in increased impervious surfaces throughout the landscape, fragmentation of green space, and a loss of naturally occurring floral vegetation. All of these changes have a negative impact on pollinator diversity. The objective of this study was to assess the abundance and richness of wild bee species throughout a small city in northwest Pennsylvania and identify how management of land throughout the city may influence bee communities. Seventeen sites across a land use gradient, moving from areas with large open spaces and mainly permeable surfaces, to sites in the city center consisting of mainly impermeable surfaces, were sampled over a 2-year period. During this time, 106 known species were identified with four state records and 1 undescribed species. Bee species richness was greatest at sites with the largest amount of permeable surface and naturally-occurring, native vegetation. Richness decreased on the college campus and city center where landscapes were highly managed and impermeable surfaces were most abundant. While floral richness was not related to bee abundance and richness, the number of open blooms near traps did have a positive impact on bee species richness. Overall, this survey revealed considerable richness never before recorded for northwest Pennsylvania, suggesting the importance of conservation management in homeowner and community yard space.     

Climate and landscape explain richness patterns depending on the type of species’ distribution data

Understanding the patterns of species richness and their environmental drivers, remains a central theme in ecological research and especially in the continental scales where many conservation decisions are made. Here, we analyzed the patterns of species richness from amphibians, reptiles and mammals at the EU level. We used two different data sources for each taxon: expert-drawn species range maps, and presence/absence atlases. As environmental drivers, we considered climate and land cover. Land cover is increasingly the focus of research, but there still is no consensus on how to classify land cover to distinct habitat classes, so we analyzed the CORINE land cover data with three different levels of thematic resolution (resolution of classification scheme ˗ less to more detailed). We found that the two types of species richness data explored in this study yielded different richness maps. Although, we expected expert-drawn range based estimates of species richness to exceed those from atlas data (due to the assumption that species are present in all locations throughout their region), we found that in many cases the opposite is true (the extreme case is the reptiles where more than half of the atlas based estimates were greater than the expert-drawn range based estimates). Also, we detected contrasting information on the richness drivers of biodiversity patterns depending on the dataset used. For atlas based richness estimates, landscape attributes played more important role than climate while for expert-drawn range based richness estimates climatic variables were more important (for the ectothermic amphibians and reptiles). Finally we found that the thematic resolution of the land cover classification scheme, also played a role in quantifying the effect of land cover diversity, with more detailed thematic resolution increasing the relative contribution of landscape attributes in predicting species richness.     

Ligands and tracers for PET studies of the 5-HT system—current status

The status of the radiochemical development and biological evaluation of radioligands and tracers for PET studies of the serotonergic system is reviewed, indicating those agents with present value and those with future potential. Practical recommendations are given for the preparation of two useful radioligands for PET studies of central 5-HT₂ receptors, namely [¹⁸F]setoperone and [¹⁸F]altanserin. Though, it has not proved possible to recommend tracers or radioligands for the study of other aspects of the serotonergic system, prospects for future radiochemical development are indicated, especially for developing radioligands for the 5-HT re-uptake site, and for the 5-HT₁ and 5-HT₃ receptors.     

Vegetation history in the Eastern Romanian Carpathians: pollen analysis of two sequences from the Mohoş crater

Two sequences of about 10.5 m originating from a peat bog in Romania were analysed for pollen (202 and 127 pollen spectra). The vegetation history, supported by 24 ¹⁴C dates is described since the Late Glacial. At the onset of the Holocene Ulmus first appears, together with Betula. Among the main components of the Quercetum mixtum (Quercus, Fraxinus, Tilia, Corylus) that became established almost simultaneously by around 9000 B.P., Quercus frequencies rarely exceed 10%. The local establishment of Carpinus is about 6000 b.p. Its maximum occurred between 4500 and 3000 b.p. Fagus pollen is regularly recorded since 8000 b.p. Its absolute dominance tooks place at about 3000 b.p. Picea pollen is present since the Late Glacial. The first indications of human activities appear at around 6500 b.p.