Are CORINE land cover classes reliable proxies of plant species assemblages? A test in Mediterranean forest landscapes

In land cover mapping, the complexity of landscapes is fitted into classes that may limit the recognition of natural variability. In this study, we tested the power of land cover classes (defined on the CORINE land cover classification scheme, a standardized legend set by EU for land cover inventory) to separate different vascular plant assemblages in forest ecosystems. In order to separately identify the role of different sources of inconsistency between land cover classes and species composition, we compared three different inventory processes, based on (i) dominant tree species as observed in the field, (ii) visual interpretation of remotely sensed images and (iii) semi-automatic supervised classification of satellite images. Our results underline that classifying forest ecosystems on the basis of their canopy species produces an over-simplification of habitat variability. Consequently, land cover maps based on non-specialized classification schemes should not be regarded as good proxies for plant biodiversity. If land cover maps are intended to describe and manage landscapes and their associated biodiversity, it is necessary to improve their capacity to represent the complexity of ecosystems.     

Are the responses of plant species to Quaternary climatic changes idiosyncratic? A demographic perspective from the Western Alps

Background: Previous studies have indicated that several plant species had shown remarkable resistance to Pleistocene climate changes and survived the Last Glacial Maximum in scattered ice-free refugia within the European Alps and peripheral areas nearby. The ‘Expansion–Contraction’ model has been proposed to describe the responses of organisms to Pleistocene climate change. Nevertheless, the timing and extent to which species were affected by Quaternary glaciations remain uncertain.

Aims: To test whether the ‘Expansion–Contraction’ model appropriately describes plant distribution responses to Pleistocene climate change in the Western Alps.

Methods: We employed two Bayesian coalescent-based methods on plastid DNA sequences to infer the demographic histories of Ranunculus kuepferi, R. glacialis, Biscutella laevigata, Saxifraga oppositifolia, Primula allionii, P. marginata, Silene cordifolia and Viola argenteria.

Results: R. kuepferi conformed to the ‘Expansion–Contraction’ model, while other species did not. For example, P. allionii showed an alarming population decline during the Middle-Late Pleistocene.

Conclusions: The application of Bayesian coalescent-based methods to plastid DNA data offers useful insights into plant demography as a function of palaeoclimatic events. Our findings favour an idiosyncratic response of plant species in the Western Alps to Pleistocene climate change.     

Do spider diversity and assemblages change in different contiguous habitats? A case study in the protected habitats of the humid chaco ecoregion, northeast Argentina

Spiders are a megadiverse group that can be useful indicators of the overall species richness and health of biotic communities. The spider diversity in subtropical forests of the Neotropical region are not yet well known, especially in Argentinean subtropical forests where systematic fieldwork has not been done until recently. The Great Chaco is very important as the unique dry subtropical forest of the earth, but it is suffering increasing degradation by the advance of agriculture. Spider communities have been shown to be more directly influenced by vegetation architecture than vegetation species composition. In this study, we aim to assess whether spider diversity and assemblages change in adjacent habitats with different types of vegetation. We compare the diversity and spider assemblages in two different contiguous protected habitats (hygrophilous woodland and savannah parkland) of the Mburucuyá National Park, (Humid Chaco ecoregion). Seasonal samples were obtained using three types of sampling methods: pitfall trapping, beating, and manual litter extraction. The spider assemblages were different in the studied areas, and the abundance, diversity, evenness, and species richness were higher in the hygrophilous woodland than the savannah parkland. These differences in spider diversity and assemblages indicate that both types of habitats are important if the biodiversity is to be conserved in the Chaco ecoregion, where different types of habitat are shown as a patchy distribution.     

Are we underestimating the diversity and incidence of insect bacterial symbionts? A case study in ladybird beetles

Vertically transmitted bacterial symbionts are common in arthropods. However, estimates of their incidence and diversity are based on studies that test for a single bacterial genus and often only include small samples of each host species. Focussing on ladybird beetles, we collected large samples from 21 species and tested them for four different bacterial symbionts. Over half the species were infected, and there were often multiple symbionts in the same population. In most cases, more females than males were infected, suggesting that the symbionts may be sex ratio distorters. Many of these infections would have been missed in previous studies as they only infect a small proportion of the population. Furthermore, 11 out of the 17 symbionts discovered by us were either in the genus Rickettsia or Spiroplasma, which are rarely sampled. Our results suggest that the true incidence and diversity of bacterial symbionts in insects may be far greater than previously thought.     

Are changes in remotely sensed canopy cover associated to changes in vegetation structure,diversity, and composition in recovered tropical shrublands?

The recovery of vegetation cover is a process that has important implications for the conservation of biodiversity and ecosystem services. Generally, the recovery of vegetation cover is documented over large areas using remote sensing, and it is often assumed that ecosystem properties and processes recover along with remotely sensed canopy cover. Here we analyze and compare the structure, composition, and diversity of trees and shrubs among plots established in a stratified random sampling design over four remotely sensed canopy cover change (CCC) categories defined according to a gradient in the percent of canopy cover. Plots were located in the Lake Cuitzeo basin (Mexico), where canopy recovery associated with agricultural abandonment has occurred in recent decades (1975–2000). We found that diversity measures, basal area, tree and shrub density, ground-truthed canopy cover, and mean plant height increased with increasing CCC category. However, Shannon index (H′) was lower in the CCC category with the most closed canopy cover category than in plots apparently not affected by agriculture. Furthermore, ordination analyses showed that composition of dominant species were not associated with CCC categories. Our results suggest that canopy closure in our study area is not associated with the recovery of species diversity, and does not result in similar species dominance as in sites not affected by agriculture.     

Do different irrigation techniques affect the small-scale patterns of plant diversity and soil characteristics in mountain hay meadows?

Traditional management practices are suggested to maintain species-rich grasslands. In the Valais, an arid region of Switzerland, hay meadows are traditionally irrigated using open water channels. However, in the past decades this irrigation technique has been increasingly replaced by sprinkler irrigation, which is assumed to result in a more homogeneous water distribution than open water channels. This study examined whether the change in irrigation technique affected the small-scale distribution of plants and soil characteristics in hay meadows in the Valais. Three plots consisting of 13 subplots of increasing size (0.1 × 0.1 to 6.4 × 6.4 m) were installed in six traditionally and six sprinkler-irrigated meadows. In all subplots, plant species richness and soil characteristics [moisture, pH, total organic nitrogen, organic matter content (SOM), total and plant available phosphorus] were recorded. The type of irrigation technique did not affect the shape of the plant species–area relationship. In none of the meadows did the species area–curves reach the asymptote within the range of plot sizes examined. Mantel r statistics showed that spatial autocorrelation in the soil characteristics examined was low and their small-scale distributions were not influenced by the irrigation technique except for soil pH and SOM. Our results indicate a pronounced small-scale heterogeneity in the distribution of plant species and soil characteristics for both types of irrigation technique. This can partly be explained by the fact that sprinklers distribute the water less homogeneously than commonly assumed. As applied in the Valais, sprinkler irrigation does not reduce the spatial heterogeneity and hence biodiversity of hay meadows.     

Does diversity beget diversity? A case study of crops and weeds

Abstract. The ecological literature is ambiguous as to whether the initial diversity of a plant community facilitates or deters the diversity of colonizing species. We experimentally planted annual crop species in monoculture and polyculture, and examined the resulting weed communities. The species composition of weeds was similar among treatments, but the species richness of weeds was significantly higher in the polycultures than in the monocultures. This supports the ‘diversity begets diversity’ hypothesis. Environmental microheterogeneity, diversity promoters, and ecological equivalency do not seem able to explain the observed patterns.     

Are the adult odonate species found in a protected area different from those present in the surrounding zone? A case study from eastern Amazonia

We studied 30 streams in eastern Amazonia, 17 of which were located within a protected area (PA) and the other 13 in the surrounding zone, with the objective of evaluating the diversity of adult Odonata and if there was a difference between the physical habitat variables of the two environments. We hypothesized that a greater diversity of odonate species would be found in the PA due to a greater complexity of habitats. This hypothesis was rejected, however, due to the greater odonate diversity found in the surrounding zone in comparison with the PA. Differences were also found in the species composition of the two environments. Our results indicate that there are differences between the environmental variables in the areas, and the few alterations observed in the surrounding zone may have contributed to the formation of new conditions and habitats appropriate for species that may have been rare. The PA, despite having reduced species richness and abundance in comparison with the surrounding zone, was nevertheless characterized by a more heterogeneous species composition. A quarter of the species were common to both environments, while 34 % were exclusive to the surrounding zone. In this case, it appears that the combination of the protected area and the surrounding zone, which has a low level of disturbance, conserves a wider range of specialist species than either area on its own. The great challenge in the future is finding a way to identify the disturbance levels that would be acceptable, and to prevent over-exploitation of resources in such areas.     

What causes changes in plant litter quality and quantity as consequence of grazing in the Patagonian Monte: Plant cover reduction or changes in species composition?

In Patagonian Monte, as in other arid ecosystems, grazing has triggered changes in vegetation and soil such as plant cover reduction, changes in species composition and soil nutrient losses. Several mechanisms were proposed interconnecting these changes, but evidence supporting them is very scarce. On the basis of published data concerning plant cover by species along grazing gradients and leaf litter production of dominant species, we estimated the effects of grazing on a – quality (N, soluble phenolics and lignin concentrations) and b – quantity (leaf litterfall (LLF) and inputs of nitrogen, soluble phenolics and lignin to the soil) of leaf litter in the Patagonian Monte, discriminating the effect of plant cover reduction from that of species composition. We also evaluated the relationship between senesced leaves traits and the response of species to grazing (i.e. their relative change in plant cover). Grazing causes a reduction in LLF and in the inputs of nitrogen, soluble phenolics and lignin to the soil. In the case of LLF, this reduction was not only a result of the decrease in plant cover but also due to changes in species composition. In contrast, our results showed that the reduction in nitrogen, soluble phenolics and lignin inputs to the soil by LLF is only a consequence of plant cover reduction. Additionally, litter quality was affected through increasing concentration of N and secondary compounds (soluble phenolics and lignin). N and soluble phenolics concentration on senesced leaves were positively related to the response of species to grazing, suggesting that other factors instead of N are relevant to sheep foraging decisions.     

Effects of climate change on plant composition and diversity in the Gurbantünggüt Desert of northwestern China

Understanding changes in plant diversity is important with changing climate in desert ecosystems. We analyzed the changes in species richness and plant functional types in different landscape positions and species turnover between five sub-regions of the Gurbantünggüt Desert, China, from 2009 to 2013. We also analyzed how species density, richness, and plant functional types responded to annual precipitation, mean annual temperature, and the coefficient of variation (C _v) of both daily precipitation and monthly temperature, throughout this entire desert region. The results showed significant differences in the Shannon–Weiner, Evenness, and Gleason indices between the sub-regions over the 5-year study period. Species richness varied in the order of ephemeral plants > long-lived annual plants > perennial herbs > shrubs. Species richness in the lower and inter-dune area was higher than on the upper dune and on top of dunes. About 34.8 % of total species were influenced by climate change. The density of about 8.7 % of total species declined with increasing precipitation, especially the two dominant species, Haloxylon persicum and Haloxylon ammodendron. Plant richness increased significantly with increased precipitation. Ephemeral plant made the largest contribution to increasing plant diversity in the desert, while shrubs made the smallest. Ephemeral plants play an important role in maintaining plant community composition and function. In addition, species turnover declined with increasing precipitation. We suggest that differences in flora and different landscape positions in the dunes, specifically in shaping the heterogeneous microhabitats, are important reasons for the complex responses of species to climate change.     

Are plant hybrid zones centers of vertebrate biodiversity? A test in the Quercus grisea × Quercus gambelii species complex

The plant-hybrid-zones-as-centers-of-biodiversity (hereafter, PHZCB) hypothesis posits that plant hybrid zones represent areas of elevated biodiversity, and supports the inclusion of plant hybrid zones in conservation efforts. Support for the PHZCB hypothesis is limited to a handful of cases involving insect and fungal species and to two studies involving higher trophic levels. The PHZCB hypothesis requires further testing before plant hybrid zones can be established with any certainty as centers of biodiversity. We test whether the PHZCB hypothesis holds for higher trophic levels by examining the community structure of birds and reptiles associated with the Quercus grisea × Quercus gambelii species complex. Specifically, we compare patterns of species richness and abundance of these taxa in 10 hybrid zones and 11 contact zones (i.e., zones where both parental species occur but hybrids do not). In contrast to predictions of the PHZCB hypothesis, contact zones supported significantly more species of birds and reptiles than did hybrid zones. Species abundances exhibited idiosyncratic responses to zone type, but were higher generally in the contact zones.     

Assessing the relative role of climate and human activities on vegetation cover changes in the up–down stream of Danjiangkou,China

气候与人类活动对丹江口上下游植被覆盖变化的影响 丹江口水库是南水北调中线工程的水源地,研究丹江口水库植被覆盖动态变化及其影响因素,对于了解南水北调中线工程的生态环境及制定保护措施具有重要意义。本研究采用归一化植被指数(NDVI)分析了1982–2018年丹江口大坝上下游植被的动态变化及其影响因素。研究结果表明,研究 时段内NDVI呈0.017year^-1的增加趋势(P < 0.05),显著增加的区域位于大坝上游河谷附近,显著减少的区 域主要分布在大坝下游流域和中心城区周围。气候变化和人类活动对NDVI变化的综合贡献率分别为92.03%和7.97%。大坝上游的人类活动主要体现在退耕还林等生态措施的实施,大坝下游的人类活动主要表现为城市扩张、建设用地占用耕地和林地等。     

Are wives and daughters disadvantaged in polygynous households? A case study of the Arsi Oromo of Ethiopia

Whether polygyny is harmful for women and their children is a long-standing question in anthropology. Few studies, however, have explored whether the effect of polygyny varies for women of different wife order, and whether there are different outcomes for their sons and daughters. Because males have higher reproductive variance, especially when they are allowed to take multiple wives, parents may have higher fitness returns from investing in sons over daughters in polygynous households. Moreover, previous studies have found that first wives and their children are advantaged over monogamous and second order wives (who marry into unions later). Here we test the predictions that children of first wives will have an advantage over children to monogamous or second wives, and that sex-biased investment will be strongest among first wives. Using data from the Arsi Oromo of Ethiopia (n ~ 6200 children) we test whether associations with mother's wife order extend beyond childhood into adulthood by examining simultaneously child survival, education and age at marriage. We find that polygynous first wives have no child survival disadvantage, first wives' sons benefit in terms of longer education and daughters have an earlier age at marriage than daughters of monogamous women. Second wives have lower child survival than monogamous women, but surviving children experience advantages in later life outcomes, particularly marriage. These findings challenge the view that polygynous women are always doing the ‘best of a bad job’. Rather, our results suggest that via their surviving sons and daughters there may be long-term benefits for some polygynous women.     

Long-term change in coral cover and the effectiveness of marine protected areas in the Philippines: a meta-analysis

Although coral declines have been reported from major reefs of the world, region-specific trends still remain unclear, particularly in areas with high diversity such as the Philippines. We assessed the temporal patterns of the magnitude and trajectory of coral cover change in the Philippines using survey data collected from 317 sites. We examined the rate of change in coral cover in relation to time, effects of bleaching and protection against fishing and assessed the efficacy of marine protected areas (MPAs) using meta-analysis. Results showed an overall increase in coral cover in the Philippines from 1981 to 2010. Protection from fishing contributed to the overall increase in the mean annual rate of change as the coral cover significantly increased within MPAs than outside. The significant differences in the rate of coral cover change through time were influenced by chronic anthropogenic stresses, coinciding with the timing of thermal stress and the establishment of MPAs. The rate of change in coral cover was independent of the level of protection and the age and size of MPA.     

Are monophyly and synapomorphy the same or different? Revisiting the role of morphology in phylogenetics

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In Nelson’s analysis, monophyly and synapomorphy are identical relations. Monophyly and synapomorphy, however, are not equivalent relations. Monophyly is epistemically not accessible, whereas synapomorphy is epistemically accessible through character analysis. Monophyly originates with speciation, the two sister‐species that come into being through the splitting of the ancestral species lineage forming a monophyletic taxon at the lowest level of inclusiveness. Synapomorphy provides the empirical evidence for monophyly, inferred from character analysis in the context of a three‐taxon statement. If synapomorphy and monophyly were equivalent, phylogenetic systematists should find a single tree, instead of multiple equally parsimonious trees. Understanding synapomorphy as the relevant evidence for phylogenetic inference reveals a category mistake in contemporary phylogenetics: the treatment of morphological characters mapped onto molecular trees as synapomorphies and homoplasies. The mapping of morphological characters onto nodes of a molecular tree results in an empirically empty procedure for synapomorphy discovery. Morphological synapomorphies and homoplasies can only be discovered by morphological and combined analyses. The use of morphology in phylogenetic inference in general is defended by examples from Laurales and Squamata in particular. To make empirical evidence scientifically relevant in order to search for concordance, or dis‐concordance, of phylogenetic signal, is certainly more fruitful for phylogenetics than the uncritical mapping of morphological traits on a molecular scaffold. © The Willi Hennig Society 2010.