Structure of a plant-pollinator network on a pahoehoe lava desert of the Galápagos Islands

Plant-pollinator interactions are important for the evolution and survival of the species involved. Plant-pollinator networks on oceanic islands are often small in size and as a consequence the connectance is high suggesting a substantial generalisation level. Further, linkage level for insular plants is shown to be lower than on mainland. The present study investigates a plant-pollinator network on the Galápagos Islands that is unique because of its very small size. We recorded pollinator visits to plant species as well as pollen grains on insect bodies. The combination of these data increased the observed number of interactions. The values for connectance and linkage level for plants were found to be consistent with similar values found in other network studies. There were no relation between the abundance of plant species and the number of pollinating species. The dominating pollinator species was the Galápagos carpenter bee Xylocopa darwini . Specimens of the shorthorned grasshopper Halmenus cuspidatus turned out to carry pollen from five plant species out of twelve and are probably functioning as pollinator. Bagging experiments revealed dependency on insect visits for a high seed set for most of the plant species, but only one species Plumbago scandens seemed to possess a pollen limited seed set. The network showed an asymmetric pattern of number of interactions per species with a few species having several interactions and many species a few. This pattern is supposed to result in a rather robust community, but is also fairly sensitive if the dominant species are threatened. The high connectance value found could, however, counteract this vulnerability.     

Evaluating experimental bias and completeness in comparative phosphoproteomics analysis

Unraveling the functional dynamics of phosphorylation networks is a crucial step in understanding the way in which biological networks form a living cell. Recently there has been an enormous increase in the number of measured phosphorylation events. Nevertheless, comparative and integrative analysis of phosphoproteomes is confounded by incomplete coverage and biases introduced by different experimental workflows. As a result, we cannot differentiate whether phosphosites indentified in only one or two samples are the result of condition or species specific phosphorylation, or reflect missing data. Here, we evaluate the impact of incomplete phosphoproteomics datasets on comparative analysis, and we present bioinformatics strategies to quantify the impact of different experimental workflows on measured phosphoproteomes. We show that plotting the saturation in observed phosphosites in replicates provides a reproducible picture of the extent of a particular phosphoproteome. Still, we are still far away from a complete picture of the total human phosphoproteome. The impact of different experimental techniques on the similarity between phosphoproteomes can be estimated by comparing datasets from different experimental pipelines to a common reference. Our results show that comparative analysis is most powerful when datasets have been generated using the same experimental workflow. We show this experimentally by measuring the tyrosine phosphoproteome from Caenorhabditis elegans and comparing it to the tyrosine phosphoproteome of HeLa cells, resulting in an overlap of about 4%. This overlap between very different organisms represents a three-fold increase when compared to dataset of older studies, wherein different workflows were used. The strategies we suggest enable an estimation of the impact of differences in experimental workflows on the overlap between datasets. This will allow us to perform comparative analyses not only on datasets specifically generated for this purpose, but also to extract insights through comparative analysis of the ever-increasing wealth of publically available phosphorylation data.     

Evaluating a sampling protocol for assessing plant diversity in prairie fens

Prairie fens are globally vulnerable wetlands that are considered a conservation priority due to threats to their high biodiversity and hydrological functions. Establishing a thorough and repeatable plant sampling protocol is critical to evaluating conservation and management initiatives. Our goal was to evaluate a sample methodology designed to assess prairie fen plant diversity and determine if it produced results (1) representative of site diversity, (2) comparable among fens, and (3) efficient to collect. Nineteen fens between 8.5 and 28.4 ha were surveyed twice within one growing season during 2012 and 2013 field seasons using an area-proportional, random design. The turnover in species between spring and summer sampling periods within a site ranged from 8 to 50 %. Sample coverage of total estimated plant species richness ranged from 84.8 to 95.0 % with a mean of 90.1 %. We compared results from our area-proportional, random design to simulated random samples of 10, 15, 20, 25, 30, 35 and 40 quadrats per site. No significant difference was found in sample coverage per fen when using sampling rates of 25, 30, or 35 quadrats per site versus the area-proportional design. Shannon’s diversity index and floristic quality index differed by sample period and number of quadrats sampled per fen. Our sample design produced acceptable levels of coverage and facilitated comparisons across fens. Our methodology could be applied to future research, restoration monitoring, and conservation planning efforts in Midwestern prairie fens.     

The structure of a plant-pollinator food web

The pollination biology literature is dominated by examples of specialization between plants and their pollinators. However, a recent review shows that it is generalization that prevails in the field, with most plants having a number of pollinators and most pollinators visiting a number of plants. Consequently, the vast majority of plant–pollinator interactions are embedded in a complex web of plant–pollinator interactions. These plant-pollinator webs can be studied in the manner of conventional food webs and the aim of this paper is to illustrate how contemporary methods of web construction and analysis can be applied to plant-pollinator communities.     

Private channels in plant-pollinator mutualisms

Volatile compounds often mediate plant-pollinator interactions, and may promote specialization in plant-pollinator relationships, notably through private channels of unusual compounds. Nevertheless, the existence of private channels, i.e., the potential for exclusive communication via unique signals and receptors, is still debated in the literature. Interactions between figs and their pollinating wasps offer opportunities for exploring this concept. Several experiments have demonstrated that chemical mediation is crucial in ensuring the encounter between figs and their species-specific pollinators. Indeed, chemical messages emitted by figs are notably species- and developmental stage-specific, making them reliable cues for the pollinator. In most cases, the species-specificity of wasp attraction is unlikely to result from the presence of a single specific compound. Nevertheless, a recent paper on the role of scents in the interaction between Ficus semicordata and its pollinating wasp Ceratosolen gravelyi showed that a single compound, 4-methylanisole, is the main signal compound in the floral scent, and is sufficient by itself to attract the obligate pollinator. Mainly focusing on these results, we propose here that a floral scent can act as a private channel, attracting only the highly specific pollinator.Key words: chemical mediation, ficus, agaonidae, private channel, floral filter, coevolved mutualismMutualisms are interspecies interactions in which each participant gains net benefits from interacting with its partner. Like many other interspecies interactions, mutualisms are usually mediated by chemical signals. For instance, floral scents act as pollinator attractants in numerous plant species.^1–3 We studied the chemical compounds that mediate a set of interactions which has become a model system for understanding the evolution of mutualisms: the interactions between Ficus (Moraceae) and their species-specific pollinating fig wasps (Chalcidoidea: Agaonidae). In this ‘nursery pollination mutualism’, the pollinators can breed only in receptive figs of their host tree, which depends in turn on the wasp as its sole pollinator. Each pollinator species is usually associated with a single Ficus species. Fig trees mainly grow in tropical regions, and many species can co-occur in the same forest. In these regions, the density of individual species is often quite low.⁴ Therefore, signals emitted by each species must be efficient at long distances and specific, to allow the attraction of the associated pollinator. In all of the Ficus species that have been studied so far (approximately 40 of a total of roughly 800 species worldwide), figs have been shown to release volatile compounds when they are receptive (i.e., at the stage when pollination can occur).^5–10 Behavioral tests have been performed with pollinators of several species, confirming for these species the role of fig scent in pollinator attraction (Soler et al. in prep).^5–7,9,11 In the floral scents of the fig species studied, at least two to five major compounds account for the majority of the total volatiles emitted by receptive figs.^8,10,12–15 These major volatiles emitted by receptive figs are generally compounds that are not rare in floral fragrances. The species-specificity of wasp attraction is thus usually not likely to result from the presence of only one single specific compound.^10,13 However, Chen and co-workers,¹⁶ focusing on Ficus semicordata, found that a single benzenoid compound, 4-methylanisole, is sufficient to attract its pollinator. Though 4-methylanisole occurs in floral fragrances, having been documented in floral scents of plants from 17 families (of the 90 families included in the review by Knudsen et al.),¹⁷ it usually accounts for only a fraction of total volatiles, and this was the first time that this benzenoid compound has been reported in the floral scent of a Ficus species.^7,10–12,18 To our knowledge, no previous study has shown that 4-methylanisole is attractive to pollinators of any plant, or that this compound could by itself mediate the specificity of any mutualistic interaction.Raguso (2008)³ defined a ‘private channel’ as the potential for such exclusive communication via unique signals and receptors. Moreover, according to Schaefer et al.¹⁹ private channels must fit three major criteria: (1) the identification of an intended (effective mutualist) receiver; (2) sensitive signal detection by this receiver, and finally (3) poor detection by unintended (less effective) receivers. Chen et al.¹⁶ showed that a single compound, 4-methylanisole, accounted for more than 90% of the volatile compounds emitted by receptive figs of F. semicordata. This compound is also known not to be produced by the two other sympatric Ficus species in which floral odours have also been studied, nor by any Ficus species whose scent has been analyzed (Soler et al., in preparation).^10,13 Moreover, Chen et al.¹⁶ found that the species-specificity of the attraction of Ceratosolen gravelyi, the pollinating wasp of Ficus semicordata, was due mainly, if not entirely, to this single major compound. Indeed, based on behavioural (olfactory) tests, they showed that the specialized pollinating wasp detects 4-methylanisole and is attracted by it, even at low concentrations (wasp response tested in concentrations ranging from 1.22 × 10² ng/100 µl to 1.22 × 10⁶ ng/100 µl). The last criterion for a private channel proposed by Schaefer et al.¹⁹ i.e., poor detection by unintended receivers, is the only one which has not been clearly demonstrated by Chen et al.¹⁶ In the case of fig/fig wasp mutualisms, the unintended receivers correspond obviously to the parasites of the mutualism. Indeed, many fig species harbor numerous species of chalcidoid wasps that mature within ovaries in fig inflorescences, like the pollinator, but do not carry pollen. Each of these non-pollinating fig wasps is assumed to be associated specifically with a single Ficus species²⁰ and to use fig scents as cues to detect the host species, as do pollinating fig wasps.²¹ However, in the case of the F. semicordata/C. gravelyi mutualism, no non-pollinating fig wasps have been observed ovipositing during the period when figs are at the receptive stage. This situation is quite unusual in Ficus species (Proffit M, unpublished data; Rasplus J-Y, personal communication). The apparent absence of ‘eavesdropping’ parasites at the time when pollinators are attracted to the figs suggests that the last criterion of a private channel—poor detection by potential receivers other than the specific pollinator—also holds in this case, although this has not been experimentally demonstrated.The study by Chen et al.¹⁶ is, to our knowledge, the first that attempted to test the existence of a private channel in a fig/fig wasp interaction. Nevertheless, this is not the first case of a putative private channel in a nursery pollination mutualism. Indeed, examples have been highlighted in the interactions between Yucca filamentosa (Agavaceae) and its moth pollinator Tegeticula cassandra (Prodoxidae)²² and in the interactions between Peltandra virginica (Araceae) and its pollinating fly Elachiptera formosa (Chloropidae).²³ Similarly, the existence of private channels has been suggested for several species in the family Eupomatiaceae, pollinated by beetles.²⁴ In contrast, Svensson et al.²⁵ showed that in the Breynia (Phyllanthaceae)/Epicephala (Gracillariidae) interaction, pollinators are attracted by common volatile compounds, supporting the hypothesis that no private channel exists in this case. In a review of the role of scents in plant-pollinator interactions, Raguso³ highlighted the putative examples of private channels, but noted that their existence is still debated, notably in the case of non co-specialized plant-pollinator interactions. Nevertheless, some studies have suggested that private channels do exist in this class of interactions. Most examples concern the Orchidaceae. For instance, Eltz et al.²⁶ showed that carvone oxide and ipsdienol are volatile floral rewards emitted by Neotropical orchids pollinated by male euglossine bees, which collect volatile substances for courtship displays. However, probably the best-known examples are Ophrys spp., temperate-zone terrestrial orchids whose flowers mimic the female pheromone of the pollinator to attract males, which pollinate flowers by pseudo-copulation.^27–29 In his review of the role of scents in plant pollinator interactions, Raguso³ also proposed that floral filters do not need to rely upon exclusive olfactory signals or receptors. Indeed, few studies have determined whether pollinator-attractive compounds could alone assure species-specificity (private channel), or whether specificity is mediated by more complex ‘floral filters’, of which scent is only one component. These latter may integrate mechanical or other kinds of barriers, as seems to be the case in the interaction between the dwarf palm Chamaerops humilis and the weevil Derelomus chamaeropsis.³⁰In the literature about private channels in chemical mediation of mutualisms, two points still seem unclear. One is a semantic point: do cases in which specificity is ensured by specific ratios of several more common compounds constitute a private channel, or is this concept restricted to cases in which specificity is ensured by a single rare compound? The literature on private channels emphasizes cases of the latter type. A related question is whether specificity is sometimes ensured not by a single rare compound, but by a combination of rare compounds. While all the putative cases of private channels that have attracted attention concern emission of and attraction to a single rare compound,^3,16,18 the limited number of studied cases does not allow drawing firm general conclusions. Nevertheless, we might think that a hypothetical private channel constituted by several rare compounds might be more difficult to evolve (if it requires the acquisition of several biosynthetic pathways by the plant, and of specific receptors by the insect) or counter-selected (owing to greater costs).We propose here that in the mutualism between F. semicordata and C. gravelyi, despite the existence of mechanical barriers to flower visitation (as in all Ficus species), available information on the chemical communication between plant and pollinator constitutes a strong case for the mediation of a highly specific interaction through a private channel, which acts largely alone as a floral filter that prevents ‘cheaters’ from finding and exploiting a potential resource. An interesting long-term consequence of such an adaptation in a highly co-specialized plant-pollinator interaction is that it might reduce evolutionary flexibility, preventing host shifts, and perhaps making it difficult for the mutualists to evolve counter-adaptations to a new parasite that ‘decodes’ the private channel. Private channels may be isolated adaptive peaks, even more difficult to escape than they are to reach. This could explain their apparent infrequent occurrence in nature.     

The geographical mosaic of coevolution in a plant-pollinator mutualism.

Although coevolution is widely accepted as a concept, its importance as a driving factor in biological diversification is still being debated. Because coevolution operates mainly at the population level, reciprocal coadaptations should result in trait covariation among populations of strongly interacting species. A long-tongued fly (Prosoeca ganglbaueri) and its primary floral food plant (Zaluzianskya microsiphon) were studied across both of their geographical ranges. The dimensions of the fly's proboscis and the flower's corolla tube length varied significantly among sites and were strongly correlated with each other. In addition, the match between tube length of flowers and tongue length of flies was found to affect plant fitness. The relationship between flower tube length and fly proboscis length remained significant in models that included various alternative environmental (altitude, longitude, latitude) and allometric (fly body size, flower diameter) predictor variables. We conclude that coevolution is a compelling explanation for the geographical covariation in flower depth and fly proboscis length.     

Comparative population genetic structure in a plant-pollinator/seed predator system

Comparative analyses of spatial genetic structure of populations of plants and the insects they interact with provide an indication of how gene flow, natural selection and genetic drift may jointly influence the distribution of genetic variation and potential for local co‐adaptation for interacting species. Here, we analysed the spatial scale of genetic structure within and among nine populations of an interacting species pair, the white campion Silene latifolia and the moth Hadena bicruris, along a latitudinal gradient across Northern/Central Europe. This dioecious, short‐lived perennial plant inhabits patchy, often disturbed environments. The moth H. bicruris acts both as its pollinator and specialist seed predator that reproduces by laying eggs in S. latifolia flowers. We used nine microsatellite markers for S. latifolia and eight newly developed markers for H. bicruris. We found high levels of inbreeding in most populations of both plant and pollinator/seed predator. Among populations, significant genetic structure was observed for S. latifolia but not for its pollinator/seed predator, suggesting that despite migration among populations of H. bicruris, pollen is not, or only rarely, carried over between populations, thus maintaining genetic structure among plant populations. There was a weak positive correlation between genetic distances of S. latifolia and H. bicruris. These results indicate that while significant structure of S. latifolia populations creates the potential for differentiation at traits relevant for the interaction with the pollinator/seed predator, substantial gene flow in H. bicruris may counteract this process in at least some populations.     

Evaluating interrater agreement through "case-control" sampling

An approach to evaluating interrater agreement is presented that is based on "case-control" sampling scheme, in which individuals are classified by one rating method and stratified prior to being classified by a second rating method. A new estimate of the kappa interrater agreement index that is based on the case-control scheme is also presented. Power and other economic considerations are discussed, indicating that the new approach may be useful in practice.     

Evolution of mutualism in plant-pollinator interactions on islands

The evolution and ecology of interactions between plants and pollinators are discussed based on the studies on the Izu Islands and mainland Honshu, Japan. The species assemblage is depauperate, and long-tongued pollinators are absent or rare on the islands. Bumblebees, one of the most important pollinators in Japan, are generally absent. Plants depending strongly on bumblebee pollination are absent on Izu Islands, but those depending on varied pollinators including bumblebees display smaller flower sizes and accommodate smaller pollinators than their mainland counterparts. Breeding systems of these species also shift to partial inbreeding, possibly an evolutionary result of the decrease in pollinator availability. Changes in flowering phenology between mainland and island populations also occur. Plants in the islands tend to reproduce vegetatively less frequently and produce greater numbers of smaller seeds than those in the mainland. The possibility of evolution on the side of island pollinator species is also discussed, although there are few data on this topic.     

Evaluating completeness of maternal mortality reporting in a rural health and social affairs unit in Vellore, India, 2004

Health systems in developing countries infrequently implement and evaluate maternal death surveillance. This study identified under-reported and misclassified maternal deaths among women of reproductive age between 1999 and 2004 in a rural service unit in Vellore, India. In-depth interviews, semi-structured interviews and structured questionnaires were used to identify maternal deaths known to health care providers and community leaders who regularly come in contact with pregnant women. Eighteen under-reported and misclassified cases--or 50% of maternal deaths--were reported. These included 29% of abortion-related and 7% of domestic violence-related deaths. Based on this study's fieldwork, the existing death surveillance system detected 100% of the maternal deaths reported by hospital staff; however, it missed most maternal deaths reported by community workers. The latter are more likely than deaths reported by hospital workers to result from abortion and family violence. The existing surveillance system should be augmented with a community-based death surveillance system. This comprehensive approach identified twice as many maternal deaths than previously recorded and could be applied in other settings. Appropriate public health interventions should be initiated to prevent maternal deaths in this community.     

A means of estimating the completeness of haplotype sampling using the Stirling probability distribution

I present a tool for use in phylogeography that helps estimate the completeness of haplotype sampling, based on the number of individuals analysed and the number of different haplotypes they show. Applying the Stirling probability distribution and Bayes’ theorem, a posterior probability distribution of the total number of haplotypes, including those yet to be observed, may be obtained. This enables one to deduce if the data are complete enough for further analysis. A program for calculating the posterior probabilities is available at http://www.botanik.univie.ac.at/plantchorology/haplo.htm .     

Phenotypic divergence and inter-specific trait correlation in a plant-pollinator/seed predator mutualism

Plant-pollinator interactions have been suggested as key drivers of morphological divergence and speciation of the involved taxa. These interactions can also promote sexual dimorphism in both the plant and pollinator, particularly if the pollinator is also a seed-eater and/or exerts different selection pressures on male and female plants. Here we tested the hypotheses that plant-pollinator interactions can be reflected in trait variation and sexual dimorphism in both organisms within and across populations. Across nine European populations, we examined intraspecific variation and sexual dimorphism in phenotypic traits potentially involved in the plant–insect interaction of the dioecious white campion Silene latifolia (Caryophyllaceae) and its specialist pollinator Hadena bicruris (Noctuidae). This interaction is expected to entail sex-specific selective pressures, as female moths lay eggs on female plants and the larvae predate on the seeds during their development. We compared divergence in phenotypic traits among populations and between sexes within populations, examined correlations between plant and pollinator traits, and between phenotypic distances and genetic distances among co-occurring populations for both plants and insects. We found key differences in phenotypic traits across populations of both the plant and moth, though only in the moth were these differences correlated with geographic distances. We also found evidence for sexual dimorphism in the plant but not in the pollinator. Evolution of floral sexual dimorphism in S. latifolia most likely results from the joint contribution of different selective forces, including biotic interactions with H. bicruris moths.     

The effects of cattle grazing on plant-pollinator communities in a fragmented Mediterranean landscape

The main aims of this study were to assess grazing impacts on bee communities in fragmented mediterranean shrubland (phrygana) and woodland habitats that also experience frequent wildfires, and to explain the mechanisms by which these impacts occur. Fieldwork was carried out in 1999 and 2000 on Mount Carmel, in northern Israel, a known hot-spot for bee diversity. Habitats with a range of post-burn ages and varying intensities of cattle grazing were surveyed by transect recording, grazing levels, and the diversity and abundance of both flowers and bees were measured. The species richness of both bees and flowers were highest at moderate to high grazing intensities, and path-analysis indicated that the effects of both grazing and fire on bee diversity were mediated mainly through changes in flower diversity, herb flowers being more important than shrubs. The abundance of bees increased with intensified grazing pressure even at the highest levels surveyed. Surprisingly though, changes in bee abundance at high grazing levels were not caused directly by changes in flower cover. The variation in bee abundance may have been due to higher numbers of solitary bees from the family Halictidae in grazed sites, where compacted ground (nesting resource) and composites (forage resource) were abundant. The effects of grazing on plants were clearest in the intermediate-aged sites, where cattle inhibited the growth of some of the dominant shrubs, creating or maintaining more open patches where light-demanding herbs could grow, thus allowing a diverse flora to develop. Overall, bee communities benefit from a relatively high level of grazing in phrygana. Although bee and flower diversity may decrease under very heavy grazing, the present levels of grazing on Mount Carmel appear to have only beneficial effects on the bee community.     

Large herbivores transform plant-pollinator networks in an African savanna

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Structure of a plant–flower-visitor network in the high-altitude sub-alpine desert of Tenerife, Canary Islands

Confined within a volcanic caldera at 2000 m a.s.l., the sub-alpine desert of Tenerife, Canary Islands, harbors a distinct biota. At this altitude the climate is harsh and the growing season short. Hence, plant and animal communities, constituting the sub-alpine plant–flower-visitor network, are clearly delimited, both spatially and temporally. We investigated species composition and interaction structure of this system. A total of 11 plant species (91% endemics) and 37 flower-visiting animal species (62% endemics) formed 108 interactions. Numbers of interactions among species varied ten-fold within both plant and animal communities. Generalization level of a species was positively correlated with its local abundance. Two separate network analyses revealed a significantly nested structure. In relation to a plant–flower-visitor system, nestedness implies that specialized species (animals or plants) interact with a subset of the species pool visiting (animals) or being visited (plants) by more generalized species. Therefore, specialized, locally rare plants tend to be visited by generalized, locally abundant animals, and specialized, locally rare animals tend to utilize generalized, locally abundant food plants. Such patterns could have implications for conservation of the sub-alpine network, and stress the importance of preserving not only rare species, but also the more abundant ones, which may be key food resources or pollinators in the plant–flower-visitor network.     

Spatial variation in selection in a plant-pollinator system in the wadis of Sinai,Egypt

We studied an insect-plant pollination system in adjacent steep-sided wadis and a connecting plain in the mountains of southern Sinai (Egypt): this environment creates a strongly divided habitat, which may promote the local differentiation of sub-populations. We tested for spatial differences in phenotypic reproductive characters of the only plant flowering abundantly in early spring, Alkanna orientalis (Boraginaceae), and its major pollinator at that time of year, Anthophora pauperata (Apoidea, Anthophoridae). There were significant morphological differences between sub-populations of Alkanna, mainly between plants from the narrower wadis and those on the interconnecting plain. Flowers on the plain were larger, with wider corollas and more nectar standing crop; these plants retained more flowers on the inflorescence, but received many fewer visits to flowers. There was a significant selection gradient between flower size and maternal fitness (seed set) in the plain, but not elsewhere. Natural selection may have increased resources devoted to attracting insect visitors in response to fewer pollinating visits in the plain. Consistent with this explanation, by experimentally manipulating flower number per plant, we showed that within a wadi having more flowers on a plant secured more visits.     

Evaluating the sampling bias in pattern of subterranean species richness: combining approaches

We investigated the pattern of species richness of obligate subterranean (troglobiotic) beetles in caves in the northwestern Balkans, given unequal and biased sampling. On the regional scale, we modeled the relationship between species numbers and sampling intensity using an asymptotic Clench (Michaelis–Menten) function. On the local scale, we calculated Chao 2 species richness estimates for 20 × 20 km grid cells, and investigated the distribution of uniques, species found in only one cave within the grid cell. Cells having high positive residuals, those with above average species richness than expected according to the Clench function, can be considered true hotspots. They were nearly identical to the observed areas of highest species richness. As sampling intensity in a grid cell increases the expected number of uniques decreases for any fixed number of species in the grid cell. High positive residuals show above average species richness for a certain level of sampling intensity within a cell, so further sampling has the most potential for additional species. In some cells this was supported by high numbers of uniques, also indicating insufficient sampling. Cells with low negative residuals have fewer species than would be expected, and some of them also had a low number of uniques, both indicating sufficient sampling. By combining different analyses in a novel way we were able to evaluate observed species richness pattern as well as identify, where further sampling would be most beneficial. Approach we demonstrate is of broad interest to study of biota with high levels of endemism, small distribution ranges and low catchability.     

Patterns of root architecture adaptation of a phreatophytic perennial desert plant in a hyperarid desert

Plant root systems can respond to nutrient availability and distribution by changing the three-dimensional deployment of their root architecture. The year after year variation of root architecture was investigated in a perennial phreatophyte in the controlled condition vegetation situated in the oasis in the Chinese Taklamakan desert with the goal to elucidate their adaptation to hyperarid environment. The whole plants of an indigenous perennial legume Alhagi sparsifolia Shap. with intact root systems were excavated at the end of each growing season from 2007 to 2009 and analyzed for architecture, above and belowground biomass, root/shoot ratio, root depth, seed yields and ramet. Changes in water availability were found to have stupendous effects on taproot depth, lateral root length and ramet quantity. Relative to shoot dry weight, taproot depth decreased with increasing water availability. In contrast, lateral root elongation was promoted by higher water availability.We tested the hypothesis that (1) irrigation increases root biomass and the quantity of ramets, and (2) A. sparsifolia Shap. develops an efficient root architecture that could absorb soil water and nutrition.