Leonardo R. Jorge

Land-use intensification causes multitrophic homogenization of grassland communities.

Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

An integrated framework to improve the concept of resource specialisation

Resource specialisation, although a fundamental component of ecological theory, is employed in disparate ways. Most definitions derive from simple counts of resource species. We build on recent advances in ecophylogenetics and null model analysis to propose a concept of specialisation that comprises affinities among resources as well as their co-occurrence with consumers. In the distance-based specialisation index (DSI), specialisation is measured as relatedness (phylogenetic or otherwise) of resources, scaled by the null expectation of random use of locally available resources. Thus, specialists use significantly clustered sets of resources, whereas generalists use over-dispersed resources. Intermediate species are classed as indiscriminate consumers. The effectiveness of this approach was assessed with differentially restricted null models, applied to a data set of 168 herbivorous insect species and their hosts. Incorporation of plant relatedness and relative abundance greatly improved specialisation measures compared to taxon counts or simpler null models, which overestimate the fraction of specialists, a problem compounded by insufficient sampling effort. This framework disambiguates the concept of specialisation with an explicit measure applicable to any mode of affinity among resource classes, and is also linked to ecological and evolutionary processes. This will enable a more rigorous deployment of ecological specialisation in empirical and theoretical studies.

Ecological literacy and beyond: Problem-based learning for future professionals

Ecological science contributes to solving a broad range of environmental problems. However, lack of ecological literacy in practice often limits application of this knowledge. In this paper, we highlight a critical but often overlooked demand on ecological literacy: to enable professionals of various careers to apply scientific knowledge when faced with environmental problems. Current university courses on ecology often fail to persuade students that ecological science provides important tools for environmental problem solving. We propose problem-based learning to improve the understanding of ecological science and its usefulness for real-world environmental issues that professionals in careers as diverse as engineering, public health, architecture, social sciences, or management will address. Courses should set clear learning objectives for cognitive skills they expect students to acquire. Thus, professionals in different fields will be enabled to improve environmental decision-making processes and to participate effectively in multidisciplinary work groups charged with tackling environmental issues.

Morphometric Differentiation of Fruit Fly Pest Species of the Anastrepha fraterculus Group (Diptera: Tephritidae)

ABSTRACT Fruit flies (Tephritidae) include pests of quarantine importance, some of which belong to the genus Anastrepha. Some species in this group are difficult to identify. We tested the accuracy of morphometric techniques to distinguish three species of the fraterculus group (A. fraterculus, A. obliqua, and A. sororcula), using images of the aculeus and wing. The geometric morphometrics of the wings, using 17 landmarks, indicated differences in the wing shape of each species, separating them successfully into distinct groups. The conventional morphometrics of seven measurements of the aculeus tip, by linear discriminant analysis, also indicated differences in the species, separating them into three groups.

Phylogenetic trophic specialization: a robust comparison of herbivorous guilds.

Resource specialization is a key concept in ecology, but it is unexpectedly difficult to parameterize. Differences in resource availability, sampling effort and abundances preclude comparisons of incompletely sampled biotic interaction webs. Here, we extend the distance-based specialization index (DSI) that measures trophic specialization by taking resource phylogenetic relatedness and availability into account into a rescaled version, DSI*. It is a versatile metric of specialization that expands considerably the scope and applicability, hence the usefulness, of DSI. The new metric also accounts for differences in abundance and sampling effort of consumers, which enables robust comparisons among distinct guilds of consumers. It also provides an abundance threshold for the reliability of the metric for rare species, a very desirable property given the difficulty of assessing any aspect of rare species accurately. We apply DSI* to an extensive dataset on interactions between insect herbivores from four folivorous guilds and their host plants in Papua New Guinean rainforests. We demonstrate that DSI*, contrary to the original DSI, is largely independent of sample size and weakly and non-linearly related with several host specificity measures that do not adjust for plant phylogeny. Thus, DSI* provides further insights into host specificity patterns; moreover, it is robust to the number and phylogenetic diversity of plant species selected to be sampled for herbivores. DSI* can be used for a broad range of comparisons of distinct feeding guilds, geographical locations and ecological conditions. This is a key advance in elucidating the interaction structure and evolution of highly diversified systems.

High specialization and limited structural change in plant-herbivore networks along a successional chronosequence in tropical montane forest

Secondary succession is well-understood, to the point of being predictable for plant com-munities, but the successional changes in plant-herbivore interactions remains poorly explored. This is particularly true for tropical forests despite the increasing importance of early successional stages in tropical landscapes. Deriving expectations from successional theory, we examine properties of plant-herbivore interaction networks while accounting for host phylogenetic structure along a succession chronosequence in montane rainforest in Papua New Guinea. We present one of the most comprehensive successional inves-tigations of interaction networks, equating to > 40 person years of field sampling, and one of the few focused on montane tropical forests. We use a series of nine 0.2 ha for-est plots across young secondary, mature secondary and primary montane forest, sampled almost completely for woody plants and larval leaf chewers (Lepidoptera) using forest fell-ing. These networks comprised of 12 357 plant-herbivore interactions and were analysed using quantitative network metrics, a phylogenetically controlled host-use index and a qualitative network beta diversity measure. Network structural changes were low and spe-cialisation metrics surprisingly similar throughout succession, despite high network beta diversity. Herbivore abundance was greatest in the earliest stages, and hosts here had more species-rich herbivore assemblages, presumably reflecting higher palatability due to lower defensive investment. All herbivore communities were highly specialised, using a phylo-genetically narrow set of hosts, while host phylogenetic diversity itself decreased through-out the chronosequence. Relatively high phylogenetic diversity, and thus high diversity of plant defenses, in early succession forest may result in herbivores feeding on fewer hosts than expected. Successional theory, derived primarily from temperate systems, is limited in predicting tropical host-herbivore interactions. All succession stages harbour diverse and unique interaction networks, which together with largely similar network structures and consistent host use patterns, suggests general rules of assembly may apply to these systems.

Phylogenetic tree of the endophagous insect species

This is an informal tree constructed by taxonomic substitution (sensu Bininda-Edmonds et al. 2001) of the available phylogenetic information for the insect species collected in our study. Starting with a purely taxonomic tree, we added information on the relationships between taxa whenever available (Supplementary material 1 Figure A1).

Host-Plant Specialization Mediates the Influence of Plant Abundance on Host Use by Flower Head-Feeding Insects

Abstract Among-population variation in host use is a common phenomenon in herbivorous insects. The simplest and most trivial explanation for such variation in host use is the among-site variation in plant species composition. Another aspect that can influence spatial variation in host use is the relative abundance of each host-plant species compared to all available hosts. Here, we used endophagous insects that develop in flower heads of Asteraceae species as a study system to investigate how plant abundance influences the pattern of host-plant use by herbivorous insects with distinct levels of host-range specialization. Only herbivores recorded on three or more host species were included in this study. In particular, we tested two related hypotheses: 1) plant abundance has a positive effect on the host-plant preference of herbivorous insects, and 2) the relative importance of plant abundance to host-plant preference is greater for herbivorous species that use a wider range of host-plant species. We analyzed 11 herbivore species in 20 remnants of Cerrado in Southeastern Brazil. For 8 out of 11 herbivore species, plant abundance had a positive influence on host use. In contrast to our expectation, both the most specialized and the most generalist herbivores showed a stronger positive effect of plant species abundance in host use. Thus, we found evidence that although the abundance of plant species is a major factor determining the preferential use of host plants, its relative importance is mediated by the host-range specialization of herbivores.

Segmentation of similar images using graph matching and community detection

In this paper, we propose a new method to segment sets of similar images using graphmatching and community detection algorithms. The images in a database are represented by Attributed Relational Graphs, allowing the analysis of structural and relational information of the regions (objects) inside them. The method gathers such information by matching all images to each other and stores them in a single graph, called Match Graph. From it, we can check the obtained pairwise matchings for all images of the database and which objects relate to each other. Then, with the interactive segmentation from one single image from the dataset (e.g. the first one) we can observe these relationships between them through a color label, thus leading to the automatic segmentation of all images. We show an important biological application on butterfly wings images and a case using images taken by a digital camera to demonstrate its effectiveness.