A multidimensional functional trait analysis of resource exploitation in European ants

The major factors explaining ecological variation in plants have been widely discussed over the last decade thanks to numerous studies that have examined the covariation that exists between pairs of traits. However, multivariate relationships among traits remain poorly characterized in animals. In this study, we aimed to identify the main multivariate trait dimensions that explain variance in important functional traits related to resource exploitation in ants. To this end, we created a large ant trait database. This database includes information on 11 traits that are important in ant resource exploitation; data were obtained for 150 European species found in different biomes. First, we examined the pairwise correlations between the traits included in the database. Second, we used multivariate analyses to identify potential trait dimensions. Our study shows that, to a great extent, resource exploitation strategies align along two main trait dimensions. The first dimension emerged in both the overall and group-specific analyses, where it accounted for the same pairwise trait correlations. The second dimension was more variable, as species were grouped by levels of taxonomy, habitat, and climate. These two dimensions included most of the significant pairwise trait correlations, thus highlighting that complementarity, but also redundancy, exists among different pairs of traits. The first dimension was associated with behavioral dominance: dominance was associated with large colony size, presence of multiple nests per colony, worker polymorphism, and a collective foraging strategy. The second dimension was associated with resource partitioning along dietary and microhabitat lines: it ranged from species that consume liquid foods, engage in group foraging, and mainly nest in the vegetation to species that consume insects and seeds, engage in individual foraging, and demonstrate strictly diurnal activity. Our findings establish a proficient ecological trait-based animal research that minimizes the number of traits to be measured while maximizing the number of relevant trait dimensions. Overall, resource exploitation in animals might be framed by behavioral dominance, foraging strategy, diet, and nesting habitat; the position of animal species within this trait space could provide relevant information about their distribution and abundance, for today as well as under future global change scenarios.Peer reviewe

Dinàmica postincendi i interaccions entre plantes i formigues mediterrànies

Consultable des del TDXTítol obtingut de la portada digitalitzadaEn els ecosistemes mediterranis, la recuperació postincendi de les comunitats de plantes i animals és molt variable, depenent tant de factors biòtics com abiòtics. La dinàmica de les poblacions d'animals i plantes ve clarament condicionada per les interaccions que s'estableixen amb altres organismes i són importants en la dinàmica de la recuperació després del foc. Però, són pocs els estudis que analitzen conjuntament la recuperació postpertorbació de les comunitats de plantes i animals. Les interaccions entre les formigues i les plantes són extraordinàriament diverses, i es realitzen en ambdues direccions: les formigues poden actuar sobre les plantes com depredadores o dispersives de llavors, mentre que les plantes poden oferir a les formigues recursos, llocs de nidificació o recobriment. L'objectiu d'aquesta tesi és analitzar l'efecte del foc sobre les comunitats de plantes i formigues mediterrànies i valorar les interaccions entre ambdós grups en l'escenari postincendi. Es demostra com la recuperació postincendi de les comunitats de plantes i formigues de les principals comunitats forestals de Catalunya depèn de la recuperació postincendi de les principals espècies arbòries i/o arbustives, mostrant així un paral·lelisme en la recuperació després del foc d'ambdós grups. També es mostra que la recuperació de les comunitats de plantes i de formigues segueixen un gradient caracteritzat pel dèficit hídric a l'estiu, essent la recuperació superior en àrees més seques que humides. En el cas de la vegetació, una proporció superior de germinadores permet una recuperació més ràpida de la comunitat de plantes pocs anys després del foc; això es deu a les característiques pròpies de les germinadores i a l'escala de temps considerada. La proporció de les diferents estratègies de resposta al foc varia a través del gradient climàtic, augmentant la proporció de germinadores amb la sequera. Per la seva part, les comunitats de formigues de zones més seques es recuperen millor perquè en aquestes zones trobem més espècies característiques d'ambients oberts, els quals són hàbitats similars a aquells generats pel foc. D'altra banda, també es demostra com la vegetació condiciona l'estructura i composició de les comunitats de formigues en els primers anys després del foc a escala més local, de manera que una reducció dels recursos alimentaris i de l'ombra associats a la vegetació per separat produeixen una reducció del número d'espècies de formigues. Les diferents combinacions d'aquests dos factors produeixen un canvi en la composició de la comunitat de formigues. Pocs anys després de la pertorbació, els efectes del foc encara són molt presents, i les comunitats de formigues no segueixen els patrons d'estructuració de comunitats madures. Per altra banda, es demostra com les formigues granívores augmenten les distàncies de dispersió de les espècies de plantes amb curtes distàncies de dispersió abiòtica, i canvien el patró espacial de distribució de les seves llavors. Mitjançant un model demogràfic, es mostra la importància d'aquestes formigues com depredadores, i també, encara que en menor grau, com dispersives. En aquesta tesi es constata clarament l'existència d'interaccions entre les comunitats de plantes i de formigues mediterrànies en un escenari postincendi. Podem afirmar que la recuperació postincendi de les comunitats de plantes condiciona la recuperació de les comunitats de formigues a través de les espècies clau, però en la recuperació de les comunitats de formigues també és important la inèrcia anterior al foc. D'altra banda, i a escala més petita, demostrem que les formigues poden condicionar la dinàmica d'algunes espècies de plantes. Encara que aquest efecte sembla petit, podria ser que amb els anys durant el procés de successió postincendi es vagi acumulant i tingui importants repercussions en la recuperació postincendi d'algunes espècies de plantes, i conseqüentment de les seves comunitats.In Mediterranean ecosystems, post-fire recovery of plant and animal communities is very variable, depending both on biotic and abiotic factors. Animals and plants population dynamics is conditioned by the interaction with other organisms, which is important for the post-fire recovery dynamics. However, there are few studies that analyse the post-disturbance recovery of animal and plant communities alike. Specifically, plant-ant interactions are extraordinarily diverse, and their implications are two-fold: ants can act on plants like seed predators or dispersers, while plants can offer resources, nesting sites and cover to ants. The aim of my PhD Thesis is to study the impact of fire on Mediterranean plant and ant communities, and to evaluate ant-plant interactions in the post-fire scenario. We show that post-fire recovery of plant and ant communities, in main forest communities of Catalonia, depends on the post-fire recovery of the main tree and/or shrub species. That indicates a strong parallelism between plants and ants regarding their post-fire recovery. Post-fire recovery depends also on the climatic gradient (defined as summer water deficit), the recovery being higher in drier areas. Concerning plants, a higher proportion of obligate seeders allows a quicker recovery of plant communities several years after fire; this is due both to the characteristics of the seeders and to the time scale considered in the study. The proportion of the different functional groups (characterized by their post-fire strategy) varies along the climatic gradient, whereby the proportion of seeders increases with dryness. Concerning ants, communities living on drier areas recover better, because of the higher abundance of species commonly found in open habitats (i.e. habitats similar to those generated by fire). On the other hand, we also demonstrate that the vegetation locally determines the structure and composition of ant communities during the first years after fire. Thus, a reduction either in food resources or in level of shade associated with vegetation causes a decrease in species number. The different combinations of these two factors give rise to changes in the ant community composition. Few years after disturbance, fire effects are still very present, as ant communities do not yet follow the structure pattern of mature communities. On the other hand, we also show that granivorous ants increase the dispersal distance of plant species with short abiotic dispersal distances, and they also change the spatial pattern of their seed distribution. By means of a demographic model we illustrate the importance of ants both as seed predators and, although less importantly, as seed dispersers. In my PhD Thesis, we demonstrate the existence of interactions between Mediterranean ants and plants in a post-fire scenario. We conclude that the post-fire recovery of plant communities in turn determines the post-fire recovery of ant communities through key plant species. Post-fire recovery of ant communities relies also on the inertia before fire. On the other hand, at smaller scale, we demonstrate that ants can modify the dynamics of some plant species. Although this effect is seemingly small, its cumulative effect in the years following the fire may have important consequences for the recovery of some plant species and their communities

És homogènia la recuperació, després del foc, de les comunitats de plantes i de formigues dels boscos de Catalunya?

Es presenten les principals conclusions de diversos estudis amb l'objectiu d'avaluar la resiliència dels boscos de Catalunya després d'un incendi. Es mostra que hi ha un ventall ampli de respostes, que inclou boscos amb una alta resiliència al foc i que recuperen ràpidament l'espècie o espècies arbòries dominants, però també altres boscos en què l'espècie dominant abans del foc no es recupera i són substituïts per altres formacions boscoses o arbustives. La substitució de les espècies dominants i estructuradores del bosc comporta que tota la comunitat de plantes i de formigues que hi viuen tinguin menor resiliència al foc que les dels boscos que mantenen les mateixes espècies dominants d'abans del foc. Aquests resultats impliquen repensar algunes idees sobre les possibles conseqüències dels focs sobre la biodiversitat i quins han de ser els objectius de la gestió de determinades zones cremades.¿Es homogénea la recuperación, tras el incendio, de las comunidades de plantas y de hormigas de los bosques de Cataluña? Se presentan las principales conclusiones de diversos estudios con el objetivo de evaluar la resiliencia de los bosques de Cataluña después de un incendio. Se muestra que existe un amplio abanico de respuestas, que incluye bosques con una alta resiliencia al fuego y que recuperan rápidamente la especie o especies arbóreas dominantes, pero también otros bosques donde la especie dominante no se recupera y son sustituidos por otras formaciones boscosas o arbustivas. La sustitución de estas especies dominantes y estructurantes del bosque supone que toda la comunidad de plantas y de hormigas que viven tengan menor resiliencia al fuego que las de los bosques que mantienen las mismas especies dominantes antes del fuego. Estos resultados implican replantear algunas ideas sobre las posibles consecuencias de los fuegos sobre la biodiversidad y cuáles deben ser los objetivos de gestión de determinadas zonas quemadas.Is homogeneous the postfire recovery of plant and ant communities in Catalan forests? We presents the main conclusions of different studies to analyze the forest resilience in Catalonia after fire. It shows how there is a sufficiently broad range of responses, which include forests with high resilience to fire and quickly recover the species or dominant tree species, but also other forests where before fire, the dominant species are not recovered and then, are replaced by other types of woodland and shrubs. In these cases, the replacement of dominant species and forest structure means that the whole community of plants and ants that live in these forests have less resilience to fire than forests that maintain the same dominant species before fire. These results imply think about the possible consequences of fires on biodiversity and also what should be the objectives of management of certain areas burned

Spatial variability of hosts, parasitoids and their interactions across a homogeneous landscape

Species assemblages and their interactions vary through space, generating diversity patterns at different spatial scales. Here, we study the local-scale spatial variation of a cavity-nesting bee and wasp community (hosts), their nest associates parasitoids), and the resulting antagonistic network over a continuous and homogeneous habitat. To obtain bee/wasp nests, we placed trap-nests at 25 sites over a 32 km2 area. We obtained 1,541 nests (4,954 cells) belonging to 40 host species and containing 27 parasitoid species. The most abundant host species tended to have higher parasitism rate. Community composition dissimilarity was relatively high for both hosts and parasitoids, and the main component of this variability was species turnover, with a very minor contribution of ordered species loss (nestedness). That is, local species richness tended to be similar across the study area and community composition tended to differ between sites. Interestingly, the spatial matching between host and parasitoid composition was low. Host β-diversity was weakly (positively) but significantly related to geographic distance. On the other hand, parasitoid and host-parasitoid interaction β-diversities were not significantly related to geographic distance. Interaction β-diversity was even higher than host and parasitoid β-diversity, and mostly due to species turnover. Interaction rewiring between plots and between local webs and the regional metaweb was very low. In sum, species composition was rather idiosyncratic to each site causing a relevant mismatch between hosts and parasitoid composition. However, pairs of host and parasitoid species tended to interact similarly wherever they co-occurred. Our results additionally show that interaction β-diversity is better explained by parasitoid than by host β-diversity. We discuss the importance of identifying the sources of variation to understand the drivers of the observed heterogeneity

Global life trait spectra of resource exploitation in European ants

Relatório de Estágio em Comunicação e Jornalismo, orientado pela Doutora Isabel Maria Ribeiro Ferin Cunha, apresentado ao Departamento de Filosofia, Comunicação e Informação da Faculdade de Letras da Universidade de Coimbra.A assessoria comunicacional tem um papel importante nas organizações públicas e privadas e pode utilizar diversos meios de comunicação. É possível dizer que um desses mesmos meios de comunicação é o jornalismo em linha, sendo que cada vez mais empresas e instituições se publicitam através deste meio os seus eventos e produtos. A Universidade de Coimbra utiliza como forma de contacto com o seu público a plataforma Notícias UC. Esta encontra-se disponível com os mais variados conteúdos não só dedicados à Universidade de Coimbra, mas também relacionados com a cidade que alberga a instituição de ensino superior com 725 anos. Este relatório de estágio pretende abordar a forma de trabalho da Notícias UC e o seu conteúdo noticioso a partir da estrutura de classificação utilizada na consulta e nas quais os artigos são classificados. Tomando como objetivo inicial a análise do número de notícias por faculdade, este relatório fornece não só um estudo sobre o website, mas também aborda a necessidade de uma página que transmita conteúdos mediáticos para o exterior do espaço académico. Palavras-chave: Jornalismo online; assessoria comunicacional; jornalismo multimédia; Notícias UC.Communication consultancy has an important paper in public and private organizations and uses several mediums. Online journalism can be considered as being one of these, as most of the companies and institutions advertise themselves through events or its products. As a connection with the audience, Notícias UC is available with several contents not only concerning the University of Coimbra, but also about the city that harbours the 725-year-old academy. In this report the working methods on Notícias UC will be addressed as its news content through its several categories, in which the articles are classified. Starting with the number of news per faculty, this report aims to provide not only a study about the website, iv but also to deal with the need of a page that broadcasts mediatic contents to the space outside the university. Key-words: Online Journalism; communication consultancy; multimedia journalism; Notícias UC

Interaction strength in plant-pollinator networks : Are we using the right measure?

Understanding how ecological networks are assembled is important because network structure reflects ecosystem functioning and stability. Quantitative network analysis incorporates measures of interaction strength as an estimate of the magnitude of the effect of interaction partners on one another. Most plant-pollinator network studies use frequency of interaction between individual pollinators and individual plants (encounter) as a surrogate of interaction strength. However, the number of flowers visited per encounter may strongly vary among pollinator and plant species, and therefore not all encounters are quantitatively equivalent. We sampled plant-pollinator interactions in a Mediterranean scrubland and tested whether using a measure of interaction strength based on the number of flowers visited resulted in changes in species (species strength, interaction species asymmetry, specialization) and network descriptors (nestedness, H2', interaction evenness, plant generality, pollinator generality) compared to the encounter-based measure. Several species (including some of the most abundant ones) showed important changes in species descriptors, notably in specialization. These changes were especially important in plant species with large floral displays, which became less specialized with the visit-based measure of interaction strength. At the network level we found significant changes in all properties analysed. With the encounter-based approach plant generality was much higher than pollinator generality (high specialization asymmetry between trophic levels). However, with the visit-based approach plant generality was greatly reduced so that plants and pollinators had similar levels of generalization. Interaction evenness also decreased strongly with the visit-based approach. We conclude that accounting for the number of flowers visited per encounter provides a more ecologically relevant measure of interaction strength. Our results have important implications for the stability of pollination networks and the evolution of plant-pollinator interactions. The use of a visit-based approach is especially important in studies relating interaction network structure and ecosystem function (pollination and/or exploitation of floral resources)

Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics

Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation) and benefits (seed dispersal), the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength

A multidimensional functional trait analysis of resource exploitation in European ants

Abstract. The major factors explaining ecological variation in plants have been widely discussed over the last decade thanks to numerous studies that have examined the covariation that exists between pairs of traits. However, multivariate relationships among traits remain poorly characterized in animals. In this study, we aimed to identify the main multivariate trait dimensions that explain variance in important functional traits related to resource exploitation in ants. To this end, we created a large ant trait database. This database includes information on 11 traits that are important in ant resource exploitation; data were obtained for 150 European species found in different biomes. First, we examined the pairwise correlations between the traits included in the database. Second, we used multivariate analyses to identify potential trait dimensions. Our study shows that, to a great extent, resource exploitation strategies align along two main trait dimensions. The first dimension emerged in both the overall and group-specific analyses, where it accounted for the same pairwise trait correlations. The second dimension was more variable, as species were grouped by levels of taxonomy, habitat, and climate. These two dimensions included most of the significant pairwise trait correlations, thus highlighting that complementarity, but also redundancy, exists among different pairs of traits. The first dimension was associated with behavioral dominance: dominance was associated with large colony size, presence of multiple nests per colony, worker polymorphism, and a collective foraging strategy. The second dimension was associated with resource partitioning along dietary and microhabitat lines: it ranged from species that consume liquid foods, engage in group foraging, and mainly nest in the vegetation to species that consume insects and seeds, engage in individual foraging, and demonstrate strictly diurnal activity. Our findings establish a proficient ecological trait-based animal research that minimizes the number of traits to be measured while maximizing the number of relevant trait dimensions. Overall, resource exploitation in animals might be framed by behavioral dominance, foraging strategy, diet, and nesting habitat; the position of animal species within this trait space could provide relevant information about their distribution and abundance, for today as well as under future global change scenarios