Biology subjects

Pinheiro, R. B. P.

Publications and source records attributed to Pinheiro, R. B. P..

5 recordsLinked to original sources

bioRxiv2026

Specialization between foliar fungal endophyte and plant communities decreases toward the tropics

Associations among species are hypothesized to become fewer and more specialized toward the tropics. However, evidence for the latitudinal specialization gradient (LSG) remains mixed and restricted to plant-animal and host-parasite models, with increasing recognition that our understanding of LSG is often complicated by differences in species richness and sampling effects. Here, we tested whether specialization between foliar fungal endophytes - fungi that live within plant leaves - and their plant hosts increased toward the tropics by surveying 1,539 plants that spanned a 55-degree latitudinal gradient in Central and North America. Contrary to expectations, endophytes and plants formed a greater number of associations that were more evenly distributed toward tropical latitudes and were thus less specialized, even after accounting for differences in endophyte and plant community structure. Endophyte-plant communities were most specialized where evaporative demand and plant richness were low, and where water availability and primary productivity were high. Our findings show a reversed LSG where the specialization between endophytes and plants decreased toward the tropics and provides evidence that many species of endophytes can coexist even when there is high overlap in their host niches.

ecology↗

bioRxiv2021

A novel perspective on the meaning of nestedness with conceptual and methodological solutions

O_LINestedness is a common pattern in metacommunities and interaction networks, whose causes are still subject to investigation. Nestedness inference is challenging because, beyond calculating an index, we need to compare observed and expected values using null models. There are many different null models and the choice between them strongly affects test outcomes. Furthermore, there is no theoretical basis to guide this choice. C_LIO_LIHere, we propose a different look at the meaning of nestedness that improves our understanding of its causes and directly links null models to hypotheses. The nestedness of a matrix is the combination of marginal sum inequality and high overlap. The higher the overlap, the more predictable the cell values by marginal sums. Therefore, the only way a process can increase nestedness is by promoting marginal sum inequalities, without concomitantly introducing preferences. We propose a combination of null models to test for different topological hypotheses. In these null models, interactions are randomized following a probability matrix. The probability matrix of the equiprobable model excludes marginal sum inequalities and consequently all nestedness-generating mechanisms, providing a distribution of expected values for nestedness significance tests. The probability matrix of the proportional model, by conserving marginal sums and maximizing overlap, conserves nestedness-generating mechanisms and excludes nestedness-disrupting mechanisms, thereby yielding the expected nestedness values for fully nested matrices. C_LIO_LIWe advance a new protocol to test for nestedness in binary and weighted matrices, in which those two null models represent different topological hypotheses. Our protocol helps to tell apart cases in which nestedness is different from expected by chance and cases in which nestedness represents the best topological archetype. We also evaluate the efficiency of applying this protocol using some common nestedness indices. Analyses based on weighted data proved to be highly efficient and informative, while binary analyses induced severe distortions. Finally, we empirically illustrate our approach using a plant-pollinator network. C_LIO_LIThrough a shift of perspective, our approach reconciliates contradictions in null model analysis and provides a guideline for nestedness interpretation. C_LI

ecology↗

bioRxiv2018

Insights on the assembly rules of a continent-wide multilayer network

Introductory paragraphHow are ecological systems assembled? Here, we aim to contribute to answering this question by harnessing the framework of a novel integrative hypothesis. We shed light on the assembly rules of a multilayer network formed by frugivory and nectarivory interactions between bats and plants in the Neotropics. Our results suggest that, at a large scale, phylogenetic trade-offs separate species into different layers and modules. At an intermediate scale, the modules are also shaped by geographic trade-offs. And at a small scale, the network shifts to a nested structure within its modules, probably as a consequence of resource breadth processes. Finally, once the topology of the network is shaped, morphological traits related to consuming fruits or nectar determine which species are central or peripheral. Our results help understand how different processes contribute to the assemblage of ecological systems at different scales, resulting in a compound topology.

ecology↗

bioRxiv2018

A new model explaining the origin of different topologies in interaction networks

The architecture of interaction networks has been extensively studied in the past decades, and different topologies have been observed in natural systems. Despite several phenomenological explanations proposed, we still understand little of the mechanisms that generate those topologies. Here we present a mechanistic model based on the integrative hypothesis of specialization, which aims at explaining the emergence of topology and specialization in consumer-resource networks. By following three first-principles and adjusting five parameters, our model was able to generate synthetic weighted networks that show the main patterns of topology and specialization observed in nature. Our results prove that topology emergence is possible without network-level selection. In our simulations, the intensity of trade-offs in the performance of each consumer species on different resource species is the main factor driving network topology. We predict that interaction networks with low species diversity and low dissimilarity between resources should have a nested topology, although more diverse networks with large dissimilarity should have a compound topology. Additionally, our results highlight scale as a key factor. Our model generates predictions consistent with ecological and evolutionary theories and real-world observations. Therefore, it supports the IHS as a useful conceptual framework to study the architecture of interaction networks.

ecology↗

bioRxiv2017

The compound topology of a continent-wide host-parasite network explained by an integrative hypothesis of specialization.

Is there a prevalent pattern among interaction networks: nestedness or modularity? Must consumers always trade-off generalism for average performance in resource exploitation? These two questions have been addressed in various systems, with contradictory results. A recent integrative hypothesis combines both questions within a common theoretical framework, proposing that ecological specialization is structured by different prevailing processes in smaller and larger network units. This should produce both a compound interaction network, formed by internally nested modules, and a scale-dependence on the relationship between consumer performance and generalism. Here, we confirm both predictions in a large dataset on host-parasite interactions. We show that modules indeed constrain nestedness at the whole network level, and that the relationship between parasite generalism and performance on their hosts changed from negative at large to positive at small scales. Our results shed light on both debates, and provide some clues to their integration and solution.

ecology↗