Basic research on biodiversity has concentrated on individual species-naming new species, studying distribution patterns, and analyzing their evolutionary relationships. Yet biodiversity is more than ...a collection of individual species; it is the combination of biological entities and processes that support life on Earth. To understand biodiversity we must catalog it, but we must also assess the ways species interact with other species to provide functional support for the Tree of Life. Ecological interactions may be lost well before the species involved in those interactions go extinct; their ecological functions disappear even though they remain. Here, I address the challenges in studying the functional aspects of species interactions and how basic research is helping us address the fast-paced extinction of species due to human activities.
Mutualistic interactions among plants and animals have played a paramount role in shaping biodiversity. Yet the majority of studies on mutualistic interactions have involved only a few species, as ...opposed to broader mutual connections between communities of organisms.Mutualistic Networksis the first book to comprehensively explore this burgeoning field. Integrating different approaches, from the statistical description of network structures to the development of new analytical frameworks, Jordi Bascompte and Pedro Jordano describe the architecture of these mutualistic networks and show their importance for the robustness of biodiversity and the coevolutionary process.
Making a case for why we should care about mutualisms and their complex networks, this book offers a new perspective on the study and synthesis of this growing area for ecologists and evolutionary biologists. It will serve as the standard reference for all future work on mutualistic interactions in biological communities.
1. Dispersal is a key individual-based process influencing many life-history attributes and scaling up to population-level properties (e.g. metapopulation connectivity). A persistent challenge in ...dispersal ecology has been the robust characterization of dispersal functions (kernels), a fundamental tool to predict how dispersal processes respond under global change scenarios. Particularly, the rightmost tail of these functions, that is the long-distance dispersal (LDD) events, are difficult to characterize empirically and to model in realistic ways. 2. But, when is it a LDD event? In the specific case of plants, dispersal has three basic components: (i) a distinct (sessile) source, the maternal plant producing the fruits or the paternal tree acting as a source of pollen; (ii) a distance component between source and target locations; and (iii) a vector actually performing the movement entailing the dispersal event. Here, I discuss operative definitions of LDD based on their intrinsic properties: (i) events crossing geographic boundaries among stands; and (ii) events contributing to effective gene flow and propagule migration. 3. Strict-sense long-distance dispersal involves movement both outside the stand geographic limits and outside the genetic neighbourhood area of individuals. Combinations of propagule movements within/outside these two spatial reference frames result in four distinct modes of LDD. 4. Synthesis. I expect truncation of seed dispersal kernels to have multiple consequences on demography and genetics, following to the loss of key dispersal services in natural populations. Irrespective of neighbourhood sizes, loss of LDD events may result in more structured and less cohesive genetic pools, with increased isolation by distance extending over broader areas. Proper characterization of the LDD events helps to assess, for example, how the ongoing defaunation of large-bodied frugivores pervasively entails the loss of crucial LDD functions.
Recording species interactions is one of the main challenges in ecological studies. Frugivory has received much attention for decades as a model for mutualisms among free‐living species, and a ...variety of methods have been designed and developed for sampling and monitoring plant–frugivore interactions. The diversity of techniques poses an important challenge when comparing, combining or replicating results from different sources with different methodologies. With the emergence of modern techniques, such as molecular analysis or multimedia remote recorders, issues when combining data from different sources have become especially relevant. We provide an overview of all the techniques used for monitoring endozoochorous primary seed dispersal, focusing on a critical appraisal of the advantages and limitations, as well as the context‐dependency nature, of the different methods. We propose five data merging approaches potentially useful to combine frugivory interactions data from different methodologies. Additionally, we provide two case studies where we combine empirical data from plant–animal interactions in Mediterranean shrublands using different methodologies. Data merging resulted in a net increase in the number of distinct pairwise interactions recorded and compensated biases inherent to different methods, resulting in a more robust estimation of network topological descriptors. These case studies clarify the context‐dependent character of the merging approaches, highlighting the value of collecting detailed information on the sampling effort in terms of reliable results and reproducibility. Finally, we discuss the trends with different methodological approaches used in the last decades and future perspectives in this field.
The mutually beneficial interactions between plants and their animal pollinators and seed dispersers have been paramount in the generation of Earth's biodiversity. These mutualistic interactions ...often involve dozens or even hundreds of species that form complex networks of interdependences. Understanding how coevolution proceeds in these highly diversified mutualisms among free-living species presents a conceptual challenge. Recent work has led to the unambiguous conclusion that mutualistic networks are very heterogeneous (the bulk of the species have a few interactions, but a few species are much more connected than expected by chance), nested (specialists interact with subsets of the species with which generalists interact), and built on weak and asymmetric links among species. Both ecological variables (e.g., phenology, local abundance, and geographic range) and past evolutionary history may explain such network patterns. Network structure has important implications for the coexistence and stability of species as well as for the coevolutionary process. Mutualistic networks can thus be regarded as the architecture of biodiversity.
ABSTRACT
Synzoochory is the dispersal of seeds by seed‐caching animals. The animal partner in this interaction plays a dual role, acting both as seed disperser and seed predator. We propose that this ...duality gives to synzoochory two distinctive features that have crucial ecological and evolutionary consequences. First, because plants attract animals that have not only positive (seed dispersal) but also negative (seed predation) impacts on their fitness, the evolution of adaptations to synzoochory is strongly constrained. Consequently, it is not easy to identify traits that define a synzoochorous dispersal syndrome. The absence of clear adaptations entails the extra difficulty of identifying synzoochorous plants by relying on dispersal traits, limiting our ability to explore the full geographic, taxonomic and phylogenetic extent of synzoochory. Second, the positive and negative outcomes of interactions with synzoochorous animals are expressed simultaneously. Consequently, synzoochorous interactions are not exclusively mutualistic or antagonistic, but are located at some point along a mutualism–antagonism continuum. What makes synzoochory interesting and unique is that the position of each partner along the continuum can be evaluated for every plant–animal interaction, and thus the continuum can be precisely described by assessing the relative frequency of positive and negative interaction events in each pairwise interaction. Herein we explore these two main features of synzoochory with a comprehensive quantitative survey of published studies on synzoochory. Synzoochory has been recorded for at least 1339 plant species differing in life forms, from annual and short‐lived herbs to long‐lived trees, belonging to 641 genera and 157 families widely distributed across the globe and across the seed plant phylogeny. Over 30 animal families belonging to five disparate taxonomic groups (rodents, marsupials, birds, insects, and land crabs) potentially act as synzoochorous dispersers. Although synzoochory appears to be fundamentally a secondary dispersal mode, many abundant and dominant trees are primarily synzoochorous. In addition, we found evidence of the existence of diplosynzoochory (caching animals acting both as primary and secondary dispersers of the same individual seed), mostly in nut‐bearing trees. Finally, we found that synzoochorous interactions are widely spread across the mutualism–antagonism continuum. Nevertheless, there were some differences among disperser species and functional groups. Corvids and some rodents (cricetids, nesomyids, sciurids) were located in the positive‐effects region of the continuum and presumably behave mostly as dispersers, whereas land crabs and insects were located in the negative‐effects extreme and behave mostly as seed predators. Our review demonstrates that synzoochory is not an anecdotal ecological interaction. Rather, it is pivotal to the functioning of many ecosystems where the natural regeneration of keystone plant species depends on the activity of granivorous animals that play a dual role. This distinctive interaction should not be ignored if we wish to have an accurate understanding of the functioning of natural systems.
The honeybee is the primary managed species worldwide for both crop pollination and honey production. Owing to beekeeping activity, its high relative abundance potentially affects the structure and ...functioning of pollination networks in natural ecosystems. Given that evidences about beekeeping impacts are restricted to observational studies of specific species and theoretical simulations, we still lack experimental data to test for their larger-scale impacts on biodiversity. Here we used a three-year field experiment in a natural ecosystem to compare the effects of pre- and post-establishment stages of beehives on the pollination network structure and plant reproductive success. Our results show that beekeeping reduces the diversity of wild pollinators and interaction links in the pollination networks. It disrupts their hierarchical structural organization causing the loss of interactions by generalist species, and also impairs pollination services by wild pollinators through reducing the reproductive success of those plant species highly visited by honeybees. High-density beekeeping in natural areas appears to have lasting, more serious negative impacts on biodiversity than was previously assumed.
Growth in seed dispersal studies has been fast-paced since the seed disperser effectiveness (SDE) framework was developed 17 yr ago. Thus, the time is ripe to revisit the framework in light of ...accumulated new insight. Here, we first present an overview of the framework, how it has been applied, and what we know and do not know. We then introduce the SDE landscape as the two-dimensional representation of the possible combinations of the quantity and the quality of dispersal and with elevational contours representing isoclines of SDE. We discuss the structure of disperser assemblages on such landscapes. Following this we discuss recent advances and ideas in seed dispersal in the context of their impacts on SDE. Finally, we highlight a number of emerging issues that provide insight into SDE. Overall, the SDE framework successfully captures the complexities of seed dispersal. We advocate an expanded use of the term dispersal encompassing the multiple recruitment stages from fruit to adult. While this entails difficulties in estimating SDE, it is a necessary expansion if we are to understand the central relevance of seed dispersal in plant ecology and evolution.
modularity of pollination networks Olesen, Jens M; Bascompte, Jordi; Dupont, Yoko L ...
Proceedings of the National Academy of Sciences - PNAS,
12/2007, Letnik:
104, Številka:
50
Journal Article
Recenzirano
Odprti dostop
In natural communities, species and their interactions are often organized as nonrandom networks, showing distinct and repeated complex patterns. A prevalent, but poorly explored pattern is ...ecological modularity, with weakly interlinked subsets of species (modules), which, however, internally consist of strongly connected species. The importance of modularity has been discussed for a long time, but no consensus on its prevalence in ecological networks has yet been reached. Progress is hampered by inadequate methods and a lack of large datasets. We analyzed 51 pollination networks including almost 10,000 species and 20,000 links and tested for modularity by using a recently developed simulated annealing algorithm. All networks with >150 plant and pollinator species were modular, whereas networks with <50 species were never modular. Both module number and size increased with species number. Each module includes one or a few species groups with convergent trait sets that may be considered as coevolutionary units. Species played different roles with respect to modularity. However, only 15% of all species were structurally important to their network. They were either hubs (i.e., highly linked species within their own module), connectors linking different modules, or both. If these key species go extinct, modules and networks may break apart and initiate cascades of extinction. Thus, species serving as hubs and connectors should receive high conservation priorities.
A core interest in studies of mutualistic interactions is the ‘effectiveness’ of mutualists in providing benefits to their partners. In plant‐animal mutualisms it is widely accepted that the total ...effect of a mutualist on its partner is estimated as (1) a ‘quantity’ component multiplied by (2) a ‘quality’ component, although the meanings of ‘effectiveness,’ ‘quantity,’ and ‘quality’ and which terms are applied to these metrics vary greatly across studies. In addition, a similar quantity × quality = total effect approach has not been applied to other types of mutualisms, although it could be informative. Lastly, when a total effect approach has been applied, it has invariably been from a phytocentric perspective, focussing on the effects of animal mutualists on their plant partner. This lack of a common framework of ‘effectiveness’ of mutualistic interactions limits generalisation and the development of a broader understanding of the ecology and evolution of mutualisms. In this paper, we propose a general framework and demonstrate its utility by applying it to both partners in five different types of mutualisms: pollination, seed dispersal, plant protection, rhizobial, and mycorrhizal mutualisms. We then briefly discuss the flexibility of the framework, potential limitations, and relationship to other approaches.
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