Many models of mutualism have been proposed and studied individually. In this paper, we develop a general class of models of facultative mutualism that covers many of such published models. Using mild assumptions on the growth and self-limiting functions, we establish necessary and sufficient conditions on the boundedness of model solutions and prove the global stability of a unique coexistence equilibrium whenever it exists. These results allow for a greater flexibility in the way each mutualist species can be modelled and avoid the need to analyse any single model of mutualism in isolation. Our generalization also allows each of the mutualists to be subject to a weak Allee effect. Moreover, we find that if one of the interacting species is subject to a strong Allee effect, then the mutualism can overcome it and cause a unique coexistence equilibrium to be globally stable.
- MeSH
- Models, Biological * MeSH
- Population Dynamics MeSH
- Symbiosis * MeSH
- Publication type
- Journal Article MeSH
Both the abiotic environment and the composition of animal and plant communities change with elevation. For mutualistic species, these changes are expected to result in altered partner availability, and shifts in context-dependent benefits for partners. To test these predictions, we assessed the network structure of terrestrial ant-plant mutualists and how the benefits to plants of ant inhabitation changed with elevation in tropical forest in Papua New Guinea. At higher elevations, ant-plants were rarer, species richness of both ants and plants decreased, and the average ant or plant species interacted with fewer partners. However, networks became increasingly connected and less specialized, more than could be accounted for by reductions in ant-plant abundance. On the most common ant-plant, ants recruited less and spent less time attacking a surrogate herbivore at higher elevations, and herbivory damage increased. These changes were driven by turnover of ant species rather than by within-species shifts in protective behaviour. We speculate that reduced partner availability at higher elevations results in less specialized networks, while lower temperatures mean that even for ant-inhabited plants, benefits are reduced. Under increased abiotic stress, mutualistic networks can break down, owing to a combination of lower population sizes, and a reduction in context-dependent mutualistic benefits.
Ant-gardens (AGs) are ant/plant mutualisms in which ants farm epiphytes in return for nest space and food rewards. They occur in the Neotropics and Australasia, but not in Africa, and their evolutionary assembly remains unclear. We here use phylogenetic frameworks for important AG lineages in Australasia, namely the ant genusPhilidrisand domatium-bearing ferns (Lecanopteris) and flowering plants in the Apocynaceae (HoyaandDischidia) and Rubiaceae (Myrmecodia,Hydnophytum,Anthorrhiza,MyrmephytumandSquamellaria). Our analyses revealed that in these clades, diaspore dispersal by ants evolved at least 13 times, five times in the Late Miocene and Pliocene in Australasia and seven times during the Pliocene in Southeast Asia, afterPhilidrisants had arrived there, with subsequent dispersal between these two areas. A uniquely specialized AG system evolved in Fiji at the onset of the Quaternary. The farming in the same AG of epiphytes that do not offer nest spaces suggests that a broadening of the ants' plant host spectrum drove the evolution of additional domatium-bearing AG-epiphytes by selecting on pre-adapted morphological traits. Consistent with this, we found a statistical correlation between the evolution of diaspore dispersal by ants and domatia in all three lineages. Our study highlights how host broadening by a symbiont has led to new farming mutualisms.
- MeSH
- Apocynaceae * MeSH
- Biological Evolution * MeSH
- Ants * MeSH
- Phylogeny MeSH
- Ferns * MeSH
- Rubiaceae * MeSH
- Symbiosis * MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- Africa MeSH
- Australasia MeSH
- Fiji MeSH
Anthropogenic disturbance and the spread of non-native species disrupt natural communities, but also create novel interactions between species. By-product mutualisms, in which benefits accrue as side effects of partner behaviour or morphology, are often non-specific and hence may persist in novel ecosystems. We tested this hypothesis for a two-way by-product mutualism between epiphytic ferns and their ant inhabitants in the Bornean rain forest, in which ants gain housing in root-masses while ferns gain protection from herbivores. Specifically, we assessed how the specificity (overlap between fern and ground-dwelling ants) and the benefits of this interaction are altered by selective logging and conversion to an oil palm plantation habitat. We found that despite the high turnover of ant species, ant protection against herbivores persisted in modified habitats. However, in ferns growing in the oil palm plantation, ant occupancy, abundance and species richness declined, potentially due to the harsher microclimate. The specificity of the fern-ant interactions was also lower in the oil palm plantation habitat than in the forest habitats. We found no correlations between colony size and fern size in modified habitats, and hence no evidence for partner fidelity feedbacks, in which ants are incentivised to protect fern hosts. Per species, non-native ant species in the oil palm plantation habitat (18 % of occurrences) were as important as native ones in terms of fern protection and contributed to an increase in ant abundance and species richness with fern size. We conclude that this by-product mutualism persists in logged forest and oil palm plantation habitats, with no detectable shift in partner benefits. Such persistence of generalist interactions in novel ecosystems may be important for driving ecosystem functioning.
- MeSH
- Arecaceae MeSH
- Herbivory * MeSH
- Rainforest * MeSH
- Species Specificity MeSH
- Ecosystem MeSH
- Ants * classification MeSH
- Ferns * MeSH
- Plant Roots MeSH
- Microclimate MeSH
- Plant Diseases MeSH
- Disease Resistance MeSH
- Symbiosis * MeSH
- Conservation of Natural Resources * MeSH
- Agriculture * MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Borneo MeSH
Many mutualisms involve inter-specific resource exchanges, making consumer-resource approaches ideal for studying their dynamics. Also in many cases these resources are short lived (e.g. flowers) compared with the population dynamics of their producers and consumers (e.g. plants and insects), which justifies a separation of time scales. As a result, we can derive the numerical response of one species with respect to the abundance of another. For resource consumers, the numerical responses can account for intra-specific competition for mutualistic resources (e.g. nectar), thus connecting competition theory and mutualism mechanistically. For species that depend on services (e.g. pollination, seed dispersal), the numerical responses display saturation of benefits, with service handling times related with rates of resource production (e.g. flower turnover time). In both scenarios, competition and saturation have the same underlying cause, which is that resource production occurs at a finite velocity per individual, but their consumption tracks the much faster rates of population growth characterizing mutualisms. The resulting models display all the basic features seen in many models of facultative and obligate mutualisms, and they can be generalized from species pairs to larger communities.
- MeSH
- Models, Biological * MeSH
- Ecosystem MeSH
- Pollination MeSH
- Population Dynamics MeSH
- Seed Dispersal MeSH
- Symbiosis * MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Biological Evolution MeSH
- Mycorrhizae physiology MeSH
- Plants microbiology MeSH
- Symbiosis physiology MeSH
- Publication type
- Congress MeSH
- Research Support, Non-U.S. Gov't MeSH
Keystone mutualisms, such as corals, lichens or mycorrhizae, sustain fundamental ecosystem functions. Range dynamics of these symbioses are, however, inherently difficult to predict because host species may switch between different symbiont partners in different environments, thereby altering the range of the mutualism as a functional unit. Biogeographic models of mutualisms thus have to consider both the ecological amplitudes of various symbiont partners and the abiotic conditions that trigger symbiont replacement. To address this challenge, we here investigate 'symbiont turnover zones'--defined as demarcated regions where symbiont replacement is most likely to occur, as indicated by overlapping abundances of symbiont ecotypes. Mapping the distribution of algal symbionts from two species of lichen-forming fungi along four independent altitudinal gradients, we detected an abrupt and consistent β-diversity turnover suggesting parallel niche partitioning. Modelling contrasting environmental response functions obtained from latitudinal distributions of algal ecotypes consistently predicted a confined altitudinal turnover zone. In all gradients this symbiont turnover zone is characterized by approximately 12°C average annual temperature and approximately 5°C mean temperature of the coldest quarter, marking the transition from Mediterranean to cool temperate bioregions. Integrating the conditions of symbiont turnover into biogeographic models of mutualisms is an important step towards a comprehensive understanding of biodiversity dynamics under ongoing environmental change.
- MeSH
- Ecosystem * MeSH
- Climate * MeSH
- Symbiosis * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The host specificity of the recently described ciliate species Tetrahymena utriculariae was tested in a greenhouse growth experiment, which included 14 different species of aquatic Utricularia as potential host plants. We confirmed the high specificity of the interaction between U. reflexa and T. utriculariae, the former being the only tested host species able to maintain colonization for prolonged time periods. We conclude that this plant-microbe relationship is a unique and specialized form of digestive mutualism and the plant-microbe unit a suitable experimental system for future ecophysiological studies.
1. vydání 95 stran : ilustrace ; 17 cm
Český biolog Anton Markoš v publikaci předkládá vlastní stanoviska k řadě problémů a otázek aktuálního přístupu v moderní biologii.
- Keywords
- biosémiotika,
- MeSH
- Biological Evolution MeSH
- Symbiosis MeSH
- Publication type
- Monograph MeSH
- Conspectus
- Obecná genetika. Obecná cytogenetika. Evoluce
- NML Fields
- biologie
elektronický časopis
- Conspectus
- Biologické vědy
- NML Fields
- cytologie, klinická cytologie
- biologie
- NML Publication type
- elektronické časopisy
