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Ficus (figs) and their agaonid wasp pollinators present an ecologically important mutualism that also provides a rich comparative system for studying functional co-diversification throughout its coevolutionary history (~75 million years). We obtained entire nuclear, mitochondrial, and chloroplast genomes for 15 species representing all major clades of Ficus. Multiple analyses of these genomic data suggest that hybridization events have occurred throughout Ficus evolutionary history. Furthermore, cophylogenetic reconciliation analyses detect significant incongruence among all nuclear, chloroplast, and mitochondrial-based phylogenies, none of which correspond with any published phylogenies of the associated pollinator wasps. These findings are most consistent with frequent host-switching by the pollinators, leading to fig hybridization, even between distantly related clades. Here, we suggest that these pollinator host-switches and fig hybridization events are a dominant feature of fig/wasp coevolutionary history, and by generating novel genomic combinations in the figs have likely contributed to the remarkable diversity exhibited by this mutualism. Figs and their wasp pollinators are a classic example of coevolution. By assembling and analysing genomes from across the Ficus clade, authors suggest that fig hybridization driven by pollinator host-switching in this obligate pollination system, is more common than previously thought. [ABSTRACT FROM AUTHOR]

The frequency and the geographical extent of symbiotic associations between ants and fungi of the order Chaetothyriales have been highlighted only recently. Using a phylogenetic approach based on seven molecular markers, we showed that ant-associated Chaetothyriales are scattered through the phylogeny of this order. There was no clustering according to geographical origin or to the taxonomy of the ant host. However, strains tended to be clustered according to the type of association with ants: strains from ant-made carton and strains from plant cavities occupied by ants (‘domatia’) rarely clustered together. Defining molecular operational taxonomic units (MOTUs) with an internal transcribed spacer sequence similarity cut-off of 99% revealed that a single MOTU could be composed of strains collected from various ant species and from several continents. Some ant-associated MOTUs also contained strains isolated from habitats other than ant-associated structures. Altogether, our results suggest that the degree of specialization of the interactions between ants and their fungal partners is highly variable. A better knowledge of the ecology of these interactions and a more comprehensive sampling of the fungal order are needed to elucidate the evolutionary history of mutualistic symbioses between ants and Chaetothyriales. [ABSTRACT FROM AUTHOR]

749I.749II.750III.754IV.758V.759760References761 Summary: Ant–plant symbioses involve plants that provide hollow structures specialized for housing ants and often food to ants. In return, the inhabiting ants protect plants against herbivores and sometimes provide them with nutrients. Here, we review recent advances in ant–plant symbioses, focusing on three areas. First, the nutritional ecology of plant‐ants, which is based not only on plant‐derived food rewards, but also on inputs from other symbiotic partners, in particular fungi and possibly bacteria. Food and protection are the most important ‘currencies’ exchanged between partners and they drive the nature and evolution of the relationships. Secondly, studies of conflict and cooperation in ant–plant symbioses have contributed key insights into the evolution and maintenance of mutualism, particularly how partner‐mediated feedbacks affect the specificity and stability of mutualisms. There is little evidence that mutualistic ants or plants are under selection to cheat, but the costs and benefits of ant–plant interactions do vary with environmental factors, making them vulnerable to natural or anthropogenic environmental change. Thus, thirdly, ant–plant symbioses should be considered good models for investigating the effects of global change on the outcome of mutualistic interactions. [ABSTRACT FROM AUTHOR]

Abstract: Obligatory interactions between species are fundamental to ecosystem functioning and are expected to be particularly sensitive to climate change. Although the effect of past and current climate changes on individual species has been thoroughly investigated, their effect on obligatory interactions has been overlooked. In this review, we present predictions about the effects of climate change on obligatory interactions and illustrate these predictions with examples from the literature. We focus on abrupt past climate change, especially during the Quaternary, because knowing past responses is useful for understanding and predicting the response of organisms and ecosystems to the current climate change. We also pinpoint the need for better time calibration of demographic events from genetic data, and for more studies focused on particularly suitable biological models. We hope that this review will stimulate interaction between the earth sciences and the life sciences on this timely topic. [Copyright &y& Elsevier]

Background and Aims Plant defence traits against herbivores incur production costs that are usually difficult to measure. However, estimating these costs is a prerequisite for characterizing the plant defence strategy as a whole. Myrmecophytes are plants that provide symbiotic ants with specialized nesting cavities, called domatia, in exchange for protection against herbivores. In the particular case of stem domatia, production of extra wood seems to be the only associated cost, making this indirect defence trait a particularly suitable model for estimating the cost of defence. Methods Measurements were made of growth pattern and cumulative production cost of domatia over secondary growth in the myrmecophyte Leonardoxa africana subsp. africana, whose internodes display both a solid basal segment and a hollow distal part (the domatium), thus allowing paired comparison of investment in wood. Key Results Previous studies showed that ‘overconstruction’ of the hollow part of internodes during primary growth is needed for mechanical support. In this study, it is shown that the relationship between the woody cross-sectional area of the solid and hollow parts of internodes is negatively allometric at the beginning of secondary growth and nearly isometric later on. Thus, in hollow stems, the first phase of slow secondary growth compensates for the ‘overconstruction’ of the ring of wood during primary growth. Moreover, the cumulative production cost of a domatium (estimated as the additional volume of wood required for a hollow stem compared with a solid one) is very high at the beginning of secondary growth and then quickly tends to zero. Conclusions Making domatia incurs high costs early in ontogeny, costs that are then amortized later in development of stems and of individual plants. Characterizing ontogenetic variation of the net cost of this peculiar defence mechanism will help us build more accurate theoretical models of resource allocation in myrmecophytes. [ABSTRACT FROM AUTHOR]

Abstract: Climate oscillations produce dramatic changes in species distribution, even in the tropics. The ant–plant Leonardoxa africana africana hosts and feeds the ant Petalomyrmex phylax, which provides protection against herbivores in return. Both partners of this symbiosis present a recent southward range expansion. To test whether the higher investment in sexuals (and thus lower investment in protective workers) previously documented on the colonization front is compensated by a more effective protective behaviour, we compared ant behavioural investment in plant defence between two populations, one in the core of the range and one on the colonization front. We induced ant patrolling activity by artificially damaging leaflets and measured this activity by counting patrolling ants and calculating the increase relative to constitutive patrolling activity measured on control (undamaged) leaflets. Contrary to our expectation, ant behavioural investment in plant defence was lower on the colonization front. Thus, production of fewer workers is not compensated by more protective behaviour of each. Instead, both traits contribute to a phenotype that is less mutualistic as a whole. By favouring increased allocation to dispersal, range expansion can shape ant behavioural traits and potentially the outcome of mutualism. [Copyright &y& Elsevier]