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In many animals, sex differences in hormones, behavior, and immunity lead to differences in their gut microbial communities. One of the best-known examples of mutualistic symbiosis is that between lower termites and their intestinal protozoa. Although differences in the protozoan communities of different castes have been studied in lower termites, nothing is known about the sex differences in protozoan communities in neuter castes. Here, we show that termite workers have different protozoan communities according to sex depending on the colony. We investigated the communities of symbiotic protozoa living in lower termites, Reticulitermes speratus, and how they are affected by sex and caste. Workers had the largest numbers of protozoa, followed by soldiers, whereas reproductives (primary kings and secondary queens) had no protozoa. Workers showed colony-dependent sex differences in the total abundance of protozoa, whereas soldiers showed no such sex differences. There were significant sex effect and/or interaction effect between colony and sex in abundances of five species of protozoa in workers. Workers also showed significant sex differences and/or colony-dependent sex differences in proportion of six species of protozoa. These may result in sex differences in the host–symbiont interaction due to physiological or behavioral sex differences in workers that have not been recognized previously. This study has an important implication: although workers are not engaged in reproduction, their potential sex difference may affect various aspects of social interactions.

Summary Pantoea are emerging as widespread bacteria engaged in associations with a variety of hosts, including plants, insects and humans. Recently, mutualistic Pantoea gut symbionts have also been reported in pentatomid stinkbugs. In the present study, we examine the incidence and evolutionary history of these Pantoea symbionts in pentatomid stinkbug populations from 14 species, characterising the processes that shape their diversity. We identify midgut crypts of pentatomid stinkbugs as harboring a remarkable diversity of Pantoea. Present in 10 of the 14 sampled host species, multi-locus typing revealed the presence of 10 novel Panteoa lineages, all highly differentiated from the known Panteoa species. Rearing experiments of two pentatomid stinkbug species confirmed that these novel Panteoa are maternally inherited through egg smearing and engaged in mutualistic interactions with their hosts. Phylogenetic investigations further revealed that the Pantoea evolutionary history in pentatomid stinkbugs was notably complex: it has been shaped not only by horizontal transfers with frequent host turnover but also by strict vertical transmission over long evolutionary periods, resulting in host-symbiont codiversification.

People have been recording wildlife for centuries and the resulting datasets lead to important scientific research. The Biological Records Centre (BRC), established in 1964, is a national focus for terrestrial and freshwater species recording in the United Kingdom (UK). BRC works with the voluntary recording community (i.e. a mutualistic symbiosis) through support of national recording schemes (i.e. ‘citizen science’, but unlike most citizen science it is volunteer led) and adds value to the data through analysis and reporting. Biological recording represents a diverse range of activities, involving an estimated 70 000 people annually in the UK, from expert volunteers undertaking systematic monitoring to mass participation recording. It is an invaluable monitoring tool because the datasets are long term, have large geographic extent and are taxonomically diverse (85 taxonomic groups). It supports a diverse range of outputs, e.g. atlases showing national distributions (12 127 species from over 40 taxonomic groups) and quantified trends (1636 species). BRC pioneers the use of technology for data capture (online portals and smartphone apps) and verification (including automated verification) through customisable, inter-operable database systems to facilitate efficient data flow. We are confident that biological recording has a bright future with benefits for people, science, and nature.

Many authors state that sustainability is purely a matter of the management of scarce and ever-diminishing “negentropy,” while others still pretend that unlimited exploitation of the environment is possible. Either view rests on fundamental misunderstandings of ecosystems. Ecologically, sustainability must mean a mutualistic symbiosis. It is useful to understand symbiosis from a thermodynamic point of view. Many organisms—including humans in principle—are able to modulate large flows of free energy, directing it into the formation of organized structures, while expending a proportionately small amount of free energy in the process. They are thus able to capture useful energy for their ecosystem as a whole. Ecosystems can thus maintain a high degree of internal coherence and, just as can individual organisms, apparently defy the Second Law of Thermodynamics within their own boundaries. The breakdown of ecosystem coherence we observe in the world today is thus a symptom not so much of the “Law of Entropy” but of the undermining of the ecosystem’s autopoietic capacity by human parasitism. A guarded optimism about the possibility of sustainability is thus possible, so long as we grasp the particular way in which humans can contribute to ecosystem vitality. Even very subtle features of human culture may contribute positively to the physical vitality of the ecosystem.

In geological history, rapid speciation, called adaptive radiation, has occurred repeatedly. The origins of such newly developing taxa often evolved from the symbiosis of different species. Mutualistic symbioses are generally considered to evolve from parasitic relationships. As well as the previous model of host population with discrete generations, a differential equation model of host population with overlapping generations shows that vertical transmission, defined as the direct transfer of infection from a parent host to its progeny, is an important factor which can stimulate reduction of parasite virulence. Evolution of the vertical transmission rate from both points of view, the parasite and the host, is analyzed. There is a critical level of the rate, below which an evolutionary conflict arises (the parasite would want an increase in the rate while the host would not), and above which both species would correspond to increase the rate. Therefore, once the parasite dominates the evolutionary race so as to overcome this critical level, one-way evolution begins toward a highly mutualistic relationship with a high vertical transmission rate, possibly creating a new organism through symbiosis with perfect vertical transmission. Changes in other parameters may decrease the critical level, initiating one-way evolution. However, changes in traits, probably developed through a long interrelationship in parasitism, do not necessarily induce the evolution of mutualism. Establishment of the ability to make use of metabolic and digestive wastes from the partner certainly facilitates the evolution of mutualism, while improvements in reproductive efficiency of parasites and reduction of negative effects from exploitation in hosts on the contrary disturb mutualism.