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With recent evidence of hybridization events in the field, the phenotypic traits of F1 hybrid colonies of 2 destructive subterranean termite species, Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) remain to be investigated. In this study, laboratory colonies of 2 conspecific pairings and 2 heterospecific pairings (hybrid F = ♀C. formosanus × ♂C. gestroi, hybrid G = ♀C. gestroi × ♂C. formosanus) were examined in Florida, USA, and in Taiwan. Colony nest architecture for both hybrids displayed disorganized carton materials compared to the defined trabecular carton of both parental species. Soldier head measurements were not a reliable approach for diagnostic purposes, as soldier morphometric traits widely overlapped across all mating combinations, except for hybrid F soldiers displaying abnormally long mandibles. Hybrid F soldiers’ mandibles also remained parallel when at rest. However, 4 qualitative morphological differences in soldiers were determined for diagnostic purposes. First, the fontanelle in both hybrids is horizontally ellipsoid whereas subcircular in C. gestroi and trianguliform in C. formosanus. Second, sclerotized striations along the postmental sulcus are present in C. gestroi, absent in C. formosanus, and intermediate in both hybrid soldier types. Third, each lateral margin of the fontanelle is flanked by 2 setae in C. formosanus and both hybrids, while a single seta resides on each side of the fontanelle in C. gestroi. Finally, C. gestroi and hybrid soldiers’ heads are characterized by a bulging vertex that is lacking in C. formosanus. Therefore, a combination of these 4 characteristics now allows for soldier identification of hybrid Coptotermes.

 

Many host-symbiont relationships are maintained through vertical transmission. While maternal symbiont transmission is common, biparental transmission is relatively rare. Protist-dependent termites are eusocial insects that harbor obligate, cellulolytic protists in their hindguts. Protists are vertically transmitted by winged reproductives (alates), which disperse to biparentally establish new colonies. Vertical transmission in protist-dependent termites is imperfect, as the protist communities of alates are often incomplete. Biparental transmission of protists may make it unnecessary for alates to harbor complete communities, as colonies would acquire symbionts from both founding kings and queens, which together may harbor sufficient inoculums. To investigate this hypothesis, the protist communities of Coptotermes gestroi and C. formosanus alates and colonies were examined using 18S rRNA amplicon sequencing. The complete protist communities of these Coptotermes species are composed of five parabasalid species each. Whereas alates often harbored 1–3 protist species, nearly all colonies harbored 4–5 species, implying biparental transmission. The probability of each protist species being present in at least one founding alate was used to determine expected protist occurrence in colonies. For most protists, expected and observed occurrence did not significantly differ, suggesting that each protist species only needs to be harbored by one founding alate to be acquired by colonies. Our results imply that biparental transmission allows founding reproductives to transmit adequate symbiont communities to colonies despite their individual communities being incomplete. We discuss biparental transmission in protist-dependent termites in the context of other biparentally transmitted symbioses. 

In eusocial organisms, cooperative brood care within a colony represents a situation where the ancestral parental care duties have shifted away from the reproductive parent(s) towards their offspring. The shift to alloparental care was often instrumental in the initial emergence of eusociality, as it ultimately contributed to the establishment of the reproductive division of labour.

Remarkably, eusocial taxa such as ants and termites, which still display an ancestral independent colony foundation phase, must go through an obligatory parental care period, as a temporary subsocial family unit. In termites specifically, an incipient colony inherently remains a woodroach family unit until alloparental care is established. Colony foundation success can then be limited by a series of factors that may include environmental, behavioural, symbiotic and physiological constraints.

In this study, 450 incipient termite colonies (Coptotermes gestroi) were established to investigate the timing of physiological changes in founders during the transition from biparental to alloparental care. Results showed that the finite initial internal nutritional resources that alates carry during the dispersal flight are a primary limiting factor for successful colony establishment. TheCoptotermesqueen and king must rapidly establish (<150 days) their first cohort of offspring to reach alloparental care or simply run out of resources and die. Alates, therefore, carry just enough internal resources to produce the first few alloparents (< 15 workers) to prime the system towards colony ergonomic growth, with a definitive shift to solely reproductive functions.

Eusocial insect primary reproductive traits were optimized for three successive functions within the life cycle of a colony: alate dispersal (sexual reproduction), colony foundation (parental care) and colony growth (increased egg production towards colony maturity). However, results suggest that trade‐offs involving these functions appear to primarily favour dispersal ones (quantity vs. quality of alates), as founder(s) carry minimal resources and have no room for parental care inefficiency and as they then fully rely on their alloparents for further reproductive output.

The transition towards alloparental care during colony foundation of eusocial insects may, therefore, reflect on the initial evolutionary transition from ancestral subsociality to eusociality.

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ABSTRACT Termites have a unique ability to effectively digest lignocellulose with the help of mutualistic symbionts. While gut bacteria and protozoa have been relatively well characterized in termites, the virome remains largely unexplored. Here, we report two genomes of microviruses (termite-associated microvirus-1 [TaMV-1] and termite-associated microvirus-2 [TaMV-2]) associated with the gut of Coptotermes formosanus . 

Coptotermes formosanusShiraki andCoptotermes gestroi(Wasmann) (Blattoidea: Rhinotermitidae) are invasive subterranean termite pest species with a major global economic impact. However, the descriptions of the mutualistic protist communities harbored in their respective hindguts remain fragmentary. TheC. formosanushindgut has long been considered to harbor three protist species,Pseudotrichonympha grassii(Trichonymphida),Holomastigotoides hartmanni, andCononympha(Spirotrichonympha)leidyi(Spirotrichonymphida), but molecular data have suggested that the diversity may be higher. Meanwhile, theC. gestroicommunity remains undescribed except forPseudotrichonympha leei. To complete the characterization of these communities, hindguts of workers from both termite species were investigated using single‐cell PCR, microscopy, cell counts, and 18S rRNA amplicon sequencing. The two hosts were found to harbor intriguingly parallel protist communities, each consisting of onePseudotrichonymphaspecies, twoHolomastigotoidesspecies, and twoCononymphaspecies. All protist species were unique to their respective hosts, which last shared a common ancestor ~18 MYA. The relative abundances of protist species in each hindgut differed remarkably between cell count data and 18S rRNA profiles, calling for caution in interpreting species abundances from amplicon data. This study will enable future research inC. formosanusandC. gestroihybrids, which provide a unique opportunity to study protist community inheritance, compatibility, and potential contribution to hybrid vigor.