B. Mantovani

Breeding systems and reproductive strategies in Italian Reticulitermes colonies (Isoptera: Rhinotermitidae)

Biological traits and colony structure are difficult to analyze in subterranean termites owing to their cryptic lifestyle and their often elusive breeding system. However, the use of molecular markers in a population genetics framework allows the investigation of such aspects. We present here the colony genetic structures of 12 samples collected along the Italian peninsula of two Reticulitermes species (the native R. lucifugus and the introduced R. urbis) analyzed through nuclear microsatellite markers. Reproductive strategies and colony breeding systems differ between the two species. Secondary reproductives of R. lucifugus, collected in three colonies, are all females; genotyping comparisons between these females and their nest mate workers clearly indicate the presence of asexual queen succession (AQS) events in this species, as observed in the Japanese R. speratus and in the North-American R. virginicus. Two other R. lucifugus colonies have a mixed family genetic pattern, possibly as the result of colony fusion events: accordingly, relatedness estimates indicate the presence of genetically unrelated workers. On the contrary, all R. urbis colonies have a genetic structure compatible with the presence of multiple secondary reproductives, as expected on the basis of previous analyses. Moreover, neotenics’ sex ratio is balanced and their heterozygosity is comparable to that of nest mate workers, suggesting that AQS is lacking in this taxon. The differences observed in such biological traits between the two species are discussed in the light of their invasive potential.

Conserved domains and SINE diversity during animal evolution

Eukaryotic genomes harbour a number of mobile genetic elements (MGEs); moving from one genomic location to another, they are known to impact on the host genome. Short interspersed elements (SINEs) are well-represented, non-autonomous retroelements and they are likely the most diversified MGEs. In some instances, sequence domains conserved across unrelated SINEs have been identified; remarkably, one of these, called Nin, has been conserved since the Radiata-Bilateria splitting. Here we report on two new domains: Inv, derived from Nin, identified in insects and in deuterostomes, and Pln, restricted to polyneopteran insects. The identification of Inv and Pln sequences allowed us to retrieve new SINEs, two in insects and one in a hemichordate. The diverse structural combination of the different domains in different SINE families, during metazoan evolution, offers a clearer view of SINE diversity and their frequent de novo emergence through module exchange, possibly underlying the high evolutionary success of SINEs.

Non-LTR R2 Element Evolutionary Patterns: Phylogenetic Incongruences, Rapid Radiation and the Maintenance of Multiple Lineages

Retrotransposons of the R2 superclade specifically insert within the 28S ribosomal gene. They have been isolated from a variety of metazoan genomes and were found vertically inherited even if their phylogeny does not always agree with that of the host species. This was explained with the diversification/extinction of paralogous lineages, being proved the absence of horizontal transfer. We here analyze the widest available collection of R2 sequences, either newly isolated from recently sequenced genomes or drawn from public databases, in a phylogenetic framework. Results are congruent with previous analyses, but new important issues emerge. First, the N-terminal end of the R2-B clade protein, so far unknown, presents a new zinc fingers configuration. Second, the phylogenetic pattern is consistent with an ancient, rapid radiation of R2 lineages: being the estimated time of R2 origin (850–600 Million years ago) placed just before the metazoan Cambrian explosion, the wide element diversity and the incongruence with the host phylogeny could be attributable to the sudden expansion of available niches represented by host’s 28S ribosomal genes. Finally, we detect instances of coexisting multiple R2 lineages showing a non-random phylogenetic pattern, strongly similar to that of the “library” model known for tandem repeats: a collection of R2s were present in the ancestral genome and then differentially activated/repressed in the derived species. Models for activation/repression as well as mechanisms for sequence maintenance are also discussed within this framework.

Mitochondrial and nuclear markers highlight the biodiversity of Kalotermes flavicollis (Fabricius, 1793) (Insecta, Isoptera, Kalotermitidae) in the Mediterranean area.

The biodiversity of the European termite Kalotermes flavicollis is here studied through the analysis of mitochondrial (303 bp of control region and 912 bp of COI/tRNA(Leu)/COII) and nuclear (five microsatellite and 20 Inter-SINE loci) markers on 18 colonies collected in Southern France, Corsica, Sardinia, peninsular Italy, the Balkans and Greece. Different statistical analyses (Bayesian phylogenetic analysis,parsimony network, F-statistics, PCA) were performed. Mitochondrial sequences produced an unresolved polytomy including samples from peninsular Italy, Balkans and Greece, and three main clades: southern France, Corsica-Sardinia and Portoscuso(SW Sardinia). Nuclear markers confirm these data, further highlighting a more significant divergence at the regional scale. The results obtained for the peri-Tyrrhenian area agree with major paleogeographic and paleoclimatic events that shaped the biodiversity of the local fauna. K. flavicollis biodiversity and its phylogeographic pattern are also evaluated in the light of the data available for the other native European termite taxon (genus Reticulitermes), in order to produce a more complete scenario of the Mediterranean. In the area comprised between southern France and Italy, the degree of diversity is similar; however, in the eastern area, while K. flavicollis is differentiated only at the population level, the genus Reticulitermes comprises at least six entities of specific and/or subspecific level. This discrepancy may be explained by taking into account the different evolutionary histories of the two taxa.

Colony Breeding Structure of the Invasive Termite Reticulitermes urbis (Isoptera: Rhinotermitidae)

ABSTRACT Invasive species cause severe environmental and economic problems. The invasive success of social insects often appears to be related to their ability to adjust their social organization to new environments. To gain a better understanding of the biology of invasive termites, this study investigated the social organization of the subterranean termite, Reticulitermes urbis, analyzing the breeding structure and the number of reproductives within colonies from three introduced populations. By using eight microsatellite loci to determine the genetic structure, it was found that all the colonies from the three populations were headed by both primary reproductives (kings and queens) and secondary reproductives (neotenics) to form extended-family colonies. R. urbis appears to be the only Reticulitermes species with a social organization based solely on extended-families in both native and introduced populations, suggesting that there is no change in their social organization on introduction. F-statistics indicated that there were few neotenics within the colonies from urban areas, which did not agree with results from previous studies and field observations. This suggests that although several neotenics may be produced, only few become active reproductives. The results also imply that the invasive success of R. urbis may be based on different reproductive strategies in urban and semiurbanized areas. The factors influencing an individual to differentiate into a neotenic in Reticulitermes species are discussed.

Evolutionary dynamics of R2 retroelement and insertion inheritance in the genome of bisexual and parthenogenetic Bacillus rossius populations (Insecta Phasmida)

Theoretical and empirical studies have shown differential management of transposable elements in organisms with different reproductive strategies. To investigate this issue, we analysed the R2 retroelement structure and variability in parthenogenetic and bisexual populations of Bacillus rossius stick insects, as well as insertions inheritance in the offspring of parthenogenetic isolates and of crosses. The B. rossius genome hosts a functional (R2Brfun) and a degenerate (R2Brdeg) element, their presence correlating with neither reproductive strategies nor population distribution. The median‐joining network method indicated that R2Brfun duplicates through a multiple source model, while R2Brdeg is apparently still duplicating via a master gene model. Offspring analyses showed that unisexual and bisexual offspring have a similar number of R2Br‐occupied sites. Multiple or recent shifts from gonochoric to parthenogenetic reproduction may explain the observed data. Moreover, insertion frequency spectra show that higher‐frequency insertions in unisexual offspring significantly outnumber those in bisexual offspring. This suggests that unisexual offspring eliminate insertions with lower efficiency. A comparison with simulated insertion frequencies shows that inherited insertions in unisexual and bisexual offspring are significantly different from the expectation. On the whole, different mechanisms of R2 elimination in unisexual vs bisexual offspring and a complex interplay between recombination effectiveness, natural selection and time can explain the observed data.

Origin and evolution of the Italian subterranean termite Reticulitermes lucifugus (Blattodea, Termitoidae, Rhinotermitidae)

The Holarctic genus Reticulitermes shows seven species within the Mediterranean Basin. While phylogeny and systematics at continental level has been deeply investigated, a few studies concentrated on local ranges. To gain a clearer picture of the diversity and evolution of the Italian species Reticulitermes lucifugus, we analyzed the mitochondrial cytochrome oxidase II (COII) gene marker in newly collected colonies across the Peninsula. Data were gathered with all R. lucifugus sequences available from previous studies; COII sequences of the closely related Iberian taxa were also added to the data set. Maximum-likelihood, median-joining and statistical parsimony network elaborations on the resulting 119 colonies all agreed in indicating that: (i) the Sardo-Corsican subspecies R. lucifugus corsicus, strictly related to Southern Italian populations (including the Sicilian ones), is phylogenetically closer to the Iberian Reticulitermes grassei; and (ii) R. lucifugus lucifugus peninsular populations are structured into three clusters. The phylogenetic relationships and the biogeography of extant taxa suggest a scenario in which R. lucifugus ancestors colonized the Italian region through the Sardo-Corsican microplate during its Oligocene-Miocene anticlockwise rotation. Moreover, well after the colonization took place, northward range expansion might have produced the presently observed genetic diversity, as inferred from haplotype and nucleotide diversity estimates. On the whole, this study highlights the evolution of Italian Reticulitermes taxa and supports the importance of a wide taxon sampling especially when dealing with organisms easily dispersed by human activities.

Cryptic diversity in Australian stick insects (Insecta; Phasmida) uncovered by the DNA barcoding approach.

The barcoding approach was applied to analyze 16 Australian morphospecies of the order Phasmida, with the aim to test if it could be suitable as a tool for phasmid species identification and if its discrimination power would allow uncovering of cryptic diversity. Both goals were reached. Eighty-two specimens representing twelve morphospecies (Sipyloidea sp. A, Candovia annulata, Candovia sp. A, Candovia sp. B, Candovia sp. C, Denhama austrocarinata, Xeroderus kirbii, Parapodacanthus hasenpuschorum, Tropidoderus childrenii, Cigarrophasma tessellatum, Acrophylla wuelfingi, Eurycantha calcarata) were correctly recovered as clades through the molecular approach, their sequences forming monophyletic and well-supported clusters. In four instances, Neighbor-Joining tree and barcoding gap analyses supported either a specific (Austrocarausius mercurius, Anchiale briareus) or a subspecific (Anchiale austrotessulata, Extatosoma tiaratum) level of divergence within the analyzed morphospecies. The lack of an appropriate database of homologous coxI sequences prevented more detailed identification of undescribed taxa.