Stridulations Reveal Cryptic Speciation in Neotropical Sympatric Ants

The taxonomic challenge posed by cryptic species underlines the importance of using multiple criteria in species delimitation. In the current paper we tested the use of acoustic analysis as a tool to assess the real diversity in a cryptic species complex of Neotropical ants. In order to understand the potential of acoustics and to improve consistency in the conclusions by comparing different approaches, phylogenetic relationships of all the morphs considered were assessed by the analysis of a fragment of the mitochondrial DNA cytochrome b. We observed that each of the cryptic morph studied presents a morphologically distinct stridulatory organ and that all sympatric morphs produce distinctive stridulations. This is the first evidence of such a degree of specialization in the acoustic organ and signals in ants, which suggests that stridulations may be among the cues used by these ants during inter-specific interactions. Mitochondrial DNA variation corroborated the acoustic differences observed, confirming acoustics as a helpful tool to determine cryptic species in this group of ants, and possibly in stridulating ants in general. Congruent morphological, acoustic and genetic results constitute sufficient evidence to propose each morph studied here as a valid new species, suggesting that P. apicalis is a complex of at least 6 to 9 species, even if they present different levels of divergence. Finally, our results highlight that ant stridulations may be much more informative than hitherto thought, as much for ant communication as for integrative taxonomists

Allozymes, mtDNA and microsatellites study introgression in a stocked trout population in France

International audienceA comparative study of disturbed (downstream) and undisturbed (upstream) populations in a French Mediterranean river (the Sorgue) was conducted to assess the fate of introgressing hatchery-genes in the aboriginal gene pool. Variation was assessed at 27 protein-coding loci, three microsatellite loci and two mtDNA restriction sites. The results were compared to those from another Mediterranean drainage basin (that of the river Orb). The genetic pattern observed among markers and drainage basins was found to be noticeably different. A reduction in population size is hypothesized to explain the lower variability observed in the upper part of the river Sorgue. Estimations of hatchery gene flow were different between loci but in the same range of values between markers

Is the socio-spatial distribution of mound-building mice, Mus spicilegus, compatible with a monogamous mating system?

International audienceWe tested whether the socio-spatial distribution of mound-building mice, Mus spicilegus, could be compatible with a monogamous mating system as suggested by several behavioural laboratory studies. A five day trapping session took place in an agricultural field in the Gyöngyös region (Hungary) at the end of April 2000. The species was identified through genetic techniques based on the microsatellite locus Musmcka. In total 43 animals were captured, and recapture rate was high (6/10 for males, 17/33 for females). Out of the 33 captured females, 17 were pregnant. Animals were generally recaptured in the same trap. Spatial associations (animals captured in the same trap) were observed between a male and a female (six cases) but also between females (six pairs and two trios) with or without a male. Based on these results we questioned the occurrence of monogamy and we proposed that polygyny could occur at least during the beginning of the reproductive season and in this studied population. Female biased sex-ratio and high population density may have favoured polygyny. However, associations between females could have resulted from the development of strong social bounds during the six months spent together during winter inside the mound. A possible consequence is that polygyny might be restricted to the over-wintering generation

Microsatellite polymorphism and genetic impact of restocking in Mediterranean brown trout (Salmo trutta L.)

International audienceThe genetic impact of restocking Mediterranean brown trout populations with hatchery stocks was investigated in the Orb River drainage (France), using genetic data from three microsatellite loci. We sampled two wild populations, the main river which is restocked each year and one of its tributaries which has not been restocked for 6 years. Each sample was divided into two age groups (juveniles/ adults). Introgression of each native population by hatchery stocks was previously estimated using allele frequencies from two diagnostic protein-coding loci and one mtDNA haplotype. The genetic structure and allelic frequency at three microsatellite loci in native populations were compared with two hatchery samples belonging to stocks usually used for restocking this drainage. High levels of polymorphism (23±27 alleles per locus) were detected for two loci, whereas the third was less polymorphic. Polymorphism was signi®cantly higher in the restocked population than in the now undisturbed population. Signi®cant dierences between age groups were observed in the main river, but not in its tributary. The introgression estimates using microsatellites were compared to those obtained from proteins and mtDNA. The dierent possible origins of alleles common to hatcheries and wild populations (homoplasy, ancestral polymorphism or introgression) are discussed

Socio-genetic structure of mound-building mice, Mus spicilegus, in autumn and early spring

International audienceMus spicilegus has become a popular biological model species in the last decade because of the evolutionary interest of its behavioural particularities (the building of mounds, bi-parental care and monogamous mating system). The genetic structure of M. spicilegus populations should reflect those life-history traits. Although many studies have reported on mound-building mouse populations in the field or in a semi-natural enclosure, only one used hyper variable genetic markers to assess parentage and social structure. In the present study conducted in Hungary, we analysed individuals from seven highly populous mounds in autumn with the set of loci used in a previous study. Our results confirmed that mounds are inhabited by juveniles from several parental units, but revealed population differences. In a capture–recapture field session in spring, we assessed genetic relationships between individuals after dispersal from the mounds, the other key moment of the life cycle of this species. The results indicate that the social structure at this moment reflects a transition phase between the large over-wintering groups and the monogamous pairs described later in the year. Social bounds forged during the long winter cohabitation may have lasting effects on social and genetic structure of this species. This scenario is discussed in respect of the available literature on this species as well as other species

Discrimination of the Social Parasite Ectatomma parasiticum by Its Host Sibling Species (E. tuberculatum)

Among social parasites, workerless inquilines entirely depend on their host for survival and reproduction. They are usually close phylogenetic relatives of their host, which raises important questions about their evolutionary history and mechanisms of speciation at play. Here we present new findings on Ectatomma parasiticum, the only inquiline ant described in the Ectatomminae subfamily. Field data confirmed its rarity and local distribution in a facultative polygynous population of E. tuberculatum in Mexico. Genetic analyses demonstrated that the parasite is a sibling species of its host, from which it may have diverged recently. Polygyny is suggested to have favored the evolution of social parasite by sympatric speciation. Nevertheless, host workers from this population were able to discriminate parasites from their conspecifics. They treated the parasitic queens either as individuals of interest or as intruders, depending on their colonial origin, probably because of the peculiar chemical profile of the parasites and/or their reproductive status. We suggest that E. parasiticum could have conserved from its host sibling species the queen-specific substances that produce attracting and settling effect on workers, which, in return, would increase the probability to be detected. This hypothesis could explain the imperfect social integration of the parasite into host colonies

Egg cannibalism in a facultative polygynous ant: conflict for reproduction or strategy to survive?

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Socio-genetic structure and mating system of a wild boar population

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