New microsatellite markers for Xerophyta dasylirioides (Velloziaceae), an endemic species on Malagasy inselbergs.

PREMISE: Microsatellite markers were developed for Xerophyta dasylirioides (Velloziaceae), a species endemic to the Malagasy inselbergs, to explore the impact of its island-like distribution on genetic diversity and gene flow. METHODS AND RESULTS: A total of 7110 perfect microsatellite loci were recovered by shotgun sequencing on an Illumina MiSeq platform. Primer pairs were designed for 40 arbitrarily selected loci. Fifteen primer pairs that generated distinct PCR products were used to genotype 80 individuals of X. dasylirioides from three inselberg populations. All markers were polymorphic, revealing two to 17 alleles in the overall sampling. Levels of observed and expected heterozygosity per locus ranged from zero to 1.000 and from zero to 0.850, respectively. Success rates of cross-amplification in 10 additional species of Xerophyta (X. croatii, X. decaryi, X. isaloensis, X. labatii, X. lewisiae, X. pinifolia, X. retinervis, X. setosa, X. spekei, X. tulearensis) ranged from zero to 70%. CONCLUSIONS: Fifteen newly developed microsatellite markers provide a toolkit for assessing population genetic parameters of X. dasylirioides in its unique island-like habitats.

(Cryptic) sex in the microsporidian Nosema granulosis--evidence from parasite rDNA and host mitochondrial DNA.

Microsporidia are single-celled, intracellular eukaryotes that parasitise a wide range of animals. The Nosema/Vairimorpha group includes some putative asexual species, and asexuality is proposed to have originated multiple times from sexual ancestors. Here, we studied the variation in the ribosomal DNA (rDNA) of 14 isolates of the presumed apomictic and vertically transmitted Nosema granulosis to evaluate its sexual status. The analysed DNA fragment contained a part of the small-subunit ribosomal gene (SSU) and the entire intergenic spacer (IGS). The mitochondrial cox1 gene of the host Gammarus duebeni (Crustacea) was analysed to temporally calibrate the system and to test the expectation of cophylogeny of host and parasite genealogies. Genetic variability of the SSU gene was very low within and between the isolates. In contrast, intraisolate (within a single host) variability of the IGS felt in two categories, because 12 isolates possess a very high IGS genetic diversity and two isolates were almost invariable in the IGS. This difference suggests variable models of rDNA evolution involving birth-and-death and unexpectedly concerted evolution. An alternative explanation could be a likewise unattended mixed infection of host individuals by more than one parasite strain. Despite considerable genetic divergence between associated host mitochondrial haplotypes, some N. granulosis 'IGS populations' seem not to belong to different gene pools; the relevant tests failed to show significant differences between populations. A set of recombinant IGS sequences made our data incompatible with the model of a solely maternally inherited, asexual species. In line with recent reports, our study supports the hypothesis that some assumed apomictic Microsporidia did not entirely abstain from the evolutionary advantages of sex. In addition, the presented data indicate that horizontal transmission may occur occasionally. This transmission mode could be a survival strategy of N. granulosis whose host often populates ephemeral habitats.

The mitogenome of Gammarus duebeni (Crustacea Amphipoda): A new gene order and non-neutral sequence evolution of tandem repeats in the control region.

We determined the complete mitogenome sequence of Gammarus duebeni (Peracarida, Amphipoda). The mitogenome is circular and has a length of 15,651bp. The content corresponds to typical mitogenomes of metazoans. The gene order and transcriptional polarity of the protein-coding genes is identical to the pancrustacean ground pattern. Six tRNA genes are rearranged, making the gene order unique. Thus it will bring forward the understanding of mitogenome evolution within the Peracarida, for which much more derived gene orders are known. We postulate that the gene string trnA-trnS1 (AGN)-trnN-trnE-trnR constitutes an apomorphic character for the Amphipoda. In contrast to the relatively large genome size, we found two extremely truncated rRNA genes. The rrnL gene is the shortest (986bp) reported up until now for crustaceans. A six-time imperfect tandem repeat was observed within the control region. The inferred deterministic pattern of variation between the repeat units makes it likely, that functional constraints play an important role in the evolutionary dynamics and extant appearance of the repeat array.