“Jack‐of‐all‐trades” is parthenogenetic

Sex is evolutionarily more costly than parthenogenesis, evolutionary ecologists therefore wonder why sex is much more frequent than parthenogenesis in the majority of animal lineages. Intriguingly, parthenogenetic individuals and species are as common as or even more common than sexuals in some major and putative ancient animal lineages such as oribatid mites and rotifers. Here, we analyzed oribatid mites (Acari: Oribatida) as a model group because these mites are ancient (early Paleozoic), widely distributed around the globe, and include a high number of parthenogenetic species, which often co‐exist with sexual oribatid mite species. There is evidence that the reproductive mode is phylogenetically conserved in oribatid mites, which makes them an ideal model to test hypotheses on the relationship between reproductive mode and species'' ecological strategies. We used oribatid mites to test the frozen niche variation hypothesis; we hypothesized that parthenogenetic oribatid mites occupy narrow specialized ecological niches. We used the geographic range of species as a proxy for specialization as specialized species typically do have narrower geographic ranges than generalistic species. After correcting for phylogenetic signal in reproductive mode and demonstrating that geographic range size has no phylogenetic signal, we found that parthenogenetic lineages have a higher probability to have broader geographic ranges than sexual species arguing against the frozen niche variation hypothesis. Rather, the results suggest that parthenogenetic oribatid mite species are more generalistic than sexual species supporting the general‐purpose genotype hypothesis. The reason why parthenogenetic oribatid mite species are generalists with wide geographic range sizes might be that they are of ancient origin reflecting that they adapted to varying environmental conditions during evolutionary history. Overall, our findings indicate that parthenogenetic oribatid mite species possess a widely adapted general‐purpose genotype and therefore might be viewed as “Jack‐of‐all‐trades.”     

Homology in coding and non-coding DNA sequences: a parsimony perspective

Putative synapomorphy assessment (primary homology assessment) is distinct for DNA strings having a codon structure (hereafter, coding DNA) versus those lacking it (hereafter, non-coding DNA). The first requires the identification of a reading frame and of usually few in-frame insertions and deletions. In non-coding DNA, where length variation is much more common, putative synapomorphy assessment is considerably less straightforward and highly depends on the alignment method. Appreciating the existence of evolutionary constraints, alignments that consider patterns associated with specific putative evolutionary events are favored. Once the sequences have been aligned, the postulated putative evolutionary events need to be coded as an additional step. In order for the alignments and the alignment coding to be falsifiable, they should be carried out using justified and explicitly formulated criteria. Alternative coding methods for the most common patterns present in alignments of non-coding DNA are discussed here. Simpler putative synapomorphy assessment will not always correlate to more reliable phylogenetic information because simplicity does not necessarily correlate to the degree of homoplasy. The use of non-coding DNA can result in more laborious coding, but at the same time in more corroborated hypotheses, mirroring their accuracy for phylogenetic inference.     

Blütenmorphologische und palynologische Untersuchungen an Littorella

In the monograph of the Plantaginaceae by Pilger (1937) Littorella is looked upon as a genus with three species. The indigenous Littorella uniflora (L.) Aschers. — native to the Atlantic Europe — is closely related to L. americana Fern., distributed in Eastern North America. In South America there occurs the most interesting species, L. australis Griseb., in two part-areas (in Southern Chile near Panguipulli-Lake and more southern near Lake San Martin to Seno de Ultima Esperenza and on Eastern Falkland-Island). Littorella is a perennial water-or swamp plant, growing on sandy and muddy soils. It can be living submersely throughout life without flowering and propagating by runners in this case. Its occurence, the structure of its inflorescence and ovary apparently quite different and the position of the male flower gave repeatedly rise in literature to the opinion, to seperate Littorella and Plantago far from each other. Indeed, in Littorella as well as in Plantago and the third genus Bougueria, native to the Andes of Peru and Bolivia, the leaves are arranged in rosettes, but the steams are extremely compressed. In the first enumerated genera, the axillary leafless main-axis is ending into a spherical to cylindrical ear, whereas in Littorella there is only one male flower (rarely two!) at the base of which there are sitting several female ones. These different opinions on the inflorescence of Littorella and its relationships to Plantago are discussed. In this connection, a flower- and pollenmorphological elaboration of the three species of the genus seemed to be useful. An evaluation of numerous flowers furnished the proof, that, also here, the ostensibly strict fourfoldness of the corolla is broken through and thus, indications for a possible derivation from a pentamere structure of the flower are to be found.