(Sea)ways of Perception: an Integrated Maritime-Terrestrial Approach to Modelling Prehistoric Seafaring

The seaways have played a significant role in the movement of people, goods and ideologies since prehistory; yet, the ephemerality of movement combined with the paucity of direct evidence for prehistoric seafaring has challenged more refined understandings of the role of early seafaring in anthropogeny. Advances in digital methodologies within archaeology, such as least-cost approaches, allow more nuanced models of movement to be generated but suffer from dichotomous approaches to land and sea. These disentangled land-sea perspectives have long been criticised as ineffectual for understanding past maritime cultures, and previous discussions of prehistoric seafaring more specifically have advocated the consideration of the unique character of maritime space in order to more closely actuate a seafarer’s perspective. Drawing on these ideas, this paper argues that more nuanced approaches to past seafaring are not only necessary but also achievable through holistic perspectives, heuristic methods and scaled-down resolutions, which allow for a more contextualised understanding of the spatiality and temporality—i.e. the human-scale—of maritime movement. This will be demonstrated through an integrated land-sea least-cost method to model Neolithic seafaring around the Outer Hebrides of Scotland. It is not the intention of this paper to advocate solely for the methodology outlined here but rather to demonstrate the need to consider and understand the unique character of maritime space and its many influences on the practices being studied. Only through such contextualised cognition can the perspectives and ideologies of past seafarers and the role of seafaring in anthropogeny truly be understood.

Stress fields of ancient seismicity recorded in the dynamic geometry of pseudotachylyte in the Outer Hebrides Fault Zone, UK

Heterogeneous sequences of exhumed fault rocks preserve a record of the long-term evolution of fault strength and deformation behaviour during prolonged tectonic activity. Along the Outer Hebrides Fault Zone (OHFZ) in NW Scotland, numerous pseudotachylytes record palaeoseismic slip events within sequences of mylonites, cataclasites and phyllonites. To date, the kinematics and controls on seismicity within the long active history of the OHFZ have been poorly constrained. Additional uncertainties over the relative location of a meteorite impact and possible pre-OHFZ brittle faulting also complicate interpretation of the diffuse seismic record. We present kinematic analyses of seismicity in the OHFZ, combining observations of offset markers, en echelon injection veins and injection vein geometry to reconstruct slip directions and stress fields. This new dataset indicates that a range of fault orientations, slip directions and slip senses hosted seismicity in the OHFZ. Such complexity requires several stress field orientations, in contrast with the NW–SE Caledonian compression traditionally attributed to frictional melting along the OHFZ, indicating that seismicity had a long-term presence across the fault zone. Persistence of strong frictional failure alongside the simultaneous development of weak fault rocks and phyllonitic shear zones in parts of the OHFZ has significant implications for understanding seismic hazard along mature continental faults.Supplementary material: Tables listing analysed orientation measurements plus further information and sensitivity testing of palaeostress analysis parameters are available at https://doi.org/10.6084/m9.figshare.c.5134797

Multiple colonisations and Wolbachia infections influence the fine-scale population structure of the widespread Common Blue butterfly (Polyomattus icarus) in the British Isles

Deeply divergent mitochondrial genomes can reveal hidden diversity within species, however robust assessments of diversity require corroborative divergence in the nuclear genome. Previous phylogeographic analysis of the Common Blue butterfly (Polyommatus icarus) revealed a deeply divergent mitotype in Europe. Here, we reconstruct the phylogeography of this butterfly in the British Isles using both mitochondrial and nuclear DNA. We found strong geographical structuring of three distinct CO1 mitotypes with an ancient lineage restricted to the Outer Hebrides. The short time (c. 20,000 years) available for colonization of the British Isles and an expanded CO1 phylogeography from the species’ entire range supports a hypothesis of at least 3 colonization events with sequential replacement of mtDNA. Analysis of ddRADSeq genomic markers from 184 individuals across the British Isles indicates that genetic clustering is similar but divergence weaker at the nuclear level, consistent with a biogeographic scenario of multiple colonisations. We were also able to use the ddRADSeq to infer the infection status of all individuals sequenced. Interestingly, we found evidence for high frequency (>70%) infections by two different Wolbachia strains, with strong mitotype associations, in the Northern populations of the British Isles. Wolbachia-induced cytoplasmic incompatibility may be sufficient to explain the mito-nuclear discordance observed across an admixture zone on the mainland and the complete dominance of a deeply divergent mitotype on the Outer Hebrides. Moreover, the strain (wIca1), largely restricted to the Outer Hebrides potentially causes phenotypic feminisation of genetic males, a known but rare phenotypic effect of Wolbachia in Lepidoptera. Therefore, the impact of Wolbachia on the biology and genetic diversity of this butterfly merits further attention.

Aegiochus gracilipes (Hansen, 1895) a senior synonym of Aegiochus tara Bruce, 2009 (Crustacea: Isopoda: Aegidae)

Aegiochus gracilipes Hansen, 1895 was described from a single immature specimen accompanied by three figures (Hansen 1895). Hansen (1916) subsequently reported the species without figures. Over the next 100 years A. gracilipes only appeared in the literature as a citation in larger review and cataloguing studies. Most significantly, Bruce (2009) transferred A. gracilipes from Aega Leach, 1815 to Aegiochus Bovallius, 1885, as part of a broader study redefining the morphological characters used to distinguish Aegiochus. To the present day A. gracilipes, described from the north-eastern Atlantic off the Outer Hebrides, Scotland, is known only from the original figures and its limited primary description.