Glacial History of the North Atlantic Marine Snail, Littorina saxatilis, Inferred from Distribution of Mitochondrial DNA Lineages

The North Atlantic intertidal gastropod, Littorina saxatilis (Olivi, 1792), exhibits extreme morphological variation between and within geographic regions and has become a model for studies of local adaptation; yet a comprehensive analysis of the species' phylogeography is lacking. Here, we examine phylogeographic patterns of the species' populations in the North Atlantic and one remote Mediterranean population using sequence variation in a fragment of the mitochondrial cytochrome b gene (607 bp). We found that, as opposed to many other rocky intertidal species, L. saxatilis has likely had a long and continuous history in the Northwest Atlantic, including survival during the last glacial maximum (LGM), possibly in two refugia. In the Northeast Atlantic, several areas likely harboured refugial populations that recolonized different parts of this region after glacial retreat, resulting in strong population structure. However, the outlying monomorphic Venetian population is likely a recent anthropogenic introduction from northern Europe and not a remnant of an earlier wider distribution in the Mediterranean Sea. Overall, our detailed phylogeography of L. saxatilis adds an important piece to the understanding of Pleistocene history in North Atlantic marine biota as well as being the first study to describe the species' evolutionary history in its natural range. The latter contribution is noteworthy because the snail has recently become an important model species for understanding evolutionary processes of speciation; thus our work provides integral information for such endeavours

Establishment Failure in Biological Invasions: A Case History of Littorina littorea in California, USA

The early stages of biological invasions are rarely observed, but can provide significant insight into the invasion process as well as the influence vectors have on invasion success or failure.We characterized three newly discovered populations of an introduced gastropod, Littorina littorea (Linné, 1758), in California, USA, comparing them to potential source populations in native Europe and the North American East Coast, where the snail is also introduced. Demographic surveys were used to assess spatial distribution and sizes of the snail in San Francisco and Anaheim Bays, California. Mitochondrial DNA was sequenced and compared among these nascent populations, and various populations from the North American East Coast and Europe, to characterize the California populations and ascertain their likely source. Demographic and genetic data were considered together to deduce likely vectors for the California populations. We found that the three large California L. littorea populations contained only adult snails and had unexpectedly high genetic diversity rather than showing an extreme bottleneck as typically expected in recent introductions. Haplotype diversity in Californian populations was significantly reduced compared to European populations, but not compared to East Coast populations. Genetic analyses clearly suggested the East Coast as the source region for the California introductions.The California L. littorea populations were at an early, non-established phase of invasion with no evidence of recruitment. The live seafood trade is the most likely invasion vector for these populations, as it preferentially transports large numbers of adult L. littorea, matching the demographic structure of the introduced California L. littorea populations. Our results highlight continued operation of live seafood trade vectors and the influence of vectors on the demographic and genetic structure of the resulting populations, especially early stages of the invasion process

Older People’s Adherence to Community-Based Group Exercise Programmes: A Multiple-Case Study

Physical inactivity is a global phenomenon, with estimates of one in four adults not being active enough to achieve health benefits, thus heightening the risk of developing non-communicable diseases. In order to realise the health and wellbeing gains associated with physical activity the behaviour must be sustained. Community-based group exercise programmes (CBGEP) utilising social support have been shown to be one means of not only increasing activity levels for older people, but sustaining physical activity. A mixed-methods systematic review revealed a gap in the literature around older people’s long-term adherence to real-life CBGEP within a UK context. This study therefore sought to address this gap by understanding older people’s ongoing adherence to CBGEP with a view to gaining further insight about which factors contribute to enabling people to sustain their physical activity levels. A multiple case study research design was employed to understand older people’s (≥ 60 years, n=27) adherence (≥ 69%, for ≥ 1 year) to three current CBGEP in the South- West of England. Qualitative data (participant observation, focus groups, documents, and interviews) were collected and analysed using inductive thematic analysis followed by the analytic technique of explanation building. In order to gain deeper insights into adherence, the humanisation framework was utilised in an a priori manner to further understand adherence from a humanising perspective. Quantitative data were analysed using descriptive statistics and used to set the context of the study. This study found that older people’s adherence to CBGEP was mediated through six factors: factors relating to the individual, the instructor, programme design, social features, participant perceived benefits, and a humanised exercise environment. These all served to explain older people’s adherence to CBGEP. The humanising qualities of these CBGEP must be considered if we wish to support older people in sustaining a physically active lifestyle as they age. These findings are of interest to practitioners and policy makers in how CBGEP serve to aid older people in maintaining a physically active lifestyle with a view to preventing non-communicable diseases and in maintaining social connectivity