Population differentiation in the context of Holocene climate change for a migratory marine species, the southern elephant seal.

Understanding observed patterns of connectivity requires an understanding of the evolutionary processes that determine genetic structure among populations, with the most common models being associated with isolation by distance, allopatry or vicariance. Pinnipeds are annual breeders with the capacity for extensive range overlap during seasonal migrations, establishing the potential for the evolution of isolation by distance. Here, we assess the pattern of differentiation among six breeding colonies of the southern elephant seal, Mirounga leonina, based on mtDNA and 15 neutral microsatellite DNA markers, and consider measures of their demography and connectivity. We show that all breeding colonies are genetically divergent and that connectivity in this highly mobile pinniped is not strongly associated with geographic distance, but more likely linked to Holocene climate change and demographic processes. Estimates of divergence times between populations were all after the last glacial maximum, and there was evidence for directional migration in a clockwise pattern (with the prevailing current) around the Antarctic. We discuss the mechanisms by which climate change may have contributed to the contemporary genetic structure of southern elephant seal populations and the broader implications.

Postoperative morbidity survey, mortality and length of stay following emergency laparotomy.

Thirty-day mortality following emergency laparotomy is high, and greater amongst elderly patients. Studies systematically describing peri-operative complications are sparse, and heterogeneous. We used the postoperative morbidity survey to describe the type and frequency of complications, and their relationship with outcomes for 144 patients: 114 < 80 years old, and 30 ≥ 80 years old. Cumulative postoperative morbidity survey scores and patterns of morbidity were similar (p = 0.454); however, 28-day mortality was higher in the elderly (10/30 (33.3%) vs. 11/114 (9.6%), p = 0.008), and hospital stay was longer (median (IQR [range]) 17 (13-35 [6-62]) days vs. 11 (7-21 [2-159]) days, p = 0.006). Regression analysis indicated that cardiovascular, haematological, renal and wound complications were associated with longer hospital stay, and that cardiovascular complications predicted mortality. The postoperative morbidity survey system enabled structured mapping of the number and type of complications, and their relationship with outcome, following emergency laparotomy. These results indicate that rather than a greater propensity to complications following surgery, it was the failure to tolerate these that increased mortality in the elderly.

Environmental factors associated with genetic and phenotypic divergence among sympatric populations of Arctic charr (Salvelinus alpinus).

The mechanisms by which phenotypic and genetic divergence may occur among sympatric, conspecific populations have been widely discussed but are still not well understood. Possible mechanisms include assortative mating based on morphology or variation in the reproductive behaviour of phenotypes, and both have been suggested to be relevant to the differentiation of salmonid populations in post-glacial lakes. Here, we studied Arctic charr (Salvelinus alpinus) in Windermere, where putative populations are defined by spatial and temporal variation in spawning. Genetic differentiation was assessed based on nine microsatellite loci, and phenotypic variation was assessed from morphometric characters. We test hypotheses about the relative role of morphology, spawning season and spawning habitat in the evolution of genetic divergence among these populations. Distinct from other lake systems, we find that both morphological and genetic differentiation are restricted primarily to one of two interconnecting basins, that genetic and morphological differentiation are decoupled in this lake and that both phenotype and environment have changed over the last 20 years. The implication is that breeding habitat plays a primary role in isolating populations that differentiate by drift and that phenotypically plastic changes, potentially related to foraging specializations, have either become secondarily decoupled from the genetically defined populations or were never fundamental in driving the evolution of genetic diversity in the Windermere system.