Abstract: Antarctica is structured by a narrow and deep continental shelf that sustains a remarkable number of benthic species. The origin of these species and their affinities with the deep-sea fauna that borders the continent shelf are not clear. To date, two main hypotheses have been considered to account for the evolutionary connection between the faunas: (1) either shallow taxa moved down to deep waters (submergence) or (2) deep-sea taxa colonized the continental shelf (emergence). The regular sea urchin genus Sterechinus is a good model to explore the evolutionary relationships among these faunas because its five nominal species include Antarctic and Subantarctic distributions and different bathymetric ranges. Phylogenetic relationships and divergence times among Sterechinus species were established using the COI mitochondrial gene by assuming a molecular clock hypothesis. The results showed the existence of two genetically distinct main groups. The first corresponds exclusively to the shallow-water Antarctic species S. neumayeri, while the second includes all the other nominal species, either deep or shallow, Antarctic or Subantarctic. Within the latter group, S. dentifer specimens all formed a monophyletic cluster, slightly divergent from all other specimens, which were mixed in a second cluster that included S. agassizi from the continental shelf of Argentina, S. diadema from the Kerguelen Plateau and S. antarcticus from the deep Antarctic shelf. These results suggest that the deeper-water species S. dentifer and S. antarcticus are more closely related to Subantarctic species than to the shallow Antarctic species S. neumayeri. Thus, for this genus, neither the submergence nor emergence scenario explains the relationships between Antarctic and deep-sea benthos. At least in the Weddell quadrant, the observed genetic pattern suggests an initial separation between Antarctic and Subantarctic shallow species, and a much later colonization of deep water from the Subantarctic region, probably promoted by the geomorphology of the Scotia Arc.

Abstract: The limits of linear moment-tensor inversions from long-period teleseismic body waves are analysed in detail, using inverse methods. We focus our attention on single-station and few-stations methods. Information on the feasibility of full or deviatoric moment-tensor determinations prior to inversion are deduced from the system conditioning. The resolution and correlation of the momenttensor components are analysed using the resolution matrix. Conclusions on the importance and independence of the data are drawn from the information matrix. The single--station case and its implications are discussed in greater detail, as well as possible constraints on the inversion.

Abstract: Ilkka Hanski may be best known for his work on insect and metapopulation dynamics, but he also contributed significantly to small mammal research. In the early 1980s he became interested in shrew dynamics, energetics, and of course, shrew metapopulations. He aimed at understanding the population biological consequences of body size in different shrew species. Feeding habits and environmental stochasticity affect shrew species in profoundly different ways: due to their short survival time small species have high extinction rates but their dispersal and colonization capacity is high which enables them to survive as metapopulations. After Hansson and Henttonen reported the Fennoscandian gradients in vole dynamics in the mid-1980s, Hanski became interested in vole and lemming cycles. The first models on this were published with Henttonen and Hansson in 1991 where the roles of specialist and generalist predators were assessed. Later, the models were further developed with Korpimäki and Turchin, with model parametrization from Microtus biology and including both specialist mammalian predators as well as avian predators. A special case was the model with Henttonen on competing vole species with a shared predator (apparent competition), which was related to the long-term fading out of vole cycles in Finnish Lapland in the mid-1980s (which though returned in the early 2010s). Later Hanski became interested in the work of Sittler and Gilg in Greenland. Together they modelled the very simple vertebrate community and showed how stoats played a pivotal role in generating a population cycle in the collared lemming. In addition to these specific works, Hanski was leading collaborator in several reviews on small rodent cycles and predation. He intended to return to shrew biology, but that never realized. Hanski was a fearless field biologist, but he always aimed at understanding natural phenomena at more general, theoretical level.

Abstract: In the Kerguelen Islands, the multiple effects of climate change are expected to impact coastal marine habitats. Species distribution models (SDM) can represent a convenient tool to predict the biogeographic response of species to climate change but biotic interactions are not considered in these models. Nevertheless, new species interactions can emerge in communities exposed to environmental changes and the structure of biotic interactions is directly related to the potential resilience of ecosystems. Trophic interaction studies can help predict species vulnerability to environmental changes using carbon (δ13C) and nitrogen (δ15N) stable isotope ratios to generate trophic models. Using new available data inputs, we generated robust SDM and trophic interaction models to assess the potential response and sensitivity of three echinoid species to future worst-case scenarios of environmental change in the Kerguelen Plateau region. The two modelling approaches provide contrasting insights into the potential responses of each species to future environmental changes with both approaches identifying Abatus cordatus to be particularly vulnerable due to its narrow ecological niche and endemism to near-shore areas. Coupling insights gained from trophic niche ecology with species distribution modelling represents a promising approach that can improve our understanding and ability to predict the potential responses of species to future habitat changes.