From about 40 Mya, while Antarctica geographically isolated from the rest of the world, the marine shelf fauna faced a dramatic decrease in water temperatures. Many lineages went extinct, while others adapted and flourished. The Antarctic clade of the amphipod family Iphimediidae was among the successful ones. Here, a range of cutting-edge phylogenetic comparative and morphometric methods are used to investigate the evolutionary processes which generated the exceptional diversity of this clade. To this purpose, three types of data were collected: (1) a novel phylogeny of the family was first reconstructed using a multigene molecular dataset, (2) 3D shape data were obtained by applying 3D-geometric morphometric methods on micro-CT scans of the specimens and (3) stable isotope d13C and d15N were measured and used as variables describing the trophic ecology of the species. First, possible evolutionary correlations between 3D-morphometric dataset of mouthparts (mandible, maxilliped) and stable isotope ratios were assessed. Significant correlations suggest an adaptation of the mandible shape to the food source. Secondly, as a prerequisite to the study of species diversification, species boundaries were investigated using a combination of DNA-based delimitation methods and detailed morphological/morphometric analyses. The latter showed that species diversity in Antarctic iphimediids is greatly underestimated, as most of the described species appear to be complexes of multiple morphologically similar species. Finally, potential changes in the rate of lineage diversification were explored in parallel to the evolution of morphological traits (mouthparts 3D shape data) along the phylogeny. On one hand, we found no evidence of an early burst of lineage diversification. On the other hand, late bursts (appr. 7-3 Mya) were detected in two subclades. Such late radiations could result from the invasion of novel ecological niches, as a late partitioning of mouthparts’ shape diversity along the phylogeny is also observed. Plio-Pleistocene glacial cycles, which have been hypothesized to act as a diversity pump, might also have promoted late diversification events in Antarctic iphimediids. By applying such an integrative approach for the first time on Antarctic invertebrates, this study improves our general understanding of the evolutionary dynamics shaping the standing Antarctic shelf biodiversity.
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RBINS Staff Publications 2025
Barchan dunes are crescentic aeolian landforms of loose, mostly well-sorted sand with a convex side directed upwind and two horns pointing downwind. Their migration is mainly controlled by sand supply, dune size, wind patterns, vegetation cover and human impact. In Qatar, their distribution is limited to the southeastern part of the peninsula, where they play an important role for tourism and camping activities among locals. We investigate the variability of dune migration in Qatar over a time period of 50 years using high-resolution satellite and aerial imagery. We then explore its relation to the regional Shamal wind system (NNW–SSE), teleconnection patterns, and limitations in sand supply associated with the transgression of the Arabian Gulf, which explain the fact that Qatar is gradually being stripped from aeolian landforms with a remaining dune population in the southeast. Strong size-dependent differences in migration rates of individual dunes as well as significant decadal variability on a dune-field scale are detected, the latter closely correlating with summer Shamal activity. The summer Shamal itself is mainly driven by pressure differences between the stationary anticyclone over the eastern Mediterranean and the established summer heat low over Iran and adjacent areas. It seems to be related to the intensity of the North Atlantic Oscillation and the Indian Summer Monsoon, in particular during years of relatively strong (weak) summer Shamals. High uncertainties associated with the extrapolation of migration rates back into the Holocene, however, do not permit further refining of the timing of the loss of sand supply and the onset of the mid-Holocene relative sea-level (RSL) highstand. For the youngest phase considered in this study (2006–2015), human impact has significantly accelerated dune migration under a more or less stable Shamal regime through systematic sand mining and excessive vehicle traffic upwind of the core study area, which started in 2007.
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RBINS Staff Publications 2018
