Invasion success of a Lessepsian symbiont-bearing foraminifera linked to high dispersal ability, preadaptation and suppression of sexual reproduction

Among the most successful Lessepsian invaders is the symbiont-bearing benthic foraminifera Amphistegina lobifera. In its newly conquered habitat, this prolific calcifier and ecosystem engineer is exposed to environmental conditions that exceed the range of its native habitat. To disentangle which processes facilitated the invasion success of A. lobifera into the Mediterranean Sea we analyzed a ~ 1400 bp sequence fragment covering the SSU and ITS gene markers to compare the populations from its native regions and along the invasion gradient. The genetic variability was studied at four levels: intra-genomic, population, regional and geographical. We observed that the invasion is not associated with genetic differentiation, but the invasive populations show a distinct suppression of intra-genomic variability among the multiple copies of the rRNA gene. A reduced genetic diversity compared to the Indopacific is observed already in the Red Sea populations and their high dispersal potential into the Mediterranean appears consistent with a bridgehead effect resulting from the postglacial expansion from the Indian Ocean into the Red Sea. We conclude that the genetic structure of the invasive populations reflects two processes: high dispersal ability of the Red Sea source population pre-adapted to Mediterranean conditions and a likely suppression of sexual reproduction in the invader. This discovery provides a new perspective on the cost of invasion in marine protists: The success of the invasive A. lobifera in the Mediterranean Sea comes at the cost of abandonment of sexual reproduction

Adaptive strategies for obsolete downtown neighborhoods

Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, February, 2020Thesis: S.M. in Architecture Studies, Massachusetts Institute of Technology, Department of Architecture, February, 2020Cataloged from student-submitted PDF of thesis.Includes bibliographical references (pages 214-223).Tackling the problem of obsolescence in North American cities, this thesis interrogates the question of how we should plan for the regeneration of aging office buildings. I argue that current whole-building, coarse-grained office-to-residential conversion results in entire urban neighborhoods turning into "sanitized vertical suburbia" (Moss 2017) that fail to create balanced, affordable, and inclusive communities. In response, this thesis offers a new floor-by-floor "fine-grained" (Lynch 1981) framework for space conversion. As a case study, I look at conversions In Manhattan's busy financial district that have created an instant elite neighborhood, with 10,000 new luxury units developed over the past fifteen years. To address hyper-gentrification generated by current conversion methods, I introduce a 3D Design and Data Toolkit (DDT) that redefines the conversion process and offers a selective, floor-by-floor approach to balance the quantity and mix of new residential units with the quality of urban life. This tool helps city planners, urban designers, and developers identify spaces for conversion and match demand and supply across scales. As such, this work offers a strategic, multi-scaled approach aimed at reducing grain, increasing market potential, and reinforcing urban vitality in a new conversion process.by Yair Titelboim.M.C.P.S.M. in Architecture StudiesM.C.P. Massachusetts Institute of Technology, Department of Urban Studies and PlanningS.M.inArchitectureStudies Massachusetts Institute of Technology, Department of Architectur

Thermal stress reduces carbonate production of benthic foraminifera and changes the material properties of their shells

The data accompanies the following paper: Titelboim, D., et al. (2021). " Thermal stress reduces carbonate production of benthic foraminifera and changes the material properties of their shells". This dataset contains three-dimensional X-Ray tomographic datasets that reflectance the thermal stress response of two benthic foraminifera species. The data also include the raw measurements at the basis of this study including the morphological and Raman analysi

SSU+ITS rRNA gene sequences, and associated metadata, of the larger benthic foraminifera Amphistegina lobifera across its invasive range

The larger benthic foraminifera species Amphistegina lobifera has been successfully invading the Mediterranean Sea, despite different temperature regimes from their original source location in the Red Sea. To investigate possible genetic (pre)adaptations in the invasive populations, we analyzed the population structure of Amphistegina lobifera across the invasive range (source, pioneer invaders, and invasion front). We snorkelled at four sites across the invasive range to collect living foraminifera individuals attached to macroalgae and pebbles. Each individual was isolated and stored at -80°C until DNA extraction. We amplified the SSU and the hypervariable ITS rRNA 18S gene regions and purified the PCR products. The purified PCR products were cloned, a final PCR was performed and the samples were sent for Sanger sequencing. We compared our results to other populations across the globe (for which only the SSU region is available). Our dataset includes the sequences of the SSU+ITS rRNA regions, which are available on NCBI under the accession numbers OP610171-OP610543, and the associated metadata

Environmental impacts on the structural integrity of British rhodoliths

Abstract Coralline algae form complex habitats which are biodiversity hotspots. Experimental studies suggest that climate change will decrease coralline algal structural integrity. These experiments, however, lack information on local morphological variability and how much structural change would be needed to threaten habitat formation. Here, using finite element modelling, we assess variability in cellular structure and chemical composition of the carbonate skeleton of four coralline algal species from Britain in contemporary and historical specimens collected over the last 130 years. Cellular and mineral properties are highly variable within species, between sites and through time, with structurally weaker cells in the southern species and contemporary material compared to northern taxa and historical material. Yet, temporal differences in strength were smaller than spatial differences. Our work supports long term experiments which show the adaptation potential of this group. Our results suggest that future anthropogenic climate change may lead to loss of habitat complexity in the south and expansion of structurally weaker southern species into northern sites