The growth of the number of persons pursuing education outside of their home country has created a relatively new population of transnationally mobile students who experience a pivotal developmental period crossing and across international borders. There are few suitable theoretical models to examine the developmental experiences of this growing population. In his last publication, Urie Bronfenbrenner acknowledged his ecological model was a developmental yet evolving model to be tested and amended by incorporating new evidence. This conceptual paper draws from existing empirical work to advance the ecological model and revise it to be more applicable to and explanatory of developmental experiences of international students in the United States. The resulting model, which we call the Spanning Systems model, can be used to identify spaces of potential contradictions or learning in a student’s development.

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Spadefoot toad species display extreme variation in larval period duration, due in part to evolution of thyroid hormone (TH) physiology. Specifically, desert species with short larval periods have higher tail tissue content of TH and exhibit increased responsiveness to TH. To address the molecular basis of larval period differences, we examined TH receptor (TR) expression across species. Based on the dual function model for the role of TR in development, we hypothesized that desert spadefoot species with short larval periods would have 1) late onset of TR expression prior to the production of endogenous TH and 2) higher TR levels when endogenous TH becomes available. To test these hypotheses, we cloned fragments of TRα and TRβ genes from the desert spadefoot toads Scaphiopus couchii and Spea multiplicata and their non-desert relative Pelobates cultripes and measured their mRNA levels in tails using quantitative PCR in the absence (premetamorphosis) or presence (natural metamorphosis) of TH. All species express TRα and TRβ from the earliest stages measured (from just after hatching), but S. couchii, which has the shortest larval period, had more TRα throughout development compared to P. cultripes, which has the longest larval period. TRβ mRNA levels were similar across species. Exogenous T3 treatment induced faster TH-response gene expression kinetics in S. couchii compared to the other species, consistent with its increased TRα mRNA expression and indicative of a functional consequence of more TRα activity at the molecular level. To directly test whether higher TRα expression may contribute to shorter larval periods, we overexpressed TRα via plasmid injection into tail muscle cells of the model frog Xenopus laevis and found an increased rate of muscle cell death in response to TH. These results suggest that increased TRα expression evolved in S. couchii and contribute to its higher metamorphic rates.

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As the global mobility of students has continued to grow, many of those who obtain their degrees abroad are seeking opportunities to stay in the countries where they received their education. Responding to these trends, several host countries have devised visa schemes to enable international graduates to remain in the country and work after graduation. Using a summative content analysis approach, this article provides an analysis of the content of the Optional Practical Training and Temporary Graduate Visa programmes situated within the economic, political and social contexts of the United States and Australia respectively. Graduation from a domestic institution is the core requirement of these programmes, directly implicating higher education in immigration issues and placing higher education institutions at the border of the state. As such, we must consider HEIs not only as a temporary home for globally mobile student sojourners but as the starting point for transnational talent on complex migration journeys.