Azim Premji University is an Indian non-profit private university, located in Bangalore, Karnataka which is established by the Azim Premji University Act (2010) recognized by the University Grants Commission under Section 2F.
Identifying climatic niche dynamics of invasive species and the factors that drive them is important for assessing invasion risk and prioritizing management actions. Multispecies studies, mostly conducted at a global scale, compared climatic niches between the species' native and introduced ranges to assess the niche dynamics. We hypothesized that a species' socio-ecological traits, biogeographic characteristics, and invasion history can influence its climatic niche dynamics, especially at a regional scale, and tested this hypothesis for 101 invasive alien plant species (IAPS) in India. We constructed a gridded environmental space from the species' distribution range and assessed their realized climatic niche dynamics in the analogue climate space. The interactive influence of 11 biotic and abiotic variables on the niche estimates was then assessed by regression models and mediation analysis based on seven hypothesized relationships. More than 60% of the species showed a climatic niche shift in India. A significantly higher expansion was observed in species that are perennial, inhabit freshwater habitats, originated from the Americas, and naturalized in the Asia-Tropical. The regression analysis revealed minimum residence time and naturalized range size as the important variables for niche dynamics, whereas a significant negative relationship was found only between naturalized range size and niche expansion. Overall, our findings recommend exercising caution while forecasting invasion risk, as species undergoing climatic niche shifts in India could underestimate the invasion potential of these species. Given that biogeography and residence time drive the climatic niche shift of invasive species, we recommend considering these variables in the risk assessment framework and management actions for the IAPS in India.
Biological invasions rank among the greatest anthropogenic threats to global biodiversity and ecosystem functioning, but measuring and comparing their relative magnitudes across regions and taxa remains challenging. The absence of a unified metric hinders scientific advancement, public awareness, and policy development. We propose a simple, standardized metric to quantify and communicate the magnitude of biological invasions: total biomass of nonnative species. This metric approximates the amount of native biomass co-opted, displaced, consumed, or replaced by the populations of invasive species. We illustrate how this metric can be applied to different research themes and contexts such as temporal and spatial invasion dynamics, management strategies, and invasion forecasts. Although not a metric for impact, this magnitude will be useful to quantify the extent of impact of invasive populations. Total biomass can provide a common currency to assess the magnitude of biological invasions, facilitating comparisons, syntheses, and innovations across invasion science.
Quantifying root zone soil moisture (RZSM) is critical for assessing water availability to crops and identifying agricultural drought across Africa, with access to reliable and timely RZSM data essential for informed decision-making. While rainfall is frequently used to assess crop growing conditions, it alone may not reliably reflect crop water availability due to the impact of evapotranspiration on soil moisture and rainfall not always reflective of concurrent soil water content at rooting depth. To provide robust information on agricultural drought, this paper describes a new, operational RZSM dataset, called TAMSAT soil moisture (TAMSAT-SM), available from 1983-present at 0.25° spatial resolution. TAMSAT-SM is derived using the JULES land surface model, forced with TAMSAT rainfall estimates and other meteorological variables from the NCEP reanalysis, and tuned to SMAP satellite soil moisture observations. Comparison against other RZSM products and independent satellite-derived vegetation health data show TAMSAT-SM can reliably capture the spatial and temporal RZSM and vegetation health patterns across Africa and can be a useful tool to support existing agricultural drought monitoring efforts.
We study the verification of parameterised secrecy for cryptographic protocols in the Dolev-Yao model, where the number of protocol sessions is unbounded and treated as a parameter. This differs fundamentally from classical Dolev-Yao secrecy, which asks whether a protocol leaks a secret irrespective of the number of executions; our question is whether secrecy holds uniformly across all system sizes, where such a size is a parameter. This parameterised perspective captures how attacks scale with the number of participants and provides a formal basis for the empirical effectiveness of small-instance analysis. Secrecy (parameterised or not) is undecidable in general, even under bounded freshness or bounded message size. We identify two structural restrictions that make parameterised secrecy decidable: (i) global bounded freshness per role, and (ii) a Dolev-Yao intruder restricted to well-typed substitutions. Under these assumptions, protocol executions admit a finite representation up to a collapsing map on agents and terms. Our main result is that parameterised secrecy is decidable in this setting. We obtain a cut-off theorem: secrecy violations in systems with arbitrarily many sessions are always witnessed in systems of bounded size. The cut-off is self-contained; more strongly, the induced transition system forms a well-structured transition system (WSTS) under a bound-based ordering, so secrecy also reduces to a coverability problem in WSTS. This provides a structural explanation for the existence of finite witnesses in symbolic protocol analysis and connects Dolev-Yao verification with parameterised verification techniques.
