Narayani Barve

Do Ecological Niche Model Predictions Reflect the Adaptive Landscape of Species?: A Test Using Myristica malabarica Lam., an Endemic Tree in the Western Ghats, India

Ecological niche models (ENM) have become a popular tool to define and predict the “ecological niche” of a species. An implicit assumption of the ENMs is that the predicted ecological niche of a species actually reflects the adaptive landscape of the species. Thus in sites predicted to be highly suitable, species would have maximum fitness compared to in sites predicted to be poorly suitable. As yet there are very few attempts to address this assumption. Here we evaluate this assumption. We used Bioclim (DIVA GIS version 7.3) and Maxent (version 3.3.2) to predict the habitat suitability of Myristica malabarica Lam., an economically important tree occurring in the Western Ghats, India. We located populations of the trees naturally occurring in different habitat suitability regimes (from highly suitable to poorly suitable) and evaluated them for their regeneration ability and genetic diversity. We also evaluated them for two plant functional traits, fluctuating asymmetry – an index of genetic homeostasis, and specific leaf weight – an index of primary productivity, often assumed to be good surrogates of fitness. We show a significant positive correlation between the predicted habitat quality and plant functional traits, regeneration index and genetic diversity of populations. Populations at sites predicted to be highly suitable had a higher regeneration and gene diversity compared to populations in sites predicted to be poor or unsuitable. Further, individuals in the highly suitable sites exhibited significantly less fluctuating asymmetry and significantly higher specific leaf weight compared to individuals in the poorly suitable habitats. These results for the first time provide an explicit test of the ENM with respect to the plant functional traits, regeneration ability and genetic diversity of populations along a habitat suitability gradient. We discuss the implication of these resultsfor designing viable species conservation and restoration programs.

Mapping current and future potential snakebite risk in the new world

Snakebite envenoming is an important public health concern worldwide. In the Americas, ~300,000 bites occur annually, leaving 84,110–140,981 envenomings and 652–3466 deaths. Here, we modeled current and future snakebite risk using ecological niche models (ENMs) of 90 venomous snake taxa. Current snakebite risk predictions were corroborated by incidence data from eight regions/periods with different characteristics. Detailed projections of potential future range shifts on distributions of the medically most relevant species indicated that North American species’ ranges are likely to increase in the future, but mixed results were obtained for Latin American snakes. A likely expansion of overall risk area and an increase of rural population at risk were observed from a consensus model among future scenarios. Our study highlights the capacity of ENMs to provide detailed information on current and future potential distributions of venomous snakes, as well as useful perspectives on snakebite risk, at least broad scales.

Climatic niche and flowering and fruiting phenology of an epiphytic plant

Each species passes through various life stages, and each life stage may have different requirements in terms of climate, soil, topography or other abiotic factors. The phenological stage is one such critical life stage in the plant life cycle. We examined the availability of optimal ecophysiological parameters in 22 years of high temporal climate data during the flowering and fruiting stage of an epiphytic plant, Spanish Moss, with a hemisphere-wide distribution. We used herbarium specimens to establish the flowering period. We found that most populations experience sub-optimal conditions in at least one environmental dimension and most populations are constrained by minimum temperature during the flowering/fruiting stage.