Abundance and habitat-suitability relationship deteriorate in fragmented forest landscapes: a case of Adinandra griffithii Dyer, a threatened endemic tree from Meghalaya in northeast India

Abstract

Introduction: A strong positive 'abundance and habitat-suitability' relationship is crucial for conservation of species. Nevertheless, anthropogenic alteration of natural landscapes leading to land use and land cover change, habitat loss, and species extinctions (may) have putatively disturbed this relationship. Hence, it is important to study the nature of the relationship in such human influenced landscapes. Methods: In this study, we endeavored to understand the consistency of the relationship in the fragmented natural landscapes in the Khasi, Garo, and Jaintia hills of Meghalaya in northeast India, with Adinandra griffithii (an endangered endemic tree) as a model species. We reconstructed the distribution of its suitable habitats as a function of the remotely sensed vegetation phenology (i.e., EVI data), using point occurrence data and ecological niche modeling (ENM) tool. Estimation of the abundance and habitat characterization was done through field surveys following standard methods. Results: The study revealed that remotely sensed landscape-level vegetation phenology could effectively discriminate the suitable and unsuitable habitats of threatened species. Linear regression model showed a weak positive correlation between abundance and predicted habitat suitability for adult trees indicating (plausible) deterioration in the relationship. However, sapling and seedling populations did not show a precise trend in this respect. Field-based studies revealed that removal of the species from the suitable habitats because of anthropogenic disturbances possibly weakened the abundance-suitability relationship. Conclusions: The findings of the study enjoin the need for re-establishment of the species in the suitable areas for its conservation and perpetuation.

Species Distribution Models predict abundance and its temporal variation in a steppe bird population

“…As previously suggested (Muñoz et al, 2015;Jiménez-Valverde et al, 2021), our results indicate that linear regressions tend to mask more complex relationships between abundance and HSI. Studies investigating the linear relationship between local abundance and HSI have reported a generally positive relationship (Tellería et al, 2012;Weber et al, 2017;Lunghi et al, 2018) but not consistently associated with a strong correlation (Bean et al, 2014;Adhikari et al, 2018). In our study, the residuals of the linear models between mean and maximum local abundances with HSI exhibit non-constant variances along the range of predicted values (Appendix S5), thus violating one of the assumptions of linear regressions.…”

No place to hide: Rare plant detection through remote sensing

“…Medium resolution RS‐only SDMs are also very useful for predicting rare plant occurrences. Suitable habitats for the endemic tree Adinandra griffithii Dyer were accurately predicted (AUC = 0.99) by using EVI time series (Adhikari et al., 2018). Similarly, robust predictions were achieved for the narrow‐range endemic species Antirrhinum lopesianum Rothm.…”

“…& Kurita, because of its sprouting period (early spring) and rapid growth, could directly contribute to the spectral information captured in early May, which was one of the most important predictors for both species. Likewise, the flowering phenological stage of the endemic tree A. griffithii played an important role in predicting its distribution, since the EVI for the periods of June and July were the most influential predictors (Adhikari et al., 2018).…”

Ecology, distribution mapping and conservation implications of four critically endangered endemic plants of Kashmir Himalaya

“…Moreover, the highly specific ecological niches of these species may also hinder their dispersal and range expansion as has been observed in some other threatened species including Adinandra griffithii ( Adhikari et al 2018 ) and Magnolia rabaniana ( Mir et al 2017 ). Since these species are confined to alpine and sub-alpine habitats which experience severe climates like high humidity, subzero temperatures and acidic soils which prevents them to acclimatize outside their natural setting ( Qu et al 2018 ).…”