Abstract
In a period of ongoing climate changes, identifying drivers of overall and endemic species diversity is a key element in constructing new ecological patterns and determining the main goals of conservation. Such studies are especially crucial if they concern biodiversity hotspot areas. In this study, we explore patterns and drivers of plant endemism (the proportion of endemic plant species to overall plant species richness; PE) in Tajikistan. We used three groups of climatic measures featuring the contemporary and glacial climates as well as climatic changes since the Last Glacial Maximum in the Pleistocene (LGM). To explore relationships between PE and climatic groups, and the most important climatic variables, we applied the Generalised Additive Model and regression trees method respectively. Glacial climate predicted PE variation the most (74.3%), followed by climate stability (55.4%) and current climate (62.4%). The most important variables represented change in precipitation of driest quarter, glacial mean annual temperature and current annual precipitation. LGM climate and its change to date have the greatest influence on contemporary PE patterns in Tajikistan, revealing the evolutionary dependencies between limited-range plants and past climate. Accordingly, annual temperature and precipitation regimes have been the most crucial drivers of PE since the LGM until today. The study revealed the dependence of the PE on a stabilized water-energy supply. The changing temperature and precipitations regimes during the ongoing climate warming may, therefore, increases the threat to geographically isolated cryophilous plants of Tajikistan, while their escape potential to suitable cold habitats is highly topographically limited.
Highlights
Tajikistan is a mountainous Central Asian country, located almost entirely within the Pamir-Alai Mountains (Mts)
The aim of this study is to investigate patterns of plant endemism in Tajikistan in relation to contemporary and glacial (Last Glacial Maximum, Last Glacial Maximum in the Pleistocene (LGM)) climate as well as climatic stability
We found that the precipitation in the driest quarter in the LGM period was an important influential factor for current endemism
Summary
Tajikistan is a mountainous Central Asian country, located almost entirely within the Pamir-Alai Mountains (Mts). There are large and wide, often geographically isolated valleys with gentle slopes in the colline and montane belts that have not been glaciated and play the role of refuge sanctuary for Pleistocene or Tertiary s pecies[2]. These unique environmental conditions promote a high rate of endemism. To the richest genera belongs Astragalus, comprising 173 endemic species, with its exceptional richness probably related to niche diversification in the middle to late Pleistocene[5]. In Tajikistan, the Pleistocene glaciers in the Pamir and the Alai–Turkestan ranges have been valley glaciers, except for the glaciers on the Pamirian Plateau, which have formed local piedmont glaciations. In some ranges of south-eastern Pamir (e.g. Shahdarian Mts., Wakhan Mts.) is it likely that indirect monsoonal influence may have been responsible for the existence of the Late Glacial moraine stages in this area[7]
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