Abstract

Mass elevation and lee effects markedly influence snow lines and tree lines in high mountain systems. However, their impact on other phenomena or groups of organisms has not yet been quantified. Here we quantitatively studied their influence in the Himalaya–Tibet orogen on the distribution of ground beetles as model organisms, specifically whether the ground beetle distribution increases from the outer to the inner parts of the orogen, against latitudinal effects. We also tested whether July temperature and solar radiation are predictors of the beetle’s elevational distribution ranges. Finally, we discussed the general importance of these effects for the distributional and evolutionary history of the biota of High Asia. We modelled spatially explicit estimates of variables characterizing temperature and solar radiation and correlated the variables with the respective lower elevational range of 118 species of ground beetles from 76 high-alpine locations. Both July temperature and solar radiation significantly positively correlated with the elevational ranges of high-alpine beetles. Against the latitudinal trend, the median elevation of the respective species distributions increased by 800 m from the Himalayan south face north to the Transhimalaya. Our results indicate that an increase in seasonal temperature due to mass elevation and lee effects substantially impact the regional distribution patterns of alpine ground beetles of the Himalaya–Tibet orogen and are likely to affect also other soil biota there and in mountain ranges worldwide. Since these effects must have changed during orogenesis, their potential impact must be considered when biogeographic scenarios based on geological models are derived. As this has not been the practice, we believe that large biases likely exist in many paleoecological and evolutionary studies dealing with the biota from the Himalaya-Tibet orogen and mountain ranges worldwide.

Highlights

  • One of the most basic and general biogeographic patterns is the elevational increase in species ranges, species assemblages, and ecosystems from the poles to the equator [1], largely driven by the latitudinal temperature gradient

  • As mass elevation effect (MEE) and lee effect (LEE) have changed during orogenesis, we provide a general assessment of the importance of these effects for describing the distributional and evolutionary history of the orogen biota

  • Since the results were practically identical, we only report the models with the nontransformed parameters

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Summary

Introduction

One of the most basic and general biogeographic patterns is the elevational increase in species ranges, species assemblages, and ecosystems from the poles to the equator [1], largely driven by the latitudinal temperature gradient. The importance of temperature compared to other. Mass elevation and lee effects determine species ranges abiotic factors, e.g., precipitation and geology, varies among species, assemblages, and ecosystems but is naturally highest for temperature-determined patterns, such as tree lines [2,3]. The tree line, which per definition represents the lower border of the alpine belt, occurs at surprisingly uniform growing-season temperatures worldwide [4]. Other types of biogeographic drivers, e.g., annual precipitation and thermal sums, do not explain the location of tree lines on a global scale [4,5]

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