Topographic heterogeneity and temperature amplitude explain species richness patterns of birds in the Qinghai–Tibetan Plateau

Current Zoology, 2017, 63(2), 131–137 doi: 10.1093/cz/zow024 Advance Access Publication Date: 22 April 2016 Article Article Topographic heterogeneity and temperature amplitude explain species richness patterns of birds in the Qinghai–Tibetan Plateau Chunlan ZHANGa,b,c,**, Qing QUANa,b,**, Yongjie WUd, Youhua CHENe, Peng HEf, Yanhua QUa,*, and Fumin LEIa,* a Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China, bCollege of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China, c Guangdong Entomological Institute (South China Institute of Endangered Animals), Guangzhou 510260, China, d Key Laboratory of Bioresources and Ecoenvironment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu 610064, China, and eDepartment of Zoology, University of British Columbia, Vancouver, V6T 1Z4, Canada, and fNational Zoological Museum, Chinese Academy of Sciences, Beijing 100101, China *Address correspondence to Yanhua Qu, E-mail: ; and Fumin Lei, E-mail: . **These authors contributed equally to this work. Received on 18 December 2015; accepted on 12 January 2016 Abstract Large-scale patterns of species richness have gained much attention in recent years; however, the factors that drive high species richness are still controversial in local regions, especially in highly diversified montane regions. The Qinghai–Tibetan Plateau (QTP) and the surrounding mountains are biodiversity hot spots due to a high number of endemic montane species. Here, we explored the factors underlying this high level of diversity by studying the relationship between species richness and environmental variables. The richness patterns of 758 resident bird species were summarized at the scale of 1 1 grid cell at different taxonomic levels (order, family, genus, and species) and in different taxonomic groups (Passeriformes, Galliformes, Falconiformes, and Columbiformes). These richness patterns were subsequently analyzed against habitat heterogeneity (topographical heterogeneity and land cover), temperature amplitude (annual temperature, annual precipitation, precipitation seasonality, and temperature seasonality) and a vegetation index (net primary productivity). Our results showed that the highest richness was found in the southeastern part of the QTP, the eastern Himalayas. The lowest richness was observed in the central plateau of the QTP. Topographical heterogeneity and temperature amplitude are the primary factors that explain overall patterns of species richness in the QTP, although the specific effect of each environmental variable varies between the different taxonomic groups depending on their own evolutionary histories and ecological requirements. High species richness in the southeastern QTP is mostly due to highly diversified habitat types and temperature zones along elevation gradients, whereas the low species richness in the central plateau of the QTP may be due to environmental and energetic constraints, as the central plateau is harsh environment. Key words: birds, habitat heterogeneity, Qinghai–Tibetan plateau, species richness, temperature amplitude, topography. C The Author (2016). Published by Oxford University Press. V 131 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact 132 Understanding species richness patterns is fundamental to biodiversity conservation (Olson et al. 2001). In the passing decades, most studies have focused on large-scale patterns of species richness at global scales (Brown 1984; Myers 2000). Plenty of hypotheses, including water and energy availability, productivity, habitat heterogeneity, climatic variability, and geometric constraints, have been proposed to explain the mechanisms underlying these patterns (Nores 1999; Colwell and Lees 2000; Gaston 2000; Rahbek and Graves 2001a, 2001b; Hawkins et al. 2003b; Hurlbert, 2004; Diniz et al. 2007; Hawkins et al. 2007;). Some of these factors, (e.g., water and energy availability and climatic variability) may well explain overall patterns of richness, but the predominant factors are still unclear and controversial in local regions (Evans et al. 2005: Rahbek 2005: Wu et al. 2013a). Thus, most studies have been focused on organisms with wide distributions at continental scales. In contrast, patterns of species richness and their underlying driving factors in local regions may be largely dependent on the location of the study areas and the groups of species selected for study (Wu et al. 2013a). Montane regions contain half of the currently recognized biodiversity hot spots, mostly as a consequence of the large number of endemic and endangered species (Stattersfield et al. 1998; Fjeldså et al. 2012). Because montane areas are composed of rugged landscapes and heterogeneous habitats, habitat heterogeneity must be considered to fully explain the high diversity in the mountain regions (Rahbek and Graves 2000, 2001a, 2001b). In addition, temperature amplitude (including seasonal and elevational temperature amplitude) may also contribute to species richness in montane regions (Janzen 1967). Montane species can evolve narrow thermal tolerance and thereby be able to permanently reside within distinct elevation zones. This pattern, in turn, leads to high species turnover on elevational gradients and thus contributes to high species richness (Ghalambor et al. 2006; McCain 2009). Habitat heterogeneity and temperature amplitude are mostly studied in tropical montane regions (Ghalambor et al. 2006; Fjeldså & Bowie 2008; McCain 2009; Fjeldsa 2012) but have rarely been studied in temperate regions (e.g., in the Qinghai–Tibetan Plateau [QTP]). The QTP is the highest plateau in the world, with an average elevation of 4,500 meter above sea level (m.a.s.l.) and an area of more than 2.3 million km2 (Lei et al. 2014). The QTP represents one of the most prominent topographic structures, with a flat interior surrounded by high montane ranges. The southeastern part of the QTP, the eastern Himalayas, contains the highest number of species and endemic species in China (Lei et al. 2003a, 2003b). In contrast to the rather flat central platform of the QTP, the eastern Himalayas are characterized by a series of parallel alpine ranges climbing to altitudes more than 5,000 m.a.s.l., with the differences in altitude from valley to mountaintops often exceeding 2,000 m.a.s.l. This broad altitudinal range has created dramatic habitat heterogeneity. In addition to geomorphological differentiation, the climate is also drastically varied in the QTP. The central platform is characterized by a constant low temperature and arid climate, while topog (...truncated)