Temperature-Dependent Growth and Life Cycle of Nemoura Sichuanensis (Plecoptera: Nemouridae) in a Chinese Mountain Stream
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Internat. Rev. Hydrobiol. 94 2009 5 595–608 DOI: 10.1002/iroh.200911180 FENGQING LI1, 2, QINGHUA CAI*, 1 and JIANKANG LIU1 1State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, People’s Republic of China; e-mail: [email protected] 2Graduate University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China Research Paper Temperature-Dependent Growth and Life Cycle of Nemoura sichuanensis (Plecoptera: Nemouridae) in a Chinese Mountain Stream key words: Nemoura sichuanensis, univoltine, temperature-dependent, growth Xiangxi River Abstract Plecoptera constitute a numerically and ecologically significant component in mountain streams all over the world, but little is known of their life cycles in Asia. The life cycle of Nemoura sichuanensis and its relationship to water temperature was investigated during a 4-year study in a headwater stream (known as the Jiuchong torrent) of the Xiangxi River in Central China. Size structure histograms suggest that the life cycle was univoltine, and the relationships between the growth of Nemoura sichuanensis, physiological time, and effective accumulated water temperature were described using logistic regres- sions. The growth pattern was generally similar within year classes but growth rates did vary between year-classes. Our field data suggest a critical thermal threshold for emergence in Nemoura sichuanensis, that was close to 9 °C. The total number of physiological days required for completing larval develop- ment was 250 days. The effective accumulated water temperature was 2500 degree-days in the field. Development during the life cycle increased somewhat linearly with the physiological time and the effective accumulated water temperature, but some non-linear relationships were best developed by logistic equations. 1. Introduction Plecoptera, commonly called stoneflies, live on all continents except Antarctica, and constitute a numerically and ecologically significant component of freshwater ecosystems (FOCHETTI, 2008). Plecoptera mainly colonize cold, well-oxygenated running waters, although some species can also be found in lakes. Their diversity is greatest in cool temperate zones (ZWICK, 2004). As an important feeding group, Plecoptera have the reputation of being engineers of aquatic ecosystem (MERRITT et al., 2007). More than 3497 species of Plecoptera have been described in the world (FOCHETTI, 2008). The fauna of Plecoptera in the Western Hemisphere and Oceania are relatively well-known, whereas the limited knowledge about Central and South America is not likely representative of the region’s true diversity. Africa has a reduced diversity. The Plecoptera fauna of Asia * Corresponding author © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1434-2944/09/510-0595 596 F. LI et al. are much richer than those of Europe or North America despite the fact that, except for Japan and Asiatic Russia, Asia has been poorly studied (FOCHETTI, 2008). For the Chinese mainland, 350 species of Plecoptera were described by DU and HE (2001). The Nemouridae, currently some 633 species, has a Holarctic distribution and has some genera reaching the Oriental Region (FOCHETTI, 2008). The evolution of life cycle traits and their plasticity determines the population and com- munity dynamics of species (STEARNS, 1992) and is fundamental to understand how organ- isms exploit their environment (TAUBER and TAUBER, 1981). For aquatic ecologists, the explanatory power of life cycle information in studying the structure and function of inverte- brate communities has barely been tapped (VERBERK et al., 2008a and 2008b). Insects show a wide variety of life cycles. In a review of the life cycle of Chironomus imicola in tropical Africa, MCLACHLAN (1983) found that this species has a life cycle as short as 12 days. In contrast, the moth Gynaephora groenlandica takes 14 years (DANKS, 1994). Life cycles of Plecoptera species last from a half-year to several years, but there is some variation dependent on species and water temperature (BRITTAIN, 1973; BRITTAIN and LILLEHAMMER, 1987; WILLIAMS et al., 1995). The importance of water temperature has long been recognized, and has been identified as responsible for the distribution and richness of species along altitudinal and latitudinal gradients (QUINN and HICKEY, 1990; REYJOL et al., 2001). Generally, water temperature is a key factor influencing the embryonic development, larval growth, emergence, metabolism and survival of many taxa (WATANABE et al., 1999; HAIDEKKER and HERING, 2008). Other factors of influence are photoperiod and hydroperiod (JOHANSSON et al., 2001; ALTWEGG, 2002; SHAMA and ROBINSON, 2009). Photoperiod may prevent Odonata larvae from emerging early in the season, yet CORBET (1999) stressed that the most important factor was water temperature. LIESKE and ZWICK (2007), studying the relationship between food preference and growth of Nemurella pictetii, concluded that high growth rates of Nemurella pictetii observed in the field in late spring and summer could be explained by available food. From their study of the alpine caddisfly, SHAMA and ROBINSON (2009) concluded that temporally constrained environments (i.e., those with short seasonal of growth or hydroperiods) put strong selection on life cycles. In general, life cycle strate- gies can provide insight into how aquatic assemblages deal with prevailing environmental conditions. Although the development of organisms increases almost linearly with temperature (KUMAR et al., 1999; ABELLANA et al., 2003), once development reaches an optimum, growth rate decreases and finally stops. Therefore, taken together, growth rates are non-linearly related to temperature (LAPPALAINEN et al., 2008). In our present study, we used a logistic regression model to describe the relationship between the life cycle of Nemoura sichuanensis (LI and YANG, 2006) and water temperature. In China, attention has been given to the taxonomy of adult Plecoptera (FOCHETTI and ERMINIA, 2000; DU and HE, 2001; TIERNO and FOCHETTI, 2002; YANG et al., 2004; LI and YANG, 2006), yet only little is known of the larval stage. Published studies of life cycles of Plecoptera are rare, and little information is available in the Chinese mainland, although the Xiangxi River has been a focus of studies on benthic macroinvertebrates (QU et al., 2005; JIANG et al., 2008; LI et al., 2009). As part of a comprehensive study of the Xiangxi River, we chose Jiuchong Stream (a headwater stream of the Xiangxi River) to: 1) study the life cycle of Nemoura sichuanensis in the Xiangxi River Watershed, and 2) quantify the effects of physiological time and effec- tive accumulated water temperature on the life cycle of Nemoura sichuanensis. The results can provide a useful reference for future river studies in the region of the nearby Three Gorges Dam. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.revhydro.com Temperature-Dependent Growth of Nemoura sichuanensis 597 2. Materials and Methods 2.1. Study Site The study was performed in the Jiuchong Stream which originates in the mountains of the Shennongjia forest and then flows southeast into the Xiangxi River. The Xiangxi River later joins the Yangtze River at Xiangxi, Zigui County (TANG et al., 2006; WU et al., 2009). The study section (31°26′22″ N, 110°32′06″ E), about 10 km from the source, has a catchment area of 56 km2 (YE, 2006). During the study, the stream width ranged from 5 to 12 m and water depth from 0.5 to 1.5 m. A 100 m reach of the stream bed con- sisted chiefly of boulders with bryophytes, pebbles and gravels. Nemoura sichuanensis is abundant in many mountain headwater streams, and its diet consists chiefly of coarse particulate organic matter, such as leaves, that have fallen into the stream (MERRITT et al., 2007). Leaves from nearby Juglans cathayen- sis, Cotinus coggygria var. pubescens, Acer oliverianum, and Acer flabellatum (CHEN and JIANG, 2006) were present in this stream in all seasons and provided a food base for Nemoura sichuanensis. Water samples were collected on every sampling occasion and analyzed using standard methods (HUANG et al., 2000). Table 1 gives the ranges of the major environmental variables measured. During the study period, the water temperature ranged from 3.9 to 18.5 °C and dissolved oxygen ranged from 7.1 to 11.5 mg L–1 the nutrients (e.g., nitrogen and phosphorus) were somewhat limiting. Generally, however, this study section provided a clean, cool and well-oxygenated habitat, that was good for colonization by Nemoura sichuanensis (LI et al., 2007). 2.2. Field Sampling Nemoura sichuanensis were sampled monthly in the Jiuchong Stream for four years (from July 2003 to June 2007). A 0.42 mm mesh Surber sampler was used to take 2–3 samples on each occasion. The net mouth area of the samples was 900 cm2. The samples were preserved in 10% formalin. During July 2004 and April 2007, no samples were collected because of landslides. 2.3. Water Temperature Water temperature data were available at monthly intervals (some daily data were also collected). Continuous daily water temperatures were estimated as follows: monthly mean air temperatures were derived from an automatic continuous weather station in the town of Gufu (31°20′42″ N, 110°44′46″ E, nearly 20 km far away from the sampling site) between January 2003 and December 2008 (hourly mean air temperatures were derived after January 2007). By using linear regressions, we were able to Table 1. The ranges of water quality parameters measured across the sampling site. Index Mean value ± SD Index Mean value ± SD Alkalinity (mg L–1) 149 ± 15 Water hardness (mg L–1) 151.3 ± 15.3 Calcium (mg L–1) 31.7 ± 6.2 Water temperature (°C) 9.7 ± 4.3 Chloride (mg L–1) 4.0 ± 3.9 Silicon (mg L–1) 3.4 ± 1.7 COD (mg L–1) 4.8 ± 1.7 TN (mg L–1) 0.78 ± 0.57 –1 – –1 Conductivity (μS cm ) 242 ± 46 NO3 –N (mg L ) 0.51 ± 0.26 –1 + –1 DO (mg L ) 9.2 ± 1.8 NH4 –N (mg L ) 0.05 ± 0.05 – –1 pH 8.42 ± 0.49 NO2 –N (μg L ) 3.4 ± 2.9 Salinity (mg L–1) 0.06 ± 0.05 TP (mg L–1) 0.02 ± 0.02 –1 3– –1 TDS (mg L ) 149 ± 21 PO4 –P (mg L ) 0.01 ± 0.01 © 2009 WILEY-VCH Verlag GmbH & Co.