碩士 / 國立臺南大學 / 生態暨環境資源學系生態旅遊碩士班 / 107 / Local adaption makes the local population to have better fitness than non-local population. When populations occupy different environments, divergent selection pressures can result in phenotypic differentiation in traits that confer a local fitness advantage. Both altitude and latitude influence thermal condition in temporal variation and ambient temperature, and for ectotherms, is recognized as a strong determinant of individual’s thermal performance curves (TPCs), that reaction norms of development and growth related to fitness. TPCs exhibit a characteristic shape, their variation can be described in terms of three distinct modes: horizontal shift (in optimal temperature, Topt), vertical shift (in overall fitness, h) and generalist-specialist variation (niche width, w). Rhacophorus moltrechti is widely distributed, ranging from near sea level to an elevation about 2700 m. There is a cline in breading season among populations. Lowland populations breed in winter (October to March), middle-altitude (1000–1500 m) populations breed throughout the year with highest breeding activity in spring (January to April), and high-altitude (c. 2000 m) populations breed in spring and summer (April to September). Although shifting in breeding season, different populations unavoidably have to face different thermal regimes in different altitudes, mainly temporal variations in thermal conditions and seasonal time constraints. This study investigated whether growth and development performance curves exhibit differences among high-altitude, middle-altitude and low-altitude populations. I tested two hypotheses: (1) Because temperatures in higher altitudes vary over a much greater range than lowlands, I hypothesize that middle-altitude and high-altitude tadpoles should exhibit a thermal generalist phenotype while the lowland tadpoles should exhibit a thermal specialist phenotype. (2) Previous study show that the summer water temperatures may be stressful to larval growth and development of Rh. moltrechti, thus limit the length of the growing season for lowland tadpoles. I hypothesize that lowland tadpoles exhibit a cogradient variation in larval development because of the time constraints imposed on lowland tadpole development by warm summer water temperatures. I reared tadpoles in a common laboratory experiment at six different water temperatures (10, 15, 17.5, 20, 25 and 30℃) from three altitudinal populations. I investigated population divergence of thermal performance in growth and development among populations of different altitudes using the template mode of variation (TMV). I found that middle and highland tadpoles exhibit a thermal generalist phenotype and lowland tadpole exhibit a specialist phenotype. In addition, cogradient variation (vertical shift) also occurred in larval development. Lowland tadpoles exhibited an overall faster larval development then middle-altitude and high-altitude tadpoles. At 20 and 25℃ both of which has a significant heavier metamorphic mass and shorter larval period. However, at 17.5℃ the growth of lowland tadpoles was significant slower than that of middle and high altitude tadpoles. Overall larval period and overall growth rate was significantly shorter and faster, respectively, in lowland tadpoles than in middle and high-altitude tadpoles. TMV model also suggested the observed results. The major mode of thermal adaptation were the exhibition of an inter-population generalist-specialist tradeoff (niche width) in larval growth (91%) and development (59.40%), whereas a vertical shiftschange in overall performance across temperaturesalso contributed to the larval development (33.97%). Under natural conditions, daily thermal variability in larval growing season of lowland populations is relatively low and higher average temperature will shorten larval period. This leads lowland populations to adopt a specialist strategy and exhibited narrower performance width and higher maximum performance in growth and development, as well as heavier metamorphic mass and shorter larval period in intermediate temperatures to maximize their reproductive success and fitness. In contrast, daily thermal variability in larval growing season of middle-altitude and high-altitude populations is relatively high and lower average temperature will longer larval period that means middle- and high-altitude population have a high risk to face the temperature variation. Thus, middle-altitude and high-altitude populations adopt a generalist strategy and exhibit overall lower growth and developmental rates, overall smaller size at metamorphosis and longer larval periods at constant laboratory temperatures even though these temperatures are within the normal range for larval growth. Our study detected genetically based inter-population divergence in larval life-history traits in Rh. moltrechti, suggesting that natural selection in local thermal conditions may be the main force driving local adaptation.
| Identifer | oai:union.ndltd.org:TW/107NTNT0708001 |
| Date | January 2018 |
| Creators | HUANG, YI-SIN, 黃議新 |
| Contributors | CHANG, YUAN-MOU, WU, CHI-SHIUN, 張原謀, 巫奇勳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 77 |
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