Trip Elizabeth D L, Clements Kendall D, Raubenheimer David, Choat J Howard
School of Biological Sciences, University of Auckland, Auckland, New Zealand.
Faculty of Veterinary Science and School of Biological Sciences, Charles Perkins Centre, The University of Sydney, Sydney, Australia.
J Anim Ecol. 2014 Jul;83(4):866-75. doi: 10.1111/1365-2656.12183. Epub 2013 Dec 10.
In ectotherms, growth rate, body size and maturation rate covary with temperature, with the direction and magnitude of variation predicted by the Temperature-Size Rule (TSR). Nutritional quality or availability of food, however, may vary over latitudinal gradients, resulting in ambiguous effects on body size and maturation rate. The Temperature-Constraint Hypothesis (TCH) predicts that marine herbivorous ectotherms are nutritionally compromised at latitudes exceeding 30°. This provides an opportunity to resolve the contrasting demographic responses of ectotherms to variation in temperature and nutritional status over latitudinal gradients. This study uses analysis of demographic rates to evaluate the predictions of the TSR in a marine herbivorous ectotherm sampled over a significant latitudinal gradient. The direction and magnitude of demographic variation was established in the marine herbivorous fish, Odax pullus (the butterfish), and compared with that of a phylogenetically related but trophically distinct species, the carnivorous Notolabrus fucicola (the banded wrasse). Both species were sampled at three locations across the length of New Zealand covering latitudes between 35°S and 49°S. Growth rate, mean size-at-age, age- and size-at-maturity, life span and abundance were estimated for each species at each location. Demographic traits of both taxa varied with latitude. Both species showed slower initial growth rates, and matured later at a larger body size at higher latitudes than populations sampled at lower latitudes. In addition, abundances increased significantly at higher latitudes in both species. These results were consistent with the TSR but not with the TCH, confirming that nutritional ecology (herbivore vs. carnivory) did not determine demographic patterns over a biologically significant latitudinal gradient. Results from this study suggest that the absence of herbivorous reef fishes from the higher latitudes of the Northern Hemisphere may not reflect a general physiological mechanism as suggested by the TCH and highlights the need to clarify the evolutionary histories of the marine biota of each hemisphere.
在变温动物中，生长速率、体型大小和成熟速率与温度共同变化，其变化方向和幅度由温度-体型规则（TSR）预测。然而，食物的营养质量或可获得性可能会随纬度梯度而变化，从而对体型大小和成熟速率产生不明确的影响。温度限制假说（TCH）预测，海洋草食性变温动物在纬度超过30°时营养状况会受到影响。这为解决变温动物在纬度梯度上对温度和营养状况变化的不同种群统计学响应提供了一个机会。本研究通过分析种群统计学速率，来评估TSR在一个沿显著纬度梯度采样的海洋草食性变温动物中的预测情况。确定了海洋草食性鱼类奥氏澳鲈（油鲂）种群统计学变化的方向和幅度，并将其与系统发育相关但营养类型不同的物种——肉食性的岩礁唇鱼（带状濑鱼）进行比较。这两个物种在新西兰全境的三个地点进行采样，涵盖南纬35°至49°之间的纬度范围。估计了每个物种在每个地点的生长速率、平均年龄时的体型大小、成熟年龄和成熟时的体型大小、寿命及丰度。两个分类单元的种群统计学特征均随纬度而变化。两个物种在较高纬度地区的初始生长速率均较慢，成熟时的体型比在较低纬度地区采样的种群更大且更晚成熟。此外，两个物种在较高纬度地区的丰度均显著增加。这些结果与TSR一致，但与TCH不一致，证实了营养生态学（草食性与肉食性）在生物学上显著的纬度梯度上并未决定种群统计学模式。本研究结果表明，北半球较高纬度地区没有草食性珊瑚礁鱼类可能并不像TCH所暗示的那样反映一种普遍的生理机制，并强调需要阐明每个半球海洋生物群的进化历史。
