Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan.
PLoS One. 2013;8(3):e59829. doi: 10.1371/journal.pone.0059829. Epub 2013 Mar 22.
High-latitude plants are often more palatable to herbivores than low-latitude conspecifics. Does increased plant palatability lead to better herbivore performance? Our field and laboratory work investigated (A) whether high-latitude plants have traits indicating that they should be higher-quality foods for herbivores; (B) whether geographic differences in plant quality are more important than local adaptation of herbivores. We studied 3 plant species and 6 invertebrate herbivores in U.S. Atlantic Coast. Past studies had shown high-latitude individuals of these plants are more palatable than low-latitude conspecifics. We documented plant traits and herbivore performance (body size) in the field across latitude. We collected individuals from different latitudes for factorial (plant region x herbivore region) laboratory experiments, examining how herbivore performance was affected by plant region, herbivore region, and their interaction (i.e., local adaptation). Field surveys suggested high-latitude plants were likely of higher quality to herbivores. Leaf nitrogen content in all plant species increased toward high latitudes, consistent with lower leaf C/N and higher leaf chlorophyll content at high latitudes. Furthermore, leaf toughness decreased toward higher latitudes in 1 species. The body size of 4 herbivore species increased with latitude, consistent with high-latitude leaves being of higher quality, while 2 grasshopper species showed the opposite pattern, likely due to life-history constraints. In the laboratory, high-latitude plants supported better performance in 4 herbivore species (marginal in the 5th). The geographic region where herbivores were collected affected herbivore performance in all 6 species; however, the pattern was mixed, indicating a lack of local adaptation by herbivores to plants from their own geographic region. Our results suggest that more-palatable plants at high latitudes support better herbivore growth. Given that geographic origin of either plants or herbivores can affect herbivore performance, the nature of plant-herbivore interactions is likely to change if climate change "reshuffles" plant and herbivore populations across latitude.
高纬度地区的植物通常比低纬度地区的同种植物对食草动物更具吸引力。植物的可食性增加是否会导致食草动物表现更好？我们的野外和实验室工作研究了：（A）高纬度地区的植物是否具有表明它们应该是食草动物高质量食物的特征；（B）植物质量的地理差异是否比食草动物的本地适应性更为重要。我们在美国大西洋沿岸研究了 3 种植物和 6 种无脊椎草食动物。过去的研究表明，这些植物的高纬度个体比低纬度的同种植物更可口。我们在整个纬度范围内记录了植物特征和草食动物的表现（体型）。我们从不同纬度采集个体进行因子（植物区域 x 食草动物区域）实验室实验，研究食草动物的表现如何受到植物区域、食草动物区域及其相互作用（即本地适应性）的影响。野外调查表明，高纬度地区的植物对食草动物来说可能质量更高。所有植物物种的叶片氮含量都随着纬度的升高而增加，这与高纬度地区较低的叶片 C/N 和较高的叶片叶绿素含量相一致。此外，在 1 个物种中，叶片韧性随着纬度的升高而降低。4 种食草动物的体型随着纬度的增加而增加，这与高纬度地区的叶片质量较高相一致，而 2 种蝗虫则表现出相反的模式，这可能是由于生活史的限制。在实验室中，高纬度植物支持 4 种食草动物（第 5 种食草动物表现出边缘效应）的表现更好。食草动物采集地的地理区域影响所有 6 种食草动物的表现；然而，模式是混合的，表明食草动物对来自其自身地理区域的植物没有本地适应性。我们的研究结果表明，高纬度地区更可口的植物可以支持食草动物更好地生长。鉴于植物或食草动物的起源地都可能影响食草动物的表现，如果气候变化“重新排列”植物和食草动物的种群在纬度上，那么植物-食草动物相互作用的性质可能会发生变化。
