BACKGROUND & AIMS:
:Reproductive output is a central attribute of life history, providing a measure of individual and population performance. The fields of ecology, biogeography, and evolutionary biology take disparate approaches in addressing spatial variation in reproduction, and thus we lack clear predictions for how reproductive output should vary geographically. We empirically investigate these contrasting theoretical approaches by determining geographic patterns in reproductive output for intertidal populations of the purple sea urchin, Strongylocentrotus purpuratus, at 15 sites spanning a large geographic distance (9 degrees span of latitude) from central California, USA, to Baja California, Mexico. Contrary to predictions from biogeography, some of the highest values of reproductive output are at sites near the species' southern range boundary. Additionally, sea urchins do not exhibit a latitudinal gradient in reproduction, but rather show considerable mesoscale variation in reproductive output. Spatial analyses reveal that this variation is correlated with coastal topographic features that are known to influence the pattern of nearshore nutrient flux and circulation. We hypothesize that urchins' reproductive output may be driven by the spatial distribution of their food supply, drift macroalgae, the abundance of which is influenced by both nutrient supply and alongshore transport processes that are coupled to topographic features. Large-scale studies such as this provide valuable insight into the causes of species' range limits, population connectivity, habitat reserve design, and forecasting the effects of climate change on species' distributions.
背景与目标:
: 生殖产出是生活史的核心属性,可以衡量个人和人口的表现。生态学,生物地理学和进化生物学领域在解决繁殖的空间变化方面采取了不同的方法,因此我们缺乏关于繁殖产出应如何在地理上变化的明确预测。我们通过确定从美国中部加利福尼亚到墨西哥下加利福尼亚的15个地理距离 (纬度9度跨度) 的15个地点的紫海胆潮间带种群的繁殖产出的地理模式,对这些对比理论方法进行了经验研究。与生物地理学的预测相反,生殖产出的一些最高值位于该物种南部范围边界附近。此外,海胆在繁殖中没有表现出纬度梯度,而是在生殖输出中显示出相当大的中尺度变化。空间分析表明,这种变化与已知会影响近岸养分通量和环流模式的沿海地形特征有关。我们假设,海胆的生殖输出可能是由其食物供应的空间分布,漂移的大型藻类驱动的,其丰度受营养供应和与地形特征相关联的沿岸运输过程的影响。诸如此类的大规模研究为物种范围限制,种群连通性,栖息地保护区设计以及预测气候变化对物种分布的影响的原因提供了宝贵的见解。