Environmental variation, organism-environment feedback and managed populations

环境条件的变化是种群动态的重要预测因子。极端的温度和湿度条件往往会减少种群的成功。不幸的是，气候变化预测表明环境条件的变化会增加。为了减轻负面影响，生物经常寻找或创造条件更稳定的栖息地。例如，小龙虾挖的洞穴比开阔的沼泽温度更恒定，水位变化更小。同样，植物树冠下的温度和湿度可能与空气温度有很大的不同，并影响到生活在那里的昆虫。在一定范围内，这些新栖息地的创造可以让物种克服极端气候的负面影响。我建议开发、测试和应用简单的预测模型来描述环境变异性和物理环境的生物修饰对入侵物种、有害生物和濒危物种的影响。首先，我将检查良好和恶劣条件的可变性对非本地物种在新地点增加到大密度（即成为入侵）的可能性的影响。当平均温度过高时，气候变化的增加通常是非常有害的（即通常是致命的），而低温的变化则有利于喜欢温暖气候的物种。此外，异常良好条件的“运行”也可能暂时增加人口密度，并可能产生巨大影响。我将开发包括这些想法的入侵风险模型，并在受控条件下使用实验室生物进行测试。然后我将确定这些想法是否适用于巨型猪草。这种大型入侵植物在接触时会导致皮肤灼伤，因此即使是这种物种密度的暂时增加也会对社会经济产生重要影响。其次，使用豌豆植物，我将确定植物形状如何改变树冠下的当地环境条件，并影响生活在那里的蚜虫物种。此外，由于植物形状也会影响益虫捕食者（如瓢虫）捕捉猎物的能力，我将开发模型来预测哪些植物形状有助于捕食者，同时为猎物创造不适宜的环境条件，从而减少害虫的数量。我将在温室里用豌豆植物、豌豆蚜虫和有益的捕食者来测试这些预测。这样的预测可以用来选择虫害爆发趋势较低的作物品种。第三，我将研究捕食者物种改变环境对其猎物的影响。通常我们认为捕食者会减少猎物的数量，但如果捕食者也创造了有利的环境，它们实际上可能会使猎物物种受益。环境条件的可变性决定了极端事件（如干旱）发生的频率，也将决定捕食者是否能对其猎物产生净有益影响。我将开发一些这种关系的一般模型，用实验室生物进行测试，然后将这些想法应用于濒危的海恩祖母绿蜻蜓的管理。这种湿地物种的水生幼虫很容易受到干旱的影响，但可能会在掠食性小龙虾的洞穴中避难，这些小龙虾会潜到地下水位。因此，与直觉相反，濒危蜻蜓的恢复策略可能需要其已知捕食者的保护。这些项目将共同提供理论、理论预测的实验检验和应用，以证明在预测未来人口规模时考虑环境变化和环境的生物修饰的重要性。

Variability in environmental conditions is an important predictor of population dynamics. Extremes in temperature and moisture conditions often decrease the success of populations. Unfortunately, climate change predictions point to increased variation in environmental conditions. To mitigate negative impacts, organisms often seek out or create habitats with more constant conditions. For example, crayfish create burrows that have more constant temperatures and less variable water levels than the open marsh. Similarly, temperature and humidity under plant canopies may differ substantially from air temperatures, and affect the insects that live there. Within limits, creation of these new habitats could allow species to overcome the negative effects of climate extremes. I propose to develop, test and apply simple predictive models that describe the effects of environmental variability, and organism modification of the physical environment, on invasive, pest, and endangered species. First, I will examine the impact of the variability of good and bad conditions on the probability that non-native species will increase to large density in new locations (i.e. become invasive). While increased variation when mean conditions are too hot is usually very detrimental (i.e. often lethal), variation about cool temperatures can benefit species that prefer warmer climates. Moreover, “runs” of abnormally good conditions can also temporarily increase population density and potentially create large impacts. I will develop models of invasion risk that include these ideas and test them using lab organisms under controlled conditions. I will then determine if these ideas could apply to giant hogweed. This large invasive plant causes skin burns on contact, and so even a temporary increase in the density of this species could have important socio-economic impacts. Second, using pea plants, I will determine how plant shape alters the local environmental conditions under the canopy and affects the aphid pest species that live there. In addition, since plant shape also affects the ability of beneficial insect predators, such as ladybugs, to catch prey, I will develop models to predict which plant shapes aid predators and simultaneously create inhospitable environmental conditions for the prey, so that the pest population is reduced. I will test these predictions in the greenhouse using pea plants, pea aphids and beneficial predators. Such predictions could be used to select crop varieties that have a lower tendency for insect pest outbreaks. Third, I will examine the effect of predator species that modify the environment on their prey. Normally we expect predators to decrease prey populations, but if predators also create beneficial environments, they might actually benefit the prey species. Variability in environmental conditions that determines the frequency of extreme events, such as drought, will determine whether a predator can have a net beneficial impact on its prey. I will develop some general models of this relationship, test them using lab organisms, and then apply these ideas to the management of the endangered Hine's emerald dragonfly. The aquatic larvae of this wetland species are vulnerable to drought, but may take shelter in the burrows of predatory crayfish, which reach down to the water table. Therefore, counterintuitively, a recovery strategy for the endangered dragonfly might require the protection of its known predator. Together these projects will provide theory, experimental tests of theoretical predictions, and applications that may demonstrate the importance of considering both environmental variability and organism-modification of the environment when predicting future population size.