Doctoral Dissertation Improvement: The effects of light level and color vision on the foraging behavior of cathemeral red-bellied lemurs (Eulemur rubriventer)

人类和许多其他灵长类动物都有三色视觉，这赋予了区分长（如红色）和中（如绿色）波长色度的能力。在胎盘哺乳动物中，这种特征是灵长类动物所特有的，但三色视的潜在遗传基础在不同的谱系中是不同的。重要的是，有利于三色进化的选择压力仍在讨论中。在人类，旧大陆的猴子和猿，以及新热带的吼猴中，大多数个体都有三色视觉的能力。相比之下，大多数新热带猴子和马达加斯加狐猴保持着性别连锁多态性，这使得只有杂合的雌性具有三色的潜力，而所有雄性和纯合的雌性都是红绿色盲（二色）。这种情况提供了一个独特的机会来研究具有三色和二色视觉的潜在优点和缺点。例如，长期以来人们一直假设三色视者在寻找红色食物时比二色视者更有优势。然而，对于三色觅食优势的经验支持，特别是在野生种群中，是有限的。最近的研究表明，三色视者在昏暗的光线下（如黎明和黄昏）比在明亮的光线下更有明显的觅食优势。在帕特里夏·赖特博士的指导下，博士生雷切尔·雅各布斯（Stony Brook University）进行了一项研究，在马达加斯加拉诺马法纳国家公园的多态和花状（全天24小时活动）红腹狐猴（Eulemur rubriventer）的野生种群中，测试了不同类型的色觉在明亮或昏暗的光线条件下赋予觅食优势的假设。这些假设是通过以下方法来验证的：1)系统的行为数据收集，2)基因分析来确定个体的颜色视觉状态（行为观察者不会意识到这种状态），以及3)利用红腹狐猴食物的反射光谱来测量颜色。这项研究解决了长期以来关于灵长类动物三色和多态色觉的适应性意义的假设。在更广泛的范围内，该项目为一名马达加斯加学生和当地村民提供培训，支持多个国家和国际合作，并正在开展一项大规模的红腹狐猴研究工作，极大地促进了对该物种的未来研究。

Humans and many other primates have trichromatic color vision, which confers the ability to discriminate between long (e.g., red) and middle (e.g., green) wavelength chromaticities. Among placental mammals, this feature is unique to primates, but the underlying genetic basis for trichromacy varies across lineages. Importantly, the selective pressures favoring the evolution of trichromacy are still being discussed.In humans, Old World monkeys and apes, as well as Neotropical howler monkeys, most individuals in a population have the capacity for trichromatic color vision. In contrast, most Neotropical monkeys and Malagasy lemurs maintain a sex-linked polymorphism, which provides only heterozygous females the potential for trichromacy, while all males and homozygous females are red-green color blind (dichromatic). This situation provides a unique opportunity to investigate the potential advantages and disadvantages to having trichromatic and dichromatic color vision. For example, it has long been hypothesized that trichromats have an advantage over dichromats when foraging on red-colored food. Empirical support for trichromatic foraging advantages, however, particularly in wild populations, is limited. Recent studies suggest that trichromats might experience more pronounced foraging advantages under dim light, such as during dawn and dusk, rather than under bright light levels.Research conducted by doctoral student Rachel Jacobs (Stony Brook University), supervised by Dr. Patricia Wright, tests hypotheses that different types of color vision confer foraging advantages under bright or dim light conditions in a wild population of polymorphic and cathemeral (active throughout a 24-hour day) red-bellied lemurs (Eulemur rubriventer) in Ranomafana National Park, Madagascar. These hypotheses are tested using a combination of 1) systematic behavioral data collection, 2) genetic analyses to determine individual color vision status (behavioral observers will be unaware of the status), and 3) color measurements using reflectance spectra of red-bellied lemur food items. This research addresses long-held hypotheses regarding the adaptive significance of trichromatic and polymorphic color vision in primates. On a broader scale, this project provides training for a Malagasy student and local Malagasy villagers, supports multiple national and international collaborations, and is initiating a large-scale research effort on red-bellied lemurs, greatly facilitating future research on this species.