Mullerian mimicry and the colouration patterns of sympatric coral snakes

This dataset cointains data used for the study of Müllerian mimicry in coral snakes. Coral snakes in the genus Micrurus are venomous, aposematic organisms that signal danger to predators through vivid colouration. Previous studies found that they serve as models to several harmless species of Batesian mimics. However, the extent to which Micrurus species engage in Müllerian mimicry remains poorly understood. We integrate detailed morphological and geographical distribution data to investigate if coral snakes are Müllerian mimics. We found that colouration is spatially structured and that Micrurus species tend to be more similar where they co-occur. Though long supposed, we empirically demonstrate Müllerian mimicry for the first time in coral snakes. Additionally, we found that the length of red-coloured rings in Micrurus is conserved, even at large geographic scales. This finding suggests that bright red rings may be under more substantial stabilizing selection than other aspects of colouration, and probably function as a generalized signal for deterring predators.

Methods
We examined museum specimens of Micrurus brasiliensis, M. frontalis, M. ibiboboca, M. lemniscatus, and M. surinamensis by taking high-quality digital photographs from the dorsum of 1528 preserved snakes. We measured the number of red rings, relative length of red rings (length of red ring / total length), relative length of external black rings ((length of black ring I + length of black ring III) / total length) / 2), relative length of white rings ((length of white ring I + length of white ring II / total length) / 2), and relative length of internal black rings (length of black ring II / total length). We calculated the colour variation through the geographic distribution of each species coupled with a multivariate spatial analysis approach.

本数据集包含用于珊瑚蛇（coral snakes）缪勒拟态（Müllerian mimicry）研究的相关数据。珊瑚蛇属（Micrurus）的物种均为有毒的警戒性生物，通过鲜明的体色向捕食者传递危险信号。既往研究表明，它们是多种无害贝茨拟态（Batesian mimicry）物种的拟态模型。然而，珊瑚蛇属物种参与缪勒拟态的程度仍有待进一步阐明。
本研究整合详细的形态学与地理分布数据，以探究珊瑚蛇是否属于缪勒拟态物种。研究结果显示，珊瑚蛇的体色具有空间结构特征，且同域分布的珊瑚蛇属物种体色更为相似。尽管该类假说长期存在，但本研究首次在珊瑚蛇中通过实证证实了缪勒拟态的存在。此外，本研究发现，即便在大地理尺度下，珊瑚蛇属物种的红色环纹长度也保持保守。该结果表明，相较于体色的其他特征，鲜红色环纹可能承受了更强的稳定选择压力，其功能或为通用的捕食者威慑信号。

研究方法
我们对巴西珊瑚蛇（Micrurus brasiliensis）、M. frontalis、M. ibiboboca、饰纹珊瑚蛇（M. lemniscatus）以及苏里南珊瑚蛇（M. surinamensis）的馆藏标本开展研究：为1528号馆藏蛇类的背部拍摄高清数码照片。我们测量了以下指标：红色环纹数量、红色环纹相对长度（红色环纹长度/蛇体总长度）、外侧黑环相对长度【（第I黑环长度+第III黑环长度）/蛇体总长度】/2、白色环纹相对长度【（第I白环长度+第II白环长度）/蛇体总长度】/2，以及内侧黑环相对长度（第II黑环长度/蛇体总长度）。本研究结合各物种的地理分布数据与多变量空间分析方法，计算了体色变异情况。