Geographic variation in Caluromys derbianus and Caluromys lanatus (Didelphimorphia: Didelphidae)

We analyzed the geographic variations in the shape and size of the cranium and mandible of two woolly opossums, Caluromys derbianus and Caluromys lanatus. Using geometric morphometrics we analyzed 202 specimens of C. derbianus and 123 specimens of C. lanatus, grouped in 7 and 9 populations, respectively. We found sexual dimorphism in shape variables only in the dorsal view of the cranium of Caluromys derbianus, which is not associated with geographical origin. We detected geographic variation in the size of the mandible in two populations (Nicaragua and Northern Panama), but no geographic variation in shape. The size of the cranium of C. lanatus varies significantly, with clinal variation in peri-Amazon populations, with a break between two populations, Bolivia and Paraguay. Shape analyses also revealed some separation between the Paraná population and all other populations. Our results suggest that the available name, Caluromys derbianus, should be maintained for all individuals throughout the geographic range of the species. The same is true for Caluromys lanatus, which can be separated into two distinct morphologic units, Caluromys lanatus ochropus, from the Amazon and Cerrado, and Caluromys lanatus lanatus, from the Atlantic forest.

本研究针对两种绵毛负鼠——德比安绵毛负鼠（Caluromys derbianus）与拉瑙绵毛负鼠（Caluromys lanatus）——的颅骨（cranium）与下颌骨（mandible）的形态及尺寸地理变异展开分析。本研究采用几何形态测量学（geometric morphometrics）方法，对202件德比安绵毛负鼠标本与123件拉瑙绵毛负鼠标本进行分析，上述标本分别被划分为7个与9个种群。研究发现，仅在德比安绵毛负鼠的颅骨背视图（dorsal view）形态变量中存在性二态性（sexual dimorphism），且该性二态与地理起源无关联。我们在尼加拉瓜种群与巴拿马北部种群的下颌骨尺寸中检测到地理变异，但未发现形态层面的地理差异。拉瑙绵毛负鼠的颅骨尺寸存在显著分化，其亚马逊周边种群呈现渐变变异（clinal variation）模式，且玻利维亚种群与巴拉圭种群之间存在变异断点。形态分析还表明，巴拉那种群（Paraná population）与其余所有种群间存在一定程度的分化。本研究结果提示，应将德比安绵毛负鼠的有效学名保留给该物种地理分布范围内的全部个体。拉瑙绵毛负鼠同样可被划分为两个独立的形态单元（morphologic unit）：分布于亚马逊与塞拉多（Cerrado）的Caluromys lanatus ochropus，以及分布于大西洋森林的指名亚种Caluromys lanatus lanatus。