Data from: Evidence of trait shifts in response to forest disturbance in Taiwanese Carabus masuzoi (Coleoptera: Carabidae)

Shifts of functional traits are important because phenotypic responses of species to environmental changes caused by natural and anthropogenic disturbances are fundamental in determining the risk of population extinction. This study tested the effect of forest thinning on the body shape and male genital size of an endemic ground beetle species Carabus masuzoi (Imura and Satô 1989) (Coleoptera, Carabidae) in cypress plantations started approximately 30 years ago in central Taiwan. The beetles were sampled and compared from (1) natural broadleaf forest, (2) non-thinned cypress plantation, and (3) 45% thinned cypress plantation. Female prothorax length from the non-thinned plantation was significantly greater than that of the natural forest, and the 45% thinned plantation had a higher frequency of the small (S-type) and a lower frequency of the large (L-type) male genitalia than in the natural forest. The results indicated that, within a short ecological time frame, the prothorax shapes and male genital sizes of C. masuzoi populations might respond to changes induced by different forest types and forest thinning, respectively. We hypothesized that the difference in thoracic shape was related to locomotory ability in forest understories, whereas the changes in male genital sizes might have been a result of different levels of intraspecific sexual selection, random effects of population fluctuations/dispersal or pleiotropy.

功能性状 (functional traits) 的演变偏移具有重要意义，物种对自然与人为干扰 (anthropogenic disturbances) 引发的环境变化所产生的表型响应 (phenotypic response)，是决定种群灭绝风险的基础性因素。本研究以台湾中部始建约30年的杉木人工林为研究对象，探究森林疏伐 (forest thinning) 对特有步甲物种*Carabus masuzoi*（鞘翅目步甲科，Imura及Satô, 1989）的体型形态与雄性外生殖器 (male genitalia) 大小的影响；研究人员分别从（1）天然阔叶林、（2）未疏伐杉木人工林以及（3）疏伐强度达45%的杉木人工林中采集步甲样本并开展对比分析。结果显示，未疏伐杉木人工林种群的雌性步甲前胸背板长度 (prothorax length) 显著高于天然阔叶林种群；而疏伐强度45%的人工林种群中，雄性外生殖器小型（S型）的出现频率更高，大型（L型）的出现频率则显著低于天然阔叶林种群。本研究结果表明，在较短的生态时间尺度 (ecological time frame) 内，*C. masuzoi*种群的前胸背板形态与雄性外生殖器大小，可分别响应不同林型及森林疏伐引发的环境变化。我们提出如下假说：前胸背板形态的差异与该步甲在林下层生境中的运动能力相关；而雄性外生殖器大小的变化，可能源于不同强度的种内性选择 (intraspecific sexual selection)、种群波动/扩散的随机效应，或是基因多效性 (pleiotropy) 作用。