Muscles are vital for the process of movement, mating and escape of predators in amphibians. During evolution, the morphological and genetic characteristics as well as the size of muscles in species will change to adapt different environments. Theory predicts that low male-male competition in high-altitude/latitude selects for small limb muscles. Here, we used the Andrew’s toad (Bufo andrewsi) as a model animal to test this prediction by analyzing geographical variation in the mass of limb muscles across nine populations from the Hengduan Mountains in China. Inconsistent with the prediction, we found that latitude and altitude did not affect the relative mass of total combined limb muscles and mass of combined hindlimb muscles among populations. Meanwhile, the relative mass of combined forelimb muscles, the two forelimb muscles (flexor carpi radialis and extensor carpi radialis) and the four hindlimb muscles (e.g. biceps femoris, semimebranous, semitendinosus and peroneus) was lowest in middle latitude and largest in low latitude whereas gracilis minor was largest in high latitudes. However, we did not find any correlations between the two forelimb muscles and the four hindlimb muscles and altitude. Our findings suggest that combined forelimb muscles, flexor carpi radialis, extensor carpi radialis, biceps femoris, semimebranous, semitendinosus and peroneus are largest in low latitudes due to pressures of mate competition.
Sheng Nan Yang, Xiao Fu Huang, Mao Jun Zhong and Wen Bo Liao
Ye-Ming Cheng, Xiao-Nan Yang, Zhe-Feng He, Bing Mao and Ya-Fang Yin
We describe a new species, Gleditsioxylon jiangsuensis (Leguminosae), a new record of Robinia zirkelii (Platen) Matten, Gastaldo & Lee (Leguminosae), and a new record of Moroxylon xinhuaensis Yin, Liu & Cheng (Moraceae) from the early Miocene strata of Sihong County in Jiangsu Province, eastern China. Gleditsioxylon jiangsuensis sp. nov. is the first report of Gleditsioxylon fossil wood from China. These fossil woods, combined with paleontological records, may indicate that the boundary between the subtropical and the temperate zones in eastern China during the early Miocene was located north of its modern location.