皖南凹耳臭蛙地理分布格局与生境选择

凹耳臭蛙(Odorrana tormota)是一种小型山溪蛙类,由于叫声独特,种内具有超声通讯功能而引起国内外相关专家的广泛关注。首次针对皖南凹耳臭蛙地理分布、生境选择以及人为干扰强度对种群密度的影响进行了研究。共调查了9县1区32条不同的山溪,发现其中的16个有凹耳臭蛙分布,除黄山区的香溪和浮溪具文献记录外,其余14个分布点均为首次报道。基于现存凹耳臭蛙分布点的水系关系,推测该物种在皖南的分布呈现出以青弋江、新安江和水阳江三大水系为纽带、间断分布的格局。对其中10个分布点222只凹耳臭蛙生境选择的统计结果表明,在夜晚活动周期内,该物种对乔木、灌木丛、草本植物、岩石、沙滩和倒伏朽木等不同生境的选择具有显著差异(F5,54=25.75,P0.001),栖息在草本植物和灌丛中蛙的数量明显多于栖息在其它几种生境类型中的蛙类。暗示溪流沿岸的草本植物和灌丛对该物种的生存和繁衍具有重要意义,乔木对其非活动周期的隐蔽可能具有不可替代的作用。根据人类活动对其栖息地破坏程度,将人为干扰程度划分为强、中和弱3种不同强度,对不同干扰强度下种群相对密度进行单因素方差分析。结果表明,中等干扰强度下的种群密度显著高于其它两种强度下的种群密度(F2,13=8.155,P=0.005)。推测适度的人为干扰可能增加了栖息地内昆虫的种类和数量,对蛙类的生存和繁衍更为有利。但随着人为干扰强度的增强,对溪流沿岸植被的破坏更为剧烈,种群密度显著下降。

The geographic distribution pattern and habitat selection of the Chinese concave- eared torrent frog in southern Anhui Province

The concave-eared frog, Odorrana tormota, is a rare species native to eastern China and the first non-mammalian vertebrate demonstrated to both produce and perceive ultrasonic frequencies. In the current study, for the first time, we reported the geographic distribution, habitat selection, and relationship between different disturbance intensity and relative population density of the species in southern Anhui Province. A total of 32 different mountain streams were investigated from April 2012 to August 2013. Among these investigated streams, the species was detected in 16 streams. Except for Xiangxi and Fuxi in Huangshan District, this is the first record of the species in the remaining14 streams. The distribution range of the species within the stream varied among different streams from the shortest range less than 1 km to the longest range of more than 20 km. The 16 mountain streams are the tributaries of Qinyi, Xin''an, or Shuiyang river, and the species was not found in any tributary of other rivers (such as Qiupu and Qimen river, etc.) in the region. These results suggested that at present, the concave-eared frog of southern Anhui Province have survived in some isolated mountain streams linked by Qinyi, Xin''an, or Shuiyang rivers. In order to reveal the strategies of habitat selection of the species, we tested the differences in frog numbers among six different habitat types including trees, shrubs, or herbaceous plants along river banks, benchland and rocks or other objects above the water. In total, 222 individuals from 10 different mountain streams were analyzed and significant difference in number of frogs was detected (F_5,54=25.75, P < 0.001) in herbaceous vegetation and shrubland, which harbored significantly more individuals than other habitat type, suggesting that the two habitat types along mountain streams play an important role in species'' proper survival and reproduction during the nighttime. It should be noted that, although the recorded frog number in arbors was significantly less than in herbaceous vegetation and shrubland during the surveyed period, arbors might provide indispensable hideout place for the species during the daytime. Additionally, we evaluated the impact of human disturbance on relative population density of the species. Initially, we obtained the relative population density for each of the 16 streams through a calling-based method. The number of male frogs'' calls in the 100-m range along each stream was recorded and used as the value of relative population density. We classified human disturbance on a three-point scale: strong, medium, and weak according to the degree of destruction as a result of human activity on the habitat of the species. One-way analysis of variance (ANOVA) was used to test the effects of human disturbance on relative population density. The results showed that human disturbances significantly affected population density (F_2,13=8.155, P=0.005). The least significant difference (LSD) tests revealed that relative population density under medium disturbance intensity was the highest. Our findings suggested that moderate anthropogenic interference might increase the species number and quantity of insects and then attract more frogs. However, with the increase of disturbance intensity, the damage to vegetation along the stream is more intense causing dramatic decrease in population density.