大凉螈繁殖生态

Reproductive ecology of the Taliang crocodile newt (Liangshantriton taliangensis)

大凉螈是我国特有的珍稀有尾两栖动物,其种群数量目前呈现明显下降趋势,然而涉及该物种保护的繁殖生态学研究仍十分匮乏。通过融合围栏陷阱及标志重捕的样方调查法,对大凉螈石棉栗子坪种群繁殖个体和变态登陆幼体的迁徙、繁殖群体种群大小、繁殖场内雌雄有效性比变化等进行了研究。运用Jolly-Seber法估测了繁殖种群大小,运用单因素方差分析或Kruskal-Wallis秩和检验比较了不同时期进入繁殖场的雄性大凉螈头体长及体重,运用t检验或者Wilcoxon秩和检验比较了雌雄性间形态上的差异,运用t检验、t′检验或Wilcoxon秩和检验比较了野外抱对雄性与非抱对雄性间的体征差别,运用Pearson相关分析探讨了雌性产卵量与其身体形态的关系,同时观察了卵的孵化情况。研究结果表明:大凉螈的繁殖季为每年的4月下旬到7月下旬,幼体最早于8月上旬变态登陆。估测调查地繁殖场内雄性大凉螈繁殖种群大小约为391尾,雄螈较雌螈更早进入繁殖场且在场内停留时间更长,体重较轻的雄螈较晚迁入繁殖场。有效性比明显偏雄(雌/雄:0.03—0.10)。雌雄间具明显性二型性,雌性个体的头体长、体重及肥满度均大于雄性,而雄性的尾高和尾长占全长的比例则大于雌性。对比自然抱对雄性和非抱对雄性个体发现,抱对个体在头体长、体重和尾高等体征方面显著大于非抱对个体,暗示这些形态特征可能在雄性竞争配偶的过程中起到关键作用。雌螈在室内条件下平均产卵数为176枚,产卵历时2—4 d,产卵量与雌性肥满度正相关,卵的平均孵化期为15.7 d,孵出幼体平均全长为9.74 mm。

The Taliang crocodile newt(Liangshantriton taliangensis)is a rare urodelean species that is endemic to China.Its population has significantly decreased,but studies of the reproductive ecology of the species,which contribute to its conservation,are limited.By introducing the quadrat method,which involved pitfall trapping and marked-recapture,we evaluated the migration of courting adults and metamorphosed larvae,population size of mature individuals,and operational sex ratio change during the breeding season at the Liziping National Nature Reserve in Shimian County.We used the Jolly-Seber model to estimate the population size of breeding males.One-way analysis of variance and Kruskal-Wallis test were used to examine the differences in the snout-vent length and body mass of male newts that entered the breeding pond at different periods.Sexual dimorphism between male and female was tested by Student′s t-test and Wilcoxon rank-sum test.Additionally,t-test,t′-test,or Wilcoxon rank-sum test was used to compare morphological parameters between amplectant and unamplectant male L.taliangensis,which we observed in the field.Pearson correlation coefficient was calculated to determine the relationship between egg-laying number and morphological traits in the female.We also examined incubation of the spawn.The results showed that the breeding season of L.taliangensis was from late April to late July and the first batch of hatched larvae finished metamorphosis and landed in early August.The population size of breeding males at the studied site was approximately 391.Male newts entered the breeding pond earlier than the female and stayed longer,while males with lighter body masses accessed the pond at a later time.The operational sex ratio skewed to male from 0.03 to 0.10 during the entire breeding season.Sexual dimorphism was overt in this species,with female newts possessing significantly longer snout-vent lengths,heavier body masses,and bigger fatness indices than males,whereas males had higher tail fins and higher tail proportions.We also found that amplectant males had greater snout-vent lengths and body masses and higher tail fins than unamplectant males,suggesting that these morphological characters play important roles in intrasexual competition for mates.Additionally,we counted the egg-laying number of 28 individual females in captivity:the average was 176,the spawning period lasted for 2—4 days for an individual female,and the egg-laying number was positively correlated with the female′s fatness.The incubating process occurred in 15.7 days on average and newly hatched larva were approximately 9.74 mm long.