Asato Hitomi, Toda Mamoru
Graduate School of Engineering and Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Tropical Biosphere Research Center, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Curr Zool. 2024 Jul 16;71(2):184-195. doi: 10.1093/cz/zoae038. eCollection 2025 Apr.
There are many short-lived animals, but those displaying a lifecycle with more than one generation per year (multivoltine lifecycle) are rare among terrestrial vertebrates. The multivoltine lifecycle requires rapid growth and maturation and a long active season. Thus, small lizards in humid tropical or subtropical areas are candidates for multivoltine lifecycles. To test this prediction, we conducted a capture-mark-recapture study of a subtropical grass lizard, , endemic to Miyako Islands, Japan. Juveniles grew very quickly, averaging 0.3 mm/day in the warm season, and attained sexual maturity at 2.5 months post-hatching. The breeding season was very long, and hatchlings emerged from May to November. The prolonged breeding season and rapid growth to maturity allowed some individuals to produce a second generation in their first year. Estimates of hatching date from growth rates indicated that many females that hatched in May-June became gravid 76-120 days after hatching and 122-165 days after oviposition of the eggs from which they hatched. Analyses of juvenile survivorship and month of hatching suggest that nearly half of breeding adults were members of multivoltine generations, although the 2 generations were not discrete. The species is short-lived, with only 16% of individuals surviving beyond 12 months, and few individuals reproduced in a second year. We refer to this condition as a "semi-multivoltine lifecycle." Individuals that hatch late in the season defer reproduction until the following year and become founders of the next season's cohort. This putative advantage of late-hatching individuals may have driven the evolution of this lifecycle.
有许多寿命短暂的动物，但在陆生脊椎动物中，那些每年具有不止一代生命周期（多化性生命周期）的动物却很罕见。多化性生命周期需要快速生长和成熟以及漫长的活跃季节。因此，潮湿热带或亚热带地区的小型蜥蜴是具有多化性生命周期的候选者。为了验证这一预测，我们对日本宫古岛特有的一种亚热带草蜥进行了标记重捕研究。幼体生长非常迅速，在温暖季节平均每天生长0.3毫米，并在孵化后2.5个月达到性成熟。繁殖季节很长，幼体从5月到11月孵化。延长的繁殖季节和快速生长至成熟使得一些个体在第一年就能产生第二代。根据生长速率估算的孵化日期表明，许多在5月至6月孵化的雌性在孵化后76 - 120天以及产下它们所孵化卵后的122 - 165天就怀孕了。对幼体存活率和孵化月份的分析表明，尽管这两代并非完全分离，但近一半的繁殖成年个体属于多化性世代。该物种寿命短暂，只有16%的个体能存活超过12个月，很少有个体能在第二年繁殖。我们将这种情况称为“半多化性生命周期”。在季节后期孵化的个体将繁殖推迟到次年，并成为下一季群体的奠基者。这种晚孵化个体的假定优势可能推动了这种生命周期的进化。
