Zoological Studies

Vol. 36 No. 1, 1997

Variations of Reproductive Traits of Two Semi-terrestrial Isopods, Ligia exotica and L. taiwanensis (Crustacea: Ligiidae), in Southern Taiwan

Min-Li Tsai* and Han-Cheng Chen

Dept. of Zoology, National Taiwan Univ., Taipei, Taiwan 106

Min-Li Tsai and Han-Cheng Chen (1997) Both inter- and  intraspecific reproductive traits of 2 semiterrestrial isopods were examined and compared in an attempt to provide insights into  the adaptive strategies  of  reproduction. Gravid  females  of Ligia exotica (Roux) from  the  littoral  zone and Ligia taiwanensis (Lee) from  mountain brooks show differences in repro- ductive allocation per brood (F1,198 = 706, p < 0.001), weight-specific egg weight (F1,198 = 166, p < 0.001), and weight-specific fecundity (F1,198 = 120, p < 0.001), but they also display similarities  in the interrelation- ships  between reproductive traits.
The reproductive traits of L. taiwanensis, such as larger weight-specific egg size and lower reproductive allocation, seem more in accordance with theoretical predictions for K-selected traits than those of L. exotica. When theeffects of body size are removed,both species  show a significant  positive correlation between fecundity and brood weight (L. exotica: r = + 0.49, t = 5.50, p < 0.001; L. taiwanensis: r = + 0.96, t = 36.09, p < 0.001), and a negative correlation  between fecundity  and egg size (L. exotica: r = - 0.77, t = 11.78, p < 0.001; L.  taiwanensis: r =
- 0.32, t = 3.41, p < 0.001) intraspecifically. The  reciprocal  rela- tionships  between egg size and fecunidity  in L. exotica and L. taiwanensis seem to  match the  assumption of optimality theories of life-history evolution.

Key words: Ligia, Reciprocal relationship, Life-history evolution.

*Correspondence: Tel: 886-2-363-0231 ext. 3324, Fax: 886-2-3638554. E-mail: D1205001@ccms.ntu.edu.tw