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 (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.
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.
Keywords
Ligia, Reciprocal relationship, Life-history evolution.
