60
Life Cycle Tactics and Development
Table 5.1. Comparison of life history characteristics of the diplopod A. t. judaicus from a mesic
and xeric habitat. (Bercovitz and Warburg 1985)
Life history traits
Larval stages in the first year
Age at maturity (years)
Life span (years)
Egg wet weight (mg)
Egg caloric content (cal)
Mesic habitat
3-4
8
11
5.96±O.40
22.12±O.60
Xeric habitat
6-7
6
9
7.26±O.10
25.93±O.91
dium vulgare. In a different habitat, Iatrou (1989) suggested environment-independent reproductive strategies, while he reported environment-dependent oviposition schedules in Glomeris balcanica. Apparently, it is difficult to
assign key demographic features to Mediterranean arthropods.
Comparative studies of the demography of arthropods from Mediterranean and other habitats are illustrative. Evaluation of relevant data indicates the
prominent variability of Mediterranean environmental gradients, showing
that differences within semi-arid Mediterranean habitats may be more pronounced than differences among temperate and subhumid Mediterranean
habitats. Indeed, intraspecific comparisons (Bercovitz and Warburg 1985,
1988; Crawford et al. 1987) reveal that pronounced differences in the appearance of life history traits have been recorded in populations of the millipede
Archispirostreptus tumuliporus judaicus from different semi-arid habitats, in
addition to negligible differences in morphometric characteristics. In xeric
habitats, animals grow faster, reach maturity at a younger age, have a shorter
life span and a higher energy investment in eggs (Table 5.1). Clutch size is
higher in xeric environments, while pellet production is delayed in mesic
habitats for about 3 months. Development within egg pellets and postemergence development are faster in xeric than in mesic habitats and adults attain
maturity 2 years earlier. The age at maturity is 6 years in xeric and 8 years in
mesic habitats. Finally, the life span in the xeric environment is 9 years compared with 11 years in mesic habitats. The authors viewed these differences
as a mechanism to counterbalance environmental adversity. Larval mortality
in more hostile xeric habitats is expected to be higher, and shortening the larval stage may save the animals from dying. These differences can also be considered in terms of heat budgets. In fact, lower heat budgets may result in a
longer life span, longer generation time and lower investment in eggs in
mesic habitats where lower average temperatures are recorded. Different
populations also differ with regard to their developmental schedules. This is
probably due to differences in the occurrence and duration of favourable seasons. In mesic environments moulting occurs during the dormant period in
winter, while in xeric habitats it occurs after dormancy. Moreover, hibernation is shorter in xeric environments than in mesic ones.
In contrast, the other hand, interspecific comparison of the life cycle development of the millipedes Glomeris marginata from a temperate habitat (data
Life Cycle Tactics and Development
Table 5.1. Comparison of life history characteristics of the diplopod A. t. judaicus from a mesic
and xeric habitat. (Bercovitz and Warburg 1985)
Life history traits
Larval stages in the first year
Age at maturity (years)
Life span (years)
Egg wet weight (mg)
Egg caloric content (cal)
Mesic habitat
3-4
8
11
5.96±O.40
22.12±O.60
Xeric habitat
6-7
6
9
7.26±O.10
25.93±O.91
dium vulgare. In a different habitat, Iatrou (1989) suggested environment-independent reproductive strategies, while he reported environment-dependent oviposition schedules in Glomeris balcanica. Apparently, it is difficult to
assign key demographic features to Mediterranean arthropods.
Comparative studies of the demography of arthropods from Mediterranean and other habitats are illustrative. Evaluation of relevant data indicates the
prominent variability of Mediterranean environmental gradients, showing
that differences within semi-arid Mediterranean habitats may be more pronounced than differences among temperate and subhumid Mediterranean
habitats. Indeed, intraspecific comparisons (Bercovitz and Warburg 1985,
1988; Crawford et al. 1987) reveal that pronounced differences in the appearance of life history traits have been recorded in populations of the millipede
Archispirostreptus tumuliporus judaicus from different semi-arid habitats, in
addition to negligible differences in morphometric characteristics. In xeric
habitats, animals grow faster, reach maturity at a younger age, have a shorter
life span and a higher energy investment in eggs (Table 5.1). Clutch size is
higher in xeric environments, while pellet production is delayed in mesic
habitats for about 3 months. Development within egg pellets and postemergence development are faster in xeric than in mesic habitats and adults attain
maturity 2 years earlier. The age at maturity is 6 years in xeric and 8 years in
mesic habitats. Finally, the life span in the xeric environment is 9 years compared with 11 years in mesic habitats. The authors viewed these differences
as a mechanism to counterbalance environmental adversity. Larval mortality
in more hostile xeric habitats is expected to be higher, and shortening the larval stage may save the animals from dying. These differences can also be considered in terms of heat budgets. In fact, lower heat budgets may result in a
longer life span, longer generation time and lower investment in eggs in
mesic habitats where lower average temperatures are recorded. Different
populations also differ with regard to their developmental schedules. This is
probably due to differences in the occurrence and duration of favourable seasons. In mesic environments moulting occurs during the dormant period in
winter, while in xeric habitats it occurs after dormancy. Moreover, hibernation is shorter in xeric environments than in mesic ones.
In contrast, the other hand, interspecific comparison of the life cycle development of the millipedes Glomeris marginata from a temperate habitat (data