contents remain fairly constant during the growing season, but the compositions of
catechin, gallocatechin, and two leucodelphinidins (flavonoid) change seasonally in
Quercus robur leaves [107]. Total phenolic content in Ribes nigrum leaves increases
from June to August, but their compositions differ with seasons [109].
The first seasonal pattern of the secondary metabolites may be effective to avoid
young leaves from herbivore’s predation, because some insects suffer higher mortality and reduction of growth when fed young leaves [100]. The second seasonal
pattern in which the secondary metabolites increase during the growing season may
be also the successive defensive response to herbivore’s feeding, because in some
insects, the period of the highest attack on leaves corresponds to the time when
phenolic contents are absent or minimum [107]. However, the evolutionary processes between plant defense and herbivore’s attack with detoxification or tolerance
are sometimes arms races.
In other cases, the level of chlorogenic acid in the leaves of Olea europaea
increases markedly in winter (January) and decreases to a minimum level in spring
(April), thereafter, the chlorogenic acid level gradually increases again and reaches
the maximum level in summer (July–August) [110]. However, the level of caffeic
acid is high from winter to spring (January to April) and reaches its highest value in
spring, and it starts to decrease and reaches the minimum value in summer
(June–August) [110].
Comparisons of leaf chemicals between dry and wet seasons of seven tree species
(Senegalia caffra, Vachellia karroo, Burkea africana, Combretum molle,
Combretum zeyheri, Searsia lancea, and Terminalia sericea) suggest that condensed
tannins are little different between seasons [111]. Water limitation induced experimentally has little impact on overall leaf secondary metabolite concentrations of
Eucalyptus leaves, although a few components of them decrease by limiting water
[112]. The proportions of young leaves in forest also differ between dry and wet
seasons. Young leaves are more available in the wet season, which contain more
protein and lower fiber, and lessor weasel lemurs select protein-rich leaves [41]. In
the dry season, however, chemical differences among available leaves become
unclear.
4
A Case Study: Seasonal Changes in Leaf Chemicals and the
Giant Flying Squirrel’s Feeding Behavior
The giant flying squirrel (Fig. 2 left) is an exclusively arboreal, nocturnal, and largesized herbivore and distributed on Kyushu, Shikoku, and Honshu Islands of Japan
[113]. Adult squirrels reach weights of up to 1.3 kg [113]. The home range size is
0.4–5.2 ha, usually larger in males than females, with considerable overlap between
the sexes and between males [114, 115]. This large body size may be maintained by
nutrition from specialized cecal microbiota, which are known to convert diverse
plant materials into absorbable nutrients in the congeneric species Petaurista
alborufus lena [60].
15 Tree-Leaf Chemicals and Feeding Behavior of Arboreal Mammals in Seasonal. . .
365
catechin, gallocatechin, and two leucodelphinidins (flavonoid) change seasonally in
Quercus robur leaves [107]. Total phenolic content in Ribes nigrum leaves increases
from June to August, but their compositions differ with seasons [109].
The first seasonal pattern of the secondary metabolites may be effective to avoid
young leaves from herbivore’s predation, because some insects suffer higher mortality and reduction of growth when fed young leaves [100]. The second seasonal
pattern in which the secondary metabolites increase during the growing season may
be also the successive defensive response to herbivore’s feeding, because in some
insects, the period of the highest attack on leaves corresponds to the time when
phenolic contents are absent or minimum [107]. However, the evolutionary processes between plant defense and herbivore’s attack with detoxification or tolerance
are sometimes arms races.
In other cases, the level of chlorogenic acid in the leaves of Olea europaea
increases markedly in winter (January) and decreases to a minimum level in spring
(April), thereafter, the chlorogenic acid level gradually increases again and reaches
the maximum level in summer (July–August) [110]. However, the level of caffeic
acid is high from winter to spring (January to April) and reaches its highest value in
spring, and it starts to decrease and reaches the minimum value in summer
(June–August) [110].
Comparisons of leaf chemicals between dry and wet seasons of seven tree species
(Senegalia caffra, Vachellia karroo, Burkea africana, Combretum molle,
Combretum zeyheri, Searsia lancea, and Terminalia sericea) suggest that condensed
tannins are little different between seasons [111]. Water limitation induced experimentally has little impact on overall leaf secondary metabolite concentrations of
Eucalyptus leaves, although a few components of them decrease by limiting water
[112]. The proportions of young leaves in forest also differ between dry and wet
seasons. Young leaves are more available in the wet season, which contain more
protein and lower fiber, and lessor weasel lemurs select protein-rich leaves [41]. In
the dry season, however, chemical differences among available leaves become
unclear.
4
A Case Study: Seasonal Changes in Leaf Chemicals and the
Giant Flying Squirrel’s Feeding Behavior
The giant flying squirrel (Fig. 2 left) is an exclusively arboreal, nocturnal, and largesized herbivore and distributed on Kyushu, Shikoku, and Honshu Islands of Japan
[113]. Adult squirrels reach weights of up to 1.3 kg [113]. The home range size is
0.4–5.2 ha, usually larger in males than females, with considerable overlap between
the sexes and between males [114, 115]. This large body size may be maintained by
nutrition from specialized cecal microbiota, which are known to convert diverse
plant materials into absorbable nutrients in the congeneric species Petaurista
alborufus lena [60].
15 Tree-Leaf Chemicals and Feeding Behavior of Arboreal Mammals in Seasonal. . .
365