6 research outputs found
Heteroligus meles Billberg (Col., Scarabacidae) : un bon matériel d'étude de l'équateur biologique
Heteroligus meles Bilberg (Col., Scarabeidae): un good study material for the biological equatorial zone
The Yam beetle Heteroligus meles is found in tropical Africa both North
and South of the equator, and in savannas (in humid areas along watercourses)
as well as in rain-forests.
This species is monovoltine in West Africa. Its life-cycle is characterized
by two migrating flights : one (the feeding migration) takes place at the
beginning of the rains away from the areas where the larvae have developped ;
it is effected by imagos of low body weight. The second migration flight (the
breeding migration) occurs at the outset of the dry season in a reverse direction
and is effected by heavier imagos.
At Makokou (Gabon), which is Iocated South of the climatic equator, but
North (0.4°N) of the geographie equator, preliminary observations suggest the
coexistence of two sympatric populations of yam beetles, one with a boreal
life-cycle and the other with an austral life-cycle - as it is the case for the
bat Hipposideros caffe
Heteroligus meles Billberg (Col., Scarabacidae) : un bon matériel d'étude de l'équateur biologique
The tuberous plants of the Central African rain forest
The different species of rain-forest plants developing starchy tubers were
studied around Makokou (N.E. Gabon) and in the Lobaye River district (S.W.
Central African Republic).
A detailed description of the tuberous parts is given, particularly in wild
yarns (Dioscorea spp.) to help to elucidate the taxonomie status of a number
of species. The unusual morphology of yams belonging to the Enanthiophyllum
section required the use of three new descriptive terms borrowed from the Aka
pygmies, namely « Mbolo » for a lignified plateau, « Mosway » for the fingerlike expansions, and « Yoko » for the spherical terminal edible parts.
The different underground storage structures are considered as adaptive
to the rain-forest environment. During the long period that most plants spend
in the shade of the undergrowth (as the « set of the future » , Oldeman, 1 974),
the energy stored in tubers is more likely to escape insect and/or vertebrate
predation than the aerial parts of other plant species. Accordingly, many
tuberous plant taxa, both dicots and monocots, might well have originated in
rain-forest areas rather than in more seasonal woodlands or savannas.
Counts were made along very narrow transects to estimate the number per
hectare of stems visible above ground level (Tables III to V). The number
of stems averaged 97/ha in the closed forest of the Lobaye, but can reach
locally higher values (up to 24,000/ha) in open areas. In the latter places the
distribution of tuberous plants was clumped, and therefore more likely to be
successfully exploited by animal consumers ; most of their tubers, however,
were poisonous. By contrast, the tuberous plants found in the closed forest
did not con tain highly toxic alkaloids and were rich in starch (up to 80 % , dry
weight) and protein (up to 10 % ) (Tables VII to IX). Stem densities were
lower in Gabon than in the Central African Republic.
An estimate of the underground tuber biomass bas been made at Makokou
(Table VI). The tuber biomass was even higher in the Lobaye District ; a standing
crop of more than 5000 kg of wild yams can remain available throughout
the year on the home range of an Aka pygmy group.
The benefits of energy storage in tubers and the reproductive strategies
of the various plant species concerned are discussed in relation to the selective
pressures exerted by animal consumers, not forgetting human traditional huntergatherer