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The work began with the classification of the individuals of the hybrid swarm
from a morphological point of view. On the basis of this classification, the phenological behavior of each group of individuals was studied, and based on this behavior some descriptive parameters were estimated on the possible mating system that
reigns in the hybrid swarm. The morphological classification of the trees was carried out taking into account leaf and fruit characters. Group 1, individuals with
intermediate morphological characteristics; group 2, individuals of P. flexuosa; and
group 3, individuals of P. chilensis. The individual flowering of each tree was monitored and the intensity of flowering (Flower Production Index) was estimated. The
opening of the flowers and their receptive stage (at which time the flowers can be
fertilized) were taken into account.
An important regularity was found regarding the number of days that elapsed
between the beginning of the flowering of one group with respect to the others and
the moment of the flowering peak. This regular behavior of the groups defined suggests that both the onset of flowering and the time at which the maximum production of flowers (flowering peak) occurs would be determined genetically and that
these groups respond differentially in their interaction with the environment.
With all this information a first approximation was made to the description of the
mating system of the hybrid swarm, trying to elucidate between which individuals
and groups mating is possible and the frequency with which mating occurs. For this,
the recorded data of the flowering were taken into account and some assumptions
were made: (1) all the trees of the stand that have produced flowers can participate
in the crosses; (2) two individuals can only cross if they bloom simultaneously; (3)
it is considered that 10% of crosses come from self-fertilization; (4) the rest of the
crosses can occur between individuals of the same or different groups; and (5) the
amount or probability of crossing between trees of the same or different groups
depends on (a) the number of flowers that the tree presents at that time, without
considering those that will be fertilized by flowers of the same individual (equivalent to 10% of their flowers), and (b) the probability that at any given moment a tree
A fecundates a tree B depends on the relative contribution of flowers of tree A with
respect to the total number of flowers present at that moment in the stand.
Finally, the mating preference within and between the morphological groups was
calculated. The trees of group 1 (individuals with intermediate morphological characteristics) show preference to mate with individuals of their own group, avoiding
crossing with the trees of groups 2 (P. flexuosa) and 3 (P. chilensis). Mating between
individuals of this group are 7 or 4.5 times more frequent than expected by random
whereas the opposite occurs with groups 2 and 3, which mate less than expected by
random. Group 2 also had a greater preference for mating with the trees of group 1,
while mating between trees in the same group is similar to that expected at random.
The number of crosses between the trees of the group will increase or decrease as
their density increases or decreases, respectively. Individuals of group 3 have a
greater preference for trees of group 1, than with those of their same group and repel
or avoid mating with group 2.
The number of hybrids in the stand would tend to increase in each generation. It
can be said that the trees have preference to mate with the individuals of group 1,
C. Vega et al.
The work began with the classification of the individuals of the hybrid swarm
from a morphological point of view. On the basis of this classification, the phenological behavior of each group of individuals was studied, and based on this behavior some descriptive parameters were estimated on the possible mating system that
reigns in the hybrid swarm. The morphological classification of the trees was carried out taking into account leaf and fruit characters. Group 1, individuals with
intermediate morphological characteristics; group 2, individuals of P. flexuosa; and
group 3, individuals of P. chilensis. The individual flowering of each tree was monitored and the intensity of flowering (Flower Production Index) was estimated. The
opening of the flowers and their receptive stage (at which time the flowers can be
fertilized) were taken into account.
An important regularity was found regarding the number of days that elapsed
between the beginning of the flowering of one group with respect to the others and
the moment of the flowering peak. This regular behavior of the groups defined suggests that both the onset of flowering and the time at which the maximum production of flowers (flowering peak) occurs would be determined genetically and that
these groups respond differentially in their interaction with the environment.
With all this information a first approximation was made to the description of the
mating system of the hybrid swarm, trying to elucidate between which individuals
and groups mating is possible and the frequency with which mating occurs. For this,
the recorded data of the flowering were taken into account and some assumptions
were made: (1) all the trees of the stand that have produced flowers can participate
in the crosses; (2) two individuals can only cross if they bloom simultaneously; (3)
it is considered that 10% of crosses come from self-fertilization; (4) the rest of the
crosses can occur between individuals of the same or different groups; and (5) the
amount or probability of crossing between trees of the same or different groups
depends on (a) the number of flowers that the tree presents at that time, without
considering those that will be fertilized by flowers of the same individual (equivalent to 10% of their flowers), and (b) the probability that at any given moment a tree
A fecundates a tree B depends on the relative contribution of flowers of tree A with
respect to the total number of flowers present at that moment in the stand.
Finally, the mating preference within and between the morphological groups was
calculated. The trees of group 1 (individuals with intermediate morphological characteristics) show preference to mate with individuals of their own group, avoiding
crossing with the trees of groups 2 (P. flexuosa) and 3 (P. chilensis). Mating between
individuals of this group are 7 or 4.5 times more frequent than expected by random
whereas the opposite occurs with groups 2 and 3, which mate less than expected by
random. Group 2 also had a greater preference for mating with the trees of group 1,
while mating between trees in the same group is similar to that expected at random.
The number of crosses between the trees of the group will increase or decrease as
their density increases or decreases, respectively. Individuals of group 3 have a
greater preference for trees of group 1, than with those of their same group and repel
or avoid mating with group 2.
The number of hybrids in the stand would tend to increase in each generation. It
can be said that the trees have preference to mate with the individuals of group 1,
C. Vega et al.