de-Lucas et al. 2008
Fri Jul 10 2009
Mating system and pollen gene flow in Mediterranean maritime pine
Mating systems define the mode of gene transmission across
generations, helping to determine the amount and distribution
of genetic variation within and among populations of plant
species. A hierarchical analysis of Mediterranean maritime
pine mating system (61 mother trees from 24 plots, clustered
in three populations) was used to identify factors affecting
mating patterns and to fit pollen dispersal kernels. Levels of
ovule and seed abortion, multi- and single-locus outcrossing
rates and correlated paternity were estimated from progeny
arrays and correlated with ecological stand variables and
biometric tree measures. Pollen dispersal kernels were fitted
using TwoGener and KinDist indirect methods and simula-
tions were carried out to identify relevant factors affecting
correlated paternity. Maritime pine showed high outcrossing
rates (tm and ts B0.96) and relatively low levels of correlated
paternity [an rp of 0.018 (Ritland’s estimate) or 0.048 (Hardy’s
estimate)], although higher than in other anemophilous tree
species. Mating system parameters had high variation at
the single-tree level (99–100%) but no stand or population effect was detected.
At the single-tree level, outcrossing rates
were correlated with tree (diameter and height) and crown
size. In addition, correlated paternity showed a significant
negative correlation with tree height, height to crown base
and height to the largest crown width, probably reflecting the
importance of the trees’ ‘ecological neighborhoods’. Indirectly
estimated pollen dispersal kernels were very leptokurtic
(exponential-power distributions with b50.5), with mean
dispersal distances from 78.4 to 174.4 m. Fitted dispersal
kernels will be useful in building explicit simulation models
that include dispersal functions, and which will contribute to
current conservation and management programs for maritime
pine. Nevertheless, the numerical simulations showed that
restricted dispersal, male fertility and phenological overlap
could only partially explain the observed levels of correlated
paternity; so other factors may also be relevant for the
management of this valuable forest tree species.
Mating systems define the mode of gene transmission across
generations, helping to determine the amount and distribution
of genetic variation within and among populations of plant
species. A hierarchical analysis of Mediterranean maritime
pine mating system (61 mother trees from 24 plots, clustered
in three populations) was used to identify factors affecting
mating patterns and to fit pollen dispersal kernels. Levels of
ovule and seed abortion, multi- and single-locus outcrossing
rates and correlated paternity were estimated from progeny
arrays and correlated with ecological stand variables and
biometric tree measures. Pollen dispersal kernels were fitted
using TwoGener and KinDist indirect methods and simula-
tions were carried out to identify relevant factors affecting
correlated paternity. Maritime pine showed high outcrossing
rates (tm and ts B0.96) and relatively low levels of correlated
paternity [an rp of 0.018 (Ritland’s estimate) or 0.048 (Hardy’s
estimate)], although higher than in other anemophilous tree
species. Mating system parameters had high variation at
the single-tree level (99–100%) but no stand or population effect was detected.
At the single-tree level, outcrossing rates
were correlated with tree (diameter and height) and crown
size. In addition, correlated paternity showed a significant
negative correlation with tree height, height to crown base
and height to the largest crown width, probably reflecting the
importance of the trees’ ‘ecological neighborhoods’. Indirectly
estimated pollen dispersal kernels were very leptokurtic
(exponential-power distributions with b50.5), with mean
dispersal distances from 78.4 to 174.4 m. Fitted dispersal
kernels will be useful in building explicit simulation models
that include dispersal functions, and which will contribute to
current conservation and management programs for maritime
pine. Nevertheless, the numerical simulations showed that
restricted dispersal, male fertility and phenological overlap
could only partially explain the observed levels of correlated
paternity; so other factors may also be relevant for the
management of this valuable forest tree species.