Abstract:
Aim:
Natural and human-induced differences in frugivore assemblages can
influence the seed dispersal distances of trees. An important issue in seed dispersal
systems is to understand whether differences in seed dispersal distances also affect
the genetic structure of mature trees. One possible approach to test for a
relationship between seed dispersal and the genetic structure of mature trees is to
compare the genetic structure of two closely related tree species between two
biogeographical regions that differ in frugivore assemblages and seed dispersal
distances. Previous studies on two Commiphora species revealed that Commiphora
guillauminii in Madagascar has a much lower seed dispersal distance than
Commiphora harveyi in South Africa. We tested whether the lower seed dispersal
distance might have caused decreased gene flow, resulting in a stronger genetic
structure in Madagascar than in South Africa.
Location Madagascar and South Africa.
Methods Using amplified fragment length polymorphism markers we
investigated the genetic structure of 134 trees in Madagascar and 158 trees in
South Africa at a local and a regional spatial scale.
Results:
In concordance with our hypothesis, kinship analysis suggests that gene
flow was restricted mostly to 3 km in Madagascar and to 30 km in South Africa.
At the local spatial scale, the genetic differentiation among groups of trees within
sample sites was marginally significantly higher in Madagascar (FST = 0.069) than
in South Africa (FST = 0.021). However, at a regional spatial scale genetic
differentiation was lower in Madagascar (FST = 0.053) than in South Africa
(FST = 0.163).
Main conclusions:
Our results show that lower seed dispersal distances of trees
were linked to higher genetic differentiation of trees only at a local spatial scale.
This suggests that seed dispersal affects the genetic population structure of trees at
a local, but not at a regional, spatial scale.
