Résumé
Geographical distribution and diversity of current plant species have been
strongly shaped by climatic oscillations during the Quaternary. Analyzing
the resulting divergence among species and differentiation within species
is crucial to understand the evolution of taxa like
the Vitis genus, which provides very useful genetic
resources for grapevine improvement and might reveal original
recolonization patterns due to growth habit and dispersal mode. Here, we
studied the genetic structure in natural populations of three species from
eastern North America: Vitis aestivalis, V.
cinerea and V. riparia using different marker
types. V. aestivalis and V. cinerea showed
higher diversity than V. riparia. The two former species
are less differentiated, confirming an earlier divergence of V.
riparia. V. aestivalis and V. riparia exhibited
different genetic groups on both sides of the Appalachian Mountains that
could mirror different recolonization routes from southern refugia.
Genetic structure was stronger in V. cinerea, for which
two varieties (var. berlandieri and
var. cinerea) are morphologically recognized. Our results confirm
this distinction and suggest the existence of three other lineages within
var. cinerea. These discontinuities appear linked to adaptation
of var. berlandieri to dry and limy areas of Texas and
partially to the Mississippi River Valley. Rapid range expansions from
refugia upon climate warming are also suggested by the low linkage
disequilibrium values observed. Furthermore, large variation for downy
mildew resistance was observed in the three species. Our findings appeared
consistent with the vegetation history of eastern North America.