Evolutionary transition from resprouter to seeder life history in two Erica (Ericaceae) species: insights from seedling axillary buds.
OBJECTIVE
The genus Erica represents the epitome of plant biodiversity in the South African Cape region. It includes seeder and resprouter species, but both species diversity and narrow endemism are tightly associated with the seeder habit. It also includes 'mixed' species, in which both seeder and resprouter life histories are found. This intraspecific variation in life history is genetically based.


METHODS
The cotyledonary region and basal stem of seeder and resprouter seedlings of two 'mixed' species, Erica calycina and E. coccinea, were examined to detect morphological and anatomical differences in axillary bud development between regeneration forms.


RESULTS
While at least some bud activity was observed for resprouter seedlings, none was detected for seeder seedlings. A closer examination allowed the detection of some axillary buds in seeder seedlings of the two species, but they appeared in an unequivocally atrophied state.


CONCLUSIONS
The seeder and resprouter life histories are two character states and the seeder one (i.e. loss of resprouting) is derived within these two Erica species. Results allow the hypothesis that the loss of resprouting in a fire-prone scenario such as the Cape fynbos has promoted high diversification rates in seeder Erica lineages.
Verdaguer
Dolors
D
Area de Fisiología Vegetal, Depto de Ciències Ambientals, Universitat de Girona, Campus de Montilivi, 17071-Girona, Spain.
Ojeda
Fernando
F
D005075:Biological Evolution; D018548:Cotyledon / Q000502:physiology; D029791:Ericaceae / Q000502:physiology*; D035264:Flowers / Q000502:physiology*; D036226:Seedlings / Q000502:physiology*; D012639:Seeds / Q000502:physiology*