Revista Chilena de Historia Natural 77 (3): 509-521, 2004
RESEARCH ARTICLE
Establishment and life history characteristics of the southern South American mistletoe
Misodendrum punctulatum (Misodendraceae)
Taking advantage of host annual ring formation and synchronic embedding of the
mistletoe haustorial system within the host xylem, we analyzed age-dependent life history traits and establishment conditions of
Misodendrum punctulatum (Misodendraceae) infecting two deciduous species of Nothofagus in northern
Patagonia, Argentina. Absolute determination of infection ages was performed by examining the number of host tree rings traversed by
deepest haustoria in slices/cross-sections of parasitized branches/main trunks. Concomitantly, the number of branching events and
basal stem diameters were taken from emerging aerial parts of the mistletoes. Host rings preceding the infection were used to
determine branch trunk ages during infection. Relationships between haustorial and aerial age indices indicate that: (1) branching
events are good non-destructive estimators of mistletoe age while basal diameters were poor estimators of age, (2) early development
of M. punctulatum includes a multiyear holotrophic incubation period before producing aerial shoots, (3) the incubation
period span is site and/or specie dependent being longer (4-6 yr) on the subalpine Nothofagus pumilio, and shorter (2 yr)
on the lower altitude shrub N. antarctica, (4) Mistletoes infecting subalpine trees of Nothofagus pumilio in the
harsher sites grew slower and were longer-lived than mistletoes infecting lower altitude shrubs of N. antarctica. M. punctulatum
infected only young host branches (< 4 yr) suggesting strong limitations of mechanically penetrating thicker bark. When
M. punctulatum shoots were present on Nothofagus trunks, absolute aging of haustorial systems in cross-
sections revealed non-vegetative infections when trees were saplings. Multiple discrete events of renewal of the endophytic system
spanning each about 24 yr are probably related to the maintenance of appropriate connections with functional host
xylem.
Key words:
endophytic system,
establishment, Misodendrum, mistletoes, annual tree rings, Nothofagus
