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(Collinson
2002
; Van Konijnenburg-Van Cittert
2002
) is consistent with a fire
origin of resprouting in some fern clades.
A clearer example where fire has likely played a selective role in the woody plant
evolution of resprouting is in northern hemisphere gymnosperms. Most lack any
capacity for resprouting but the few that do (e.g.
Juniperus deppeana
,
J. oxycedrus
,
Pinus canariensis
,
P. serotina
,
P. echinata
, and
P. rigida
,
Pseudotsuga macrocarpa
,
Picea
spp.,
Sequoia sempervirens
,
Taxus brevifolia and Torreya californica
) are all
components of crown fire regimes and are in clades where resprouting is largely
absent and of secondary origin (Stone & Stone
1954
; Keeley
1981
; Minore &
Weatherly
1996
; Keeley & Zedler
1998
). A similar pattern is evident in southern
hemisphere gymnosperms such as
Podocarpus
(Chalwell & Ladd
2005
),
Cunning-
hamia
(Del Tredici
2001
), and
Widdringtonia
(Keeley
et al.
1999b
). The latter genus
is of interest because it comprises two relict species that are non-resprouters
restricted to mesic sites with long-interval fire regimes (Manders
1986
). The only
other species is
Widdringtonia nodiflora
, a resprouter that has a widespread geo-
graphic range from Malawi to the Western Cape region; it occurs in fynbos and is
tolerant of frequent fires (Keeley
et al.
1999b
).
Epicormic resprouting is one of the primary means of postfire survival in
arboreal
Eucalyptus
in both MTC and non-MTC regions of Australia (Burrows
2002
). In these trees epicormic resprouting arises from seemingly unique strips of
meristematic cells well developed on the inner bark, providing a well-protected
source of new shoots following even high-intensity fires. This structure is wide-
spread in distantly related genera in the Myrtaceae, suggesting either an early
origin for this fire adaptation or multiple origins within the family (Burrows
2010
).
Molecular phylogenies for the family suggest this trait arose very early in Myrta-
ceae and points toward fire having been an important evolutionary factor through
most of the Tertiary (Crisp
et al.
2011).
Another example where a case could be made for fire playing a selective role is
in the postfire resprouting and flowering of the South African fynbos geophyte
Cyrtanthus ventricosus.
This species maintains preformed floral buds that remain
dormant for years but are triggered by smoke (Keeley
1993b
) so that they flower
only within 1-2 weeks after a fire, regardless of the season (Le Maitre & Brown
1992
). This illustrates one of the dicey problems of sorting out adaptation from
exaptations. In herbaceous perennials resprouting
per se
is not likely an adapta-
tion to fire (see
Chapter 3
) yet in
C. ventricosus
this trait has been fine tuned in
ways that clearly reflect a selective role by fire. To a lesser degree this may be true
as well of other geophytes from closed-canopy MTC ecosystems.
One thought experiment that purportedly showed resprouting in Californian
shrublands as not an adaptation to fire (Lloret
et al.
1999a
) deserves closer
examination. These authors demonstrated resprouting after an experimental fire
in MTV matorral shrublands of mainland Mexico and concluded that because this
region lacked a fire regime of frequent fires, as observed in contemporary MTC
southern California chaparral, there was little reason to assume a relationship
between fire and resprouting in either shrubland ecosystem. However, these
