0198566123.pdf

from herbaceous ancestors has been repeated
several times in some lineages, as in the
Macaronesian endemic genus Pericallis(Panero
et al. 1999).
Several reasons have been suggested for the
development of lignification on islands. As reviewed
by Givnish (1998), they include the following.

1 The competition hypothesis(Darwin 1859).
Herbaceous colonists would obtain a competitive
advantage by growing taller and developing into
shrubs/trees.
2 The longevity hypothesis (Wallace 1878).
Woodiness might allow extended lifespans,

increasing the chance of sexual reproduction

where pollinators are scarce.

3 The moderate insular climate hypothesis

(Carlquist 1974). In comparison with the closest

continents, islands typically have milder (and

moist) climates, promoting the development of

herbs to tree-like growth forms.

4 The promotion of sexual out-crossing hypothe-

sis(Böhleet al. 1996). Evolution of the woody

habit accompanies increased longevity, which pro-

vides greater likelihood of cross-pollination in

environments such as islands where pollination

services may be unreliable. This hypothesis is an

extension of hypothesis (2).

NICHE SHIFTS AND SYNDROMES 185

E. russicum

E. sabulicola

E. parviflorum

E. plantagineum

E. lusitanicum

E. albicans

E. italicum

E. asperrimum

E. vulgare

E. creticum

E. horridum

E. tuberculatum

E. rosulatum H

4.

5.

9.

Madeira

Archipelago

Canary

Islands

Cape Verde

Archipelago

Continental Species

Island Species

3.

100

100

100

100

98

100

Single

island

invasion

through

herbaceous

continental

ancestor

followed by

successive

island

colonization

and rapid

speciation

of woody

forms.

89

100

94

81

97

96

Madeira

Cape

Ve r d e

82

98

94

100

100

100

(^96) -
94
100
1.0%
H H H H H H H H H H H
E. hypertropicum W
E. vulcanorum W
E. candicans W
E. nervosum W
E. webbii W
E. aculeatum W
E. leucophaeum W
E. virescens W
E. simplex W
E. giganteum W
E. hierrense W
E. brevirame W
E. bonnetii H
E. strictum W
E. callithyrsum W
E. onosmifolium
Lobostemon
E. russicum
W
E. handiense W
E. decaisnai W
E. pininana W
E. wildpretii W
E. auberianum W
(Eastern Europe)
(South Africa)
H
L. fruticosus W
C a n a r y I s l a n d s
Figure 7.3Phylogeny and biogeography of Echiumshowing that the woody species of Macaronesia are part of a monophyletic archipelagic
radiation (source: Böhleet al. 1996). Altogether there are 29 endemic species of Echiumin Macaronesia. The numbers refer to Echiumspecies
that exemplify a growth form or habit: (1) Echium plantagineum,(2) E. humile, (3) E. rosulatum,(4) E. parviflorum,(5) E. onosmifolium, (6) E.
decaisnei,(7) E. simplex, (8) E. wildpretii,(9) Lobostemon regulareflorus. The technical details of the phylogeny are as follows. It was based on
analyses of 70 kb of non-coding DNA determined from both chloroplasts and nuclear genomes. Numbers above branches indicate the number of
times the branch was found in 100 bootstrap neighbour-joining replicates, using the Kimura distance, whereas the numbers below branches
indicate the number of times the branch was found in 100 bootstrap parsimony replicates.