ADAPTIVE RADIATION 229Table 9.3 Endemic (in bold) and non-endemic Macaronesian vascular plant genera represented by 10 or
more endemic species. (Sources: Santos-Guerra 2001 for Macaronesia; Borges et al. 2005 for the Azores;
Sziemer 2000 for Maderia; Izquierdo et al. 2001 for the Canaries; Arechavaleta et al. 2005 for the Cape Verde
islands). When total species number does not match the sum, some species are shared among archipelagos
Plant genus Azores Madeira Canaries Cape Verde Total
Aeonium – 2 28 1 31
Echium – 2 23 3 28
Lotus 1 5 19 5 28
Argyranthemum –422–26
Sideritis – 1 23 – 24
Limonium – 2 18 5 23
Sonchus – 3 18 1 22
Monanthes –116–17
Cheirolophus – 1 15 – 16
Micromeria – 1 15 1 16
Pericallis 1113–15
Euphorbia 2 2 10 1 14
Aichryson 1311–14
Crambe – 1 12 – 13
Teline –19111
Convolvulus – 1 10 – 11
Tolpis 227111
Table 9.4 Adaptive radiation in the endemic genus Argyranthemum(Asteraceae) in the Macaronesian islands (data from
Humphries 1979). Francisco-Ortega et al. (1996) recognize 26 monophyletic species in this genuss
Environment Adaptive features Islands Species
Broadleaved forests Type A: shrubby, unreduced Tenerife and Gomera A. broussonetii
leaves Madeira A. adauctumssp.
jacobaeifoliumandA.pinnatifidum
South-facing, lowland arid Type B/C: reduced Tenerife A. frutescensssp.gracilescens, and
lignification, habit, A. gracile
capitulum size, and leaf area
Gran Canaria A. filifolium
Sub-alpine and high Type D: dies back after Tenerife A. tenerifaeandA. adauctumssp.
montane flowering each year, leaves dugourii
very dissected, hairy
Exposed northern coastal Type E: reduced habit, large Canaries A. coronopifolium,
areas capitula, increased A.frutescensssp.canariae, ssp.
succulence succulentumandA. maderense
(9 species). Most endemic species have a restricted
distribution, 48% occurring on a single island, and a
further 15% on two. From this and other considera-
tions, Humphries (1979) concluded that allopatric
speciation has been crucial in the flowering plants.
Furthermore, from studies of a sample of 350 of the
endemic species, he concluded that 90% had
evolved by gradual divergence following the break-
up of a population (including migration from one
area to another), with the remainder accounted for