Rb. Srygley et Cp. Ellington, Estimating the relative fitness of local adaptive peaks: the aerodynamic costs of flight in mimetic passion-vine butterflies Heliconius, P ROY SOC B, 266(1435), 1999, pp. 2239-2245
Citations number
21
Categorie Soggetti
Experimental Biology
Journal title
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES
In a related paper, we demonstrated that mimetic Heliconius butterflies hav
e converged in wing-beat frequency and degree of asymmetry in the wing moti
on, whereas sister species are dissimilar in these same traits. Warning sig
nals of sympatric, distasteful species converge in evolutionary models in o
rder to educate their predators more efficiently that the signal is associa
ted with unprofitable prey. Barring other constraints, the behaviours of th
e different co-mimetic pairs should ultimately converge on that behaviour w
hich minimizes the energetic cost of flight. We estimated the energetic cos
t of each mimic's flight behaviour in order to predict the difference in he
ight of each fitness peak and the direction of convergent selection qualita
tively. Following adjustments for body mass, mimetic Heliconius melpomene a
nd Heliconius erato required more aerodynamic power than Heliconius cydno a
nd Heliconius sapho. This difference was attributed to the slower flight sp
eeds and higher wing-beat frequencies of H. melpomene and H. erato. Consequ
ently, H. melpomene and H, erato expended more energy per unit distance per
unit body mass than H. cydno and H. saaho. However, differences in body ma
ss may equalize energy budgets and stabilize the sympatric coexistence of t
he two pairs of co-mimics.