Embed Size (px)
Citation preview
Color pattern importance in the speciation of Heliconius heurippa (Lepidoptera: Nymphalidae)
Christian Salcedo, Entomology Department, University of Florida – McGuire Center for Lepidoptera – Universidad de los Andes, ColombiaContact: [email protected]
Study organisms
Methodology Results
H. cydno
Colombia
H. melpomene
H. heurippa
Fig. 1 Geographical distribution of Heliconius cydno, Heliconius melpomene, and Heliconius cydno. These species are found in the eastern slope of the cordillera in Colombia and Venezuela.
The question
Heliconius heurippa represents a possible case of speciation associated to introgressive hybridization. This particular species possess a wing color pattern that combines genetic elements from its possible parental species: H. melpomene and H. cydno. Butterfly models were used in approach and courtship experiments to test whether sexual selection associated to wing color pattern has influenced the speciation of H. heurippa. A total of five models were assembled from real and paper wings that resembled H. cydno, H. melpomene, H. heurippa, and H. heurippa modified (showing only red color, and showing only yellow color.
The results confirm that wing color pattern plays an important role in mate choice within these three species, specifically the “mixed” color pattern “cydno-melpomene” hold by H. heurippa. Males from H. melpomene, H. cydno and H. heurippa showed preference towards its own color pattern in all cases. This suggests that there is a positive assortative mating leaded by wing color pattern for the three species under study and, that the combination of colors that H. heurippa presents constitutes a mate choice signal. In conclusion, mate choice associated to wing color pattern is not only important to pre-zigotic reproductive isolation, but also may play a key role in the origin of H. heurippa through hybridization between H. melpomene and H. cydno.
Abstract
Did sexual selection associated to wing color pattern contribute to the speciation of H. heurippa?
Specimens were collected in the wild to build up experimental colonies. Then using wings cut from dead females, models were built by gluing the wings to paper bodies. Paper wing models were built from impressions of photographs taken to the real wing models. To make the most accurate representation several prints were made and reflectance was measured (see below Fig. 2). The experimental design is described in figure 3. Maximum likelihood was used to analyze the data.
Fig. 2 Butterfly models: 1. H. heurippa, 2. H. melpomene, 3. H. cydno, 4. H. heurippa red (modified), and 5. H. heurippa yellow (modified). The RIGHT side (A) were made up with paper wings, the LEFT side (B) were made up with real wings.
Fig. 3 Two test models (in circle) were placed inside a cage attached to the roof with clear nylon threads. The left represents the control and the right represents the experimental model. Males with the same color pattern as the control were released and approaches (individuals entering a 24 in imaginary diameter sphere around the model) and courtship (sustained fluttering over the model) were counted in 5 min intervals. In total 25 replicas per experimental model were tested for a total of more than 3000 minutes of observation. This experimental design was adapted from Jiggins et al. 2003.
Fig. 4 Probability of approach (a) and courtship (b) relative to a control model. Any point below one (1) means that the tested males (horizontal axis) do prefer their own color pattern with respect to the experimental models. Red = real wings; Blue = paper wings. P (vertical axis) was calculated using maximum likelihood.
Conclusions• Color pattern plays an important role in mate choice in the three Heliconius species used in this study. The results of this study support recent evidence found in other species of the genus, and suggests that assortative mating is leaded by wing color pattern.
•Attraction of H. heurippa for its own color pattern appears to be important not only as a pre-zigotic isolating mechanism but also suggests that sexual selection associated to wing color could have facilitated H. heurippa speciation.
•H. cydno males seem not to discriminate between the real wing model of H. heurippa modified showing only the yellow band AND their own color pattern model. This suggests that there is an additional element in the wings that attracts H. cydno males and also that the cydno “C” is not important in the female identification for these males.
References
1. Jiggins, C.D., R.E. Naisbit, L.R. Coe & J. Mallet. 2001. Reproductive Isolation caused by colour pattern mimicry. Nature 411: 302-305.
2. Giraldo, S. N. 2002. Importancia del patrón de coloración en la especiación entre Heliconius melpomene y Heliconius heurippa. Tesis de pregrado. Universidad de los Andes.
Acknowledgements
The Entomology Department and IFAS (University of Florida) provided funds to cover travel expenses to this meeting. Mauricio Linares and his laboratory members from The Universidad de los Andes (Bogotá, Colombia) contributed greatly with advice and laboratory resources; Chris Jiggins from University of Edinburgh made useful suggestions in data analysis, and Marcus Kronforst made possible to get the reflectance measurements.
Courtship
P
Male type
Real wings
Paper wings
b) Courtship
heuR
heuA
heumelp
0
0,25
0,5
0,75
1
Male type
Real wings
Paper wings
H. cydno
P
b) Courtship
heuRheuAheucord
0
0,25
0,5
0,75
1
Male type
Real wings
Paper wings
H. melpomene
b) Courtship
melpcord
heuA heuR
0
0,25
0,5
0,75
1
Male type
Real wings
Paper wings
H. heurippa
P
P
a) Approach
melp heu
heuA
heuR
0
0,25
0,5
0,75
1
Male type
Real wings
Paper wings
H. cydno
P
a) Approach
heuRheuAheucord
0
0,25
0,5
0,75
1
Male type
Real wings
Paper wings
H. melpomene
P
a) Approach
heuRheuAcordmelp
0
0.25
0.5
0.75
1
Male type
Real wings
Paper wings
H. heurippa
P
