Electronic Supplementary Material 1. Indices of abundance (IA ± standard error) of the main items (> 2% in frequency) observed in Rattus rattus feaces on Bagaud Island during spring 2006, summer 2006 and winter 2007 in the three study habitats. Fr: fruits, Le: leaves, In: inflorescences, Se: seeds, Ve: vegetative parts, Obs.: field observations or item observed in rat stomachs. In the iceplant habitat, Carpobrotus spp. fruits dominate rat diet regardless of season (this is confirmed by the stable isotope analyses of rat tissues; see Ruffino et al. 2011). In the gull habitat, rat diet is mainly composed of nitrogen-enriched plants (favoured by guano fertilization), gull-derived animal proteins and food scraps. In the scrubland habitat, the diet of rats is a mixture of various plant parts and arthropods. The fruits consumed in the scrubland are mainly represented by small Smilax aspera berries.
ICEPLANT (n=31) / SHRUBLAND (n=31) / GULL (n=25)Season / Item / IA / Item / IA / Item / IA
SPRING
Carpobrotus spp. Fr / 28.5 ± 9.3 / Carex haleriana Se / 18.9 ± 8.9 / Poaceae In / 75.7 ± 6.4
Vicia bengalensis Le / 21.5 ± 7.4 / Vicia bengalensis Le / 17.5 ± 8.2 / Gull feathers / 4.9 ± 3.4
Poaceae In / 15.4 ± 3.7 / Arthropods / 17.0 ± 4.0 / Vicia bengalensis Le / 3.5 ± 1.3
Arthropods / 11.1 ± 2.3 / Poaceae In / 16.9 ± 6.5 / Arthropods / 2.9 ± 0.1
Ruscus aculeatus Le / 4.0 ± 1.8 / Rubia peregrina Le / 5.9 ± 3.0 / Food scraps / Obs.
Euphorbia pithyusa In / 4.6 ± 2.8 / Egg shells / Obs.
Ruscus aculeatus Le / 2.7 ± 0.7
SUMMER
Carpobrotus spp. Fr / 52.8 ± 13.6 / Smilax aspera Fr / 57.9 ± 10.0 / Poaceae Ve / 24.7 ± 6.3
Smilax aspera Fr / 31.9 ± 11.6 / Arthropods / 13.4 ± 3.4 / Arthropods / 19.6 ± 7.8
Arthropods / 5.8 ± 1.6 / Phillyrea spp. Fr / 5.9 ± 2.0 / Juncus acutus Se / 16.4 ± 5.9
Lotus cytisoides Ve / 6.7 ± 3.0
Solanum nigrum Se / 3.8 ± 3.8
Smilax aspera Fr / 2.3 ± 1.6
WINTER
Carpobrotus spp. Fr / *57.7 ± 7.8 / Rubia peregrina Ve / 43.3 ± 9.3 / Lotus cytisoides Ve / 47.6 ± 12.3
Smilax aspera Fr / 10.7 ± 6.9 / Smilax aspera Fr / 13.4 ± 9.1 / Phillyrea spp. Ve / 15.4 ± 7.6
Phillyrea spp. Ve / 8.1 ± 4.1 / Pinus spp. Se / 9.3 ± 6.9 / Juncus acutus Se / 12.0 ± 8.0
Arthropods / 1.2 ± 0.4 / Carpobrotus spp. Fr / 8.6 ± 7.7 / Solanum nigrum Se / 6.6 ± 4.0
Arthropods / 5.1 ± 2.5 / Arthropods / 2.5 ± 1.3
Lotus cytisoides Ve / 5.0 ± 5.0 / Frankenia laevis Ve / 2.5 ± 2.5
Phillyrea spp. Ve/Fr / 3.5 ± 2.7
Carex haleriana Ve / 2.8 ± 1.7
Myrtus communis Se/Fr / 2.0 ± 1.0
Electronic Supplementary Material 2. Diameter, dry mass, nutrient content (percentage of water, carbohydrates, lipids, proteins), energy and water (pulp only) contents of the fruits found in the three study habitats and eaten by black rats on Bagaud Island. The seasons of maximum availability of each fruit is given by the ripening seasons. Immature fruits are also often eaten by black rats. Note the availability of large fleshy fruits rich in water during the drought season in the iceplant habitat.
Habitat / Taxa / Ripeness / Diameter (mm) / Dry mass (g) / Nutrient content(W C L P) / Energy content
(Kcal) per dry fruit / Water content
(g) per fresh fruit
SCRUBLAND / Arbutus unedo / Oct-Dec / 17.1 / 1.11 / 60 32 03 03 / 3.63 / 1.14
Asparagus acutifolius / Oct / 7.4 / 0.09 / 71 49 01 06 / / / 0.16
Juniperus phoenicea / Nov-Dec / 8.3 / 0.08 / 16 18 04 05 / 0.40 / 0.04
Lonicera implexa / Aug-Oct / 6.3 / 0.07 / 76 51 01 04 / 0.28 / 0.12
Myrtus communis / Oct-Nov / 8.5 / 0.11 / 67 46 01 03 / 0.45 / 0.26
Phillyrea angustifolia / Oct-Nov / 5.2 / 0.10 / 71 50 02 03 / 0.42 / 0.06
Pistacia lentiscus / Oct-Dec / 5.3 / 0.05 / 65 07 50 05 / 0.39 / 0.07
Ruscus aculaetus / Oct / 11.9 / 0.39 / 72 26 01 03 / 1.57 / 0.71
Smilax aspera / Sep-Nov / 7.3 / 0.06 / 84 42 01 04 / 0.24 / 0.16
ICEPLANT / Carpobrotus spp. / Jun-July / 26 / 2.12 / 78 17 0.3 01 / 1.55 / 11.7
Smilax aspera / Sep-Nov / 7.3 / 0.06 / 84 42 01 04 / 0.24 / 0.16
GULL / Solanum nigrum / Aug / 7.2 / 0.05 / 82 43 01 10 / / / 0.16
Smilax aspera / Sep-Nov / 7.3 / 0.06 / 84 42 01 04 / 0.24 / 0.16
These data have been extracted and compiled from the following references:
Debussche M, Cortez J, Rimbault I (1987) Variation in fleshy fruit composition in the Mediterranean region: the importance of ripening season, life-form, fruit type and geographical distribution. Oikos 49:244-252
Herrera CM (1982) Breeding systems and dispersal-related maternal reproductive effort of southern Spanish bird-dispersed plants. Evolution 36:1299-1314
Herrera CM (1987) Vertebrate-dispersed plants in the Iberian peninsula: a study of fruit characteristics. Ecol Monogr 57:307-331
Traveset A, Riera N, Mas RE (2001) Ecology of fruit-colour polymorphism in Myrtus communis and differential effects of birds and mammals on seed germination and seedling growth. J Ecol 89:749-760