Proboscis morphology suggests reduced feeding abilities of hybrid Limenitis butterflies (Lepidoptera: Nymphalidae).

Hybridization provides the opportunity to study speciation processes. Studies of hybridization in butterflies provide evidence for a range of life-history traits that result in reduced fitness of the hybrid offspring, but no previous studies have examined the feeding ability of adult hybrids. Butterfly mouthpart (proboscis) architecture relates to functionality and is an important structure for fitness, because malformed proboscises would hinder feeding and nutrient acquisition. The proboscis architecture of hybrid Limenitis butterflies (' rubidus ' form) was compared with parental types to determine whether hybrids might have a proboscis that impedes feeding. Scanning electron microscopy was used to image proboscises, and 12 measurements were recorded from each individual. Linear discriminant and hierarchical clustering analyses indicated that the proboscis architecture of hybrid butterflies groups separately from the parental types. The results also revealed that hybrids have a reduced proboscis compared with the parental types, which could be maladapted for feeding. Sexual dimorphisms for some structures in hybrids suggest that certain genes responsible for proboscis architecture might be sex linked. The reduced proboscis length and width of F1 hybrid females could be one reason why they have not been observed in the wild, providing an example of environmental selection associated with Haldane's rule. [ABSTRACT FROM AUTHOR]