Clutch size and host use in butterflies - and how to measure diet breadth

• The utilization of host plants is a central aspect of herbivorous insect life-history and known to promote processes of diversification in this group. In species that aggregate their eggs, female selection of a suitable egg-laying site is especially important, since a large proportion of the realized fitness will depend on few oviposition events. A cluster of larvae also requires a large resource to complete development and thus resource size may further limit the range of suitable hosts. We investigated whether there is a relationship between clutch size and diet breadth for 206 nymphalid butterfly species, using phylogenetic comparative methods. Results were consistent across several taxonomic and phylogenetic diet breadth measures, suggesting that some taxonomic measures may be as good approximations as the more cumbersome estimates based on phylogenetic distance. Treating diet breadth and clutch size as continuous data indicated no relationship between the traits, while categorizing them into binary form showed that they evolve in a correlated fashion. The discordance between analyses indicated that clutch size may be constrained among extreme generalists, as polyphagous clutch layers were rare. We found clutch-laying to be a relatively conserved trait in the phylogeny and less flexible than variation in degree of host plant specialization. Host plant growth form did not influence the clutch size diet breath relationship, but was weakly correlated with both factors. We discuss the general role of conservative life-history traits, such as clutch size, for the evolutionary dynamics of more labile traits such as diet breadth among phytophagous insects.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

egg aggregation

Nymphalidae

host range

phylogenetic diversity

PD

comparative methods

herbivorous insects

host-parasite interaction

zoologisk ekologi

Animal Ecology

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)