DOI: 10.5061/dryad.fk266
title: Data from: Evolution of larval competitiveness and associated life history traits in response to host shifts in a seed beetle

description: Resource competition is frequently strong among parasites that feed within
 small discrete resource patches, such as seeds or fruits. The properties
 of a host can influence the behavioral, morphological, and life history
 traits of associated parasites, including traits that mediate competition
 within the host. For seed parasites, host size may be an especially
 important determinant of competitive ability. Using the seed beetle,
 Callosobruchus maculatus, we performed replicated, reciprocal host shifts
 to examine the role of seed size in determining larval competitiveness and
 associated traits. Populations ancestrally associated with either a small
 host (mung bean) or a large one (cowpea) were switched to each other’s
 host for 36 generations. Compared to control lines (those remaining on the
 ancestral host), lines switched from the small host to the large host
 evolved greater tolerance of co-occurring larvae within seeds (indicated
 by an increase in the frequency of small seeds yielding two adults),
 smaller egg size, and higher fecundity. Each change occurred in the
 direction predicted by the traits of populations already adapted to
 cowpea. However, we did not observe the expected decline in adult mass
 following the shift to the larger host. Moreover, lines switched from the
 large host (cowpea) to the small one (mung bean) did not evolve the
 predicted increase in larval competitiveness or egg size, but did exhibit
 the predicted increase in body mass. Our results thus provide mixed
 support for the hypothesis that host size determines the evolution of
 competition-related traits of seed beetles; evolutionary responses to the
 host shifts were consistent among replicate lines but were asymmetric,
 with larval tolerance evolving as predicted, but not the reverse.
 Nevertheless, our results indicate that switching hosts is sufficient to
 produce repeatable and rapid, but asymmetric, changes in the competition
 strategy and fitness-related traits of insect populations.
description: Body mass at 36
 generationsThese data are the body
 masses for emerging beetles that are presented in Figure 1 of the
 manuscript (Fox & Messina). Each row is a single
 beetle.Egg length at 36
 generationsThese data are the size
 of eggs laid by emerged females (a subsample of the females from the body
 size dataset) that are presented in Figure 2 of the manuscript (Fox &
 Messina). Each row is a single female. Egg lengths are the average of
 three eggs, in mm. All eggs that are measured were laid on mung
 bean.Fecundity at 36
 generationsThese data are the
 lifetime fecundity of emerging females that are presented in Figure 3 of
 the manuscript (Fox & Messina). Each row is a single
 beetle.Larval competition
 experimentThese data are the
 survival, development time and body masses of beetles emerging from seeds
 containing either 1 or 2 larvae. These data are presented in Figures 4
 (survivorship), 5 (body mass) or 6 (development time) of the manuscript
 (Fox & Messina). Each row is a single beetle.