DOI: 10.5061/dryad.dd3ph
title: Data from: Breaking and remaking a seed and seed predator interaction in the introduced range of Scotch Broom (Cytisus scoparius) in New Zealand

description: Introduced plants may initially experience enemy release but some of those
 interactions may be reinstated through biological control. These cases
 provide opportunities to explore the dynamics of broken and re-made
 consumer-resource interactions. The European shrub broom (Cytisus
 scoparius) was introduced to New Zealand without a specialist seed
 predator (Bruchidius villosus) until a biological control programme
 reinstated this interaction in 1988. Broom produces substantially larger
 seeds throughout its non-native range and there are differences in
 seedling establishment beneath broom canopies between the native and
 introduced ranges. We hypothesised that large broom seeds produce
 seedlings with a survival advantage in shaded conditions, consistent with
 establishment under broom canopies in the introduced range. We also
 predicted that the seed-feeding beetle would experience increased fitness
 in larger seeds. We found that seedling survival was correlated with seed
 weight in shaded conditions, consistent with the observed establishment of
 seedlings beneath broom stands in the non-native range. Beetle size was
 positively correlated with seed weight and female fecundity increased with
 body size. Comparison of the size distributions of beetle populations
 before and after hibernation provided indirect evidence that overwintering
 survival of beetles is also size-dependent. These findings are consistent
 with observed higher levels of abundance of B. villosus in New Zealand,
 compared to native habitats. Selection gradients for seed size-dependent
 seedling survival on broom occupancy were explored using the Rees-Paynter
 population model, demonstrating that a fitness benefit to the plant of
 large seed size through enhanced seedling survival beneath the parental
 canopy is only likely under low disturbance scenarios and moderate
 fecundity levels. Synthesis. The dynamics of biocontrol systems provide an
 under-exploited opportunity to examine the impact of removal and
 reinstatement of species interactions. Differences in seed size between
 native and non-native ranges may result from varying intensities of
 conflicting selection pressures acting on seed size. It remains to be seen
 whether a decline in seed size towards that seen in the native range will
 result from the biocontrol agent introduction, as we have demonstrated
 that selection pressures on seed size vary with disturbance mediated
 population turnover and fecundity.
description: Seed weight and seedling
 survivalVariables: id: unique
 identifier of individual seed/seedling, letter indicates the country of
 origin and the number is the unique seed number. 300 cases. A = Australia,
 B = England, C = Corsica, CH = Chile, F = France, NZ = New Zealand, S =
 Switzerland, U = USA. weight: seed weight in mg. country: identifier of
 country of origin of seeds, 8 cases. AUS = Australia, CHILE = Chile, CORS
 = Corsica, ENG = England, FRA = France, NZ = New Zealand, SW =
 Switzerland, USA = USA. range: identifier of native or exotic status of
 seed origin, two cases. Native = native range, Exotic = exotic/non-native
 range. block: identifier of experimental block, 4 blocks. days: day number
 with day = 1 indicating germination of the seed and entry of the seedling
 into the experiment. Each date that the seedling was observed as alive
 added an additional number of days to this number. This column was derived
 from the date column where observation dates are recorded. days_post_leaf:
 the number of days since first true leaf was observed. height: seedling
 height in cm. date: date of germination of seed and entry of seedling into
 the experiment. censor: indicates if seedling was observed alive (0) or
 dead (1) at each observation date.shade_expt.csvseed size and beetle size North IslandVariables: site: 5 sites on the North Island of New Zealand. Poutu, Masterton, Frost flat, Mangahao River, Palmerston North. plant: unique plant identifier within each site. seed_size_mg: mean weight of uninfested broom seeds in mg within each plant log_seed_size: natural log of seed_size_mg. beetle_sex: sex of beetles, M=male, F=female. elytra_area: mean area of the beetle elytra in mm2. Cases: each row represents mean measurements on multiple beetles of the same sex (m/f) and mean seed size (mg) of uninfested seeds per plant in each of 5 sites.an1_N_island.csvseed size and beetle size means all sitesVariables: site: 13 sites in North and South islands of New Zealand, two records per site as male and female beetles were treated separately. East Block (Lincoln, Canterbury), FF (Frost Flat, Waikato), Hanmer Pasture (Canterbury), Hanmer River (Hanmer Riverbed, Canterbury), Hanmer Forest (Canterbury), Jack’s Pass (Canterbury), Mangahao River (Manawatu - Wanganui), Masterton (Wellington), PN (Palmerston North, Manawatu – Wanganui), Poutu (Manawatu – Wanganui), Taitapu Alt (Canterbury), Waimakariri Forest (Canterbury), Wimakariri River Bed (Canterbury). 14 sites mentioned in main text but one of these had no beetles (Waiouru, Manawatu – Wanganui). seed_size_mg: mean of seed size from multiple plants per site. log_seed_size: natural log of seed_size_mg. elytra_area: mean of elytra area for beetles on multiple plants per site, mm2. beetle_sex: sex of beetles. Cases: each row represents the mean of one sex of beetles from multiple plants per site. One male and one female beetle per plant were measured. Two seeds (each containing a beetle) were measured per plant.an2_means_all_sites.csvbeetle size and beetle fecundity 2007 & 2008Variables: elytra_area: elytra area of individual beetles in mm2. log_elytra_area: natural log of elytra_area. eggs_laid: number of eggs laid by individual beetles. log_eggs: natural log of eggs_laid. year: year of measurement, 2007 or 2008. Cases: each row represents data from one female beetle whose fecundity and size were recorded in the lab.size_fecundity_2007_2008.csvbeetle size before & after winterVariables: site_code: 3 sites, eb (East Block, Lincoln), pn (Palmerston North), po (Poutu). All three sites were visited in 2007-2008 but only pn was visited in 2010-2011. pre_post: pre, post. Factor with two levels pre and post hibernation size. sex: m=male, f=female. elytra_area: size of beetle elytra in mm2. year: 2008, 2011.size_before_after_all_years.csv