How to better predict long-term benefits and risks in weed biocontrol: an evolutionary perspective.

Classical biological control (also called importation biological control) of weeds has a remarkable track record for efficiency and safety, but further improvement is still needed, particularly to account for potential evolutionary changes after release. Here, we discuss the increasing yet limited evidence of post-introduction evolution and describe approaches to predict evolutionary change. Recent advances include using experimental evolution studies over several generations that combine -omics tools with behavioral bioassays.

Evolving while invading: rapid adaptive evolution in juvenile development time for a biological control organism colonizing a high-elevation environment.

We report evidence of adaptive evolution in juvenile development time on a decadal timescale for the cinnabar moth Tyria jacobaeae (Lepidoptera: Arctiidae) colonizing new habitats and hosts from the Willamette Valley to the Coast Range and Cascades Mountains in Oregon. Four lines of evidence reveal shorter egg to pupa juvenile development times evolved in the mountains, where cooler temperatures shorten the growing season: (i) field observations showed that the mountain populations have shorter phenological development; (ii) a common garden experiment revealed genetic determination of phenotypic differences in juvenile development time between Willamette Valley and mountain populations correlated with the growing season; (iii) a laboratory experiment rearing offspring from parental crosses within and between Willamette Valley and Cascades populations demonstrated polygenic inheritance, high heritability, and genetic determination of phenotypic differences in development times; and (iv) statistical tests that exclude random processes (founder effect, genetic drift) in favor of natural selection as explanations for observed differences in phenology. These results support the hypothesis that rapid adaptation to the cooler mountain climate occurred in populations established from populations in the warmer valley climate.

The statistical analysis of insect phenology.

We introduce two simple methods for the statistical comparison of the temporal pattern of life-cycle events between two populations. The methods are based on a translation of stage-frequency data into individual 'times in stage'. For example, if the stage-k individuals in a set of samples consist of three individuals counted at time t(1) and two counted at time t(2), the observed times in stage k would be (t(1), t(1), t(1), t(2), t(2)).

Effects of Vegetation Disturbances on Insect Biological Control of Tansy Ragwort, Senecio Jacobaea.

Our study had two major objectives: (1) to clarify the roles of buried seed and different types of localized disturbance in activating outbreaks of a pasture weed (tansy ragwort, Senecio jacobaea), and (2) to measure the effectiveness of two natural enemies (the cinnabar moth Tyria jacobaeae and a ragwort flea beetle, Longitarsus jacobaeae) in inhibiting weed population increase and spread. We conducted a 5-yr field experiment on the coast of Oregon using a randomized-block design with four blocks x three levels of disturbance (background vegetation was Tilled, Clipped, Unaltered) x two levels of cinnabar moth (Exposed, Protected) x two levels of flea beetle (Exposed, Protected) = 48 plots (each plot was 0.25 m^2).

Wind Dispersal Distances in Dimorphic Achenes of Ragwort, Senecio Jacobaea.

A mark-recapture study of wind-dispersed achenes of Senecio jacobaeo conducted in western Oregon showed that the proportion of achenes dispersing a given distance varied significantly with changes in site (inland vs. coastal), surroundings (mown vs. unmown), height of release (0-50, 50-100, 100-150, 150-200 cm), time of release (early vs late in the season), direction of dispersal, and achene type (disk vs.

Dormancy and dispersal in dimorphic achenes of tansy ragwort, Senecio jacobaea L. (Compositae).

Marginal and central florets of the capitula of tansy ragwort Senecio jacobaea yield different kinds of fruit. The central ("disk") achenes are lighter (x±SE=199±5μg), more numerous (x±SE=58±0.6 achenes per head), and are equipped with a pappus aiding wind transport and rows of trichomes aiding animal transport.