Temperature-Dependent Alterations in Host Use Drive Rapid Range Expansion in a Butterfly

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Science  25 May 2012:
Vol. 336, Issue 6084, pp. 1028-1030
DOI: 10.1126/science.1216980

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  1. Fig. 1

    Distribution and density changes of the brown argus butterfly. (A) Occurrence of brown argus in 10 × 10 km grid squares that contain rockrose (red) and Geraniaceae only (blue). Records from the period 1970–1987 [before the increase in use of Geraniaceae (B)] are in dark shades; new 10 × 10 km squares colonized in the period 1988–2009 are in light shades. (B) Increase in the fraction of brown argus distributional records from 10 × 10 km grid squares where only Geraniaceae hosts are present. (C) Mean annual density (count per kilometer) of brown argus in rockrose (solid line, solid symbols) and Geraniaceae (dashed line, open symbols) sites from 1976–2009. (D) Same as for (C), but separating 1995 to 2009 population counts into numbers for first (squares) and second (circles) adult flight periods each year. Photographs are (E) Brown argus [Jim Asher/Butterfly Conservation]; (F) rockrose [Rachel Pateman]; and (G) dove’s-foot cranesbill [Alison Jukes].

  2. Fig. 2

    Estimated decadal net increase (positive) or decrease (negative) in the fraction of all brown argus occurrences associated with Geraniaceae sites in the past (solid line, solid circles). Difference in estimated annual population growth rates, averaged across decades, between Geraniaceae and rockrose sites (mean for Geraniaceae sites minus mean for rockrose sites) (long dashed line, open circles; positive values indicate higher relative population growth on Geraniaceae, and negative values indicate higher performance on rockrose). MST for each decade (short red dashed line and triangles). Dates on scale bar refer to first year of each decade for which estimates have been calculated.

  3. Fig. 3

    Availability of rockrose and cranesbill in the landscape. 100 × 100 m grid squares with records of rockrose (red symbols), dove’s-foot cranesbill (blue symbols), or both species (purple symbols) in two well-recorded counties: (A) Bedfordshire and (B) Suffolk. Rapid range expansion took place in Bedfordshire and Suffolk, associated with the increased use of dove’s-foot cranesbill and other Geraniaceae.