Outline of Quino Recovery Plan - The Xerces Society

al. 1975, Boughton 2000). A phenological mismatch was observed in southern
California in 1996 when first instar larvae were found on plants that were
already dying, making it highly unlikely that they would support the larvae to
diapause (Parmesan, in press). In general, weather conditions that speed the
plant life cycle relative to that of the insect, such as warm, cloudy weather,
causes increased larval mortality (Singer 1983, Boughton 1999). Conversely,
conditions that slow the plant life cycle relative to that of the insect increase
larval survival. Microtopographic heterogeneity and associated microclimate
heterogeneity, on a scale that allows larvae and ovipositing adults to select
among sites, should help prolong occupancy of habitat patches (Singer 1972;
Singer and Ehrlich 1979; Weiss et al. 1987, 1988; Osborne and Redak 2000).
4. Metapopulation Structure
Distribution of the Quino checkerspot butterfly is patchy at many geographic
scales. Local resources are not evenly distributed on the scale of meters, clusters
of hostplant micro-patches are unevenly distributed to form habitat patches at the
scale of kilometers, and these in turn are patchily distributed at even larger scales
to form networks of connected habitat patches. Occupancy of habitats at each
scale is influenced by habitat patch colonization and extirpation rates at that
scale.
Local habitat patch occupancy can be maintained on a set of small patches of
hostplant (micro-patches) within a habitat patch separated by open ground or
chaparral, provided that the host micro-patches are within the typical flight range
of the butterflies (about 50-200 meters (160-660 feet)). At this scale, adult
butterflies could be expected to move among micro-patches each season. To
estimate the amount of food resources necessary to maintain a local patch,
assume that 100 adults, with a balanced sex ratio, might be typical within a
habitat patch. Life-history data from the field (Singer 1972, Moore 1989)
indicate that in a population that is neither increasing nor decreasing, each mated
female would produce, on average, 3 to 4 adults, some of which would emigrate
or fail to reproduce. If a mated female lays 3 to 4 clusters, then each egg cluster
would generate, on average, a single adult. Based on these assumptions, in a
population of 100 adults, 50 females would each need to find 3 to 4
micro-patches, so a local habitat patch would need 50 x (3 to 4), or 150-200
suitable micro-patches of 20 (or more) plants to support the habitat patch's
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