INTER-POPULATIONAL DIFFERENTIATION AND ADAPTATION IN THE PERENNIAL, DIPLOID SPECIES FRAGARIA VESCA L.

Inter-populational differentiation and adaptation in California Fragaria vesca L. were examined using plants collected from 13 natural sites, grown in a common greenhouse and analyzed for 25 quantitative traits and 2 enzyme systems. Inter-populational variation was estimated by analysis of variance and genetic identity techniques, and microand macro-environmental measurements were made at each site. Stepwise multiple regressions were completed on the morphological-environmental variations and the allozyme frequency-environmental variations. Clonal propagules were compared under three controlled environmental conditions. F. vesca likely has undergone considerable ecological differentiation since significant inter-populational variation was observed in many polygenic and monogenic traits. Numerous significant correlations between environmental and character variations were found, and in many, only a few environmental variables "explained" much of that variation. Inter-populational differences in the abilities of plants to accumulate biomass and survive under salt, nutrient and shade stresses were also found. Although many of the ecotypes of F. vesca showed some phenotypic plasticity, the species is a "specialist." Variations in root/shoot ratios occurred in biotypes grown under different conditions. Plants generally allocated more energy to aboveground biomass under shade stress and to root biomass under nutrient stress. MANY PLANT SPECIES have broad ecogeographic ranges. Two hypotheses have been proposed concerning the genetic basis of this flexibility. Either the species are "generalists," capable of surviving in diverse environments or "specialists," made up of a complex of variant ecotypes, each adapted to a specific environment (Baker, 1965; Marshall and Jain, 1968; Levins, 1968; Lewontin, 1957). Many studies have shown patterns of variability, apparently representing ecotypic differentiation. Morphological patterns have been described in Plantago maritima (Turesson, 1922 and 1925), Achillea borealis, Potentilla glandulosa (Clausen, Keck, and Hiesey, 1940, 1948), Geranium purpureum (Baker, 1957), Geranium sanguineum (B0cher and Lewis, 1962), Panicum virgatum (Quinn, Rotsettis, and Fairbrothers, 1972), and Veronica peregrina (Linhart, 1974). Allozyme variations have been shown in Avena barbata (Hamrick and Allard, 1972), Lycopersicon cheesmanii (Rick and Fobes, 1975), Taraxacum officinale (Solbrig and Simpson, 1974), Lupinus texensis (Babbel and Selander, 1974), and Erigeron annuus (Hancock and Wilson, 1976). In all these studies, habitat differences were correlated with inter-populational or intra-populational genetic variation. I Received for publication 21 February 1978; revision accepted 1 June 1978. Generalist types have also been described. Some examples of these are: Eupatorium microstemon (Baker, 1965), Festuca ovina (Bradshaw et al., 1971), Typha latifolia (McNaughton et al., 1974), and weedy species in general (Baker, 1965; Mayr, 1965). Biotypes with these traits have also been observed in Potentilla glandulosa (Clausen, Keck, and Hiesey, 1948) and in Mimulus guttalus (Vickery, 1974). These can survive and reproduce over a broad range of environments. Fragaria vesca provides excellent material for studying adaptive strategies. In California, it is found in a broad range of environments from the coastal fog belt to the Sierra Nevada and Cascade mountains, and from the San Jacinto mountains near the Mexican border to Oregon. It is hermaphroditic, self-compatible, and reproduces both sexually and asexually (by runners). The purpose of this study was to determine whether F. vesca is a generalist or specialist species. MATERIALS AND METHODS-Thirteen diverse sites were selected for study (Table 1). These sites represent most of the California environmental range of F. vesca. Over a one-month period (July 15 to August 18, 1975), runners were taken from 50 separate clones at each site whenever possible and soil samples were collected from 5 cm beneath every tenth individual sampled. Runner plants were set in a greenhouse in