Density, Dispersion, and Population Structure in Drosophila Pseudoobscura

摘要: Wild D. pseudoobscura flies were captured, marked, and released in relatively low numbers at nine separate, centrally located sites each of two Colorado, U.S.A., locations midsummer 1970. The marked by spraying with micronized dusts which fluoresce characteristic colors under ultraviolet light. are harmless, they mark the well, not transferred from one fly to another. trapping design extending out central release points contained additional traps on eight evenly spaced radii. Data number unmarked recaptured, outlying provided maximum likelihood estimates adult density dispersion. These data adjusted for presence a sibling species, lowei, means an accurate morphological technique permits classification kinds males. Preliminary analyses indicated that dispersal made during evening activity period 1 day after pertain mostly dispersion intervening morning period, when no exposed. It was necessary base both days following only few or had been exposed habitat. minimum attractive radius trap approximately 46 m. similar, averaging 0.38 flies/100 m2. An independent much simpler estimate density, based captured center trap, gave inconsistent results. This attributed accidental interference normal activity. mean distance (d) (presumably period) 176 202 m locations. mean—squared (d2°) 97 146, respectively, units 400 first location more reliable because those homogeneous extensive. patterns observed agreed well Brownian motion expectations basis comparing first— second—order moments dispersed. permitted construction graphs depict spread increasing periods. parameter °, standard deviation dispersed along direction two—dimensional environment, estimated @ assumption (°b.m.) without this (°D.F.). refer At values 141 139 m, respectively; second 162 171. Closer inspection patterns, accompanied further data, revealed departure probably serious underestimates true rates. A certain proportion rapidly outside experimental area release. Using 95.3% daily survival flies, 2—day suggested than half moved beyond earlier experiments pseudoobscura, conducted Dobzhansky Wright California, re—analyzed present methods. Midsummer wild Colorado one—seventeenth Mt. San Jacinto southern three—fifths Mather Sierra Nevada California. Comparison °d.f. rate 50% greater laboratory even though latter opportunity difference may result partly adaptive strategy habitats, fundamentally different behavior flies. large (which due areas) California suggest natural populations broken up into very small breeding within allelic variation could be stored genetic drift. Wright's panmictic circle concept yielded effective population size (Ne) between 1,000 10,000 According existing theory, these enough maintain diversity known exist enzyme loci. need sophisticated determine components most closely associated distribution emergence parents offspring is discussed.