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<br />Arizona Game and Fish Department
<br />Draft EA: Kanab Ambersnail
<br />
<br />June 1998
<br />Page 22
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<br />successfully produce offspring, However, small populations tend to lose genetic variation by genetic
<br />drift more rapidly than larger populations (Lacey 1987), Also the longer a population remains small,
<br />the more genetic variation it will lose (Leberg 1992), Genetic drift, due to random sampling of genes
<br />during transmission from one generation to the next, can be most effectively controlled by keeping
<br />breeding populations large, If all adults contribute equally to the succeeding generations, founding
<br />population sizes of 50 or more individuals would experience ~ I % loss of heterozygosity to the next
<br />generation (LaCava and Hughes 1984), the maximum amount acceptable to animal breeders (Reed
<br />et ai, 1986), Periodic immigration can drastically reduce genetic drift away from characteristics of
<br />the source population, and as few as one immigrant per two generations could be beneficial (Lacey
<br />1987) Although KASs have little or no immigration (and gene flow) among isolated populations,
<br />sequential capture and release of new founder stock is possible for maintenance of genetic variation
<br />
<br />Stevens et ai, (I997a) reports KAS egg masses having a range of 5-25 eggs each, and mean egg mass
<br />density/m2 at VP (two dates in mid-August 1995) was 5,2 to 5,3 (SD=1 I ,9 and 15,0 respectively),
<br />A captive-breeding experiment on Novisuccinea chiltenangoensis (Molloy 1995) had six founder
<br />snails that produced 130 F, hatchlings from 220 eggs (13 egg masses), but only eight F 1 snails
<br />survived to maturity (a 3.6% survivorship) Of those eight F, snails, four produced egg masses for
<br />the next generation (Molloy 1995), In August 1997, 12 egg masses from VP were relocated to NAU
<br />along with 248 young KASs for an experimental population These egg masses are believed to had
<br />0% survivorship (pers, comm, C. Nelson), Because the viability and successful hatching of
<br />transported KAS egg masses is expected to be poor, a large number of egg masses would need to be
<br />collected for an establishment effort Obtaining sufficient numbers of egg masses (total 1000
<br />eggs/site with a 5% survivorship=50 mature KASs) would require more intensive searching (possible
<br />impact) of primary vegetation at VP,
<br />
<br />KAS egg masses would be difficult to distinguish from Catinella or Deroceras egg masses, Egg
<br />masses found on watercress at VP, in mid-summer, are >90% likely to be KASs (pers, comm L
<br />Stevens), In addition, there is considerable risk of losing KAS egg masses in transit due to
<br />desiccation and maintaining appropriate temperature and humidity levels (tolerances currently
<br />unknown), Once placed at new sites KAS egg masses are subject to predation or weather-induced
<br />displacement (heavy rains or winds),
<br />
<br />CHAPTER 4: LIST OF PERSONS AND AGENCIES CONSULTED
<br />
<br />"Dennis Kubly, Terry Johnson, "Mike Mallett, "Jeff Sorensen, and Richard Winstead, Nongame
<br />Branch, Arizona Game and Fish Department
<br />
<br />Vanessa Dickinson and Nancy Olson, Habitat Branch, Arizona Game and Fish Department
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