Ms. Gaines et al., THE EFFECTS OF HABITAT FRAGMENTATION ON THE GENETIC-STRUCTURE OF SMALL MAMMAL POPULATIONS, The Journal of heredity, 88(4), 1997, pp. 294-304
We present five case studies highlighting the effects of habitat fragm
entation on the genetic structure of small mammal populations. The stu
dies reflect different spatial scales and components of genetic variat
ion, In marginal and central populations of Sigmodon hispidus we found
less allozymic variation within the marginal population, whereas patt
erns of morphological variability were the converse. In the rice rat (
Oryzomys spp.), nucleotide diversity in mtDNA was similar in an island
population in the Florida Keys to mainland populations in the Evergla
des, This observation contrasts with insular vole populations (Microtu
s spp,), where isolation on islands results in genetic structuring, Te
mporal changes in abundance in mainland populations had no effects on
genetic differentiation (F(ST)values) because subpopulations did not e
xperience bottlenecks, In an experimentally fragmented landscape, frag
mentation influenced demographic processes but not genetic structure,
We conclude that (1) with extreme fragmentation, small mammal populati
ons become depauperate of genetic variation and differentiate genetica
lly; (2) different components of genetic variation lead to different g
enetic structuring; (3) spatial and temporal scales should both be con
sidered when examining genetic structure of populations; (4) demograph
ic and ecological processes are more likely influenced by fragmentatio
n than genetic structure; and (5) there is an interaction between demo
graphic processes and genetic structure.