| dc.description.abstract | Genetic analyses of two endangered species of mammals in the Lower Keys of
Florida (Lower Keys marsh rabbit, LKMR, Sylvilagus palustris hefneri; silver rice rat,
SRR, Oryzomys palustris natator) were performed to evaluate the genetic structure of
their populations. Mitochondrial sequence data (control region; 763 base pairs (bp),
LKMR; 788 bp, SRR) were used to explore patterns of genetic variation within and
among island populations in both species. Analysis of the SRR also included 8
polymorphic nuclear microsatellite loci (9 to 16 alleles). Phylogenetic analyses of
mitochondrial sequence data for both species revealed two main lineages corresponding
to eastern and western localities, with high levels of genetic structuring (LKMR FST =
0.982, SRR ΦST = 0.916). The two species differed in the level of sequence divergence
between eastern and western populations (LKMR, 19 bp; SRR 4 bp). In addition to an
overall similar pattern of genetic subdivision, populations of both species possessed low
levels of mtDNA variation (haplotypic diversity in the LKMR = 66.1%, SRR = 58.6%).
Microsatellite analyses of the SRR revealed subdivision between eastern and western
regions. Although less pronounced than the structure observed in mtDNA, the overall pattern was still apparent. Additional examination of divergence between mainland and
Lower Keys rice rats revealed a genetic division that indicated a lack of recent gene
exchange between the regions (i.e. no shared haplotypes, the presence of private alleles,
and distinctive separation in numerous analyses). Although this degree of division does
not warrant species designation, the levels and patterns of divergence, both
morphological and genetic, do suggest genetic isolation of mainland and island forms.
This fact, along with restricted gene flow between the Lower Keys and the Everglades,
suggests that the SRR is on an evolutionary trajectory separate from its mainland
counterparts and validates its identification as a separate subspecies, Oryzomys palustris
natator. Finally, the genetic division between eastern and western populations of the
SRR and LKMR suggests that populations of both species in these two regions of the
Lower Keys should be treated as separate management units, especially when
considering the enhancement of populations via translocations. | en |
