3.2 Spatial Analysis
The appearance of among-population genetic variation can be influenced
by isolation by distance, in which geographically proximate populations
are more closely related. Isolation by distance can also affect the
appearance of genotypic correlations because data from different
populations is not independent. We therefore tested first for evidence
of spatial autocorrelation. Spatial autocorrelation was significant
among the populations both for the mean values of the circadian period
and the range of family values within each population. Clustering of
populations was limited to two specific “hot spots,” and these
accounted for the autocorrelation. First, two populations located at
highest elevation within the Snowy Range (Libby Flats (LIB) and Lewis
Lake (LEW)) had similar values for circadian period. Second, the three
easternmost populations, located in the Laramie Range of SE Wyoming
(populations Crow Creek (CRW), Happy Jack Trail (HJT), and Middle Crow
Creek (MCC)), had similar values for population mean and
within-population range. Outside of these two clusters, values were
randomly spaced across the populations. Further results are presented as
observed and after adjusting for the occurrence of spatial
autocorrelation.