Given population declines, increased fragmentation and isolation, and reduced colonization of many native Wisconsin species, we presume many populations are also declining in genetic diversity and/or experiencing inbreeding. These represent important long- and short-term genetic risks to population viability (Lande 1995, Lynch et al. 1995, Hedrick 2001, Keller and Waller 2002, Hedrick 2004, Allendorf and Luikart 2006). Furthermore, differences in dispersibility among species – inferred from their spatial scales of genetic differentiation and apparent gene flow within and among populations (Vekemans and Hardy 2004) – can affect site occupancy and metapopulation dynamics (Verheyen et al. 2003, Vellend et al. 2006).
We propose to measure the amount and spatial patterning of genetic variation within and among populations of about 40 focal species using RADseq markers (Davey et al. 2011). The species studied will be chosen from the species showing significant increases OR decreases in abundance in N and S upland forests (Wiegmann and Waller 2006, Rogers et al. 2008, Rogers et al. 2009). We will also seek to choose taxa within each dynamics-by-latitude group that differ in dispersal mechanism (gravity, animal, wind) to test the hypothesis that population structure reflects dispersal traits (ef. Williams 1994).
Our goals are to (a) quantify the amount and spatial pattern of genetic variation within and among populations of species that have undergone significant increases or declines over the last 50 years; (b) estimate the spatial scale of gene flow in these species as a proxy for dispersal ability; and (c) relate variation in these patterns to species’ functional traits, patch occupancy, and landscape context. We predict that species south of the Tension Zone (where fragmentation is more common), or those showing more fragmented ranges, greater declines in abundance, lower site occupancy, smaller spatial scales of gene flow (dispersal), or disperal mechanisms likely to result in less long-distance seed movement (e.g., myrmecochory, seed dispersal by ants) will be associated with lower local genetic diversity and greater differentiation among populations.