VAGILITY IN AN EPHEMERAL HABITAT SPECIALIST EXPLAINS PANMIXIA: A RECENT RANGE EXPANSION AND RETRACTION DO NOT

Use of ephemeral habitats may lead to high vagility and an increase in gene flow and panmixia across a species' range. Range expansions associated with habitat alterations may also spur connectivity among previously isolated habitats and reduce genetic diversity at the colonization front. A century and a half of historical and modern single nucleotide polymorphism (SNP) data for Bachman's Sparrow (Peucaea aestivalis) demonstrate that panmixia is characteristic of this ephemeral habitat specialist, not a byproduct of a recent range expansion or retraction. Furthermore, high vagility has apparently dampened expected genetic signatures at the colonization front where no consistent signal of lower genetic diversity was observed in the extralimital region compared to other regions during expansion or retraction. Overall, our data support an emerging pattern of limited genetic structure for a species associated with ephemeral habitats, for which high vagility may have evolved to help individuals locate transient habitat across large spatial scales. Nevertheless, extensive habitat loss and fragmentation in recent decades have begun to influence genetic variation in P. aestivalis with small but significant increases in genetic structure. If this exceptionally vagile ephemeral habitat specialist is unable to reach remaining isolated habitat fragments, it is likely that barriers to its dispersal are limiting gene flow in other species, even those thought to be capable of traversing long distances.