Hilchie 1982 QEv18n1_4 91_126 CC released.pdf - College of ...

Philanthus albopilosus Cresson 121
Figure 10. Distribution patterns of Philanthus albopilosus through lime, a) 70.000 B.P. hypothetical range of ancestral
stock, b) Ca. 17,000 B.P. geographic isolation of ancestral stock at the zenith of the Wisconsin, c) Ca. 7,000 B.P.
expansion of ranges from refugiom. d) recent distribution of (I) Philanthus albopilosus albopilosus (dark race) and P. a.
manuelito (pale race).
cover and being subject to wind erosion. Maximal rates of range extension may have occurred
during the Hypsithermal due to increased dune and blowout development.
In the southwestern United States, arid regions may have persisted during Wisconsinan
glaciation, permitting dune fields to remain active. Sonoran Desert floras were derived
relatively recently (Axelrod, 1979). The great diversity is due to a 'vacuum' effect, floristic
elements from surrounding zones which adapted to increasing arididty and temperature,
provide the bulk of taxa. A rise in rainfall of 250 to 300 mm would eliminate the Sonoran
Desert as a regional lowland. This would allow an oak-conifer association to cover much of the
lowland. Axelrod's data suggest that taxa survived on the driest sites in bordering zones.
A portion of the american southwest is proposed as a refugium for the southern subspecies,
P. albopilosus manuelito . Very few sites suitable for a northern refugium are available east of
the Mississippi River (Thorp et al., 1952). Most of eastern North America was cloaked in a
continuous forest (Ross 1970, Martin 1958, Freitag 1973, and others). On the Great Plains,
several sand dune areas were probably active during portions of the Wisconsinan glaciation.
Smith (1965) demonstrated that there were several periods of dune building on the Nebraska
Sand Hills, based on past movement of stabilized dunes. This large dune area may have served