Is the winter survival area of Empoasca fabae continuously expanding?

O_LIEmpoasca fabae is a migratory pest that overwinters in the Southeastern United States (US) and damages crops throughout its summer range in North America. Its spring arrival has advanced by 9.7 days between 1951 and 2012, and increased damage is linked to warmer conditions that accelerate host and pest development. Yet whether this advance is also associated with a northward expansion of its winter survival area remains an open question. C_LIO_LIHere, we analyzed 126 years of minimum temperature data across the contiguous US to address this question. Using its winter survival threshold (-9{degrees}C), we calculated the annual winter survival area for E. fabae (temperature-only) and tested for time-series trends. We also mapped the potential overwintering area (temperature + winter hosts) under evergreen and pine-only forest scenarios. C_LIO_LIThe estimated winter survival area varies over 126 years, showing a nonlinear pattern. However, we found no significant trend, change-point year, or rate of change. This lack of significance was also observed when considering the 1951-2012 period. C_LIO_LIThe Southeastern US remained consistently suitable for winter survival, while the northern edge varied latitudinally, especially within the range of 35{degrees}-40{degrees}N, with no clear trend. C_LIO_LIPotential overwintering areas extend into Central Florida and the Texas Gulf Coastal Plain but exclude parts of Tennessee. In the pine-only scenario, the area in Mississippi and Alabama would be smaller. C_LIO_LIThe winter survival area for E. fabae has not continually expanded. The Southeastern US area remains suitable for over 126 years, whereas the northern range varies dynamically. C_LI GRAPHICAL ABSTRACT AND HIGHLIGHTS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/727670v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1062508org.highwire.dtl.DTLVardef@696e4borg.highwire.dtl.DTLVardef@1c7ff29org.highwire.dtl.DTLVardef@14109c5_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIThe winter survival zone (temperature only) of Empoasca fabae has not expanded continuously over the past 126 years. C_LIO_LIThe Southeastern United States remained suitable over this period, with the maximum northward extent of potential survival reaching 45{degrees}N and high variation within the range of 35{degrees}-40{degrees}N. C_LIO_LIUpdated potential overwintering zones (temperature + winter hosts) extend into Central Florida and the Texas Gulf Coastal Plain. C_LI