Results
Stream temperatures varied across habitats based on latitude and
elevation, as expected (Figs. 1, 2). Maximum stream temperatures were
lower at latitudes above than latitudes below 35°N, but minimum stream
temperatures were similar across latitudes (Fig. 1, Table 1a,b). Thermal
breadths were lower at latitudes above compared to latitudes below 35°N
(Fig. 1, Table 1c). We did not observe broad categorical elevation
trends with any stream temperature metric (Fig. 2, Table 1 d.e, and f ).
Importantly, geographic information was not included for 74.8% of totaln = 229 records of stream maximum and minimum temperatures and
calculated thermal breadths (Figs. 1, 2). Maximum stream temperature and
thermal breadth were linearly related to habitat elevation (Fig. 3a
Table 2 s), whereas minimum stream temperature was not related to
elevation (Fig. 3a, Table 2). In contrast, stream latitude was not
linearly related with any stream habitat temperature variable (Fig. 3b,
Table 2).
We found that habitable maximum temperatures varied across voltinism and
among functional feeding guilds of species (Table 3, Figs. 4a-4c).
Specifically, multivoltine taxa had higher maximum stream temperatures
than univoltine and semivoltine taxa (Fig. 4a). Collector-gatherers
tended to have higher maximum stream temperatures (Fig. 4b), however,
effects of stream temperature among taxonomic Order were not clearly
evident (Fig. 4c, Table 3, 4). We detected significant interactions
among voltinism and feeding guilds (Table 3), however, we did not detect
differences in maximum temperatures and thermal breadth among
interactions with functional feeding guilds, voltinism, or taxonomic
Order (Figs. 4a-4c).