Results
Comparison of predicted values for co-occurrence and
presence-only
data
The average Δ CTI in the paired dataset (difference between pseudo and
co-occurrence assemblages ) for the study period (1905-2007) was low
independent of which calibration model was used, but it was
statistically significantly different when calibrating the transfer
function with the co-occurrence data only (Fig.2a-c; paired
t-test average difference = 0.062, std.error 0.016, t = 3.7068, df =
3,838, p-value <= 0.001). The model calibrated with
presence-only data showed an average difference of 0.029 (std.error
0.021, t = 1.35, df = 3,838, p-value = 0.17), and the model calibrated
with the combined dataset showed an average difference of 0.014
(std.error 0.021, t = 0.68, df = 3,838, p-value = 0.49). In all cases
the presence-only CTI were slightly higher than those of the
co-occurrence dataset.
Since the transfer function calibrated with the combined dataset
displayed the lowest difference in paired CTI (Fig. 2c ), we
relied on this calibration model as the basis for illustrating the
temporal pattern of thermophilization for both datasets (Fig.
2d ). This revealed that there was no statistically significant
difference between thermophilization trends base on the co-occurrence
and presence-only datasets, and that the thermophilization values
increased steadily around the same time (Fig. 2d ).