Table 2. Comparison of yearly euglossine bee census counts (paired ttest) to establish whether change occurred over a 20-yr interval (1980-1999 or 2000). Abundances in May and February for 33 species were compared, using the mean for 16 or 17 census years and the monthly census for 1999 or 2000. “Trend” is the tally of species displaying each of the three trends assessed by regression analysis over the indicated intervals.


Trend
Month
Period
No. years
Mean abundance per species
df
t
P
Up
Down
None
May
1999
1
21.42
32
1.47
0.15
16
8
9
May
1980-1999
17
16.56






February
2000
1
8.87
32
-1.35
0.19
4
15
14
February
1980-2000
18
11.54