3.2 Pollen DNA metabarcoding and plant-pollinator interactions
Pollen DNA metabarcoding yielded interactions between the collected
insects and 112 plant taxa. Among these, 81 (72.3%) were assigned at
species level, 28 (25%) at genus level, and 3 (2.7%) at family level.
Plant taxa found in the overall pollen transported by insects on each
island ranged between 9 and 58 (mean 26.4 ± 16.7), while the mean number
of pollen plant taxa transported by each sampled insect was 3.5 ± 2.1.
In plant-pollinator networks constructed from the DNA metabarcoding
data, the Connectance index resulted significantly and negatively
associated with the Edge density (Fig 2 b) and network size (Table 1).
Individual pollinator degree resulted significantly, positively related
to the Edge density. However, the responses of different insect species
among the widespread and most abundant ones were not homogeneous in this
case, as the values of this index significantly increased in the biggest
bee Xylocopa fenestrata ( βi = 14.9 ; p =
0.001), while it was not significant in the case of the two smaller
bees: Lasioglossum albescens ( βi = 2.94
; p = 0.52) and Braunsapis picitarsis( βi = -6.02; p = 0.24) (Fig 3).
[Fig. 2]
[Fig. 3]
[Table 1]