Assessment of species abundance from metabarcoding data
After selecting the spider families that were present in at least 10
communities, we built beta regression models with data for the remaining
14 families. Seven of the families provided appropriate models for the
proportion of weight, and six families did so for the models relating
proportion of reads and proportion of individuals (Fig. 5). In the
families for which an adequate model could not be fitted, there was
still a positive correlation between the two variables.
Although the relation between RRA and weight or abundance was positive
in all models, its slope varied across spider families. Even in the
three families where both models had a p > 0.05, the two
curves were almost overlapping in two of the families (Lycosidae and
Salticidae) but rather different in the third (Clubionidae). Also, in
some families the observations were consistently above or below the 1:1
line. In the plots linking RRA and abundance of individuals, funnel-web
(Agelenidae) and cob-weaving spiders (Theridiidae) were above the 1:1
line, while ghost spiders (Anyphaenidae) and ground-dwellers
(Clubionidae) were mostly below. In the plots linking RRA and mass,
Clubionidae ground-dwellers, Philodromidae crab spiders and Theridiidae
cob-weavers were above the 1:1 line, while Agelenidae funnel-weavers,
Araneidae orb-weavers, Gnaphosidae ground-dwellers and Lycosidae wolf
spiders were mostly below.
DISCUSSION