The proportion of insect taxa carrying pollen and the taxonomic richness of pollen carried
We collected 1,583 individual insects from 41 families, representing 10 orders. Diptera were the most abundant insect order that we sampled (911 individuals – 57% of total abundance), followed by Coleoptera (372 individuals – 23.5%), Lepidoptera (139 individuals – 9%) and Hymenoptera (77 individuals – 5%) (Table S1). Individual insect orders responded to changes in land-use intensity differently: Coleoptera, Diptera and Hymenoptera were more abundant in cropping and dairy land-uses compared with forest areas and avocado orchards (Figs. 1a-c).
We found that 373 (~24%) insects collected were carrying pollen and this varied by land-use type (Table S1). Dairy and crop sites supported the greatest number of pollinator families and individuals, but we found no statistically significant difference in the proportion of pollen carrying individuals among land-uses. Less than 25% of individuals sampled in each land-use were carrying pollen (Fig. 2a). Dominant pollen carrying insects comprised 10 families of Diptera (with 220 pollen carrying individuals - 59% of all pollen carriers) 9 families of Coleoptera (88 pollen carriers – 23.5%), unclassified Lepidopterans (24 pollen carriers – 6%) and 9 families of Hymenoptera (21 pollen carriers – 5%). We also found non-traditional insect groups carrying pollen such as spiders (Arachnida) and bugs (Hemiptera), however these were sampled in low numbers and were not included in order-level analyses (Table S1). There was no difference in the proportion of pollen carriers among insect orders (Fig. 2b).
A total of 3,369 pollen grains were sampled from 16 plant families – the most prevalent being Poaceae (1,233 grains - 37%), Asteraceae (960 grains – 29%), Myrtaceae (556 grains - 16%) and Amaranthaceae (407 grains - 12%) (Table S2). The number of plant families carried as pollen was highest in dairy and cropping land-uses (Fig. 2c). Diptera and Coleoptera carried the highest richness of pollen respectively, while Lepidoptera carried significantly less pollen richness than Diptera (Fig. 2d). Coleoptera carried eight of all recorded pollen families, Diptera carried 10, Hymenoptera carried 11 and Lepidoptera carried seven pollen families (Table S2).