Effects of agroecosystem land use on the diversity, abundance, and ecosystem functions of insect pollinators of passion (Passiflora edulis) crop

Abstract

Worldwide, crops that require wild pollinators are showing a deficiency of pollination and genetic variation. In the recent past, studies show that there has been a steady decline in production of passion fruits in Kenya. In this study, the major objective was to investigate factors causing the decline of passion fruit production using ecosystem concepts, agricultural practices and social-ecological factors using the case scenario of Mua hills in Machakos County.

The study was carried out during the wet season December, 2015 and the dry season early March, 2016. The farms sampled in each Agro-ecological zone were categorized according to three land use types; horticulture, mixed cropping, and natural patches near each farm which served as the control sites. During sampling on average 1415 insects were collected belonging to 30 species, 10 families and 8 orders. The results indicated that diversity and evenness of bees, which are the main pollinator of passion fruit was much higher in Zone V than in Zone IV and Zone III. There was seasonal variation in abundance although this did not affect the diversity of the insect pollinators. Results of Pearson’s correlation analysis between number of fruits and insect abundance per AEZ revealed that there was a positive and significant association between the abundance of the insects and the number of fruits (r = 0.504, p = 0.002). The study findings revealed that 76.7% of the farmers use the DAM, CAN, DAP type of agrochemicals while 23.3% of the respondents use other types of agrochemicals. For plant richness, a total of fifteen (15) higher plant species, three (3) shrubs and sixteen herbs (16) were recorded. This study revealed that land use type and agro-chemicals could be key factors in determining insect pollinator diversity and abundance in different agro-ecological zones. The findings from this research echo the need for environmental management of agro-ecosystems to support ecosystem services in particular pollination which improves passion fruit production.