Land-use change impact on mycorrhizal symbiosis in female and male plants of wild Carica papaya (Caricaceae)

Abstract

It has been acknowledged that land-use change has negative effects on genetic diversity and sex ratio in dioecious species, but less attention has been paid on the influence that land-use change has on the biotic interactions, especially between dioecious species and arbuscular mycorrhizal (AM) fungi. AM mutualism involves reciprocal transfer of carbohydrates and mineral nutrients between the host plant’s roots and these fungi. Here, we report spatial and temporal variation in AM colonization in dioecious wild Carica papaya plants growing in sites with different land use intensity. We tagged, recorded the basal stem circumference and collected roots of reproductive female and male Carica papaya plants in three wild sites during dry and rainy seasons of western Mexico. We also collected soil samples in each site to conduct soil chemical analyses. The sexes of C. papaya did not show significant differences in the frequency (percentage of root colonized by intraradical fungal structures) and abundance (length of intraradical hyphae) of AM fungi but the higher AM colonization was observed during the dry season, and in the site with the lowest disturbance. There was no relationship between soil chemistry and AM colonization. Overall, our findings suggest that land-use intensity has a negative effect on AM colonization and we discuss the consequences of habitat loss for the reproductive female and male plants, the implications of decreasing AM colonization for wild Carica papaya plants an important species that provides a source of genetic variation for the C. papaya varieties.