From monocots to dicots: host shifts in Afrotropical derelomine weevils shed light on the evolution of non-obligatory brood pollination mutualism

We thank the Western Cape Nature Conservation Board (permit no. CN44-30-4229), the Cape Research Centre, South African National Parks (permit no. CRC/2019-2020/012-2012/V1) and Ezemvelo KZN Wildlife permits office, KwaZulu-Natal (collecting permit KZN: OP1382-2019) for authorization to collect specimens in the Republic of South Africa. We thank Dr Madeleine Tchuinte from the Ministry of Scientific Research and Innovation of the Republic of Cameroon for the sampling permit (no. 2040) and phytosanitary certificate (no. 90499). We thank Abba Sonko (Ministry of Environment and Sustainable Development) for assistance with export permits from Senegal (no. 0231). M. S. J. Sandun Perera (University of KwaZulu-Natal, Durban, Republic of South Africa) is acknowledged for her help with the collection of immature stages of Ebenacobius hessei. We also thank all the collaborators who contributed to the sampling of specimens and all the research teams who sent the specimens for expert identification and allowed us to retain the specimens. Finally, we thank Professor Duane McKenna (University of Memphis, Memphis, TN, USA) for kindly providing detailed information on previous dating analyses and anonymous reviewers for insightful comments on early versions of this article.

International audience

Inglés. Weevils from the tribe Derelomini (Curculionidae: Curculioninae) are specialized brood pollinators engaged in mutualistic relationships with several angiosperm lineages. In brood pollination systems, reproductive plant tissues are used for the development of insect larval stages, whereas adult insects pollinate their plant hosts as a reward. The evolutionary history of derelomines in relationship to their hosts is poorly understood and potentially contrasts with other brood pollination systems, wherein a pollinator lineage is usually associated with a single host plant family. In the case of Afrotropical Derelomini, host records indicate a diverse host repertoire consisting of several families of monocot and dicot plants. In this study, we investigate their phylogenetic relationships, timing of diversification and evolution of host use. Our results suggest that derelomine lineages started their diversification ~40 Mya. Reconstructions of host use evolution support an ancestral association with the monocotyledonous palm family (Arecaceae), followed by several shifts towards other plant families in Afrotropical lineages, especially to dicotyledonous plants from the family Ebenaceae (on the genus Euclea L.). Some level of phylogenetic conservatism of host use is recovered for the lineages associated with either palms or Euclea. Multiple instances of sympatric weevil assemblages on the same plant are also unravelled, corresponding to either single or independent colonization events. Overall, the diversity of hosts colonized and the frequency of sympatric assemblages highlighted in non-obligatory plant–derelomine brood pollination systems contrast with what is generally expected from plant–insect brood pollination systems.