Uncovering Active Bacterial Symbionts in Pollen-Feeding Beetles

Microbial symbionts enable many phytophagous insects to specialize on plant-based diets through a range of metabolic services. Pollen comprises one plant tissue consumed by such herbivores. While rich in lipids and protein, its nutrient content is often imbalanced and difficult-to-access due to a digestibly recalcitrant cell wall. Pollen quality can be further degraded by harmful allelochemicals. To identify microbes that may aid in palynivory, we performed cDNA-based 16S rRNA metabarcoding on three related pollen beetles (Nitidulidae: Meligethinae) exhibiting different dietary breadths: Brassicogethes aeneus, B. matronalis, and Meligethes atratus. Nine bacterial symbionts (i.e. 97% OTUs) exhibited high metabolic activity during active feeding. Subsequent PCR surveys revealed varying prevalence of those from three Rickettsialles genera - Lariskella, Rickettsia and Wolbachia - within beetle populations. Our findings lay the groundwork for future studies on the influence of phylogeny and diet on palynivorous insect microbiomes, and roles of symbionts in the use of challenging diets.

Rosaceae, Brassicaceae and pollen beetles: exploring relationships and evolution in an anthophilous beetle lineage (Nitidulidae, Meligethes-complex of genera) using an integrative approach

Background Meligethes are pollen-beetles associated with flowers of Rosaceae as larvae. This genus currently consists of 63 known species in two subgenera, Meligethes and Odonthogethes, predominantly occurring in the eastern Palaearctic. We analyzed 74 morphological and ecological characters (169 states) of all species, as well as of 11 outgroup species from 7 Meligethinae genera (including Brassicogethes), to investigate their phylogeny. We also conducted a parallel molecular analysis on 9 Meligethes, 9 Odonthogethes, 3 Brassicogethes and 2 Meligethinus species based on DNA sequence data from mitochondrial (COI, 16S) and nuclear (CAD) genes. Results Morphological phylogenetic reconstructions supported the monophyly of the whole genus and clades corresponding to purported subgenera Meligethes s.str. and Odonthogethes. Main species-groups were mostly confirmed, however some unresolved polytomies remained. Molecular data placed members of Brassicogethes (including 42 mostly W Palearctic species associated with Brassicaceae) as sister to Odonthogethes, with this clade being sister to Meligethes s.str. This phylogenetic scenario suggests that monophyletic Meligethes s.str., Odonthogethes and Brassicogethes should be regarded alternatively as three subgenera of a monophyletic Meligethes, or three genera in a monophyletic genus-complex, with mutually monophyletic Brassicogethes and Odonthogethes. Molecular analyses estimated the origin of this lineage at ca. 14–15 Mya from a common stem including Meligethinus. Conclusions We hypothesize that the ancestor of Meligethes specialized on Rosaceae in the Middle Miocene (likely in Langhian Age) and subsequently radiated during Late Miocene and Plio-Pleistocene maintaining a trophic niche on this plant family. This radiation was primarily due to geographic isolation in E Asiatic mountain systems. Combined evidence from morphology, ancestral state parsimony reconstruction of host-plant associations and molecular evidence suggested that Rosoideae (Rosa spp.) represented the ancestral hosts of Meligethes s.str., followed by an independent shift of ancestral Odonthogethes (ca. 9–15 Mya) on Rubus (Rosoideae) and members of Rosaceae Spiraeoideae. Other ancestral Odonthogethes probably shifted again on the unrelated plant family Brassicaceae (maybe 8–14 Mya in S China), allowing a rapid westward radiation of the Brassicogethes clade.

Rosaceae, Brassicaceae and Pollen Beetles: exploring relationships and evolution in an anthophilous beetle lineage (Nitidulidae, Meligethes-complex of genera) using an integrative approach

Background: Meligethes are pollen-beetles associated with flowers of Rosaceae as larvae. This genus currently consists of 63 known species in two subgenera, Meligethes and Odonthogethes, predominantly occurring in the eastern Palaearctic. We analyzed 74 morphological and ecological characters (169 states) of all species, as well as of 11 outgroup species from 7 Meligethinae genera (including Brassicogethes), to investigate their phylogeny. We also conducted a parallel molecular analysis on 9 Meligethes, 9 Odonthogethes, 3 Brassicogethes and 2 Meligethinus species based on DNA sequence data from mitochondrial (COI, 16S) and nuclear (CAD) genes.Results: Morphological phylogenetic reconstructions supported the monophyly of the whole genus and clades corresponding to purported subgenera Meligethes s.str. and Odonthogethes. Main species-groups were mostly confirmed, however some unresolved polytomies remained. Molecular data placed members of Brassicogethes (including 42 mostly W Palearctic species associated with Brassicaceae) as sister to Odonthogethes, with this clade being sister to Meligethes s.str. This phylogenetic scenario suggests that monophyletic Meligethes s.str., Odonthogethes and Brassicogethes should be regarded alternatively as three subgenera of a monophyletic Meligethes, or three genera in a monophyletic genus-complex, with mutually monophyletic Brassicogethes and Odonthogethes. Molecular analyses estimated the origin of this lineage at ca. 14-15 Mya from a common stem including Meligethinus. Conclusions: We hypothesize that the ancestor of Meligethes specialized on Rosaceae in the Middle Miocene (likely in Langhian Age) and subsequently radiated during Late Miocene and Plio-Pleistocene maintaining a trophic niche on this plant family. This radiation was primarily due to geographic isolation in E Asiatic mountain systems. Combined evidence from morphology, ancestral state parsimony reconstruction of host-plant associations and molecular evidence suggested that Rosoideae (Rosa spp.) represented the ancestral hosts of Meligethes s.str., followed by an independent shift of ancestral Odonthogethes (ca. 9-15 Mya) on Rubus (Rosoideae) and members of Rosaceae Spiraeoideae. Other ancestral Odonthogethes probably shifted again on the unrelated plant family Brassicaceae (maybe 8-14 Mya in S China), allowing a rapid westward radiation of the Brassicogethes clade.

Floral biology and pollination strategy of Durio (Malvaceae) in Sarawak, Malaysian Borneo

Ng WS, Mohd-Azlan J, Wong SY. 2020. Floral biology and pollination strategy of Durio (Malvaceae) in Sarawak, Malaysian Borneo. Biodiversitas 21: 5579-5594. This study was carried out to investigate on the flowering mechanisms of four Durio species in Sarawak. The anthesis started in the afternoon (D. graveolens and D. zibethinus), evening (D. kutejensis) or midnight (D. griffithii); and lasted between 11.5 hours (D. griffithii) to 20 hours (D. graveolens). All four Durio species are generalists. Individuals of a fruit bat (Eonycteris spelaea, Pteropodidae) are considered as the main pollinator for D. graveolens, D. kutejensis, and D. zibethinus while spiderhunter (Arachnothera, Nectariniidae) is also proposed as a primary pollinator for D. kutejensis. Five invertebrate taxa were observed as secondary or inadvertent pollinators of Durio spp.: honeybee, Apis sp. (Apidae), stingless bee, Tetrigona sp. (Apidae), nocturnal wasp, Provespa sp. (Vespidae), pollen beetle (Nitidulidae), and thrip (Thysanoptera). Honey bees and stingless bees pollinated all four Durio species. Pollen beetles were found to pollinate D. griffithii and D. graveolens while nocturnal wasps were found to pollinate D. kutejensis and D. zibethinus. Thrips were found to pollinate D. griffithii only. Floral rewards include nectar, pollen and staminodes. The nectar production of D. graveolens, D. kutejensis, and D. zibethinus increased from the start of anthesis until just after midnight but decreased from then onwards. Durio griffithii produced consistent nectar concentration with inconsistent volume. Durio graveolens, D. griffithii, and D. zibethinus are partially self-incompatible.

Rosaceae, Brassicaceae and Pollen Beetles: exploring relationships and evolution in an anthophilous beetle lineage (Nitidulidae, Meligethes-complex of genera) using an integrative approach

Meligethes are pollen-beetles associated with flowers of Rosaceae as larvae. This genus, in its present-day concept, consists of 63 known species in two subgenera, Meligethes and Odonthogethes, predominantly occurring in the eastern Palaearctic. We analyzed 74 morphological and ecological characters (169 states) of all species, as well as of 11 outgroup species from 7 Meligethinae genera (including the believed sister-genus Brassicogethes), to investigate their phylogeny. A parallel molecular analysis was carried out on 9 Meligethes, 9 Odonthogethes, 3 Brassicogethes and 2 Meligethinus species, based on DNA sequence data from mitochondrial (COI, 16S) and nuclear (CAD) genes, to obtain additional phylogenetic information on the group. Results: Morphological phylogenetic reconstructions supported the monophyly of the genus, and clades corresponding to purported subgenera Meligethes s.str. and Odonthogethes. Main species-groups were mostly confirmed, however some unresolved polytomies remained. Molecular data placed members of Brassicogethes (including 42 mostly W Palearctic species associated with Brassicaceae) as sister to Odonthogethes, with this clade being sister to Meligethes s.str. This phylogenetic scenario suggests that monophyletic Meligethes s.str., Odonthogethes and Brassicogethes should be regarded alternatively as three subgenera of a monophyletic Meligethes, or three genera in a monophyletic genus-complex, with mutually monophyletic Brassicogethes and Odonthogethes. Molecular analyses estimated the origin of this lineage at ca. 14-15 Mya from a common stem including Meligethinus. Conclusions: We hypothesize that the ancestor of Meligethes specialized on Rosaceae in the Middle Miocene (likely in Langhian Age) and subsequently radiated during Late Miocene and Plio-Pleistocene maintaining a trophic niche on this plant family. This radiation was primarily due to geographic isolation in E Asiatic mountain systems. Combined evidence from morphology, ancestral state parsimony reconstruction of host-plant associations and molecular evidence suggested that Rosoideae (Rosa spp.) represented the ancestral hosts of Meligethes s.str., followed by an independent shift of ancestral Odonthogethes (ca. 9-15 Mya) on Rubus (Rosoideae) and members of Rosaceae Spiraeoideae. Other ancestral Odonthogethes probably shifted again on the unrelated plant family Brassicaceae (maybe 8-14 Mya in S China), allowing a rapid westward radiation of the Brassicogethes clade.

Rosaceae, Brassicaceae and Pollen Beetles: exploring relationships and evolution in an anthophilous beetle lineage (Nitidulidae, Meligethes-complex of genera) using an integrative approach

Background: Meligethes are pollen-beetles associated with flowers of Rosaceae as larvae. This genus, in its present-day concept, consists of 63 known species in two subgenera, Meligethes and Odonthogethes, predominantly occurring in the eastern Palaearctic. We analyzed 61 morphological and ecological characters (128 states) of all species, as well as of 7 outgroup species from 7 Meligethinae genera (including the believed sister-genus Brassicogethes), to investigate their phylogeny. A parallel molecular analysis was carried out on 9 Meligethes, 9 Odonthogethes, 3 Brassicogethes and 2 Meligethinus species, based on DNA sequence data from mitochondrial (COI, 16S) and nuclear (CAD) genes, to obtain additional phylogenetic information on the group. Results: Morphological phylogenetic reconstructions supported the monophyly of the genus, and clades corresponding to purported subgenera Meligethes and Odonthogethes. Main species-groups were mostly recovered intact, however some unresolved polytomies remained. Molecular data suggested a different scenario, placing members of Brassicogethes (including 42 mostly W Palearctic species associated with Brassicaceae) as sister to Odonthogethes, with this clade being sister to Meligethes s.str. This alternative phylogenetic assessment suggests that the monophyletic clades Meligethes s.str., Odonthogethes and Brassicogethes should be regarded alternatively as three subgenera of a monophyletic Meligethes, or three genera in a monophyletic genus-complex, with mutually monophyletic Brassicogethes and Odonthogethes. Molecular analyses estimated the origin of this lineage at ca. 14-15 Mya from a common stem including Meligethinus. Conclusions: We hypothesize in the Middle Miocene (likely in Langhian Age), the first Meligethes specialized on Rosaceae, on which they subsequently radiated during Late Miocene and Plio-Pleistocene. This radiation was enforced by geographic isolation in E Asiatic mountain systems, and by larval host-plant specialization. Combined evidence from morphology, ancestral state parsimony reconstruction of host-plant associations, and molecular evidence, suggested that for Meligethes s.str., Rosoideae (Rosa spp.) represented the ancestral hosts, followed by an independent shift of ancestral Odonthogethes (ca. 9-15 Mya) on Rubus (Rosoideae) and members of Rosaceae Spiraeoideae. Other ancestral Odonthogethes probably shifted again on the unrelated plant family Brassicaceae (maybe 8-14 Mya in S China), allowing a rapid westward radiation of the Brassicogethes clade.

Palms and pollen beetles: two new anthophilous beetle species of Meligethinus from Mozambique (Coleoptera: Nitidulidae: Meligethinae)

The genus Meligethinus Grouvelle, 1906 represents a small group of pollen beetles, including some twenty species distributed from southern Palaearctic areas to northern Oriental and Afrotropical regions. All constituent species appear to be strictly associated as larvae and adults to male inflorescences of palms (Monocots: Arecaceae). Two new species of this genus (Meligethinus mondlanei sp. nov. and M. hamerlae sp. nov.) were recently discovered in southern Mozambique, and are described herein. Both are associated as larvae with male inflorescences of the widespread eastern African palm Phoenix reclinata Jacq. The two new species are compared with related taxa from central Africa. Additionally, the presence of additional species of the same genus in southern Mozambique is reported, and the local associations of several Meligethinus species are discussed.