Monday, August 20, 2018

[Paleontology • 2018] Cretoparacucujus cycadophilus • Beetle Pollination of Cycads in the Mesozoic

Cretoparacucujus cycadophilus Cai & Escalona

in Cai, Escalona, Li, Yin, Huang & Engel, 2018.
Illustration: Chenyang Cai  

• A specialized beetle-mediated pollination mode is reported from Burmese amber
• The mid-Cretaceous boganiid beetle has many pollen-feeding adaptations
• The fossil boganiid was probably a pollinator of Encephalarteae cycads
• This suggests a probable ancient origin of beetle pollination of cycads in the Mesozoic

Cycads, unlike modern wind-pollinated conifers and Ginkgo, are unusual in that they are an ancient group of gymnosperms pollinated by insects [Taylor et al., 2009; Nagalingum et al., 2011; Terry et al., 2012]. Although it is well documented that cycads were diverse and abundant during the mid-Mesozoic, little is known about their biogeography and pollination before the rise of angiosperms. Direct fossil evidence illuminating the evolutionary history of cycads is extremely rare [Labandeira et al., 2007; Peris et al., 2017]. Here we report a specialized beetle-mediated pollination mode from the mid-Cretaceous of Myanmar, wherein a new boganiid beetle, Cretoparacucujus cycadophilus, with specialized pollen-feeding adaptations in its mouthparts and legs, was associated with many pollen grains of Cycadopites. Phylogenetic analyses indicate Cretoparacucujus as a sister group to the extant Australian Paracucujus, which pollinate the cycad Macrozamia riedlei. Our discovery, along with the current disjunct distribution of related beetle-herbivore (tribe Paracucujini) and cycad-host (tribe Encephalarteae) pairs in South Africa and Australia, indicate a probable ancient origin of beetle pollination of cycads at least in the Early Jurassic, long before angiosperm dominance and the radiation of flowering-plant pollinators later in the Cretaceous.

 Keywords: paleoecology, paleoethology, coevolution, plant-insect interactions, Burmese amber, pollination

Ecological reconstruction of the mid-Cretaceous beetle Cretoparacucujus cycadophilus.
Illustration: Chenyang Cai 

Figure 2. Photomicrographs of Cycad Pollen Grains Associated with Cretoparacucujus cycadophilus
 (A) General view of C. cycadophilus and aggregations of pollen grains by the beetle. (A’) Enlargement of an aggregation of three pollen grains. (A’’) Enlargement of a single grain. (B) Enlargement of three larger aggregations of pollen grains. (C) Enlargement of (B), showing 14 aggregated pollen grains. (D) Enlargement of (B), showing six aggregated pollen grains.


Systematic Paleontology
Order Coleoptera Linnaeus, 1758.

Family Boganiidae Sen Gupta and Crowson, 1966.
Subfamily Paracucujinae Endrödy-Younga and Crowson, 1986.

Cretoparacucujus cycadophilus gen. et sp. nov. Cai and Escalona.

Material: Holotype, NIGP166883, female. Mid-Cretaceous amber (ca. 99 million years ago), Tanai, Kachin State, northern Myanmar.

Etymology: The generic name is a combination of creto- and the genus Paracucujus. The specific epithet is a combination of Greek kykas (meaning, cycad) and philia (meaning, friendly love or affection).

Diagnosis: Cretoparacucujus is distinguished from other boganiids by the following combination of characters: upper body surface sub-glabrous; head large, slightly wider than pronotum; antenna filiform, without antennal club; clypeus sub-triangular, apex widely notched medially; frontal carina meeting frontoclypeal sulcus; mandible long, nearly straight; maxillary palpus elongate, with maxillary palpomere 4 much shorter than palpomere 3; protibial apex not expanded; and elytral punctation seriate.


 Chenyang Cai, Hermes E. Escalona, Liqin Li, Ziwei Yin, Diying Huang and Michael S. Engel. 2018. Beetle Pollination of Cycads in the Mesozoic. Current Biology. In Press. DOI: 10.1016/j.cub.2018.06.036 

99-million-year-old beetle trapped in amber served as pollinator to evergreen cycads via @physorg_com