Morphologically Specialized Termite Castes and Advanced Sociality in the Early Cretaceous

Abstract

A hallmark of animals that are eusocial, or those with advanced sociality, is reproductive specialization into worker and queen castes. In the most derived societies, these divisions are essentially fixed and in some arthropods, include further specialization--a tripartite system with a soldier caste that defends the colony. Eusociality has originated numerous times among insects but is believed to have appeared first in the termites (Isoptera), in the Early Cretaceous. However, all termites known from the Cretaceous have, until now, only been winged reproductives (alates and dealates); the earliest soldiers and definitive workers were known from just the Miocene (ca. 17-20 million years ago [mya]). Here, we report six termite species preserved in Early Cretaceous (ca. 100 mya) amber from Myanmar, one described as Krishnatermes yoddha gen. et sp. nov., comprising the worker/pseudergate, winged reproductive, and soldier, and a second species, Gigantotermes rex gen. et sp. nov., based on one of the largest soldier termites yet known. Phylogenetic analysis indicates that Krishnatermes are in the basal "Meiatermes-grade" of Cretaceous termites. Workers/pseudergates of another four species are briefly described, but not named. One of these workers/pseudergates reveals that ants--the most serious enemies of modern termites--lived in close proximity to termites in the Burmese paleofauna. These discoveries demonstrate the Mesozoic antiquity of specialized termite caste systems and corroborate that among all social species, termites probably had the original societies.

New Evanioid Wasps from the Cenomanian of Myanmar (Hymenoptera: Othniodellithidae, Aulacidae), with a Summary of Family-Group Names Among Evanioidea

“…Burmese amber is currently the most abundant source of Mesozoic amber inclusions, and includes the greatest diversity of arthropods discovered to date (Grimaldi et al, 2002;Ross et al, 2010). The significance of Burmese amber for understanding Cretaceous biotic evolution cannot be overestimated, and even recently these mines have revealed the earliest Palpigradi (Engel et al, 2016b), Neophasmatodea (Engel et al, 2016c), diverse ants and termites (Barden and Grimaldi, 2016;Engel et al, 2016d;Perrichot et al, 2016), as well as amber-preserved vertebrates within Squamata (Daza et al, 2016).…”

Evidence for social parasitism of early insect societies by Cretaceous rove beetles

“…The specimen represents a new genus and species, and is remarkable in exhibiting defensive modifications that are hallmarks of a socially parasitic lifestyle, and which have evolved convergently multiple times in modern aleocharines as well as in myrmecophiles and termitophiles scattered across other staphylinid subfamilies. Recent studies of stem-group ants and termites in Burmese amber report clear evidence of advanced social organization in both insect groups by the mid-Cretaceous2125. The new fossil taxon indicates that early colonies formed by these insects were targeted by specialized social parasites, extending the age of this kind of symbiosis back by ∼50 million years, close to the inferred advent of ant and termite eusociality.…”

“…Yet, gauging whether this type of symbiosis was a bona fide feature of early ant and termite ecology has proven challenging for several reasons. First, although termites are believed to have evolved in the Late Jurassic2021, and ants somewhat later in the Early Cretaceous22232425, their frequency in fossil deposits implies that both taxa remained rare for much of their early evolution. Each group comprises <1% of all insect fossils in any given Cretaceous locality202224, and only in the Cenozoic do both groups increase dramatically towards their modern abundances.…”

“…Second, the precondition for the evolution of social parasitism is the existence of resource-rich nests that invite exploitation. However, undisputed evidence that Mesozoic termites and ants were definitively eusocial has until very recently been lacking21282930, creating uncertainty as to whether either taxon formed colonies. Finally, ambiguity lies in whether aleocharines are genuinely an ancient enough group to have evolved social parasitism at this early time.…”

A New Bethylid Wasp in Lebanese Early Cretaceous Amber (Hymenoptera: Chrysidoidea), with Comments on other Mesozoic Taxa

“…While the putatively primitive subfamily Bethylinae principally victimize larval Lepidoptera, most other bethylids attack coleopterous prey and such an association is likely plesiomorphic for the family, with beetles suspected as hosts for the Cretaceous groups. Furthermore, the records of Cretaceous bethylids are our only direct source of information regarding patterns of diversification for the family across the biotic backdrop of the period, which among other things was a time when angiosperms appeared and rose to floristic dominance, ecologically dominant aculeates debuted, termite societies were diversifying, and weevils were poised to take the lead in coleopteran diversity (e.g., Grimaldi and Engel, 2005;Engel and Grimaldi, 2005;Ohl and Engel, 2007;Engel et al, 2009Engel et al, , 2016Ware et al, 2010;Michez et al, 2012;Grimaldi, 2014, 2016;McKellar et al, 2013;Krishna et al, 2013;Peris et al, 2014).…”