Basal subtribes of the Nymphidiini (Lepidoptera: Riodinidae): phylogeny and myrmecophily

A new ant-butterfly symbiosis in the forest canopy fills an evolutionary gap

Myrmecophilous butterflies can establish complex symbiotic relationships with ants. A caterpillar wandering among the brood of the aggressive ponerine ant Neoponera villosa was found inside the core of a nest built in the myrmecophytic bromeliad Aechmea bracteata. This is the first caterpillar found living inside a ponerine ant nest. Its DNA barcode was sequenced, and an integrative approach was used to identify it as Pseudonymphidia agave, a poorly known member of the subtribe Pachythonina in the riodinid tribe Nymphidiini. The cuticle of the tank-like caterpillar lacks projections or tubercles and is covered dorsally by specialized flat setae that form an armor of small plates. Ant-organs potentially related to caterpillar-ant signaling, such as perforated cupola organs and tentacle nectary organs, are present. These morphological traits, together with evidence of social integration (direct contact with host brood, protective morphology, slow movement, no host aggressiveness), suggest that P. agave is a symbiotic, social parasite of N. villosa, preying on its host brood. However, several knowledge gaps remain, including oviposition site, dependence on bromeliad association, steps to colony integration, and larval diet through development. Carnivory has been reported in all known members of the subtribe Pachythonina (caterpillars prey on honeydew-producing hemipterans) suggesting a shift to myrmecophagy inside the ant nests as a possible evolutionary transition.

The first known riodinid ‘cuckoo’ butterfly reveals deep-time convergence and parallelism in ant social parasites

Mutualistic interactions between butterflies and ants can evolve into complex social parasitism. ‘Cuckoo’ caterpillars, known only in the Lycaenidae, use multimodal mimetic traits to achieve social integration into ant societies. Here, we present the first known ‘cuckoo’ butterfly in the family Riodinidae. Aricoris arenarum remained in taxonomic limbo for > 80 years, relegated to nomen dubium and misidentified as Aricoris gauchoana. We located lost type material, designated lectotypes and documented the morphology and natural history of the immature stages. The multifaceted life cycle of A. arenarum can be summarized in three phases: (1) females lay eggs close to honeydew-producing hemipterans tended by specific Camponotus ants; (2) free-living caterpillars feed on liquids (honeydew and ant regurgitations); and (3) from the third instar onward, the caterpillars are fed and tended by ants as ‘cuckoos’ inside the ant nest. This life cycle is remarkably similar to that of the Asian lycaenid Niphanda fusca, despite divergence 90 Mya. Comparable eco-evolutionary pathways resulted in a suite of ecomorphological homoplasies through the ontogeny. This study shows that convergent interactions can be more important than phylogenetic proximity in shaping functional traits of social parasites.

Two new genera of metalmark butterflies of North and Central America (Lepidoptera, Riodinidae)

Two new genera of Riodinidae (Insecta: Lepidoptera) are described, Neoapodemia Trujano-Ortega, gen. n. (Neoapodemianais (W. H. Edwards, 1876), comb. n., N.chisosensis Freeman, 1964, comb. n.) and Plesioarida Trujano-Ortega & García-Vázquez, gen. n. (Plesioaridapalmeriipalmerii (W. H. Edwards, 1870), comb. n., P.palmeriiarizona (Austin, [1989]), comb. n., P.palmeriiaustralis (Austin, [1989]), comb. n., P.hepburnihepburni (Godman & Salvin, 1886), comb. n., P.hepburniremota (Austin, 1991), comb. n., P.murphyi (Austin, [1989]), comb. n., P.hypoglaucahypoglauca (Godman & Salvin, 1878), comb. n., P.hypoglaucawellingi (Ferris, 1985), comb. n., P.walkeri (Godman & Salvin, 1886), comb. n., P.selvatica (De la Maza & De la Maza, 2017), comb. n.). Neoapodemia Trujano-Ortega, gen. n. is distributed in the southwestern USA and northeastern Mexico, while Plesioarida Trujano-Ortega & García-Vázquez, gen. n. is present from the southern USA to Central America. Species of these genera were previously classified as Apodemia C. Felder & R. Felder but molecular and morphological evidence separate them as new taxa. Morphological diagnoses and descriptions are provided for both new genera, including the main distinctive characters from labial palpi, prothoracic legs, wing venation and genitalia, as well as life history traits. A molecular phylogeny of one mitochondrial gene (COI) and two nuclear genes (EF-1a and wg) are also presented of most species of Apodemia, Neoapodemia Trujano-Ortega, gen. n., Plesioarida Trujano-Ortega & García-Vázquez, gen. n., and sequences of specimens from all tribes of Riodinidae. We compare the characters of Apodemia, Neoapodemia Trujano-Ortega, gen. n. and Plesioarida Trujano-Ortega & García-Vázquez, gen. n. and discuss the differences that support the description of these new taxa. This is a contribution to the taxonomy of the Riodinidae of North America of which the generic diversity is greater than previously recognized.

Ancient Neotropical origin and recent recolonisation: Phylogeny, biogeography and diversification of the Riodinidae (Lepidoptera: Papilionoidea)

We present the first dated higher-level phylogenetic and biogeographic analysis of the butterfly family Riodinidae. This family is distributed worldwide, but more than 90% of the c. 1500 species are found in the Neotropics, while the c. 120 Old World species are concentrated in the Southeast Asian tropics, with minor Afrotropical and Australasian tropical radiations, and few temperate species. Morphologically based higher classification is partly unresolved, with genera incompletely assigned to tribes. Using 3666bp from one mitochondrial and four nuclear markers for each of 23 outgroups and 178 riodinid taxa representing all subfamilies, tribes and subtribes, and 98 out of 145 described genera of riodinids, we estimate that Riodinidae split from Lycaenidae about 96Mya in the mid-Cretaceous and started to diversify about 81Mya. The Riodinidae are monophyletic and originated in the Neotropics, most likely in lowland proto-Amazonia. Neither the subfamily Euselasiinae nor the Nemeobiinae are monophyletic as currently constituted. The enigmatic, monotypic Neotropical genera Styx and Corrachia (most recently treated in Euselasiinae: Corrachiini) are highly supported as derived taxa in the Old World Nemeobiinae, with dispersal most likely occurring across the Beringia land bridge during the Oligocene. Styx and Corrachia, together with all other nemeobiines, are the only exclusively Primulaceae-feeding riodinids. The steadily increasing proliferation of the Neotropical Riodininae subfamily contrasts with the decrease in diversification in the Old World, and may provide insights into factors influencing the diversification rate of this relatively ancient clade of Neotropical insects.