Friday, 5 February 2016

Butterflies of the Jurassic: Convergent evolution between Mesozoic Kalligrammatid Lacewings and modern Butterflies.

Kalligrammatid Lacewings first appeared in the fossil record in the Middle Jurassic, about 160 million years ago, and disappeared in the Early Cretaceous about 115 million years ago. They were found more-or-less exclusively in Eurasia, and are thought to have been closely related to Neuropteran groups such as Antlions, Owlflies, Silky-winged Lacewings, and Spoon and Thread-winged Lacewings. However they show a suite of features unlike any other Neuropteran group, including large conspicuous wings (with the largest species reaching 160 mm in wingspan), scales on the wings, eyespots, and siphoning mouthparts, features which have led many to compare them to modern Butterflies, a group which appeared in the fossil record during the Early Eocene about 56 million years ago, but which are estimated from molecular studies to have appeared between 70 and 80 million years ago in the Late Cretaceous. Neuropterans (Lacewings) and Lepidopterans (Butterflies and Moths) are related, but are thought to have diverged in the Middle Carboniferous, about 320 million years ago, so any similarities between Kalligrammatid Lacewings and Butterflies must have evolved convergently in the two groups in response to similar ecological pressures. 

In a paper published in the Proceedings of the Royal Society Series B: Biological Sciences on 3 February 2016, a team of scientists led by Conrad Labandeira of the College of Life Sciences at Capital Normal University and the departments of Paleobiology and Mineral Sciences at the National Museum of Natural History examine a series of Kalligrammatid Lacewings from three Mesozic Insect-bearing deposits.

The three localities examined are all fine-grained lake deposits in Asia. The oldest is the Jiulongshan Formation of Inner Mongolia, dated to 164-165 million years ago (late Middle Jurassic), the middle deposit is the Karabastau Formation of eastern Kazakhstan, thought to be about 155 million years old (Late Jurassic), while the youngest locality is the Yixian Formation of Liaoning Province, which produces Insects ranging in age from about 128.2 to 121.6 million years, with the majority of the specimens dated to about 125 million years ago (Early Cretaceous).

Kalligrammatid structural diversity. Specimens are from the late-Middle Jurassic Jiulongshan Formation (JIU), China; Late Jurassic Karabastau Formation (KAR), Kazakhstan; and mid-Early Cretaceous Yixian Formation (YIX), China. At (a–i) are nine species showing general habitus. Arrows indicate proboscis tips. (a) Kalligramma circularia (JIU); (b) Affinigramma myrioneura (JIU); (c) Affinigramma myrioneura (JIU); (d) Kallihemerobius feroculus (JIU); (e) Oregramma aureolusa (YIX); (f) Ithigramma multinervia (YIX); (g) Abrigramma calophleba (JIU); (h) Kalligramma brachyrhyncha (JIU); and (i) Oregramma illecebrosa (YIX). (i–k) Lateral views of ovipositor structure in Oregramma illecebrosa above: (i) intact specimen; (j) complete ovipositor and posteriormost abdominal segments; and (k) lateral valve pairs. (l–q): five Kalligrammatid wing eyespot and spot types. (l ) Type 1 wing eyespot with two outer rings and ca 15 contiguous ocules surrounding a central pigmented disc (Oregramma illecebrosa, YIX); (m) Type 2 wing eyespot with a single outer ring, light-hued inner area, and uninterrupted, pigmented central disc with surrounding, non-contiguous ocules (Kallihemerobius almacellus, JIU); (n) Type 2 eyespot similar to (M) (Kallihemerobius feroculus, JIU); (o) Type 3 wing eyespot with a light-hued circular area and a few, variably sized ocules in a darkly pigmented central disc (Ithigramma multinervia, YIX); (p) Type 4 wing eyespot contains a few ocules and others surrounding a pigmented central disc, a light-hued inner area and surrounding, dark outermost ring (Kalligramma circularia, JIU); and (q) Type 5 wing spot of a circular, pigmented central disc (Kallihemerobius aciedentatus, JIU). Scale bars: solid, 10 mm; striped, 1 mm. Labandeira et al. (2016).

Labandeira et al. began by examining the distribution of Butterfly-like features among different Kalligrammatid groups. The earliest and most primitive group to appear were the Sophogrammatinae. These retain mandibles similar to those seen in other Lacewings, and lack any of the other Butterfly-like features seen in more derived members of the group, but are apparently the group from which other, more advanced Kalligrammatids are derived.

Four more derived groups of Kalligrammatids have been identified; the Kalligrammatinae, comprising five genera including the specious Kalligramma, which retain small mandibles as well as having siphon-like proboscises. These mandibles are thought to have been used for pollen handling, in a similar way to those of the modern Spoon and Thread-winged Lacewings and Micropterigid Moths. The more derived Kallihemerobiinae comprises six genera, while the Meioneurinae comprises the single genus Meioneurites, and the Oregrammatinae comprises three genera including the highly derived Oregramma.

Eyespots are found in all the Kalligrammatid groups except the Sophogrammatinae. In modern Butterflies these are a defensive mechanism used against predators such as Mantises and Birds, which can be used to either startle a would-be predator or deflect an attack away from the body (Butterflies can lose fairly large proportions of their wings and still fly). Labandeira et al. divided these into six levels of complexity, ranging from simple dark patches to more complex forms with central disks surrounded by rings of pigment and whitish, oval-shaped ocules and rings. However these different spot patterns appeared to have no particular distribution within the derived Kalligrammatid groups, suggesting that once spots had appeared, gaining and losing complexity was accomplished numerous times within different lineages. This at first seems a non-useful result, as it does not allow the tracing of developing complexity within the group, however this is also the pattern seen within Butterflies, strongly supporting the idea that Kalligrammatids shared a similar ecology to Butterflies.

Phylogenetic context of wing spots and eyespots in mid-Mesozoic Kalligrammatids, with comparisons to modern Lepidopterans. The best preserved fossil material was used for this analysis. (a) Most parsimonious tree of Kalligrammatidae phylogeny, with right forewing eyespot/spot condition mapped onto terminal clades and likely wing spot and eyespot origins. Wing eyespot and spot type symbols are at upper-left; crosses are eyespot/spot absences. (b–g) Examples of right forewings with wing eyespots or spots from mid-Mesozoic Kalligrammatidae (b–f ), and modern Psychopsidae (g). These taxa correspond to a Type 1 eyespot (b), Type 2 eyespot (c), Type 3 eyespot (d ), Type 4 eyespot (e) and two Type 5 double spots (f ) matched by two spots in modern Psychopsid (red arrows) in (g). Kalligrammatid wing eyespots and spots are compared to modern Lepidoptera in (h–k), of butterfly species with Type 6 eyespots (h) and multiple Type 5 spots (i); moth lacking wing spots or eyespots ( j ); and modern Owl Butterfly eyespot (k), showing pigmentation similar to Type 2 and 3 eyespots (b), indicated by arrow pointing to an ocule series and longitudinal wing vein. Scale bars: solid, 10 mm; striped, 1 mm. Labandeira et al. (2016).

Wing scales were absent in the Sophogrammatinae but present in all the derived Kalligrammatid groups, as well as in all Lepidoptera (Butterflies and Moths). Scales seem to have appeared early in the history of the Kalligrammatinae and are present in all later members of derived groups. These scales take two forms, larger elongate scales on the major wing veins, and smaller flatter scales between the veins. This is different to the pattern seen in modern Lepidoptera, where scales are absent from the major veins.

Proboscises are found in many Insect groups, but those of Kalligrammatids are notably similar to those of Butterflies in a number of ways; they were long (8-20 mm) and appear to have been flexible and lacked stylets or other piercing structures, with some specimens being hair covered and others smooth. This similarity to the range of shapes found in Butterflies is taken as evidence of a similar lifestyle, sucking nectar or a similar substance from flowers or another plant organ. Kalligrammatids even appear to have had pump-like sucking organs in the frontal part of the head, similar to those of Butterflies.

Gross mouthpart diversity and proboscis variation in Kalligrammatid Lacewings from the Middle Mesozoic of Eastern Asia. Drawings and digital images of Kalligrammatid taxa from the late Middle Jurassic (Jiulongshan Formation, 165 Ma, JIU) of northeastern China (c, d, f, h, m, o–t, v–x), middle Late Jurassic (Karabastau Formation, 155 Ma, KAR) of Kazakhstan (l), and middle Early Cretaceous (Yixian Formation, 125 Ma, YIX) of northeastern China (a, b, e, g, i–k, n). All overlay drawings are standardized to a scale of 5 mm (double diamond scale bar) to show size relationships; head and mouthpart elements are color identified to legend at upper left. (a, g) Abrigramma calophleba (YIX, dorsal view); (b, e) Oregramma illecebrosa (YIX, dorsal view), with food canal and subterminal constriction (arrow); (c, q) Kallihemerobius aciedentatus (JIU, dorsal view); (d, m) Kallihemerobius almacellus (JIU, dorsal view); (f, s) Affinigramma myrioneura (Jiulongshan, dorsal view); (h, w) Kalligramma brachyrhyncha (Jiulongshan, dorsal view); (i) Oregramma aureolusa (YIX, ventral view), with prominent maxillary stipites (mxst); (j) Oregramma sp. (YIX, oblique lateral view); (k) Ithigramma sp. (YIX, lateral view); (l) Meioneurites spectabilis (KAR, left lateral view); (n) Ithigramma multinervia (YIX, right oblique view); (o) Kalligramma circularia (JIU, right lateral view); (p) Kallihemerobiinae gen. et sp. indet. (JIU, dorsal view); (r) Affinigramma myrioneura (JIU, left lateral view); (s) Affinigramma myrioneura (JIU, frontal view); (t) Kallihemerobius feroculus (JIU, ventral view), with modified mandibles (md) adjacent the labial plate (la) and associated bisaccate pollen, probably Pinaceae, near the left mandible; (u) Ventral view of mandibles and labial plate of an extant, pollinating South African species of Nemopteridae, for comparison to (T); (v) Another specimen of Kalligramma circularia (JIU, dorsal view); (x) Kalligramma sp. (JIU, dorsal view). Scale bars: striped, 1 mm; dotted, 10 mm. Labandeira et al. (2016).

Angiosperms (Flowering Plants) have a long symbiotic relationship with Butterflies (and some other Insect groups), but are unlikely to have been ecological partners with Kalligrammatids, a group which appeared in the Middle Jurassic and disappeared as the Angiosperms came to prominence in the Cretaceous. Of the three formations examined in the study only the youngest, the Yixian Formation, has produced Angiosperm fossils at all, and these were small aquatic plants without tubular flowers that would require probing proboscises. However a number of other Plants with flower-like structures were present in the Mesozoic, including the extant Cycads and the extinct Bennettitaleans (Cycadoids) and Caytonialeans (Seed Ferns), all of which produced tube-like structures.

Of these groups the Bennettitaleans seem the most likely partners for the Kalligrammatids, with species known from all the Kalligrammatid-producing deposits and many specimens known from Eurasia within the Kalligrammatid time range that had tubular structures through which the ovules could be reached by an organ of similar size to a Kalligrammatid proboscis, and apparent secretary glands, tentatively identified as nectaries, positioned bellow the pollen sacs.

Plant associations of Kalligrammatids. (a–f) are palynomorphs associated with Kalligrammatid taxa; (a) cf. Chasmatosporites of possible Cycadales affiliation; (b) tetrad of Classopollis cf. Classopollis annulatus of the extinct conifer Cheirolepidaceae; (c) Cycadopites nitidus attributable to Bennettitales, Cycadales, Czekanowskiales, Ginkgoales or Pentoxylales; (d) Vitreisporites pallidus of Caytoniales; (e) epifluorescence image of a Classopollis cf. Classopollis annulatus on a foreleg tarsus of Meioneurites spectabilis (KAR); and (f) Gleicheniaceous Fern spore. (a–e) Are pollen macerated from sedimentary matrix adjacent to Kallihemerobius feroculus (JIU). (g) The Bennettitalean male strobilus Weltrichia sp. (h) The earlier occurring Bennettitalean female strobilus Williamsonia sp. (i) Reconstruction of specimen on a Bennettitalean host and probing a Williamsonia. Scale bars: solid, 10 mm; striped, 1 mm; dotted, 10 ┬Ám. Labandeira et al. (2016).

See also... new species of Osmylid from the Middle Jurassic Daohugou Biota of Inner Mongolia. Osmylids (Osmylidae) are a group of Neuropteran Insects with a fossil record dating back to the Early Jurassic and are still in existence today. They appear to have been at their most numerous and diverse in the Middle-Late Jurassic, with a number of lineages apparently disappearing at the... new species of Snakefly from the Middle Jurassic of Inner Mongolia.                    Snakeflies (Raphidioptera) are a group of carnivorous flying insects related to the Lacewings, Antlions and Alderflies. They have long life cycles, with a number of larval stages, but still feed as adults. Modern Snakeflies are found throughout Europe and Temperate Asia... new species of Split-foot Lacewing from the Middle Jurassic of Inner Mongolia.                 The Split-foot Lacewings (Nymphidae) are the oldest group of...
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