S. Bruce Archibald

Seasonality, the latitudinal gradient of diversity, and Eocene insects

Abstract In the modern world, biotic diversity is typically higher in low-latitude tropical regions where there is abundant insolation (light and heat) and low thermal seasonality. Because these factors broadly covary with latitude, separating their possible effects on species diversity is difficult. The Eocene was a much more equable world, however, with low temperature seasonality extending into lower-insolation higher, cooler latitudes, allowing us to test these factors by comparing insect species diversity in (1) modern, temperate, low-insolation, highly seasonal Harvard Forest, Massachusetts, U.S.A., 42°29′N; (2) modern, tropical, high-insolation, low-seasonality La Selva, Costa Rica, 10°26′N, and; (3) Eocene, temperate, low-insolation, yet low-seasonality McAbee, British Columbia, Canada, above 50°N paleolatitude. We found insect diversity at McAbee to be more similar to La Selva than to Harvard Forest, with high species richness of most groups and decreased diversity of ichneumon wasps, indicating that seasonality is key to the latitudinal diversity gradient. Further, midlatitude Eocene woody dicot diversities at McAbee, Republic (Washington, U.S.A.), and Laguna del Hunco (Argentina) are also high, similar to modern tropical samples, higher than at the modern midlatitude Harvard Forest. Modern correlations between latitude, species diversity, and seasonal climates were established some time after the Eocene.

Bulldog Ants of the Eocene Okanagan Highlands and History of the Subfamily (Hymenoptera: Formicidae: Myrmeciinae)

Abstract The presence of the ant subfamily Myrmeciinae is established in the Early Eocene (Ypresian) Okanagan Highlands localities of Horsefly River, Falkland, McAbee (British Columbia, Canada) and Republic (Washington state, United States) and in the Mo-clay Ølst and Fur Formations (Denmark). Nine new species in four new genera (three orthotaxa: Ypresiomyrma n. gen., Avitomyrmex n. gen., and Macabeemyrma n. gen.; one parataxon: Myrmeciites n. gen.) are described. Seven are placed in the Myrmeciinae: Ypresiomyrma orbiculata n. sp., Ypresiomyrma bartletti n. sp., Avitomyrmex elongatus n. sp., Avitomyrmex mastax n. sp., Avitomyrmex systenus n. sp., Macabeemyrma ovata n. sp., and Myrmeciites herculeanus n. sp.; two further species are tentatively placed in the subfamily, Myrmeciites (?) tabanifluviensis n. sp. from Horsefly River, and Myrmeciites (?) goliath n. sp. from McAbee. Two further myrmeciine ants are treated as Myrmeciites incertae sedis, a male from Falkland and a female (worker or queen) from Republic. Pachycondyla rebekkae Rust and Andersen, from the earliest Ypresian of Denmark, is reassigned to the genus Ypresiomyrma, within the Myrmeciinae. The fossil record indicates a northern hemisphere origin of the subfamily. The presence of Ypresiomyrma in Denmark and British Columbia further reflects the well-documented Paleogene cross-North Atlantic distributions of biota. The known fossil record of the Myrmeciinae is restricted to the Eocene.

Intercontinental dispersal of giant thermophilic ants across the Arctic during early Eocene hyperthermals

Early Eocene land bridges allowed numerous plant and animal species to cross between Europe and North America via the Arctic. While many species suited to prevailing cool Arctic climates would have been able to cross throughout much of this period, others would have found dispersal opportunities only during limited intervals when their requirements for higher temperatures were met. Here, we present Titanomyrma lubei gen. et sp. nov. from Wyoming, USA, a new giant (greater than 5 cm long) formiciine ant from the early Eocene (approx. 49.5 Ma) Green River Formation. We show that the extinct ant subfamily Formiciinae is only known from localities with an estimated mean annual temperature of about 20°C or greater, consistent with the tropical ranges of almost all of the largest living ant species. This is, to our knowledge, the first known formiciine of gigantic size in the Western Hemisphere and the first reported cross-Arctic dispersal by a thermophilic insect group. This implies intercontinental migration during one or more brief high-temperature episodes (hyperthermals) sometime between the latest Palaeocene establishment of intercontinental land connections and the presence of giant formiciines in Europe and North America by the early middle Eocene.

Family Affinity of the Genus Palaeopsychops Andersen with Description of a New Species from the Early Eocene of British Columbia, Canada (Neuroptera: Polystoechotidae)

Abstract Palaeopsychops dodgeorum sp. n. from the Early Eocene Okanagan Highlands of Quilchena, British Columbia, Canada is described. The systematic position of the genus Palaeopsychops Andersen, 2001 is discussed, interpreting this as most closely associated with Polystoechotidae. Osmylites protogaea (Hagen 1862) is considered as nomen nudum and an objective synonym of Osmylites excelsa (Oppenheim, 1888), syn. n.

Ecology and Distribution of Cenozoic Eomeropidae (Mecoptera), and a New Species of Eomerope Cockerell from the Early Eocene McAbee Locality, British Columbia, Canada

Abstract Eomerope macabeensis sp. nov. (Mecoptera: Eomeropidae) is described from the Early Eocene (Ypresian) McAbee locality in British Columbia, Canada. This is the first record of the family Eomeropidae in the Okanagan Highlands fossil deposits of British Columbia (Canada) and Washington state (United States). Previously known Cenozoic occurrences of the family include Eomerope tortriciformis Cockerell 1909 from the Eocene of Florissant, CO; Eomerope pacifica Ponomarenko & Rasnitsyn 1974 from the Paleocene Tadushi Formation., and Eomerope asiatica Ponomarenko & Rasnitsyn 1974 from the Eocene or Oligocene Amgu River of far-eastern Russia; and the extant Notiothauma reedi MacLachlan, 1877, from southern Chile. The new species seems to be closely related to E. asiatica. Where environmental parameters are known, these occurrences are mostly from highlands, with upper microthermal to mid-mesothermal climates and mild winters. N. reedi is phytophagous or saprophagous. Although Cenozoic Eomeropidae are associated with Fagus, Nothofagus, or Fagopsis-dominated forests in the Western Hemisphere, the Fagaceae and Nothofagaceae are minor elements or not known in the Russian localities. Intercontinental dispersal by either Gondwanan or Beringian routes is possible.

The Eocene Apex of Panorpoid Scorpionfly Family Diversity

Abstract The scorpionfly (Mecoptera) superfamily Panorpoidea underwent an Eocene radiation, replacing the extinct Mesozoic orthophlebiid grade and reaching its greatest family-level diversity: Panorpidae, Panorpodidae, Austropanorpidae, Holcorpidae, Dinopanorpidae, and a new family proposed here, the Eorpidae. Only the Panorpidae and Panorpodidae survived the Eocene and persist to the present day. This cluster of family extinctions is exceptional within Cenozoic insects. The Eorpidae includes at least one new genus and three new species described here from four localities of the early Eocene Okanagan Highlands of British Columbia, Canada, and Washington, U.S.A.: Eorpa ypsipeda n. gen. n. sp. (McAbee and possibly Falkland, BC, Canada; and Republic, WA, U.S.A.), Eorpa elverumi n. gen. n. sp. (Republic), and Eorpa jurgeni n. gen. n. sp. (Quilchena, BC). Some of the other fragmentary and poorly preserved specimens might represent further new species. We propose that the apex of Panorpoid family diversity ended by pressures from post-Eocene icehouse world climatic stress and the rise to ecological dominance of ants, some of which would have provided strong competition in scavenging for dead arthropods.

A Diverse New Assemblage of Green Lacewings (Insecta, Neuroptera, Chrysopidae) from the Early Eocene Okanagan Highlands, Western North America

Abstract The early Eocene green lacewings (Neuroptera, Chrysopidae) of the Okanagan Highlands deposits of McAbee, and Driftwood Canyon, British Columbia (Canada) and Republic, Washington (U.S.A.) are treated in detail for the first time. At least six genera are present, one unnamed, three new, with at least 10 new species, six named: Protochrysa fuscobasalis n. sp. (McAbee) (Limaiinae, the youngest known record of the subfamily), Okanaganochrysa coltsunae n. gen. n. sp. (McAbee), Adamsochrysa aspera n. gen. n. sp. (McAbee), A. wilsoni n. gen. n. sp. (Republic), Archaeochrysa profracta n. sp. (McAbee), and Pseudochrysopa harveyi n. gen. n. sp. (Driftwood Canyon) (all Nothochrysinae, the latter provisionally). The four unnamed species include one assigned to Pseudochrysopa, two likely belonging to Adamsochrysa, and one of an unknown nothochrysine genus. Microtholi are detected on the abdominal sclerites of Adamsochrysa wilsoni, and the spermatheca and spermathecal duct in the abdomen of Pseudochrysopa harveyi, the first reported occurrences of these preserved in fossil Chrysopidae. Structures were detected on the apical wing margins of some species that appear similar to trichosors, which are unknown in Chrysopidae, but are present in some other neuropteran families. This is the richest described assemblage of the family anywhere in the fossil record. Okanagan chrysopids were also morphologically and presumably ecologically diverse, including large species with rich venation and well as those with simplified venation and the smallest known fossil species. This is the oldest reported occurrence of the family in North America.

The red queen and court jester in green lacewing evolution: bat predation and global climate change

ABSTRACT Mechanisms governing taxon replacement and subsequent radiation remain little understood. We examine possible forcing factors in a turnover of subfamily dominance seen within the fossil record of green lacewings (Neuroptera: Chrysopidae), a common, cosmopolitan, nocturnally active insect family. Analyses indicate that Nothochrysinae dominated the family in the Eocene, while today they are relictual and the cosmopolitan Chrysopinae dominates with > 97% of its > 1200 species. Our findings suggest that this turnover is consistent with two key adaptations in the Chrysopinae: a tympanum that detects echolocation sounds of bats, which appeared in the fossil record and rapidly radiated during this time (a Red Queen interaction), and increased climatic tolerance coincident with the onset of post-Eocene global icehouse world climate (a Court Jester effect).

Revision of the scorpionfly family Holcorpidae (Mecoptera), with description of a new species from Early Eocene McAbee, British Columbia, Canada

Abstract The scorpionfly family Holcorpidae (Mecoptera) has been informally discussed since the early 1960’s, but a detailed treatment in accordance with the provisions of the International Code of Zoological Nomenclature for naming families was not provided until Willmann did so in 1989; he is recognized as author of the family. The Holcorpidae concept is revised here based on examination of its two specimens of Holcorpa maculosa from the Late Eocene of Florissant, Colorado, and a third, new specimen from the Early Eocene Okanagan Highlands locality at McAbee, British Columbia, Canada. This new specimen belongs to a second, new species, which is described here, Holcorpa dillhoffi n. sp.

A NEW SPECIES OF PRIONOCERIDAE (COLEOPTERA: CLEROIDEA) FROM THE EOCENE OF BRITISH COLUMBIA, CANADA

Abstract. Prionocerites tattriei gen. and sp. nov. (Insecta: Coleoptera: Cleroidea: Prionoceridae) are described from Eocene amber associated with the Hat Creek Coal Formation, Kamloops Group, British Columbia, Canada. This is the first occurrence of the family Prionoceridae in the fossil record and from the Western Hemisphere.