Stewart B. Peck

Response of a Dung Beetle Guild to Different Sizes of Dung Bait in a Panamanian Rainforest

Pitfall traps, baited with feces, were used to sample the Scarabaeinae dung beetle fauna in lower montane rainforest in western Panama. Baits of two sizes, 2 ml and 200 ml, were used. These baits captured 22 species each, but there were clear differences in species, numbers and sizes of species, and species dominance and equitability. The evidence shows that dung size is another niche dimension along which species can specialize and reduce competitive interactions. IN SOME RAINFOREST AREAS of the New World tropics, beetles of the subfamily Scarabaeinae (Scarabaeidae) can be readily attracted to dung-baited traps. The number of both individuals and species attracted to these traps can be amazingly high (Howden and Nealis 1975, Nealis 1977, Peck and Forsyth 1982). While the beetles may be common, observable quantities of dung are not, and native dung-producing mammals in the forest are, in our experience, scarce. Unfortunately, comparative data on population densities and biomass for a rainforest mammal community are few (Bourliere 1973, Eisenberg 1980) and no quantitative data are available on dung production in neotropical forest mammal communities. Since dung serves as food for both adults and larvae, competition for this seemingly limited resource within and between species of dung beetles could be intense. A number of studies on the biology of dung scarabs have shown characteristics which result in a reduction of competitive interactions. These include preferences for specific conditions of soil and cover within a habitat (Nealis 1977, Lumaret 1978), differences in diel flight times, and differences in foraging and dung removal methods (Halffter and Matthews 1966, Peck and Forsyth 1982, Stevenson 1982). Differences in body sizes and activity temperatures of African savanna dung beetles are known to control success in scramble competition for elephant dung (Bartholomew and Heinrich 1978, Heinrich and Bartholomew 1979). Other behavioral mechanisms also minimize competition. Howden and Nealis (1978) suggested that perching behaviors of different dung scarabs in tropical forests might be related to different foraging patterns. They observed that small dung scarabs (less than 10 mm in length) tended to perch on understory leaves in rainforest, with smaller species nearer to the ground. Larger species (over 10 mm in length) tended to fly rather than perch. Howden and Nealis hypothesized that these differences represent different searching behaviors for dung: large beetles actively fly and search for dung over a larger area; smaller beetles perch and thus are able to detect small amounts of dung with small amounts of odor which may not be detectible above the level of the understory vegetation. The inference was made that the actual size of the dung resources could be important and is related to the different perching or flying behaviors which are, in turn, related to the size of the beetle species. It is reasonable to assume that larger beetles need larger dung resources for their feeding and reproduction. However, it does not necessarily follow that smaller beetles would be restricted to or prefer smaller dung resources. Species in a guild can partition food resources according to size and thus reduce competition (see Ricklefs 1973, Whittaker 1975). In this paper we report on an experiment conducted in May 1977 that tested the hypothesis that differences exist in the composition of dung beetle guilds attracted to dung units of different sizes in a Panamanian rainforest. A limitation of all the studies cited is that none have rigorously proven that dung resources are limited. However, all have used similar indirect evidence that suggests that it is, such as the general scarcity and patchy distribution of dung-producing mammals, the large numbers of beetles that find fresh dung, and the rapidity and diversity of methods used to dispose of it. We use the same indirect evidence for the assumption that dung is a limited resource in the forests we studied. MATERIALS AND METHODS Dung-baited pitfall traps have been conveniently used to attract, sample, and study dung beetle guilds (e.g., Howden and Nealis 1975, Nealis 1977, Peck and Forsyth 1982). However, these traps do not always attract all species of Scarabaeinae in an area, even though most species do not limit their activities to one kind of dung. Dung baits were made from homogenized fresh feces from I Received 29 March 1983; revised 9 October 1983; accepted 3 November 1983. BIOTROPICA 16(3): 235-238 1984 235 This content downloaded from 207.46.13.156 on Sat, 10 Sep 2016 04:15:28 UTC All use subject to http://about.jstor.org/terms several people. The bait sizes were chosen to represent different dung resource sizes that can occur naturally in a neotropical forest, but they did not represent the natural extremes of size. Large baits were 200-ml balls covered with two layers of cheesecloth. These were suspended by a wire from a stick over a 2-liter plastic bucket. Small baits consisted of 2-ml pellets placed in the center of a flat wooden stick (2 mm x 1 cm x 11.5 cm, such as those used to stir coffee or to hold frozen desserts) supported over a 200-ml plastic cup. In all cases the baits and the tops of the pit traps were flush with the forest soil surface. The traps contained an odorless solution of ethylene glycol to drown and partly preserve the beetles. A large leaf or bark flake, 15 cm above the trap opening, shielded it from rain. The traps were set parallel to narrow roads, which served as transects, running under the canopy of three remnant tracts of lower montane rainforest near El Hato del Volcan, Chiriqui Province, Panama, at elevations from 1000 to 1760 m. This region receives about 20-25 mm of rain in May, the beginning of the rainy season. There is little or no change of species composition in the dung beetle guild over this elevational range (Howden and Young 1981). All traps were spaced at least 30 m from each other, in areas with sparse understory and dense canopy vegetation. Fresh baits were added at mid-morning every day. The beetles were removed from the small traps every day and every other day from the large traps. Small baits were monitored frequently and were replaced if they had been pushed into the trap. Old baits were removed from the forests. Seven large-bait traps were operated for a total of 34 trap days. Concurrently, 35 small-bait traps were run for a total of 210 trap days. The traps never were so full that beetles could escape. In addition, two large traps were set and covered at ground level with a 12-mm mesh screen. These were run for 2 days each in two forests as controls to see if the numbers or species of small beetles caught would change when large beetles were excluded from the dung baits. Mean sizes of the beetles at a bait are summations of the number of each species multiplied by its mean length divided by the total number of beetles caught at the bait. The mean lengths of the species were determined from measurements of available individuals (N = 1-25) in the Howden collection from samples collected only in Pana-

Zoraptera wing structures: evidence for new genera and relationship with the blattoid orders (Insecta: Blattoneoptera)

Abstract. The order Zoraptera has traditionally been thought to contain only one family (Zorotypidae) and one genus (Zorotypus Silvestri). An analysis of known zorapteran wings shows that the wing venation contains character sets indicative of the existence of seven genera: Zorotypus, Brazilozoros gen.n., Centrozoros gen.n., Floridazoros gen.n., Latinozoros gen.n., Meridozoros gen.n. and Usazoros gen.n. The wing venation of Meridozoros leleupi (Weidner) from the Galapagos Islands, Ecuador and Venezuela is described here for the first time.

Eyeless arthropods of the Galapagos Islands, Ecuador: composition and origin of the cryptozoic fauna of a young, tropical, oceanic archipelago.

Fifty-six species of eyeless and reduced-eyed (obligately cryptozoic) macroscopic arthropods are now known from the Galapagos Islands. These occupy cave, ground water, and soil-litter habitats. Sixteen soil-inhabiting species have become established after their probable inadvertent introduction by humans. The number and diversity of the remaining 40 native and endemic species are remarkable because of the geologic youth (about three million years maximum) and oceanic isolation of the islands. Soil habitats contain ten species whose ancestors naturally arrived on the islands in an already eyeless condition, demonstrating that such taxa have greater powers of overwater dispersal than is generally thought. Caves and soils are inhabited by ten eyeless or reduced-eyed species which have related fully-eyed epigean (sister?) species, usually on the same island, indicating relatively recent (possibly parapatric) adaptive radiation into subterranean environments. Another 20 species have no dose Galapagos relatives, and 15 of these are probably relicts of lineages which became extinct in epigean terrestrial habitats, probably because of repeated periods of intense aridity during the Pleistocene. Similar evolutionary patterns exist in the eyeless arthropods of the Hawaiian and Canary archipelagos, indicating that there are common processes in the origins of such eyeless tropical oceanic island faunas.

Phototransduction and clock gene expression in the troglobiont beetle Ptomaphagus hirtus of Mammoth cave

SUMMARY Obligatory cave species exhibit dramatic trait modifications such as eye reduction, loss of pigmentation and an increase in touch receptors. As molecular studies of cave adaptation have largely concentrated on vertebrate models, it is not yet possible to probe for genetic universalities underlying cave adaptation. We have therefore begun to study the strongly cave-adapted small carrion beetle Ptomaphagus hirtus. For over 100 years, this flightless signature inhabitant of Mammoth Cave, the worlds largest known cave system, has been considered blind despite the presence of residual lens structures. By deep sequencing of the adult head transcriptome, we discovered the transcripts of all core members of the phototransduction protein machinery. Combined with the absence of transcripts of select structural photoreceptor and eye pigmentation genes, these data suggest a reduced but functional visual system in P. hirtus. This conclusion was corroborated by a negative phototactic response of P. hirtus in light/dark choice tests. We further detected the expression of the complete circadian clock gene network in P. hirtus, raising the possibility of a role of light sensation in the regulation of oscillating processes. We speculate that P. hirtus is representative of a large number of animal species with highly reduced but persisting visual capacities in the twilight zone of the subterranean realm. These can now be studied on a broad comparative scale given the efficiency of transcript discovery by next-generation sequencing.

Annotated Checklist of the Bark and Ambrosia Beetles (Coleoptera: Platypodidae and Scolytidae) of Tropical Southern Florida

The fauna of Scolytidae and Platypodidae is reviewed for tropical southern Florida (Collier, Broward, Dade, and Monroe Counties). The family Platypodidae is represented by 3 species, all in the genus Platypus. The family Scolytidae includes 83 species in 37 genera in the region. This total includes 20 species considered immigrants to the area. Three species previously reported from the region, Cryptocarenus spatulatus Wood, Xyleborus xylographus (Say), and Araptus politus (Blandford), probably do not occur there. Feeding habits, mating systems, hosts, and distributions are summarized for all species included.

Population structure and gene flow in Stomion : a species swarm of flightless beetles of the Galápagos Islands

Stomion is a swarm of 13 flightless tenebrionid beetle species endemic to the Galápagos Islands. Their distribution is patchy and largely restricted to the littoral and arid zones of the archipelago. Each taxon is found on one or a few geographically close islands. Thirty-five populations representing nine of the taxa were examined at eight polymorphic enzyme loci using cellulose acetate electrophoresis to measure patterns of gene flow and investigate models of dispersal in a relatively young species group exhibiting spatially isolated populations.Genetic subdivision is high, particularly among populations of taxa which inhabit more than one island, revealing restricted gene flow and confirming the high potential for reproductive isolation among subpopulations. The mean FST across taxa was 0.30. The genetic differentiation occurring between spatially isolated populations may explain the exuberant speciation of the genus in the Galápagos. Tests of gene flow models give support to the stepping-stone model of dispersal. Because of their lack of flight wings, interisland dispersal of Stomion probably occurred by oceanic drift as pleuston or on floating debris, with individuals colonizing nearby islands more frequently than ones at a greater distance.

Ecological studies of hypogeous fungi. I. Coleoptera associated with sporocarps.

SUMMARYEight species of beetles are reported from ten previously unreported hypogeous fungus substrates. The associations include: Catopocerus capizzii with Hymenogaster parksii and Zelleromyces gi...

A Survey of Insects of the Florida Keys: Post-Pleistocene Land-Bridge Islands: Introduction

This paper introduces a series investigating the fauna of selected insect and arthropod groups occurring in south (subtropical) Florida, especially in the Florida Keys. Characteristics of the region are summarized. Collections were made continuously with malaise and flight-intercept traps for 1 year or more in 21 hardwood hammock or pineland habitats, and by other methods. Based on numbers of species of trees and shrubs, a prediction is made that a conservative total of at least 5,000 insect species should occur in south Florida. Six generalizations about the insect fauna are suggested for future testing.

The Life History of the Japanese Carrion Beetle Ptomascopus Morio and the Origins of Parental Care in Nicrophorus (Coleoptera, Silphidae, Nicrophorini)

The subject of the origin and evolution of sociality in insects has a rapidly growing literature. Most of this pertains to the Hymenoptera. Within the Coleoptera, presocial or subsocial parental care and division of labor are known in at least nine families (Wilson, 1971). The most advanced form of parental care known in beetles is that of the Nierophorus carrion or burying beetles (tribe Nicrophorini). This generalization is based on the study of six European species by Pukowski (1933, 1934) which has since been abstracted and popularized by many (e.g., Balduf, 1935; Milne and Milne, 1944, 1976; Wilson, 1971, 1975). Briefly, a male and female form a conspecific pair at a carcass of a mouse or other small vertebrate. They work cooperatively to exclude competitors, to bury the carcass, and to shape it into a ball in a crypt. The male leaves after oviposition but the female tends the developing larvae, calling them to the carrion by stridulation, and repeatedly feeds them by regurgitation. Such behaviors do not exist in the other tribe of silphid carrion beetles, the Silphini. The only work on the life cycle of a North American Nicrophorus is a short note by Leech (1934) on N. defodiens (under the name N. conversator). Thus, it is not really known how general or widespread is the phenomenon of parental care in the genus, nor if all species are equally advanced behaviorally. There are about 20 species in the New World, and at least 65 species in all the world, in several lineages within the genus. As part of a series of studies on the comparative biology and evolution of silphid beetles, I undertook a study of the life history of Ptomascopus morio Kraatz of Japan, to learn something of the

Description of a Polynoncus Burmeister larva, with implications for phylogeny of the Trogidae (Coleoptera: Scarabaeoidea)

Abstract. The larva of Polynoncus seymourensis Mutchler is described from the Galapagos Archipelago, Ecuador. It is the first larva recorded of any species in the genus and has a suite of characters not found in the other trogid genera. Phylogenetic analysis of characters of larvae of all the genera supports the current phylogenetic system which was based on adults.