Occasional Species Research Articles

The system of faunacomponents conception and its application to qualify the degree of naturalness of fish assemblages

The increase of species richness in communities of natural biogeographic regions in an anthropogenic way can be expressed as biogeographic pollution. Where there is contaminated fauna, one must investigate how this occured. I studied how the members of Hungarian fishfauna could be present resident and have managed to workout a so-called system of fauna component conception which is suitable for this requirement.The expression of ’faunacomponent’ includes other expressions. That kind of species belong to a certain faunacomponent that reached the studied area in the same way. Species reached the studied area without an anthropogenious contribution are qualified as native fauna components. These kind of species are endemic species, occasional species and settlers. In contrast to native faunacomponents, some kind of human influence is always detectable in connection with the way reached the studied area by non-native species. Accordingly, group of non-native species includes directly or indirectly facilitated settlers, species that are introduced accidentally and those introduced intentionally. It is obvious that classifying a given species could be construed solely in connection with a certain area.Applying Shannon diversity index I have initiated the assemblage natural index (ANI) in order to show a way how to use the system of faunacomponent conception in practice. ANI refers to the degree of naturalness of faunistical samples. If ANI > 1 it means there are not any non-native species and ANI < 1 it means there are some non-native species in the sample respectively. In the latter case ANI decreases proportionally with the number of non-native species and specimens. In that special case when only one specimen of only one non-native species can be found in the faunistical sample ANI = 1.

Discrete and continuous change in the fish community of the Bristol Channel in response to climate change

Using a 25-year time series of monthly samples, it is shown that the fish community of Bridgwater Bay in the outer Severn estuary is rapidly responding to changes in seawater temperature, salinity and the North Atlantic Oscillation (NAO). The number of fish caught each year has followed an increasing trend, which could be related to increased temperature and decreased salinity. In contrast to this smooth change, there have been two discrete transitions in fish community structure around 1986 and 1993. The first of these step changes, which altered the relative abundance of the dominant species, was linked to a change in the NAO. The second, which was caused by a change in the set of occasional visitor species, was linked to an increase in average seawater temperature. A marked increase in population variability for many fish in recent years is linked to increased seawater temperature. Generally, the position of the southern geographical limit of a species is a good indicator of their individual responses to higher temperatures. The effects of future climate change are discussed. A 2°C increase in inshore seawater temperature is predicted to increase total species richness of fish in Bridgwater Bay by 10%, although most of this gain will be warm water tourists. Predicting future communities requires consideration of combined changes in temperature, the NAOI and salinity. While the system can change to a warmer water community, there is likely to be increased short-term community instability during periods with unfavourable combinations of the key environmental variables. Such a destabilization was observed in 2002 when the abundance of many species suddenly increased then declined. A different combination of NAO, high temperature and salinity may, in the future, produce a considerable less favourable combination resulting in recruitment collapse for many species.

Inventory of Predacious Mites in Quebec Commercial Apple Orchards Where Integrated Pest Management Programs Are Implemented

Abstract The commercial apple (Malus spp.) orchard ecosystem in Quebec has a diverse fauna of predacious mites. A systematic 2-yr survey showed Amblyseius fallacis (Garman), Typhlodromus caudiglans Schuster (Acari: Phytoseiidae), and Agistemus fleschneri Summers (Acari: Stigmaeidae) to be the most abundant species. Other phytoseiids, Typhlodromus conspicuous (Garman), Typhlodromus herbertae Chant, Typhlodromus longipilus Nesbitt, Typhlodromus bakeri (Garman), Typhlodromus pyri Scheuten, Amblyseius okanagensis (Chant), and Amblyseius finlandicus (Oudemans), were found in low numbers. Two of these species, A. finlandicus and T. conspicuus, were identified for the first time in Quebec. Other occasional species included Anystis baccarum (L.) (Acari: Anystidae) and Balaustium sp. (Acari: Erythraeidae). Tetranychid mite numbers were always less than two mites per leaf throughout the study, and none of the commercial orchards required an acaricide treatment. A notable aspect of this study was that seasonal total...

Regional species richness of families and the distribution of abundance and rarity in a local community of forest Hymenoptera

Recent investigations about the relationship between the number of species of taxonomic lineages and regional patterns of species abundances gave indecisive results. Here, it is shown that mean densities of species of a species-rich community of forest Hymenoptera (673 species out of 25 families) were positively related to the number of European species per family. The fraction of abundant species per family declined and the fraction of rare species increased with species richness. Species rich families contained relatively more species, which were present in only one study year (occasional species), and relatively fewer species present during the whole study period (frequent species).

Frequent and occasional species and the shape of relative‐abundance distributions

ABSTRACTRecently, three different models have been proposed to explain the distribution of abundances in natural communities: the self‐similarity model; the zero‐sum ecological drift model; and the occasional–frequent species model of Magurran and Henderson. Here we study patterns of relative abundance in a large community of forest Hymenoptera and show that it is indeed possible to divide the community into a group of frequent species and a group of occasional species. In accordance with the third model, frequent species followed a lognormal distribution. Relative abundances of the occasional species could be described by the self‐similarity model, but did not follow a log‐series as proposed by the occasional–frequent model. The zero‐sum ecological drift model makes no explicit predictions about frequent and occasional species but the abundance distributions of the hymenopteran species did not show the excess of rare species predicted by this model. Separate fits of this model to the frequent and to the occasional species were worse than the respective fits of the lognormal and the self‐similarity model.

Community assembly along proglacial chronosequences in the high Arctic: vegetation and soil development in north‐west Svalbard

Summary Community assembly is described for two contrasting high Arctic chronosequences representing glacial regression of up to 2000 years on Svalbard. The chronosequences included a nutrient‐poor glacier foreland (Midtre Lovénbre) and a series of nutrient‐enriched islands (Lovén Islands) progressively released from below a tidewater glacier. Soil development and community assembly paralleled proglacial sequences elsewhere but time scales were extended and mature vegetation types comprised species‐poor prostrate communities. Initial colonization by Cyanobacteria stabilized soil surfaces and raised nutrient status. Cyanobacteria formed the dominant ground cover (up to 34%) for 60 years, after when they declined. Vascular plants established slowly and represented minor components of ground cover for the first 100 years. Earliest colonizers were often species with ectomycorrhizal associations, followed by mid‐successional species that tended to disappear as ground cover increased. Some species present in the mature vegetation at the oldest sites, established only after 60+ years. Species richness of vascular plants increased for c. 100 years, beyond when only occasional species were added. Bryophytes became increasingly dominant with time. Soil development on the Midtre Lovénbre and Lovén Island chronosequences was similar after 100 years. Differences subsequently developed, with organic horizon depth, percentage organic matter and water content on the older Lovén islands significantly greater than at equivalent Midtre Lovénbre sites. This was associated with increased bryophyte cover but lower vascular plant species richness. One explanation is a slightly more favourable microclimate, coupled with nutrient input from nesting birds. Communities progressively recruit from a limited pool of effectively dispersed species, each with particular ecological requirements that determine their point of entry into the community. A measure of determinism by default is suggested in the way communities assembled. Under climate warming, in the absence of nutrient enrichment, community development will accelerate but will be constrained by nutrient limitations and a restricted species pool. Where nutrients are less limiting, acceleration towards a moss‐dominated community is expected, with a lower species richness of vascular plants.

IPM of Occasional Urban Invader Pest Species1

Occasional invader species include a variety of arthropods such as amphipods, centipedes, insects, millipedes, pill and sowbugs, scorpions, and spiders as well as nonarthropod mollusks and worms. These species present unique challenges for development of effective IPM programs. Most occasional invaders are susceptible to desiccation and temperature extremes or are in a wandering or migration phase of their life cycle. Environmental factors such as weather and the condition of homes and home landscapes affect occasional invader infestations. Successful IPM programs have been developed for the garden millipede, Oxidus gracilis Koch, and the smokybrown cockroach, Periplaneta fuliginosa (Serville). Both programs rely primarily on habitat modification based on pest biology. Results indicate that these occasional invaders can be managed without resorting to broadcast application of nonspecific insecticides.

Explaining the excess of rare species in natural species abundance distributions.

The observation that a few species in ecological communities are exceptionally abundant, whereas most are rare, prompted the development of species abundance models. Nevertheless, despite the large literature on the commonness and rarity of species inspired by these pioneering studies, some widespread empirical patterns of species abundance resist easy explanation. Notable among these is the observation that in large assemblages there are more rare species than the log normal model predicts. Here we use a long-term (21-year) data set, from an estuarine fish community, to show how an ecological community can be separated into two components. Core species, which are persistent, abundant and biologically associated with estuarine habitats, are log normally distributed. Occasional species occur infrequently in the record, are typically low in abundance and have different habitat requirements; they follow a log series distribution. These distributions are overlaid, producing the negative skew that characterizes real data sets.

Diversity of biting midges of the genus Culicoides Latreille (Diptera: Ceratopogonidae) in the area of the Yacyretá Dam Lake between Argentina and Paraguay.

The Culicoides communities have been analyzed between 1993/1998 in the area influenced by the Yacyret Dam Lake (Paran River, Argentina-Paraguay). Adults of Culicoides were collected monthly by using CDC light traps exposed for 24 h in 9 sampling sites located at both margins of the river; 21 species were recorded. Highest values of species richness were recorded during 1993/1994, being Quiteria and Corpus the sites with the higest number of species (10 and 11, respectively). The species diversity was elevated in Quiteria, Zaim n, Candelaria, Santa Tecla, Capit n Meza and Corpus (Shannon's diversity index 1.0-1.9) while Corate , Ituzaing and Aguapey showed less richness and diversity. The more abundant species were C. insignis, C. venezuelensis, C. leopoldoi, C. limai, C. flinti, C. debilipalpis, C. paraensis and C. guttatus. C. insignis, potential vector of bluetongue virus (BTV) to domestic and wild rumiants in the Neotropical region, is the predominant species in the area and was the only species widely distributed. C. paraensis, a proven vector of Oropouche virus to humans, is a common and abundant species. C. pusillus and C. lahillei, potential vectors of BTV and a filarial parasite, respectively, were occasionally collected. The taxonomic structure of communities was constant during the study period. The occasional species were not characteristic to one particular site and their presence could be related to non-intrinsic conditions.

Relationships between biomass and plant species richness in arid‐zone grazing lands

Summary The relationship between biomass and species richness in temperate vegetation has been described as a hump‐back response model. The hump‐back model predicts that herbaceous species richness is highest at an intermediate level of biomass. However, this has not been investigated in arid‐zone grazing lands. We tested the hump‐back prediction in an arid tropical grazing region in northern Kenya where a seasonal grazing exclosure system is practised. We compared vegetation structure, species richness and composition on an open range and exclosures at five sites to elucidate the potential mechanisms behind variation in species richness. More biomass was accumulated within seasonal exclosures than in continuously grazed areas. Species richness in exclosure plots varied from 5·3 to 8·3 species m−2, while that in open plots varied from 5·1 to 7·5 species m−2. A pair‐wise test showed no difference in two of the five sites with respect to both total and herbaceous species richness. The primary floristic gradient illuminated through ordination was related to biomass, while the secondary gradient was related to species richness. The exclosure plots had more abundant species, especially compared with open plots, which had more rare and occasional species. A total of 37 herbaceous species was recorded; 22% were indifferent to grazing, 30% grazing intolerant and 48% promoted by grazing. The relationship between biomass and herbaceous species richness showed (i) no trend within the exclosures (maximum biomass 800 g m−2); (ii) a positive trend in the open grazing land (maximum of 500 g m−2); and a hump‐back pattern when (i) and (ii) were analysed together. Optimum richness corresponded to a biomass level of 400–500 g m−2. Species richness declined with increase in age of exclosures. We confirmed that species richness will decline when biomass exceeds 500 g m−2, as predicted by the hump‐back model, even in arid grazing lands. Seasonal grazing exclosures may increase species richness to a certain level, but the decline in species richness with age of exclosures indicates that long‐term exclusion of grazing may not necessarily increase species richness in arid‐zone grazing lands.

Planktonic ciliates from an oligotrophic south Andean lake, Morenito Lake (Patagonia, Argentina).

In this contribution we have studied the planktonic ciliates from Morenito Lake, an oligotrophic lake situated in the South Andes of Argentina. Six species that are new records for South America or Argentina are described and illustrated. Besides, population dynamics of the ciliate species were studied during a spring-summer period. Strobilidium lacustris and Balanion planctonicum were the most abundant species, showing a maximum in mid summer. Paradileptus elephantinus was present all over the period while Urotricha furcata was observed in late summer samples. Strobilidium lacustris and S. humile were found to be occasional species during the studied period. The recorded ciliate assemblage with oligotrichs and prostomates as dominant indicate the oligotrophic condition of the lake.

The Fish Assemblage of a Newfoundland Estuary: Diel, Monthly and Annual Variation

Twice monthly sampling over two 16 month periods at a shallow site on Newfoundland's east coast showed the fish assemblage to be dominated by four taxa (Gasterosteus aculeatus, G. wheatlandi, Osmerus mordax, Gadus spp.) that accounted for 96% of the individuals collected. Of the 16479 fish measured, 65% were adults based on the estimated size of first spawning. The fish assemblage was dominated (86%) by species with demersal eggs, several of which spawn at the same shallow sites used by juveniles as nursery sites. Coastal spawning and demersal eggs maintain offspring in coastal nursery areas where survival is thought to be increased. Number of species and number of fish were both correlated with water temperature being highest from mid-summer to early autumn and lowest in winter. Temperature, time of spawning, and movements of juveniles and adults facilitated grouping species into five assemblages based on seasonal abundance: seasonal periodic species (summer and winter), regular species, regular species collected in all seasons except winter, and occasional (rare) species. At the diel scale, two consistent species groupings were observed: species that showed no significant difference between day and night and species caught primarily at night. Number of night species exceeded day species by a factor of two. No seine-caught species in shallow water exhibited significantly higher catches during the day. Observations by SCUBA divers indicated some species were more abundant during day time at slightly deeper depths. This observation in conjunction with day and night seining in shallower water, suggests these species aggregate in deeper water during day and move to shallow waters at night.

Habitat and temporal differences among soil microfungal assemblages in Ontario

A survey of the soil microfungi in the A horizons of soils taken from four sites (deciduous forest, cedar forest, old field, and alfalfa field) in Central Ontario at three times (May, June, and August) in one year was conducted to determine habitat and temporal differences of fungal assemblages. Approximately 70 species of fungi were identified. In all habitats, species in the genera Penicillium, Acremonium, Talaromyces, Cladosporium, Cunninghamella, and Paecilomyces were isolated most frequently. Cedar forest soils showed the lowest species turnover with time, and Aspergillus fumigatus (Fres.) was consistently one of the most abundant species throughout the sampling period. Total fungal abundance increased over the sampling period in cedar forest soils, a trend not observed in deciduous forest soils. Fungal abundance, as well as the total number of species, in soils from the alfalfa field and old field sites decreased in August. Narrow-amplitude, broad-amplitude, and occasional species were characterized. Results are discussed with reference to the biotic and abiotic factors that may influence fungal occurrence and abundance.Key words: fungal soil ecology, microfungi, Ontario, fungal species composition.

Distribution of the Epiphytes along the Leaves of Cymodocea nodosa in the Canary Islands

The distribution of the epiphytes along the oldest leaf of shoots of Cymodocea nodosa was studied during a two-year cycle, from June 1990 to May 1992, in terms of number of species and cover. The difference in age between the base (the youngest part) and the apex (the oldest part) of the leaves allowed a study of the effect of the age of the host on the epiphyte community. A continuous increase in the number of species was observed along the oldest leaf of each shoot, from basal to apical segments. While the permanent epiphyte species were present everywhere, the seasonal and the occasional species were concentrated on the apical segments of the leaves and the occasional epiphytes showed their highest abundance in winter. The greatest development of the individuals, the high number of species as well as the high densities found towards the apical segments resulted in remarkable differences of cover along the leaves, from 0% at the basal segments to more than 600% reached at the apical segments in some months during the study period. The highest mean percentage cover by epiphytes on the oldest leaf of a shoot was detected in winter while the lowest was obtained in spring-summer. The Rhodophyta showed a quantitative dominance of more than 90% of cover in relation to the rest of the algal divisions, the Ceramiales and the Corallinales being the epiphytes which mainly contributed throughout the year. Results on cover and number of species of epiphytes permitted the distinguishing of three stages of development of the epiphytic community along the leaves: initiation, transition and maturity. Annual variations in the number of species as well as in the cover of the epiphytes along the oldest leaves were directly related to the growth rate and life-time of the leaves of Cymodocea nodosa. During the life-time of the leaves there was no succession of species in the epiphytic community but, from basal to apical segments, the epiphyte species were more developed and abundant, and the epiphytic community became more diverse.

Comparison of Habitat Use by Estuarine Fish Assemblages in the Acadian and Virginian Zoogeographic Provinces

Comparison of the relative abundance of fish species from different life-history groups and their temporal patterns of estuarine habitat use from two estuaries north and south of Cape Cod indicates that the Cape acts as a zoogeographic boundary. Between April 1988 and December 1989, monthly seine and trawl samples were collected from nearshore, shallow-water marsh, and beach and deeper open-water habitats in Wells Harbor, Maine, and Waquoit Bay, Massachusetts. Forty-eight species and 80,341 individuals were collected from Waquoit Bay compared to 24 species and 22,561 individuals from Wells Harbor. Waquoit Bay had proportionally fewer resident species and more marine, nursery, and occasional species than Wells Harbor. Annual density and biomass values were greater across all habitats in Waquoit Bay, with the summer values from the marsh habitat an order of magnitude higher than comparable summer data from the Wells habitats. We suggest that marsh and beach habitats provide a nursery area for young-of-the-year fishes, while deeper, open-water habitats serve as a corridor for fishes moving to nearshore habitats or serve as a refuge during low tide.

The Ichthyofauna and Abiotic Hydrological Environment of the Ria de Aveiro, Portugal

The abiotic hydrological environment and the community dynamics of the fish fauna were investigated in the Ria de Aveiro, an estuarine coastal lagoon system (43 km2), which has both marine and fluvial influences. Abiotic hydrological and fish community parameters were recorded routinely during 12 months at ten stations. Temperature ranged between 9.5°C and 26.0°C, salinity between 0.0‰ and 32.0‰, dissolved oxygen between 0.8 mg 1−1 and 15.4 mg 1−1, pH between 6.1 and 9.4, and transparency between 4.4% and 100.0%. No significant differences were observed in temperature and dissolved oxygen among stations, or in seasonal variation in transparency. Nineteen thousand thirty-one fish specimens comprising 55 species were sampled. Abundance, biomass, and species richness were highest in summer and late winter at stations near the lagoon entrance. Sedentary species were most numerous, marine migratory species had the highest biomass, and the category “occasional species” had the highest number of species. Atherinidae, Mugilidae, and Gobiidae were the most important families. Eight species represented about 80% of the total fish abundance and biomass but only six species occurred in all the months and at all the stations. It was concluded that the Ria de Aveiro, with high seasonal and spatial abiotic variation, has a very rich and representative fish community compared with temperate and tropical estuaries and estuarine coastal lagoons around the world.

CHROMOSOME NUMBERS OF CAMPANULACEAE. II. THE LOBELIA TUPA COMPLEX OF CHILE

Gametic chromosome numbers are reported for 27 collections representing the four species of the Lobelia tupa complex (Campanulaceae, Lobelioideae) in Chile; all are n = 21. This represents the first report of chromosome numbers for L. bridgesii Hook. & Arn., L. excelsa Bonpl., and L. polyphylla Hook. & Arn., and confirms previous reports of this number in L. tupa L. As the basic chromosome number of Lobelioideae is x = 7, these species are interpreted as hexaploids. Higher polyploids are extremely rare among Lobelioideae; most of those previously reported have been either sporadic individuals or populations within an otherwise diploid or tetraploid species, or occasional species within an otherwise diploid and tetraploid lineage. This is the first report of an entire complex of lobelioid species that is uniformly hexaploid. This suggests that the Chilean endemics are relatively derived within Lobelia, and offers some support for the monophyly of the complex.

Sapling Survival, Growth, and Recruitment: Relationship to Canopy Height in a Neotropical Forest

Treefall gaps are through to contribute to the diversity of plants in tropical forests by providing opportunities for niche differentiation in modes of regeneration. To examine this hypothesis, we studied the survival, diameter growth, and recruitment of saplings in ≥100 species of woody plants in a 50—ha permanent plot of moist tropical forest on Barro Colorado Island, Panama, from 1982 to 1985. The performance of saplings in low—canopy sites (<10 m) was compared to that of saplings in high—canopy sites (°>10 m), and performance of common species was compared to that of rare species. Of the 108 species for which all three parameters of performance were measured, 104 fell into four response groups, each with characteristic patterns of survival, growth, recruitment, and response to canopy height. Pioneers (six species) survived poorly in both canopy—height categories, and survivors grew rapidly in low—canopy sites. Sapling recruitment was skewed toward low—canopy sites. Understory specialists (three species) survived well in high—canopy sites and poorly in low—canopy sites. They grew slowly and recruited poorly in both situations. Generalists (79 species) survived well and grew slowly in both canopy—height categories. Per—adult recruitment was usually low, and often skewed toward low—canopy sites. Poorly performing species (16 species) survived poorly, grew slowly, and recruited infrequently in both canopy—height categories. Most of the common (>10 saplings/ha) species appeared to be generalists. Many rare (<1 sapling/ha) or occasional (1—10 saplings/ha) species survived significantly (P ≤ .05) less well than the average survivorship of saplings, while many common species survived significantly better than average. Some rare or occasional species grew rapidly, either in low—canopy sites or in both canopy—height categories, while most common species grew slowly in both situations. Rare and occasional species had significantly more recruits per adult than did common species, but often this did not balance their higher mortality. Large differences in survival, growth, and recruitment between canopy—height categories were found only among rare and occasional species.

Variation in Vesicular-Arbuscular Mycorrhizal Relationships of Two Sand Prairie Species

We tested the hypothesis that western sunflower (Helianthus occidentalis) reduces abundance of prairie species within its colonies by producing allelochemics that inhibit seed germination or vesicular-arbuscular mycorrhizal (VAM) formation. Germination of seeds of prairie species was not significantly (P <0.05) inhibited by water extracts of whole sunflower plants or soil collected inside the colony. Comparisons were made of VAM inoculum potential between soil collected from within a sunflower colony and an adjacent area outside the colony dominated by sand lovegrass (Eragrostis trichodes). Significant differences in VAM inoculum potential were found due to season but not due to site of collection. Sunflower roots were significantly more colonized (75 vs. 34%) and more infectious in bioassay tests than lovegrass roots. Root mass (mg/cc) was significantly greater outside the colony than inside, possibly accounting for similarity in inoculum potential between the two areas. Differences in VAM colonization levels and infectivity between sunflower and lovegrass suggest different mycorrhizal relationships for these tapand fibrous-rooted species, respectively. INTRODUCTION Field observations suggested that many common sand prairie species had reduced abundances within dense colonies of western sunflower (Helianthus occidentalis) compared to their abundances in adjacent areas outside of the colonies. This work was initiated to determine the causes of these reduced abundances. It is possible that because of their rhizomatous growth patterns that once established, sunflower could eliminate other species from their colony through competitive exclusion. However, several workers have reported that sunflower species, including annual, ashy and prairie sunflowers, have allelopathic properties (Curtis and Cottam, 1950; Wilson and Rice, 1968; Rice, 1974; Anderson et al., 1978). We hypothesized that western sunflower produced allelochemics that either inhibited plant growth directly and/or interferred with vesicular-arbuscular mycorrhizal (VAM) formation. Interference with mycorrhizal formation in red maple by red pine has been demonstrated by Tobiessen and Warner (1980), and Kovacic et al. (1984) found that mycorrhizal inoculum was absent in the understory of ponderosa pine. Nearly all dominant sand prairie species are mycorrhizal. Sand prairie soils are droughty and contain low levels of available inorganic nutrients (Dickman et al., 1984); therefore, inhibition of mycorrhizal formation by sunflower could reduce the competitive ability of other species. Our study site is located in W central Illinois, Mason Co., in the Sand Prairie Scrub Oak Nature Preserve. The vegetation in the preserve is a mosiac of sand prairie, savannah and closed oak-hickory forest (Anderson and Brown, 1983). Western sunflower is an occasional species in the sand prairie. Our study was conducted using a single sunflower colony. METHODS The perimeter of the sunflower colony was mapped and the area of the colony estimated by drawing a scale diagram of the colony and determining the area of the diagram with a planimeter. Vegetation inside the colony and in an area immediately adjacent to the colony was sampled using a hundred 10 cm x 10 cm quadrats within and outside the colony. Quadrats were located approximately 1 m apart using a stratified random sampling procedure. Plant cover, irrespective of species, projecting over the quadrat was estimated, flowering and nonflowering rosettes of western sunflower rooted

The presence of zinc or manganese as the predominant metal in the mandibles of adult, stored-product beetles

The occurrence of zinc and/or manganese in the mandibles of 54 species of Coleoptera was determined by X-ray microanalysis. Zinc was the predominant metal in the mandibles of all Bostrichoidea examined and in occasional species from other super-families. Manganese was the more common metal in all other species examined. The zinc content of mandibles was found by atomic absorption to be in the range of 5–10 μg mg −1 dry weight for whole mandibles but of much higher concentration in the cutting edges. The implications of the metal contents of beetle mandibles in contributing to the resolution of problems concerning the evolution of the beetles are discussed.