Species diversity of bats (Mammalia: Chiroptera) in Iwokrama Forest, Guyana, and the Guianan subregion: implications for conservation

Fourteen species of bats are reported for the first time from Guyana (Saccopteryx gymnura, Micronycteris brachyotis, M. homezi, Lichonycteris obscura, Anoura latidens, Vampyressa pusilla, Vampyrodes caraccioli, Eptesicus chiriquinus, Cynomops paranus, Molossops neglectus, Molossus sp., Molossus coibensis, Molossus sinaloae, and Promops centralis) bringing the known bat diversity for the country to 121 species. Information including measurements, reproductive data, distribution, and taxonomy are provided for these species. Seven of these new records were collected in the Iwokrama International Rain Forest Programme site in central Guyana. Eighty-six bat species are now documented from Iwokrama Forest which is the highest species diversity for bats reported from any protected area in the world. There are, however, few tropical sites that have relatively complete inventories. A summary for bat species diversity in southern Venezuela, Guyana, Suriname, and French Guiana indicates that at least 146 species of bats are known from the Guianan subregion. Intense inventory surveys, especially in the often neglected subcanopy, suggest that species richness is probably underestimated in most Neotropical areas. Likewise, species-level diversity in the Guianan subregion is higher than previously suggested. Surveying and monitoring biodiversity are critical to developing a National Protected Areas System in Guyana.     

Specializations for aerial hawking in the echolocation system of<Emphasis Type="Italic"> Molossus molossus</Emphasis> (Molossidae,Chiroptera)

While searching for prey, Molossus molossus broadcasts narrow-band calls of 11.42 ms organized in pairs of pulses that alternate in frequency. The first signal of the pair is at 34.5 kHz, the second at 39.6 kHz. Pairs of calls with changing frequencies were only emitted when the interpulse intervals were below 200 ms. Maximum duty cycles during search phase are close to 20%. Frequency alternation of search calls is interpreted as a mechanism for increasing duty cycle and thus the temporal continuity of scanning, as well as increasing the detection range. A neurophysiological correlate for the processing of search calls was found in the inferior colliculus. 64% of neurons respond to frequencies in the 30- to 40-kHz range and only in this frequency range were closed tuning curves found for levels below 40 dB SPL. In addition, 15% of the neurons have double-tuned frequency-threshold curves with best thresholds at 34 and 39 kHz. Differing from observations in other bats, approach calls of M. molossus are longer and of higher frequencies than search calls. Close to the roost, the call frequency is increased to 45.0–49.8 kHz and, in addition, extremely broadband signals are emitted. This demonstrates high plasticity of call design.Abbreviations BF best frequency - CF constant frequency - IC inferior colliculus - F_max maximal frequency - F_min minimal frequency - PF peak frequency - PSTH post-stimulus time histogram - QCF quasi-constant frequency - SPL sound pressure level     

Torpor, thermal biology, and energetics in Australian long-eared bats (Nyctophilus)

Previous studies have suggested that Australian long-eared bats (Nyctophilus) differ from northern-hemisphere bats with respect to their thermal physiology and patterns of torpor. To determine whether this is a general trait of Australian bats, we characterised the temporal organisation of torpor and quantified metabolic rates and body temperatures of normothermic and torpid Australian bats (Nyctophilus geoffroyi, 7 g and N. gouldi, 10 g) over a range of air temperatures and in different seasons. The basal metabolic rate of normothermic bats was 1.36 ± 0.17 ml g⁻¹ h⁻¹ (N. geoffroyi) and 1.22 ± 0.13 ml g⁻¹ h⁻¹ (N. gouldi), about 65% of that predicted by allometric equations, and the corresponding body temperature was about 36 °C. Below an air temperature of about 25 °C bats usually remained normothermic for only brief periods and typically entered torpor. Arousal from torpor usually occurred shortly after the beginning of the dark phase and torpor re-entry occurred almost always during the dark phase after normothermic periods of only 111 ± 48 min (N. geoffroyi) and 115 ± 66 min (N. gouldi). At air temperatures below 10 °C, bats remained torpid for more than 1 day. Bats that were measured overnight had steady-state torpor metabolic rates representing only 2.7% (N. geoffroyi) and 4.2% (N. gouldi) of the basal metabolic rate, and their body temperatures fell to minima of 1.4 and 2.3 °C, respectively. In contrast, bats measured entirely during the day, as in previous studies, had torpor metabolic rates that were up to ten times higher than those measured overnight. The steady-state torpor metabolic rate of thermoconforming torpid bats showed an exponential relationship with body temperature (r ² = 0.94), suggesting that temperature effects are important for reduction of metabolic rate below basal levels. However, the 75% reduction of metabolic rate between basal metabolic rate and torpor metabolic rate at a body temperature of 29.3 °C suggests that metabolic inhibition also plays an important role. Torpor metabolic rate showed little or no seasonal change. Our study suggests that Australian Nyctophilus bats have a low basal metabolic rate and that their patterns of torpor are similar to those measured in bats from the northern hemisphere. The low basal metabolic rate and the high proclivity of these bats for using torpor suggest that they are constrained by limited energy availability and that heterothermy plays a key role in their natural biology. Accepted: 22 November 1999     

Long-term bat study on an island in the southeastern Brazilian coast with comparison of richness and composition of species among sites

Although Rio de Janeiro is one of the best sampled states of Brazil for bats, there are still some poorly studied islands on its coast. Hence, we inventoried the bat species of an island on the southwestern coast of Rio de Janeiro, compared five sites sampled within this island, and compared its bat community with seven other sites in the same region. We carried out sampling in July 1995 and from September 2006 to August 2010, comprising 58 samplings. We captured a total of 1502 individuals of 25 bat species with mist nets set far from roosts, or close to or inside roosts. The most abundant species were Artibeus lituratus, Molossus molossus, and Carollia perspicillata. Total sampling effort was 89,400 m² h. The present study was one out of five inventories carried out in the southwestern coast of Rio de Janeiro that registered more than 1000 bat individuals from more than 24 bat species. Long-term inventories on islands are still needed, because they can result in a large number of species and captures as observed in the present study.     

Fish predation and offspring survival in the prosobranch snail Viviparus ater

In this study we identified some of the predators of the freshwater snail Viviparus ater and estimated offspring survival to the end of the first summer in a natural population. Newborn V. ater were eaten by the fish Barbus barbus, Rutilus rutilus, Scardinius erythrophtalmus and Tinca tinca. Out of 137 guts of Abramis brama caught in Lake Zürich 1 contained shell fragments and an operculum of a newborn V. ater. On a 40×40 m grid near Goldbach, Lake Zürich, we counted 678 adult females of V. ater in June 1988, which together gave birth to approximately 13 300 offspring throughout the summer. In October we found 1348 V. ater of age class 0 on the grid, i.e. approximately 10% of the year's young had survived to the end of their first summer. The grid had been divided into two sections, A and B. In section A, 72 carthenware tiles had been placed as shelters for V. ater. Offspring survival was slightly but significantly higher here (10.9%) than in section B (9.6%). The observation that offspring survival in the natural habitat was 1 order of magnitude lower than in cages suggests that predation is an important cause of mortality of newborn V. ater. Average population density was 2 individuals m^–2 There was a migration from shallow (1–4 m) to deeper water (5–9 m) in September. The average distance between weekly recordings of tagged V. ater was 4.7 m in males and 3.0 m in females.     

Target ranging and the role of time-frequency structure of synthetic echoes in big brown bats,Eptesicus fuscus

Summary Echolocating bats judge the distance to a target on basis of the delay between the emitted cry and the returning echo. In a phantom echo set-up it was investigated how changes in the time-frequency structure of synthetic echoes affect ranging accuracy of big brown bats, Eptesicus fuscus.A one channel phantom target simulator and a Y/N paradigm was used. Five Eptesicus fuscus were trained to discriminate between phantom targets with different virtual distances (delays). The phantom echo was stored in a memory and broadcast from a loudspeaker after a certain delay following the bat's triggering of the system via a trigger microphone. The ranging accuracy was compared using 5 different signals with equal energy as phantom echoes: a standard cry (a natural bat cry), two kinds of noise signals, a high pass, and a low pass filtered version of the standard cry.The standard cry was recorded from one of the bats while judging the distance to a real target. The duration was 1.1 ms, the first harmonic swept down from 55 to 25 kHz and there was energy also in the second and third harmonic. Both noise signals had the same duration, power spectrum, and energy as the standard cry. One noise signal was stored in a memory and hence was exactly the same each time the bat triggered the system. The other variable noise signal was produced by storing the envelope of the standard cry and multiplying on-line with band pass filtered noise. The time-frequency structure (e.g. rise time) of this noise signal changed from triggering to triggering. The filtered signals were produced by either 40 kHz high pass or 40 kHz low pass filtering of the standard cry.The range difference thresholds for the 5 bats were around 1–2 cm (51–119 us) using the standard cry as echo. The range difference threshold with both noise signals was 7–8 cm (around 450 s delay difference). The 40 kHz high pass filtered cry increased the threshold to approximately twice the threshold with the standard cry. With the 40 kHz low pass filtered cry the threshold was increased 2.5–3 times relative to the threshold with the standard cry. A single bat was tested with a signal filtered with a 55 kHz low pass filter leaving the whole first harmonic. The threshold was the same as that with the standard signal.The reduced ranging accuracy with the filtered signals indicates that the full band width of the first harmonic is utilised for ranging by the bats. The substantial reduction in accuracy with the noise signals indicates that not only the full band width but also the orderly time-frequency structure (the FM sweep) of the cry is important for ranging in echolocating bats.Abbreviations FM frequency modulated - CF constant frequency - peSPL peak equivalent sound pressure level - SD standard deviation - SE standard error of mean - EPROM erasable programmable read only memory - FFT fast Fourier transform - S/N signal-to-noise ratio     

Variation in the Sonar of an Aerial-hawking Bat (Eptesicus nilssonii)

Echolocation calls from 10 individually marked female northern bats (Eptesicus nilssonii) were recorded as the bats foraged at three distinct feeding sites (territories) near their maternity roost in southern Sweden (57° N). In addition, recordings of unmarked bats were made in northern Sweden (65° N). The frequency at maximum amplitude of “search phase” echolocation pulses was bimodally distributed, with peaks around 29–30 kHz and 31–32 kHz and was negatively correlated with pulse duration. The frequency at maximum amplitude was related to flight altitude (bats used higher frequencies when they flew near the ground) and also differed among the feeding sites. Hence, much of the variation, probably including regional differences, was behavioural and is interpreted as short term (in the order of s or min) adaptation to current foraging situations. Variation among individual bats, caused by age and size, seemed to be of less importance. Individuals did not use exclusive frequency bands.     

Sunset-related timing of flight activity in neotropical bats

Summary The times of onset and completion of the hunting flights of three colonies of neotropical bats, each comprising 100–200 individuals, were observed for nine months. The colonies were of different species: Molossus ater (M.a.) and Molossus molossus (M.m.) of the Molossidae, and Myotis nigricans (My. n.) of the Vespertilionidae. Individuals of Phyllostomus hastatus (P.h., Phyllostomidae) were also observed. All the bats roosted in a building near Restrepo, Colombia (4°16N, 73°34W). Times of emergence in the evening and the return of the last animals in the morning were recorded on 2 to 3 successive days each month. For all bats, the emergence time changed in parallel with that of sunset, and the return paralleled sunrise (Fig. 1). Accordingly, the duration of the activity period is positively correlated with the duration of the night. No annual periodic changes in phase (re sunset/sunrise) of the onset and end of flight activity could be demonstrated, but there was a close relationship between the timing of activity and particular light intensities during twilight (Fig. 4). The first flyers of M.a. appear at the highest intensity (30–300 lx) and those of My. n. at the lowest (0.1–5 lx); the last flyers to return appear in the opposite sequence. For each species, the return to the roost usually occurs at a lower intensity than the departure. These findings, made with four neotropical bat species, differ from those of Subbaraj and Chandrashekaran (1977) with the emballonurid bat Taphozous that they studied at 9°58 N in India. The ecological factors that may play a role in timing the flight activity of tropical bats are discussed. Sunset-related timing, based on the combined effect of (a) the circadian oscillation in arousal and (b) the transition during twilight to a light-intensity range with reduced inhibition of activity (lightsampling behavior), tends to be the rule in tropical bats; time-of-day-related timing is the exception.Supported by the Deutsche Forschungsgemeinschaft (Er 59/1-3+6)     

Roosting and Foraging Behavior of Two Neotropical Gleaning Bats,Tonatia silvicola and Trachops cirrhosus (Phyllostomidae)1

We studied roosting and foraging behavior of two Neotropical gleaning bats, ?Orbigny's round-eared bat, Tonatia silvicola, and the fringe-lipped bat, Trachops cirrhosus (Phyllostomidae). Techniques included radio-tracking in a tropical lowland forest in Panama and analysis of data from long-term studies in Panama and Venezuela. Day roosts of T. silvicola were in arboreal termite nests. T. cirrhosus roosted in a hollow tree. T. silvicola emerged late (ca 60 min after sunset), and foraged close to the roosts (maximum distance 200–500 m). T. cirrhosus emerged early (ca 30 min after local sunset), and foraged farther from its roost (>1.5 km). Both bats used small foraging areas (3–12 ha) in tall, open forest. They foraged in continuous flight (maximum 27–36 min) or in short sally flights (<1 minute) from perches (“hang-and-wait” strategy). The small foraging areas of these bats and their sedentary foraging mode most likely make them vulnerable to habitat fragmentation.     

Comparative hindlimb bone morphology in noctilionid fisher bats (Chiroptera: Noctilionidae), with emphasis on Noctilio leporinus postnatal development

The hindlimbs allow bats to attach to the mother from birth, and roost during independent life. Despite the great morphological diversity in Chiroptera, the hindlimbs morphology and its postnatal development have been poorly studied. Postnatal development of hindlimbs in Noctilio leporinus is described, further comparing the morphology of adults with that of Noctilio albiventris and previously reported species (Desmodus rotundus, Artibeus lituratus, Molossus molossus). The ossification ending sequence at autopodium elements of N. leporinus does not follow the distal to proximal directional sequence described for D. rotundus, exhibiting a heterochronic delayed ossification ending for the digits of N. leporinus regarding other hindlimb elements, associated with the bigger relative autopodium size of this fisher bat regarding other bat species. Noctilionid bats share the same adult hindlimb bone morphology, except for differences at hindlimb proportions and calcar ossification degree. There are differences in the number and position of bony processes, slots and sesamoids of adult noctilionid fisher bats regarding previously reported species; most differences are concentrated at the autopodium and are related to an increased surface for muscular insertion and the structural support of claws. These facts seem to be closely associated with functional demands of the feeding strategy of noctilionid fisher bats.     

Pyrazine emission by a tropical firefly: An example of chemical aposematism?

Although famous for photic courtship displays, fireflies (Coleoptera: Lampyridae) are also notable for emitting strong odors when molested. The identity of volatile emissions and their possible role, along with photic signals, as aposematic warnings of unpalatability have been little explored, especially in tropical species. Pursuant to the observation that the widespread Neotropical fireflies, Photuris trivittata and Bicellonycha amoena, emit pungent odors, glows, and flashes when handled, we investigated their cuticular and headspace chemistry. Gas chromatography–mass spectrometry analyses revealed that both fireflies have species‐specific cuticular hydrocarbon profiles. Photuris trivittata headspace was dominated by 2‐methoxy‐3‐(1‐methylpropyl) pyrazine (hereafter, pyrazine), on the order of 1.59 ng/individual and a suite of sesquiterpenes, while B. amoena emitted 3‐methoxy‐2‐butenoic acid methyl ester and a few ketones. This is the first report of such compounds in fireflies. We investigated the role of pyrazine in P. trivittata's interactions with potential predators: sympatric ants, toads, and bats. Solvent‐washed P. trivittata painted with pyrazine incurred lower ant predation than did their solvent‐washed counterparts. Pyrazine significantly repelled ants at baits in concentrations as low as 9.8 × 10^?4 ng/μl. The toad, Rhinella marina, readily accepted intact fireflies, pyrazine‐coated and uncoated mealworms. Both Myotis nigricans and Molossus molossus bats rejected fireflies, but accepted both pyrazine‐coated and uncoated mealworms. While pyrazine repels ants, its role as an aposematic signal warning other potential predators of firefly distastefulness requires further investigation. Our results underscore the idea that multiple enemies exert conflicting selection on firefly defenses.     

Discrimination performance and echolocation signal integration requirements for target detection and distance determination in the CF/FM bat,Noctilio albiventris

Summary Bats of the speciesNoctilio albiventris were trained to detect the presence of a target or to discriminate differences in target distance by means of echolocation. During the discrimination trials, the bats emitted pairs of pulses at a rate of 7–10/s. The first was an 8 ms constant frequency (CF) signal at about 75 kHz. This was followed after about 28 ms by a short-constant frequency/ frequency modulated (short-CF/FM) signal composed of a 6 ms CF component at about 75 kHz terminating in a 2 ms FM component sweeping downward to about 57 kHz. There was no apparent difference in the pulse structure or emission pattern used for any of the tasks. The orientation sounds of bats flying in the laboratory and hunting prey under natural conditions follow the same general pattern but differ in interesting ways.The bats were able to discriminate a difference in target distance of 13 mm between two simultaneously presented targets and of 30 mm between single sequentially presented targets around an absolute distance of 35 cm, using a criterion of 75% correct responses.The bats were unable to detect the presence of the target or to discriminate distance in the presence of continuous white noise of 54 dB or higher SPL. Under conditions of continuous white noise, the bats increased their pulse repetition rate and the relative proportion of CF/FM pulses.The bats required a minimum of 1–2 successive CF/FM pulse-echo pairs for target detection and 2–3 to discriminate a 5 cm difference in distance. When the distance discrimination tasks were made more difficult by reducing the difference in distance between the two targets the bats needed to integrate information from a greater number of successive CF/FM pulse-echo pairs to make the discrimination.Abbreviations CF constant frequency - FM frequency modulation     

Frequency alternation and an offbeat rhythm indicate foraging behavior in the echolocating bat, <Emphasis Type="Italic">Saccopteryx bilineata</Emphasis>

The greater sac-winged bat, Saccopteryx bilineata (Emballonuridae), uses two distinct echolocation call sequences: a ‘monotonous’ sequence, where bats emit ~48 kHz calls at a relatively stable rate, and a frequency-alternating sequence, where bats emit calls at ~45 kHz (low-note call) and ~48 kHz (high-note call). The frequencies of these low–high-note pairs remain stable within sequences. In Panama, we recorded echolocation calls from S. bilineata with a multi-microphone array at two sites: one a known roosting site, the other a known foraging site. Our results indicate that this species (1) only produces monotonous sequences in non-foraging contexts and, at times, directly after emitting a feeding buzz and (2) produces frequency-alternating sequences when actively foraging. These latter sequences are also characterized by an unusual, offbeat emission rhythm. We found significant positive relationships between (1) call intensity and call duration and (2) call intensity and distance from clutter. However, these relationships were weaker than those reported for bats from other families. We speculate on how call frequency alternation and an offbeat emission rhythm might reflect a novel strategy for prey detection at the edge of complex habitat in this ancient family of bats.     

Auditory sensitivity and frequency selectivity in greater spear-nosed bats suggest specializations for acoustic communication

We investigated the relationship between auditory sensitivity, frequency selectivity, and the vocal repertoire of greater spear-nosed bats (Phyllostomus hastatus). P. hastatus commonly emit three types of vocalizations: group-specific foraging calls that range from 6 to 11 kHz, low amplitude echolocation calls that sweep from 80 to 40 kHz, and infant isolation calls from 15 to 100 kHz. To determine if hearing in P. hastatus is differentially sensitive or selective to frequencies in these calls, we determined absolute thresholds and masked thresholds using an operant conditioning procedure. Both absolute and masked thresholds were lowest at 15 kHz, which corresponds with the peak energy of isolation calls. Auditory and masked thresholds were higher at sound frequencies used for group-specific foraging calls and echolocation calls. Isolation calls meet the requirements of individual signatures and facilitate parent-offspring recognition. Many bat species produce isolation calls with peak energy between 10 and 25 kHz, which corresponds with the frequency region of highest sensitivity in those species for which audiogram data are available. These findings suggest that selection for accurate offspring recognition exerts a strong influence on the sensory system of P. hastatus and likely on other species of group-living bats.     

Ear morphology of the frog-eating bat (Trachops cirrhosus,family: Phyllostomidae): Apparent specializations for low-freqency hearing

The frog-eating bat (Trachops cirrhosus) is unusual among bats studied because of its reliance on low-frequency (<5 kHz) sounds emitted by frogs for prey localization. We investigated the ear of this bat in order to identify anatomical features that might serve as adaptations for low-frequency hearing. Trachops cirrhosus has a variety of anatomical features that might enhance low-frequency hearing, either by increasing sensitivity to low-frequency sounds or expanding the total frequency range to include lower frequencies. These bats have long pinnae, and a long and wide basilar membrane. The basal portion of the basilar membrane is much stiffer than the apical portion, and the basal portion of the tectorial membrane is more massive than the apical portion. There is also a concentration of mass in the apical portion of the cochlea. T. cirrhosus possesses the largest number of cochlear neurons reported for any mammal, the second highest density of cochlear neurons innervation known among mammals, and three peaks of cochlear neuron density. Other bats have two peaks of cochlear neuron density, lacking the apical concentration, while other mammals usually have only one. T. cirrhosus differs from most other small mammals and bats in characteristics of the apical portion of the cochlea, i.e., that area where the place theory of hearing predicts that low frequencies are detected.     

河南济源人工引水渠隧道蝙蝠冬眠生态学特征

2017-2020年期间,每年1月份对河南省济源市邵原镇布袋沟水库人工引水渠隧道内蝙蝠进行冬眠生态学特征调查,共发现2科5属7种蝙蝠在此冬眠,包括马铁菊头蝠（Rhinolophus ferrumequinum）、小菊头蝠（R.pusillus）、华南水鼠耳蝠（Myotis laniger）、白腹管鼻蝠（Murina leucogaster）、金管鼻蝠（Mu.aurata）、奥氏长耳蝠（Plecotus ognevi）和亚洲宽耳蝠（Barbastella leucomelas）。马铁菊头蝠是优势种（约52%-73%的冬眠个体）,其次是小菊头蝠（约19%-37%）、华南水鼠耳蝠（约5%-8%）,其余蝙蝠物种数量不足3%。2017-2020年冬眠蝙蝠个体总数呈增长趋势,但仍少于早期报道的数量。有42个隧道每年均有蝙蝠冬眠,而且不同年度冬眠数量也不尽相同。通过多元线性回归分析发现,隧道长度可能是影响蝙蝠冬眠栖息场所选择的主要影响因子（Adjusted R²=0.208,P=0.001）。每个隧道内,蝙蝠具有不同的冬眠栖点位置,约4/5的蝙蝠选择温暖且环境相对稳定的隧道深处（> 30 m）作为冬眠栖点,超过95%的个体选择长度> 60 m的隧道冬眠。蝙蝠具有不同的冬眠方式,绝大多数个体采用独栖方式进行冬眠（> 90%）,少数采用聚集方式。不同的冬眠栖点和冬眠方式可能有利于冬眠成本优化。此外,栖点温度与蝙蝠体温之间呈显著正相关（R²=0.98,P < 0.001）,而且蝙蝠冬眠期间的栖点温度具有种内和种间差异。研究结果为我国蝙蝠种群保护和冬眠场所管理提供科学依据。     

The Mode of Orientation during Flight and Approach to Landing in two Phyllostomid Bats

The use of vision during flight and approach to a landing site in two phyllostomid bat species, Phyllostomus discolor and Desmodus rotundus was investigated. Three individuals of each species were trained to traverse a 3-m flight tunnel and to land at a small illuminated grid that was randomly changed between two positions on a front wall. Analysis of the flight path by observation and different technical methods revealed that the bats oriented themselves toward the grid quite early. When the illumination was switched off the flight path diverged much later. With a dark landing grid on one side and an optical projection of it on the other the bats aimed towards this dummy, interrupted the approach 20–40 cm in front of the illusion and then tried to reach the other side or turned back. Whether microchiroptera may rely in the medium range more on vision than usually is thought is discussed.     

Emergence of Chironomidae from Findley Lake and two ponds in the Cascade Mountains,U.S.A.

From Findley Lake and two ponds in the Cascade Mountains (U.S.A.) Chironomidae started to emerge as soon as the ice thawed in 1972 and 1973. The 1051 Chironomidae that emerged per m² from Findley Lake included 307 individuals ofTanytarsus and 358 ofProcladius. Tanytarsus outnumberedChironomus at all depths from 0 to 19.3 m. The 1506 Chironomidae that emerged per m² from the 4.5 m deep pond included 997 individuals ofTanytarsus. The 1490 Chironomidae that emerged per m² from the 2 m deep pond included 1363 Tanytarsus. The emerging biomass was 216 and 186 mg dry weight per m² in Findley Lake and the 4.5 m deep pond, respectively, and only 78 mg in the 2 m deep pond. Most species had their maximum emergence where there was organic detritus from the surrounding forest.Orthocladius emerged from sand bottom at 2.7 to 5.2 m depth.Stictochironomus emerged from mud and sand at 8.4 m depth.Chironomus emerged from soft mud at 15 to 27.5 m depth.     

The role of genetic and chemical variation of <Emphasis Type="Italic">Pinus sylvestris</Emphasis> seedlings in influencing slug herbivory

This study investigated the genetic and chemical basis of resistance of Pinus sylvestris seedlings to herbivory by a generalist mollusc, Arion ater. Using feeding trials with captive animals, we examined selective herbivory by A. ater of young P. sylvestris seedlings of different genotypes and correlated preferences with seedling monoterpene levels. We also investigated the feeding responses of A. ater to artificial diets laced with two monoterpenes, Δ³-carene and α-pinene. Logistic regression indicated that two factors were the best predictors of whether seedlings in the trial would be consumed. Individual slug variation (replicates) was the most significant factor in the model; however, α-pinene concentration (also representing β-pinene, Δ³-carene and total monoterpenes due to multicollinearity) of needles was also a significant factor. While A. ater did not select seedlings on the basis of family, seedlings not eaten were significantly higher in levels of α-pinene compared to seedlings that were consumed. We also demonstrated significant genetic variation in α-pinene concentration of seedlings between different families of P. sylvestris. Nitrogen and three morphological seedling characteristics (stem length, needle length and stem diameter) also showed significant genetic variation between P. sylvestris families. Artificial diets laced with high (5 mg g⁻¹ dry matter) quantities of either Δ³-carene or α-pinene, were eaten significantly less than control diets with no added monoterpenes, supporting the results of the seedling feeding trial. This study demonstrates that A. ater selectively feed on P. sylvestris seedlings and that this selection is based, in part, on the monoterpene concentration of seedlings. These results, coupled with significant genetic variation in α-pinene concentration of seedlings and evidence that slug herbivory is detrimental to P. sylvestris fitness, are discussed as possible evidence for A. ater as a selective force on the evolution of defensive chemistry in P. sylvestris.