Low Dispersal Rates Research Articles

Can Road-Crossing Structures Improve Population Viability of an Urban Gliding Mammal?

Tree-dwelling mammals are potentially highly vulnerable to discontinuities in habitat created by roads. The authors used population modeling to assess the viability of a metapopulation of Australia’s largest gliding marsupial, the greater glider (Petauroides volans), occurring in forest remnants in the fastest-urbanizing region of Australia, where habitat is dissected by major roads. Crossing structures for arboreal mammals (consisting of a land bridge with wooden poles for gliding and adjacent rope canopy bridges) have been installed over an arterial road that separates two of these remnants (one large, one small). It is currently unknown whether this species will use the crossing structures, but available tree height and spacing do not allow a glide crossing, and fences with metal flashing prevent access to the road by terrestrial and arboreal mammals. The authors' modeling reveals that even a relatively low rate of dispersal facilitated by these structures would substantially reduce the probability of extinction of the smaller subpopulation. This rate of dispersal is plausible given the small distance involved (about 55 m). The inclusion of wildfire as a catastrophe in the model suggests that these two remnants may encounter an undesirable level of extinction risk. This can be reduced to an acceptable level by including inter-patch movement via dispersal among other forest remnants. However, this requires connection to a very large remnant 8 km away, through a set of remnants that straddle two motorways. These motorways create discontinuities in forest cover that are beyond the gliding ability of this species. Crossing structures will be required to enable inter-patch movement. A priority for future research should be whether the greater glider will use road-crossing structures. Loss of habitat and habitat connections is continuing in this landscape and is likely to have dire consequences for wildlife if land managers are unable to retain appropriate habitat cover with corridors and install effective wildlife road-crossing structures where large roads intersect wildlife habitat.

Genetic differentiation among cotton bollworm, Helicoverpa armigera (Hübner) populations of south Indian cotton ecosystems using mitochondrial DNA markers

Genetic diversity among 12 cotton bollworm, Helicoverpa armigera (Hübner) populations from different geographic regions of South India was done using mitochondrial DNA‐specific markers. Thirteen selected mtDNA universal markers/primers generated a total of 167 PCR amplicons, of which 162 were polymorphic across all 12 populations. An average of 12.85 amplicons per primer was noted. All populations could be differentiated from one another using specific primers; specific band(s) could be potentially used to differentiate individual populations. Genetic relationships between the populations were evaluated by generating a similarity matrix based on Jaccard's index and a phenetic dendrogram was generated by UPGMA method. Principal component analysis separated the 12 populations into different groups based on band‐sharing data. Populations showed varied degrees of genetic similarity within a range of 0.04–0.52. Also, the populations appeared to be more dispersed on the principal component plot indicating a wide genetic base. On a larger scale, genetic differences among populations appear to result from low dispersal rates between populations. The level of genetic variation detected between the H. armigera populations with mtDNA–PCR analysis suggests that it is an efficient marker technology for delineating genetic relationships amongst populations and estimating genetic diversity, thereby gaining insight into genetic structure of populations and its further use in formulation of appropriate area wide management strategies for this pest.

Dispersal of Phrynops geoffroanus (Chelidae) in an Urban River in Central Brazil

Abstract We studied dispersal of Phrynops geoffroanus in a polluted urban stream in central Brazil. Dispersal distances ranged from 0.0 to 115.0 m after 72 hours and home range size ranged from 0.04 to 0.12 ha. Turtle dispersal for adults and juveniles was accentuated in the first 3 hours with a predominantly upstream movement. Turtle size was significantly related to dispersal distance after 48 hours. Results suggest that the low dispersal rate and the small home range size reflect food supplementation provided by a polluted habitat.

Preferência alimentar de adultos de Metriona elatior Klug (Coleoptera: Chrysomelidae, Cassidinae) por diferentes híbridos de Solanum melogena Linnaeus (Solanaceae)

Metriona elatior Klug is a potential biocontrol agent for Solanum viarum Dunal (tropical soda apple), because larvae and adults feed on its leaves and this species shows a low dispersion rate. Specificity plays a major role in the feasibility of an organism as a biological control agent, especially in the inundative strategy. The feeding preference of M. elatior adults was evaluated to 14 eggplant (Solanum melogena Linnaeus) hybrids. Mass rearing was carried out under lab conditions, with the insect feeding directly on S. viarum leaves. The study started with dual and multiple choice tests in 24 and 48 hour feeding times, by offering leaf disks in Petri dish conditions. Survival and leaf consumption analysis were performed in newly adults in tropical soda apple and eggplant leaves kept turgid by immersing the petioles in water. The leaf area was measured before and after four days of insect exposure. M. elatior showed higher feeding preference, survival and consumption of the weed species, especially in comparison with the hybrid Ryoma. The highest feeding preference among the eggplant hybrids was observed in ‘Minikuro Kowishiki’.

Importance of Habitat Quality and Landscape Connectivity for the Persistence of Endangered Natterjack Toads

The natterjack toad (Bufo calamita) is endangered in several parts of its distribution, including Belgium, where it occurs mainly in artificial habitats. We parameterized a general model for natterjack population viability analysis (PVA) and tested its sensitivity to changes in the values of basic parameters. Then we assessed the relative efficiency of various conservation measures in 2 situations: a small isolated population and a system of 4 populations connected by rare dispersal movements. We based the population viability analysis on a stage-structured model of natterjack population dynamics. We parameterized the model in the RAMAS GIS platform with vital rates obtained from our own field experience and from published studies. Simulated natterjack populations were highly sensitive to habitat quality (particularly pond drying), to dispersal from surrounding local populations, and to a lesser extent to values of fecundity and survival of terrestrial stages. Population trajectories were nearly insensitive to initial abundances, carrying capacities, and the frequency of extreme climatic conditions. The simulations showed that in habitats with highly ephemeral ponds, where premetamorphosis mortality was high, natterjack populations nearly always had a very high extinction risk. We also illustrated how low dispersal rates (<1 dispersing individual/generation) efficiently rescued declining local populations. Such source-sink dynamics demonstrate that the identification and management of source populations should be a high priority.

Attraction of four entomopathogenic nematodes to four white grub species

To better understand the differences in the efficacy of entomopathogenic nematode species against white grub species, we are studying the various steps of the infection process of entomopathogenic nematodes into different white grub species using nematode species/strains with particular promise as white grub control agents. In this study we compared the attraction of the entomopathogenic nematodes Steinernema scarabaei (AMK001 strain), Steinernema glaseri (NC1 strain), Heterorhabditis zealandica (X1 strain), and Heterorhabditis bacteriophora (GPS11 strain) to third-instars of the scarabs Popillia japonica, Anomala orientalis, Cyclocephala borealis, and Rhizotrogus majalis, and late-instar greater wax moth, Galleria mellonella, larvae. Individual larvae were confined at the bottom of 5.5 cm vertical sand columns, nematodes added to the sand surface after 24 h, and nematodes extracted after another 24 h. Nematode attraction to hosts was strongly affected by nematode species but the effect of insect species varied with nematode species. S. glaseri had a high innate dispersal rate (i.e., in absence of insects) and was strongly attracted to insects without significant differences among insect species. S. scarabaei had a very low innate dispersal rate so that even a strong relative response to insects resulted in low absolute dispersal rates toward insects. S. scarabaei tended to be most attracted to G. mellonella and least attracted to C. borealis. H. zealandica had a high innate dispersal rate but only responded weakly to insects without significant differences among species. H. bacteriophora had limited innate dispersal and only weakly responded to insects with G. mellonella tending to be the most attractive and C. borealis the least attractive insect. It has to be noted that we cannot exclude that the use of different rearing hosts ( A. orientalis and P. japonica larvae for S. scarabaei, G. mellonella larvae for the other nematodes) might have had an impact on the nematodes dispersal and relative attraction behavior. This study indicates that host attractiveness and nematode dispersal rates may contribute but do not play a major role in the variability in white grub susceptibility and/or nematode virulence.

Cospeciation between the nasal mite Ptilonyssus sairae (Acari: Rhinonyssidae) and its bird hosts

Abstract The parasitic nasal mite Ptilonyssus sairae Castro has been classified as one species, but we find that significant sequence divergence exists between host-specific mite populations. The low level of gene flow between conspecifics is probably a result of the parasites' low rate of dispersal among different bird host species. The internal transcribed spacer (ITS) of the nuclear ribosomal RNA gene from P. sairae populations was sequenced and used for phylogenetic inference and subsequently compared to their passerine bird host phylogeny. In addition to finding restricted gene flow between host-associated parasites, the reconciliation of host and parasite gene trees reveals statistically significant levels of strict cospeciation between bird hosts and host-specific mite populations. Our findings suggest that cryptic speciation may be common in this group of mites.

Influence of climate change on the abundance, distribution and phenology of woodland bird species in temperate regions

There is now overwhelming evidence that an increase in the concentration of greenhouse gases in the Earth's atmosphere has caused global temperatures to increase by 0.6 °C since 1900 and further increases of between 1.4 and 5.8 °C are predicted over the next century. Changes in climatic conditions have already influenced the demography, phenology and distribution of a wide range of plant and animal taxa. This review focuses on the impacts, both observed and potential, of climate change on birds breeding in temperate woodlands of the Western Palaearctic, a significant proportion of which are currently declining. Changes in ambient temperatures and patterns of precipitation may have direct and indirect effects on the survival rates and productivity of bird species, thus influencing population sizes. For some species or populations, the timing of events such as egg‐laying and return from the wintering grounds is also changing in relation to shifts in the peak of food availability during the breeding season. The degree to which different individuals are able to track these temporal changes will have a significant bearing on population sizes and distributions in the future. Unless active management steps are taken, the relatively low dispersal rates of tree species may lead to a decrease in the total area of some woodland habitat types as losses at the southern edge of the range are likely to occur much more quickly than expansion at the northern edge. In addition, the dispersal rates of many woodland birds are themselves low, which could affect their ability to move to new habitat patches if currently occupied areas become unsuitable. Thus, woodland birds may be particularly susceptible to the impacts of climate change.

Recent demographic bottlenecks are not accompanied by a genetic signature in banner‐tailed kangaroo rats (Dipodomys spectabilis)

Single-sample methods of bottleneck detection are now routine analyses in studies of wild populations and conservation genetics. Three common approaches to bottleneck detection are the heterozygosity excess, mode-shift, and M-ratio tests. Empirical groundtruthing of these methods is difficult, but their performances are critical for the accurate reconstruction of population demography. We use two banner-tailed kangaroo rat (Dipodomys spectabilis) populations from southeastern Arizona (USA) that are known to have experienced recent demographic reductions to search for genetic bottleneck signals with eight microsatellite loci. Over eight total sample-years, neither population showed a genetic bottleneck signature. M-ratios in both populations were large, stable, and never fell below a critical significance value (Mc). The mode shift test did not detect any distortion of allele frequencies, and tests of heterozygosity excess were not significant in postbottleneck samples when we used standard microsatellite mutation models. The genetic effects of bottlenecks like those experienced by our study populations should be strongly influenced by rates of mutation and migration. We used genetic parentage data to estimate a relatively high mutation rate in D. spectabilis (0.0081 mutants/generation/locus), but mutation alone is unlikely to explain the temporal distribution of rare alleles that we observed. Migration (gene flow) is a more likely explanation, despite prior mark-recapture analysis that estimated very low rates of interpopulation dispersal. We interpret our kangaroo rat data in light of the broader literature and conclude that in natural populations connected by dispersal, demographic bottlenecks may prove difficult to detect using molecular genetic data.

Fine‐scale genetic structure and dispersal in the common vole (Microtus arvalis)

The genetic structure and demography of local populations is tightly linked to the rate and scale of dispersal. Dispersal parameters are notoriously difficult to determine in the field, and remain often completely unknown for smaller organisms. In this study, we investigate spatial and temporal genetic structure in relation to dispersal patterns among local populations of the probably most abundant European mammals, the common vole (Microtus arvalis). Voles were studied in six natural populations at distances of 0.4-2.5 km in three different seasons (fall, spring, summer) corresponding to different life-history stages. Field observations provided no direct evidence for movements of individuals between populations. The analysis of 10 microsatellite markers revealed a persistent overall genetic structure among populations of 2.9%, 2.5% and 3% FST in the respective season. Pairwise comparisons showed that even the closest populations were significantly differentiated from each other in each season, but there was no evidence for temporal differentiation within populations or isolation by distance among populations. Despite significant genetic structure, assignment analyses identified a relatively high proportion of individuals as being immigrants for the population where they were captured. The immigration rate was not significantly lower for females than for males. We suggest that a generally low and sex-dependent effective dispersal rate as the consequence of only few immigrants reproducing successfully in the new populations together with the social structure within populations may explain the maintenance of genetic differentiation among populations despite migration.

Host habitat patchiness and the distance decay of similarity among gastro-intestinal nematode communities in two species of Mastomys (southeastern Senegal)

Beta-diversity, or how species composition changes with geographical distance, has seldom been studied for different habitats. We present here quantitative estimates of the relationship between geographic distance and similarity of parasitic nematode communities in two closely related rodent host species that live in habitats with very different spatial configurations. In southeastern Senegal Mastomys natalensis lives exclusively inside human villages whereas M. erythroleucus is continuously distributed outside villages. Both host species and their gastro-intestinal nematodes were sampled on the same spatial scale. Beta-diversity was found to be higher in parasite communities of M. erythroleucus than in those of M. natalensis, and significantly related to geographic distance in this first species. Even on the local spatial scale studied, host dispersal limitation, and stochastic events, may affect species turnover in nematode communities of M. erythroleucus. In M. natalensis, no relationship was found between geographic distance and nematode community similarity, however, suggesting low host dispersal rates between habitat patches. Together with previous population genetic results, this study illustrates the need for different approaches with regard to dispersal in natural populations and its effect on biodiversity.

Large seeds, extinct vectors and contemporary ecology: testing dispersal in a locally distributed cycad, Macrozamia lucida (Cycadales)

The possible reasons for the localised distribution of Macrozamia lucida Johnson in south-eastern Queensland were investigated through testing and quantifying aspects of seed dispersal, ex situ germination across local substrates and the spatial distribution of plants of different ages. Seeds of cones exposed to animals were moved significantly further (108.4 ± 13 cm, n = 10 cones) than those of cones not exposed to animals (49 ± 11 cm, n = 4). Only two mammal species interacted with seeds, common brushtail possums (Trichosurus vulpecula) and bush rats (Rattus fuscipes), but relatively infrequently. The possums were both seed dispersers and predators, whereas the rats ate only sarcotesta. Seed predation and removal occurred at a constant but low rate at cones exposed to animals, compared with no seed removal at unexposed cones. Seeds with sarcotesta intact and sarcotesta alone suffered significantly higher rates of removal by mammals. Seeds in soil had a significantly higher rate of germination (50%) than those in gravel (24.4%) or leaf litter (25.6%) and partially buried seeds germinated at a significantly higher rate (51.2%) than those on the surface (23.2%) and those buried completely (25.6%). In summary, this population appears to be localised spatially by low rates of dispersal, restricted dispersal distance and limited sites for successful germination. The results are discussed in relation to the possible extinction of the original seed dispersers of these organisms and the limitations this imposes on these plants should they be exposed to an unfavourable climatic regime.

Condition-dependent dispersal of a patchily distributed riparian ground beetle in response to disturbance

In common with many habitat elements of riverine landscapes, exposed riverine sediments (ERS) are highly disturbed, naturally patchy and regularly distributed, whose specialists are strongly adapted to flood disturbance and loss of habitat due to succession. Investigations of dispersal in ERS habitats therefore provide an important contrast to the unnaturally fragmented, stable systems usually studied. The present investigation analysed the three interdependent stages of dispersal: (1) emigration, (2) inter-patch movement and (3) immigration of a common ERS specialised beetle, Bembidion atrocaeruleum (Stephens 1828) (Coleoptera, Carabidae), in a relatively unmodified section of river, using mark-resight methods. Dispersal was correlated with estimates of local population size and density, water level and patch quality in order to test for condition-dependent dispersal cues. Flood inundation of habitat was found to increase strongly the overall rate of dispersal, and the rate of emigration was significantly higher from patches that were heavily trampled by cattle. Strongly declining numbers of dispersers with distance suggested low dispersal rates during periods of low water level. Dispersal in response to habitat degradation by cattle trampling would likely lead to a higher overall population fitness than a random dispersal strategy. Dispersal distances were probably adapted to the underlying habitat landscape distribution, high-flow dispersal cues and ready means of long-distance dispersal through hydrochory. Species whose dispersal is adapted to the natural habitat distribution of riverine landscapes are likely to be strongly negatively affected by reduced flood frequency and intensity and habitat fragmentation through flow regulation or channelisation.

METACOMMUNITY INFLUENCES ON COMMUNITY RICHNESS AT MULTIPLE SPATIAL SCALES: A MICROCOSM EXPERIMENT

Large-scale processes are known to be important for patterns of species richness, yet the ways in which local and larger scale processes interact is not clear. I used metacommunities consisting of five interconnected microbial aquatic communities to examine the manner in which processes at different scales affect local and metacommunity richness. Specifically, I manipulated the potential dispersal rate, whether dispersal was localized or global, and variation in initial community composition. A repeated-measures ANOVA showed that a low dispersal rate and intermediate distance dispersal enhanced local richness. Initial assembly variation had no effect on local richness, while a lack of dispersal or global dispersal reduced local richness. At the metacommunity scale, richness was enhanced throughout the time course of the experiment by initial compositional variation and was reduced by high or global dispersal. The effects of dispersal were contingent on the presence of initial compositional variation. The treatments also affected individual species occupancy patterns, with some benefiting from large-scale processes and others being adversely impacted. These results indicate that the effects of dispersal on species richness have a complex relationship with scale and are not solely divisible into "regional" vs. "local" scales. Finally, predictions of the manner in which dispersal rate structures communities appear dependent upon species compositional variation among communities.

Spatial heterogeneity and the stability of host-parasite coexistence

Spatially heterogeneous environments can theoretically promote more stable coexistence of hosts and parasites by reducing the risk of parasite attack either through providing permanent spatial refuges or through providing ephemeral refuges by reducing dispersal. In experimental populations of Pseudomonas aeruginosa and the bacteriophage PP7, spatial heterogeneity promoted stable coexistence of host and parasite, while coexistence was significantly less stable in the homogeneous environment. Phage populations were found to be persisting on subpopulations of sensitive bacteria. Transferring populations to fresh microcosms every 24 h prevented the development of permanent spatial refuges. However, the lower dispersal rates in the heterogeneous environment were found to reduce parasite transmission thereby creating ephemeral refuges from phage attack. These results suggest that spatial heterogeneity can stabilize an otherwise unstable host-parasite interaction even in the absence of permanent spatial refuges.

Inbreeding and promiscuity in the endangered grand skink

The inbreeding avoidance hypothesis predicts that organisms that often encounter relatives as potential mates should evolve behaviours to avoid incestuous matings. Avoidance behaviours have practical importance for small populations because deleterious genetic processes may be less imminent than otherwise expected from genetic models that assume random mating. I used genetic techniques to investigate the extent of inbreeding and inbreeding avoidance behaviours in rare lizards from southern New Zealand. Grand skinks, Oligosoma grande, live in small patchily distributed groups, and have low rates of inter-group dispersal (ca. 3–20% disperse). I used data from 15 microsatellite loci to test the hypothesis that adults are likely to encounter kin as potential mates and will inbreed. These data showed that adult skinks usually inhabited rock outcrops with adult relatives of the opposite sex – up to 35% of potential mates were of equivalent relatedness as half-sibs and 17% were equivalent to full sibs. However, skinks did not preferentially breed with less related mates, and 18.2% of matings were between individuals of equivalent relatedness as full-sibs. Instead, skinks mated with partners of all levels of relatedness, and were promiscuous – almost half of adult females and nearly three quarters of adult males reproduced with multiple partners. In addition, inbreeding had no effect on survival of offspring in their first year. Two other putative mechanisms of inbreeding avoidance, sex-biased and natal dispersal, were not pronounced in this species. This study adds to a growing list of species that inbreed despite the risks.

Regional dynamics of a patchily distributed herbivore along an altitudinal gradient

Abstract. 1. Metapopulation dynamics should be more important at the borders of species distributions due to two main factors: (1) populations are less abundant and fluctuate more at the borders than in the centre of their distributions, and (2) resources in the range margins of species distributions are often more scarce and fragmented.2. Most metapopulation studies have been performed in a fraction of the entire distribution of species. The main goal here is to study the population dynamics of a narrowly distributed species including both the borders and the centre of the distribution, and to test the predictions described above.3. The density and extinction events in a patchily distributed species, Timarcha lugens, was quantified for 5 years along an altitudinal gradient including the upper and lower limits of the species distribution. The dispersal ability of Timarcha was also studied using a mark–release–recapture study.4. Extinction events and empty patches were only found at the borders of Timarcha distribution. The fluctuation in beetle density was greater in patches suffering extinction events. Resource abundance was negatively related to beetle density and positively related to extinction events. In addition, the dispersal rate among patches was very low and beetles moved distances of no further than 25 m.5. Population density governs the extinction events in this system, and its fluctuation was more evident near the border of the distribution. Both factors together with the relative population stability in patches at medium and high altitudes, and the low dispersal rate of the individuals support the idea of a source–sink metapopulation structure in T. lugens.

Does the acephaline gregarine Monocystis sp. modify the surface behaviour of its earthworm host Lumbricus terrestris?

The earthworm Lumbricus terrestris has relatively low dispersal rates. This can represent a challenge for the internal gregarine parasite Monocystis, the dispersal of which often depends on the host. Mating of Monocystis can also be restricted to parasite stages within the current host individual. Adaptations, including host behavioural modification, that improve parasite transmission and simultaneously avoid inbreeding within a single host individual should be favoured by selection. We used a correlative approach to investigate the question of parasitic manipulation in this Gregarine-Lumbricid system. We observed mature earthworms ( n=24) for 3 weeks while recording various measures of activity (surface activity, burrowing activity, surfacing delay, number of surface visits) and correlated parasite load with these activity measures. We found a significant positive correlation between surface activity and midden (or cast) production, which suggests a simple method for assessing the overall activity of local earthworm populations. However, we found no evidence of behavioural manipulation of any measure of host activity. We discuss these results in the context of inbreeding depression and host-parasite coevolution.

Population size estimate of a reef-flat aggregation of Chromodoris annulata (Opisthobranchia, Chromodoridae)

Despite numerous accounts of opisthobranch morphology, life cycle and reproduction, detailed information on field population sizes and movement distances of sea slugs remains scarce. Some recent studies have analysed growth, movement and dispersal in populations of the sea hares Aplysia vaccaria (Winkler, 1955) and A. kurodai (Baba, 1937), and the relation between environmental heterogeneity and spatial distribution in the nudibranch Onchidoris muricata (Muller, 1776), but lacked estimates of population size. Particularly little information is available for species that rarely form mating aggregations and occur at such low densities that quantitative sampling is almost impossible. As a major drawback, mark-recapturebased population size estimates in sea slugs are problematic because individual recognition is often difficult and individual tagging has thus far only been applied to large species of sea hares. Here, we present a short-term capture-recapture-study for a spatially restricted reef-flat aggregation of the tropical IndoPacific nudibranch Chromodoris annulata (Eliot, 1904). This species inhabits various sections of coral reefs, ranging from the shallow subtidal adjacent to mangrove forests up to 15 m depth near the reef crest (e.g. refs 9, 10, records by recreational divers and snorkellers at http://www.seaslugforum.net, personal observations). We surveyed a c. 3 ha (100 300 m) section of the reef-flat at Mangrove Bay (20 km south of El Quseir, Red Sea, Egypt) that covers the full gradient from the rocky and muddy intertidal next to a small mangrove mudflat to the reef crest (depth 1–3 m; Fig. 1). Following initial observations of single C. annulata, we searched the whole area on ten occasions (eight low tides, two high tides) in the eight-day period 5 to 12 May 2003. Most C. annulata were confined to a small area adjacent to the mangrove patch (Fig. 1). We therefore focused our survey effort on this 1435 m (41 m 35 m) core area. Coral rock was only sparsely covered by algae and sponges, but formed many small crevices and holes that served as hides for C. annulata. During low tide the area was partly exposed with a number of submerged small tide pools. At high tides water depths ranged between 30 and 50 cm. Highly variable patterns of purple rings around the rhinophores and orange blotches scattered over the upper mantle (Fig. 2) allowed individual recognition and were sketched for comparison with earlier observations. Sampling locations were recorded on a map in order to calculate minimum movement distances based on straight Euclidian distances between subsequent recordings. This measurement was then divided by the delay between recordings to obtain approximate minimum movement distances per day. We further estimated population size with the modified Lincoln index. This index has been developed for closed populations; i.e. it ignores immigration, emigration, births, and deaths. A closed population appears a realistic approximation for our survey period, since (i) only a single slug was found outside the study area and specimens were concentrated in the centre of the core study area, suggesting low dispersal rates, and (ii) body size distribution of C. annulata (1.5 to 8 cm; mean 4.5 cm) indicated that most animals were adult so that birth did not have a major impact on our population in the course of the study. Given the high recovery rates (see below), mortality was also assumed to be close to zero. For each survey we estimated population size as

Biology, Habitat Preference, and Larval Description of Cicindela cursitans Leconte (Coleoptera: Carabidae: Cicindelinae)

Cicindela cursitans LeConte is a small, flightless tiger beetle with a widely scattered distribution in the Great Plains, the Ohio Valley, and the north-central Gulf Coast region. Many aspects of the life history of C. cursitans are poorly known, and the larval stages have remained undescribed until now. We designed experiments to determine specific habitat preference, female oviposition preference, and daily activity cycles of the adults. In addition, we describe the entire pre-adult life history. Adults are most numerous on moist clay soils with sparse to patchy vegetation, but they may also occur in tall-grass prairies. Females oviposit strictly in moist soils consisting of fine particles. Adults are both diurnal and crepuscular, and presumably spend the nighttime hours hiding among vegetation. Larvae occur in the same habitats as the adults and are typically clustered near the bases of plants. The larvae are the smallest of any tiger beetle species described in North America (body length of first instars ¼ 2.6‐3.2 mm, second instars ¼ 5.4‐6.7 mm, third instars ¼ 8.4‐10.1 mm) and most similar in morphology to Cicindela debilis Bates. Knowledge of the life history and habitats used by this species will allow a better understanding of its distribution and abundance, and its association with prairie habitats. This information as well as low dispersal rates may make this species useful for assessment of habitat quality and restoration success. Cicindela cursitans LeConte is a small flightless tiger beetle. At less than 1 cm in length, adults are among the smallest species in North America (Graves and Brzoska 1991). It is also among the more poorly known species, despite having been first described by LeConte in 1857 (LeConte 1857). The species is associated with bunchgrass prairies near rivers (Tinerella and Rider 2000; M. L. Brust, pers. obs.); however, its pre-adult life history remains very poorly known. It is a summer-active species in the adult stage and is most numerous in June and July (Graves and Pearson 1973; Knisley et al. 1987; Larochelle and Lariviere 2001). Because of its small size and general resemblance to ants it is easily overlooked (Graves and Brzoska 1991), and its North American distribution is probably underestimated (Graves and Pearson 1973; Graves