Patterns of species assemblages and geographical distributions associated with mandible size differences in coastal tiger beetles in Japan

Nine species of tiger beetle (Cicindelidae) occur in coastal habitats in Japan, with two to four species co-occurring at each locality. To examine the patterns of coexistence and geographical distribution, the mandible size of co-occurring species at 17 localities in Japan was examined, based on the assumption that competition for food is an important factor in determining these patterns. The interspecific overlap of mandible length was absent or very low in localities with two or three species, whereas it was more or less evident in localities with four species. For four large coastal species, the geographical distributions of two species with similar mandible lengths are either allopatric or parapatric, whereas those of two species with different mandible lengths largely overlap. These results strongly suggest that size-assortment in mandible length is important in determining species assemblage and distribution in coastal tiger beetles in Japan.An erratum to this article can be found at     

Genital variation in a dimorphic moth Selenia tetralunaria (Lepidoptera, Geometridae)

Insect genitals vary greatly among species and provide a key tool for species-level taxonomy. Insects differing in the genitalia are often treated as discrete, reproductively isolated species. This principle dates back to the lock-and-key hypothesis, which states that genitalia vary between species in order to provide a mechanical reproductive isolation system. Thus, the hypothesis assumes low within-species variability in genital traits. However, recent studies suggest that sexual selection may be responsible for the evolution of insect genitalia. We studied allometry and genital size and shape variation in a dimorphic moth Selenia tetralunaria . We found that the genitalia showed negative allometry in relation to body size as reported in many insect and spider species. This allometry was stronger in internal genital structures than it was in external genitalia. We also found that there was more variation in internal compared with external genitalia. Finally, we found that the shape of genital structures differed between morphs in all three examined areas. S. tetralunaria is among the first reported cases of genitally dimorphic insect species. Considerable variation in internal genitalia and especially the presence of genital shape differences between morphs were not consistent with the predictions of the lock-and-key hypothesis.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 297–307.     

Evidence for lock-and-key mechanisms in the internal genitalia of the Apamea moths (Lepidoptera, Noctuidae)

Abstract. Fifty of the fifty-six species of the genus Apamea known from North America and three Palaearctic species were analysed for lock-and-key characters in their internal genitalia, mainly in the male vesica and the female bursa copulatrix. There were an average of 4.5 such characters per species, structurally corresponding in the two sexes. Anatomically they form a postcopulatory but prezygotic isolation mechanism. In some closely related species, the internal genitalia are very similar, but these species have a precopulatory isolation mechanism in the presence or absence of male abdominal coremata. Closely related species did not have more lock-and-key characters than unrelated species, which is taken to indicate absence of character displacement. The anatomical distribution of the lock-and-key characters was examined and the organs of eight species are illustrated.
The lock-and-key hypothesis has been abandoned by several earlier authors but mainly on consideration of external genitalia. In Apamea the invariable functional correspondence between sexes in the sperm transferring organs, and the overall species-specifity of characters but non-existence of interspecific differences under a precopulatory mechanism indicate that (a) lock-and-keys are functioning and (b) they act as isolation mechanisms. Alternative hypotheses of genitalic evolution are reviewed.     

Morphological variability in Lophyra flexuosa (Fabricius, 1787) (Coleoptera,Cicindelidae) in desert countries is affected by sexual dimorphism and geographic aspect

Lophyra flexuosa, a eurytopic tiger beetle characterized by long phenological activity, wide geographic and altitudinal distribution, and occurring in the highest number of habitats among all Cicindelidae known from North Africa, was chosen to study its geographic variation in morphology and sexual dimorphism. Here, we found significant sexual dimorphism exhibited in larger body size of females and longer mandibles in males, which can be explained by different roles of particular sexes in courtship. Moreover, we recorded significant differences in body sizes between western and eastern Maghreb populations which could suggest genetic isolation between these populations. As the species is related to habitats placed close to the water reservoirs, which in the desert countries are under significant human pressure (including climate change), we expect a reduction of habitat occupied by this taxon. Therefore, the geographic morphological variability that we observe today in the tiger beetle Lophyra flexuosa in the future could lead to speciation.     

Reproductive isolation via divergent genital morphology due to cascade reinforcement in Ohomopterus ground beetles

Secondary contact between incipient species and selection against maladaptive hybridization can drive reinforcement between populations in contact and result in reproductive character displacement (RCD). Resultant divergence in mating traits within a species may generate downstream reproductive isolation between populations with displaced and non-displaced traits, referred to as the cascade reinforcement hypothesis. We examined this hypothesis using three allopatric populations of the ground beetle Carabus maiyasanus with a genital lock-and-key system. This species shows RCD in male and female genital morphologies in populations in contact with the sister species C. iwawakianus. In a reciprocal mating experiment using three allopatric populations with differences in male and female genital sizes, insemination failure increased as the difference in genital size increased. Based on the reproductive isolation index, insemination failure was the major postmating-prezygotic isolation barrier, at least in one population pair with comparable total isolation to those of other species pairs. By contrast, there was only incomplete premating isolation among populations. These results suggest that RCD in genital morphologies drives incipient allopatric speciation, supporting the cascade reinforcement hypothesis. These findings provide insight into the roles of interspecific interactions and subsequent trait diversification in speciation processes.     

Species designation of the Bruneau Dune tiger beetle (Cicindela waynei) is supported by phylogenetic analysis of mitochondrial DNA sequence data

Beetles comprise nearly one quarter of described species and show high levels of morphological and ecological diversification. Because of their wide distribution, ease of detection, and correlation of species richness patterns with other taxa, tiger beetles have been recommended for use as a global indicator of regional biodiversity, requiring accurate taxonomic designations. The Bruneau Dune tiger beetle (Cicindela waynei), whose habitat consists of an isolated dune field in southern Idaho, was recently described as a distinct species from the St. Anthony Dunes tiger beetle (C. arenicola) based on morphological characteristics. While these characteristics include distinct differences in genital morphology that could indicate intrinsic reproductive isolation, morphological characteristics have sometimes been misleading in tiger beetle taxonomy. To evaluate genetic support for this species designation, we analyzed 1,751 base pairs of mitochondrial DNA sequence from 147 tiger beetles collected throughout the range of both C. arenicola and C. waynei. Maximum-likelihood and Bayesian phylogenetic analyses indicated monophyly for C. waynei on a well-supported, short branch nested within C. arenicola. Bayesian species delimitation analyses strongly supported C. waynei as a distinct species (speciation probability = 1.0) with the estimated time of divergence ca. 14,500–67,000 years ago. This lack of reciprocal monophyly and recency of speciation is consistent with C. waynei as a member of an evolutionary front where speciation has occurred at a rapid rate. Mitochondrial sequence data supports the species designation of C. waynei, emphasizing the need to determine appropriate management for this species and its restricted habitat.     

Status and conservation of an imperiled tiger beetle fauna in New York State,USA

New York has 22 documented species of tiger beetles (Coleoptera: Cicindelidae). Over half of these species are considered rare, at risk, or potentially extirpated from the state. These rare species specialize on three sandy habitat types under threat from human disturbance: beaches, pine barrens, and riparian cobble bars. In 2005, we began a status assessment of eight of New York’s rarest tiger beetles, examining museum records, searching the literature, and conducting over 130 field surveys of historical and new locations. Significant findings included (1) no detections of four of the eight taxa; (2) no vehicle-free beach habitat suitable for reintroducing Cicindela dorsalis dorsalis; (3) C. hirticollis at only 4 of 26 historical locations; (4) C. patruela patruela at only one site statewide; and (5) C. ancocisconensis at only 3 of 28 de novo survey sites. Additional species that might be declining deserve our attention, as do some threats to tiger beetle habitats, like lack of beach wilderness, fire suppression in pine barrens, and river damming. Rarity in tiger beetles is a result of varying ecologies, which suggest different conservation strategies. Future inventory and documentation of tiger beetle occurrences need to take into account the metapopulation structure and imperfect detectability of these rare insects.     

Diurnal Tiger Beetles (Coleoptera: Cicindelidae) Capture Prey Without Sight

Although much research has examined the process of prey capture by tiger beetles, an underlying assumption in this work is that tiger beetles are principally, or even exclusively, visual predators. Because this assumption is untested, we performed a series of experiments on four diurnally active tiger beetles in the Genus Cicindela. Individual beetles were placed in chambers in complete darkness and allowed to forage on apterous Drosophila for 6 h. Contrary to expectations, adults of all tested species captured more than 90% of prey items. These results show that other modalities can be used by tiger beetles during prey capture. Beyond potentially providing an explanation for observed night activity in tiger beetle species, the significance of these findings lies in the need to test underlying assumptions of even well-studied organisms.     

Use of simple remote sensing tools to expedite surveys for rare tiger beetles (Insecta: Coleoptera: Cicindelidae)

Tiger beetles (Insecta: Coleoptera: Cicindelidae) often occupy small patches of suitable habitat in otherwise unsuitable landscapes. Such patches are easily overlooked, which may lead to underestimates of both the number of occurrences and the overall population size. In this study, simple World Wide Web-based tools (Google Earth and Microsoft Terraserver) were used to search high-resolution satellite imagery for patches of suitable habitat for globally and regionally rare tiger beetles on a 3,278 ha wildlife refuge in Maryland, USA. This tract is largely forested but contains scattered small open areas of sand and clay soils that are potential habitat for tiger beetles of conservation concern. Visual inspection of remotely sensed imagery resulted in the identification of 19 potential habitat patches, 15 of which yielded tiger beetle populations when surveyed on the ground. The number of species of tiger beetles recorded from this tract was increased from 3 to 8 and two new sites were discovered for the state sensitive species Cicindela scutellaris rugifrons Dejean. In addition, a small population of C. splendida Hentz was discovered, a species last reported from Maryland in 1948. The technique described here shows great promise for locating small patches of potential tiger beetle habitat in otherwise unsuitable landscapes.     

Host acceptance behaviour of the jack pine tip beetle, Conophthorus anksianae and the red pine cone beetle, C. resinosae

The jack pine tip beetle, Conophthorus banksianae McPherson (Coleoptera: Scolytidae) and the red pine cone beetle, C. resinosae Hopkins, are doubtful sibling species. However, it is possible that these two taxa are valid species that maintain reproductive isolation because they accept different hosts. In a series of laboratory and field cage experiments, the host acceptance behaviours of these two species under choice and no choice conditions were compared. The field experiments demonstrated that the two species have a similar propensity to accept jack pine cones and shoots for feeding, but differ consistently in their acceptance of red pine cones, and variably in their acceptance of red pine shoots. However, the laboratory experiments did not indicate a difference between the two species in their propensity to accept red pine cones for feeding. In field cages, C. resinosae accepted significantly more red pine cones for oviposition than C. banksianae; the situation was reversed for jack pine shoots. In comparison to C. banksianae, C. resinosae is a more generalist feeder. The results from this study suggest that host acceptance behaviour is a permeable barrier unable to ensure reproductive isolation between the two species. Although there are differences in the host acceptance behaviours between C. banksianae and C. resinosae, we conclude that these differences do not necessarily support their designation as distinct species.     

How unique is the tiger beetle fauna (Coleoptera,Cicindelidae) of the Balkan Peninsula?

The tiger beetle fauna of the Balkan Peninsula is one of the richest in Europe and includes 19 species or 41% of the European tiger beetle fauna. Assembled by their biogeographical origins, the Balkan tiger beetle species fall into 14 different groups that include, Mediterranean, Middle Oriental, Central Asiatic, Euro-Siberian, South and East European, Pannonian-Sarmatian, West Palaearctic, Turano-European and Afrotropico Indo-Mediterranean species. The Mediterranean Sclerophyl and the Pontian Steppe are the Balkan biogeographical provinces with the highest species richness, while the Balkan Highlands has the lowest Cicindelidae diversity. Most species are restricted to single habitat types in lowland areas of the Balkan Peninsula and only Calomera aulica aulica and Calomera littoralis nemoralis occur in respectively 3 and 4 different types of habitat. About 60% of all Balkan Cicindelidae species are found in habitats potentially endangered by human activity.     

Are we doomed to repeat history? A model of the past using tiger beetles (Coleoptera: Cicindelidae) and conservation biology to anticipate the future

Studies of conservation biology involving tiger beetles have become increasingly common in the last 15 years. Governments and NGOs in several countries have considered tiger beetles in making policy decisions of national conservation efforts and have found tiger beetles useful organisms for arguing broad conservation issues. We trace the evolution of the relationship between tiger beetle studies and conservation biology and propose that this history may in itself provide a model for anticipating developments and improvements in the ability of conservation biology to find effective goals, gather appropriate data, and better communicate generalizations to non-scientific decision makers, the public, and other scientists. According to the General Continuum of Scientific Perspectives on Nature model, earliest biological studies begin with natural history and concentrate on observations in the field and specimen collecting, followed by observing and measuring in the field, manipulations in the field, observations and manipulations in the laboratory, and finally enter theoretical science including systems analysis and mathematical models. Using a balance of historical and analytical approaches, we tested the model using scientific studies of tiger beetles (Coleoptera: Cicindelidae) and the field of conservation biology. Conservation biology and tiger beetle studies follow the historical model, but the results for conservation biology also suggest a more complex model of simultaneous parallel developments. We use these results to anticipate ways to better meet goals in conservation biology, such as actively involving amateurs, avoiding exclusion of the public, and improving language and style in scientific communication. CXLV, Studies of Tiger Beetles     

Lessons from a Beetle and an Ant: Coping with Taxon-Dependent Differences in Microsatellite Development Success

Microsatellites are powerful markers often isolated de novo for species yet to be investigated. Enriched genomic libraries are usually used for isolation purposes. We critically evaluate the outcome of an enrichment-based protocol applied to two insect species (the ant Lasius austriacus and the beetle Pityogenes chalcographus) which yielded contrasting numbers of suitable loci. Our findings of differences in microsatellite isolation are consistent with the available data on differences in genomic characteristics across these taxa. In the beetle repeated isolation of identical motifs, difficulties in primer development, and multibanded products caused loss of most candidate clones. We identified critical steps during marker development. Reviewing Editor: Dr. John Oakeshott     

Static antennae act as locomotory guides that compensate for visual motion blur in a diurnal,keen-eyed predator

High visual acuity allows parallel processing of distant environmental features, but only when photons are abundant enough. Diurnal tiger beetles (Carabidae: Cicindelinae) have acute vision for insects and visually pursue prey in open, flat habitats. Their fast running speed causes motion blur that degrades visual contrast, forces stop-and-go pursuit and potentially impairs obstacle detection. We demonstrate here that vision is insufficient for obstacle detection during running, and show instead that antennal touch is both necessary and sufficient for obstacle detection. While running, tiger beetle vision appears to be photon-limited in a way reminiscent of animals in low-light habitats. Such animals often acquire wide-field spatial information through mechanosensation mediated by longer, more mobile appendages. We show that a nocturnal tiger beetle species waves its antennae in elliptical patterns typical of poorly sighted insects. While antennae of diurnal species are also used for mechanosensation, they are rigidly held forward with the tips close to the substrate. This enables timely detection of path obstructions followed by an increase in body pitch to avoid collision. Our results demonstrate adaptive mechanosensory augmentation of blurred visual information during fast locomotion, and suggest that future studies may reveal non-visual sensory compensation in other fast-moving animals.     

Mutualism is not restricted to tree-killing bark beetles and fungi: the ecological stoichiometry of secondary bark beetles,fungi, and a scavenger

1. All bark beetles are in symbiosis with fungi. Although obligate mutualisms with fungi are common with tree-killing bark beetles (primaries), fungi associated with non-tree-killing bark beetles (secondaries) are usually dismissed as commensals. 2. Using an ecological stoichiometric approach, we show secondaries are also involved in nutrition-based mutualisms, some of which appear obligate, and that differences in symbiont provisioning efficiency have a potent effect on beetle carbon (C): nitrogen (N): phosphorus (P) ratios. 3. Some secondary beetles have high P contents and require efficient P provisioning via fungi, while others have low P contents that may allow them to exploit less efficient fungi or a broader range of species with variable efficiencies. A co-occurring scavenger that feeds on nutrient-poor bark beetle frass (excrement/boring residues) exhibited the lowest phosphorus content yet recorded for an invertebrate. 4. Our results generally support the growth-rate hypothesis that posits differences in C:P and N:P ratios in consumers are due to differential allocation of P to P-rich RNA to support growth. However, while the beetle species that accumulated the most biomass was considerably enriched in P and that with the least biomass was P-poor, one beetle species that was P-rich was also small possibly due to limitation by an element other than P. 5. Our results indicate that fungi are important to a broader range of bark beetles than previously recognised. Additional research is needed to describe how these various symbioses influence forest ecosystems via differential effects of fungi on host beetle fitness.     

Adaptation and the origin of species

As reflected in the title of his masterwork On the Origin of Species, Darwin proposed that adaptation is the primary mechanism of speciation. On this, Darwin was criticized for his neglect of reproductive isolation, his lack of appreciation for the role of geographic barriers, his failure to distinguish varieties from species, and his typological species concept. Two developments since Darwin, the biological species concept of Ernst Mayr and the methods of Coyne and Orr for estimating the contribution of different barriers to the total reproductive isolation, provide a framework for reconciling Darwin's view on the primacy of adaptation in speciation with later proposals that emphasize reproductive isolation. A review of the few studies that have estimated the contributions of multiple isolating barriers suggests that habitat isolation and other barriers that operate before hybrid formation are much stronger than intrinsic postzygotic isolation. In light of these data, I suggest that Darwin's focus on adaptation in the origin of species was essentially correct, a conclusion that calls for future studies that explore the links between adaptation and speciation, in particular, ecogeographic isolating barriers that result from adaptive divergence in habitat use. The recent revival in thinking about ecological factors and adaptive divergence in the origin of species echoes Darwin's much-criticized "principle of divergence" and suggests that the emerging views from today's naturalists are not so different from those espoused by Darwin some 150 years ago.     

The accumulation of reproductive isolation in early stages of divergence supports a role for sexual selection

Models of speciation by sexual selection propose that male–female coevolution leads to the rapid evolution of behavioural reproductive isolation. Here, we compare the strength of behavioural isolation to ecological isolation, gametic incompatibility and hybrid inviability in a group of dichromatic stream fishes. In addition, we examine whether any of these individual barriers, or a combined measure of total isolation, is predicted by body shape differences, male colour differences, environmental differences or genetic distance. Behavioural isolation reaches the highest values of any barrier and is significantly greater than ecological isolation. No individual reproductive barrier is associated with any of the predictor variables. However, marginally significant relationships between male colour and body shape differences with ecological and behavioural isolation are discussed. Differences in male colour and body shape predict total reproductive isolation between species; hierarchical partitioning of these two variables' effects suggests a stronger role for male colour differences. Together, these results suggest an important role for divergent sexual selection in darter speciation but raise new questions about the mechanisms of sexual selection at play and the role of male nuptial ornaments.     

Ontogeny of head and caudal fin shape of an apex marine predator: The tiger shark (Galeocerdo cuvier)

How morphology changes with size can have profound effects on the life history and ecology of an animal. For apex predators that can impact higher level ecosystem processes, such changes may have consequences for other species. Tiger sharks (Galeocerdo cuvier) are an apex predator in tropical seas, and, as adults, are highly migratory. However, little is known about ontogenetic changes in their body form, especially in relation to two aspects of shape that influence locomotion (caudal fin) and feeding (head shape). We captured digital images of the heads and caudal fins of live tiger sharks from Southern Florida and the Bahamas ranging in body size (hence age), and quantified shape of each using elliptical Fourier analysis. This revealed changes in the shape of the head and caudal fin of tiger sharks across ontogeny. Smaller juvenile tiger sharks show an asymmetrical tail with the dorsal (upper) lobe being substantially larger than the ventral (lower) lobe, and transition to more symmetrical tail in larger adults, although the upper lobe remains relatively larger in adults. The heads of juvenile tiger sharks are more conical, which transition to relatively broader heads over ontogeny. We interpret these changes as a result of two ecological transitions. First, adult tiger sharks can undertake extensive migrations and a more symmetrical tail could be more efficient for swimming longer distances, although we did not test this possibility. Second, adult tiger sharks expand their diet to consume larger and more diverse prey with age (turtles, mammals, and elasmobranchs), which requires substantially greater bite area and force to process. In contrast, juvenile tiger sharks consume smaller prey, such as fishes, crustaceans, and invertebrates. Our data reveal significant morphological shifts in an apex predator, which could have effects for other species that tiger sharks consume and interact with. J. Morphol. 277:556–564, 2016. © 2016 Wiley Periodicals, Inc.     

<Emphasis Type="Italic">Geosmithia</Emphasis> Fungi are Highly Diverse and Consistent Bark Beetle Associates: Evidence from their Community Structure in Temperate Europe

Geosmithia spp. (Ascomycota: Hypocreales) are little-studied, dry-spored fungi that occur in galleries built by many phloeophagous bark beetles. This study mapped the distribution and environmental preferences of Geosmithia species occurring in galleries of temperate European bark beetles. One hundred seven host tree samples of 16 tree species infested with 23 subcortical insect species were collected from across Europe during the years 1997–2005. Over 600 Geosmithia isolates from the beetles were sorted into 17 operational taxonomic units (OTUs) based on their phenotype similarity and phylogeny of internal transcribed spacer (ITS) region of rDNA (ITS1-5.8S-ITS2). The OTUs represent six known species and eight undescribed taxa. Ninety-two samples infested with subcortical insects were characterized by the presence/absence of OTUs and the similarity among the samples was evaluated. Geographically distant populations of the same beetle species host relatively uniform Geosmithia communities across large geographic areas (ranging from southern Bulgaria to the Czech Republic). This suggests effective dispersal of Geosmithia spp. by bark beetles. Clustering of similar samples in ordination analysis is correlated predominantly with the isolation source (bark beetles and their respective feeding plant), but not with their geographical origin. The composition of the Geosmithia OTU community of each bark beetle species depends on the degree of isolation of the species’ niches. Thus, Geosmithia communities associated with regularly co-occurring bark beetle species are highly similar. The similarity decreases with decreasing frequency of beetle species’ co-occurrence, a pattern resembling that of entomochoric ophiostomatoid fungi. These findings suggest that: 1) communities of Geosmithia spp. are vector-specific; 2) at least in some cases, the association between Geosmithia OTUs and bark beetles may have been very stable and symbioses are likely to be a fundamental factor in the speciation of Geosmithia fungi; and 3) that even nonsticky spores of Geosmithia are suitable for maintaining an insect–fungus association, contrary to previous hypotheses. An erratum to this article can be found at     

Bioluminescence and chemiluminescence literature: 1987 literature,part III

In studying beetle bioluminescence in the early 1960s, Dr McElroy and his colleagues found that the Jamaican click beetle, Pyrophorus plagiophthalamus, was capable of emitting different colours of light. They further found that the luciferin substrate used by this beetle was the same as that in the firefly, demonstrating that the different colours of bioluminescence were due to differences in the structure of the luciferases. We have recently cloned cDNAs from this beetle species which code for at least four different luciferases. The luciferases are distinguishable by their different colours of bioluminescence when expressed in Escherichia coli. The sequence differences between these different luciferases are few, so the amino acids responsible for the different colours of emission must also be few. Through the construction of hybrid luciferases, by rearranging fragments of the original cDNA clones, we have identified some of these amino acid determinants of colour.