Intra- and interspecific copulations in the two congeneric green stink bugs,Nezara antennata andN. viridula (Heteroptera,Pentatomidae), with reference to postcopulatory changes in the spermatheca

Intra- and interspecific copulations betweenNezara antennata andN. viridula were investigated, with reference to postcopulatory changes in the spermatheca. The duration of copulation was significantly shorter in the case ofN. viridula males andN. antennata females than it was in the other 3 combinations. Both sperm and pulpy substance were transferred into the spermatheca during the intraspecific copulation of each species. No sperm was found in the spermatheca after interspecific copulation. However, the pulpy substance was found in the dilated portion of spermathecal ducts of someN. viridula females copulated with anN. antennata male, whereas no such substance was found in the case of theN. antennata females copulated with anN. viridula male. Most of the pulpy substance appeared to have been absorbed from the spermatheca within a 5-day period after the copulation. This absorption was observed for theN. viridula females copulated with anN. antennata male, as well as for the females of each of the species copulated with a conspecific male. It was suggested that this pulpy substance was a male-derived nutrient.     

Some like it hot! Rapid climate change promotes changes in distribution ranges of Nezara viridula and Nezara antennata in Japan

We compared past and current limits of the distribution range of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), in central Japan. In the early 1960s, the northern limit of the range was in Wakayama Prefecture and was limited by a +5 °C isothermal line for the mean January temperature. In 2006–2007, a new survey demonstrated that this northern limit had shifted northwards by 85 km (i.e., at a mean rate of 19.0 km per decade). The shift was most likely promoted by milder winter conditions. The mean January to February temperature in the region was 1.03–1.91 °C higher in 1998–2007 than in 1960–1969. The number of cold days (with the mean temperature below +5 °C) also significantly decreased, while the annual lowest temperature significantly increased. Nezara viridula was found mostly close to those locations where (i) the mean January temperature exceeded +5 °C, (ii) the mean number of cold days did not exceed 26 in January to February, and (iii) where the mean annual lowest temperature did not drop below –3.0 °C. The general linear model shows that the mean January temperature and number of cold days are the most important factors controlling the northern limit of distribution of N. viridula. All the climatic data suggest that over the last 45 years, environmental conditions have become more favourable for overwintering of N. viridula at many locations in central Japan. This has probably promoted the northward spread of the species, representing a direct response to climate warming. A sympatrically distributed congeneric, Nezara antennata Scott, seems to respond to the warming by a retreat from the ocean coast towards cooler elevated habitats, which might be a complex response to elevated temperature and interspecific mating with N. viridula. It is suggested that the range changes in both species will continue in response to further climate change.     

Impacts of global warming on Nezara viridula and its native congeneric species

Climate change and biological invasion are two of the most important ecological issues. Nezara viridula (SGS) is a good example of an alien species that increased in response to recent land use changes and global warming. The range limit of SGS coincided with the 5 °C isotherm of the mean monthly temperature for January. Since 2000, it has been warm enough for SGS to overwinter successfully outside its original range. Most invaded areas are now either occupied by SGS only or by mixed species of Nezara indicating that SGS is replacing its congeneric species, Nezara antennata, through interspecific mating.SGS population dynamics studies performed during 1961–1965 demonstrated that SGS abundance was density dependent and the independent processes worked alternately during the breeding season and winter. Although global warming would improve the winter survival of SGS adults, population density would be regulated at a new equilibrium specific to the area.Life tables demonstrated that all traits related to reproduction were poorly realized in the 2nd generation that occurs during summer. Heat stress syndrome due to global warming may be becoming apparent in SGS in spite of its subtropical origin. N. antennata may be able to avoid heat stress by aestivation. Whether SGS could continue to have a higher reproductive potential at the cost of heat stress over N. antennata is a significant ecological issue.     

Search behaviour of two hemipteran species using vibrational communication

The ability of conspecifics to recognize and locate each other in the environment depends on the efficiency of intraspecific communication. We compared the mate searching strategies of southern green stinkbug Nezara viridula (male searches for a continuously calling female) and the leafhopper Aphrodes makarovi (partners form a precisely coordinated duet). Males of both species were tested on plants in playback experiments. One leaf was vibrated with unaltered conspecific female signals or with various conspecific signals using modified temporal parameters. The results showed that the onset of searching was faster in A. makarovi than in N. viridula. Changes in temporal parameters of female replies had negative effect on the searching behaviour of A. makarovi. Males located the source of longer female replies faster than the short female call and they failed to locate the source of a female reply with temporal parameters outside the species-specific values. In contrast, in N. viridula, searching males successfully located also the source of a female song with parameters outside the species-specific values. The results are discussed with regard to male behavioural strategies in species with different vibrational communication systems and different male mating investment.     

Comparison of Substrate-Borne Vibrational Signals of Two Congeneric Stink Bug Species, Thyanta pallidovirens and T. custator accerra (Heteroptera: Pentatomidae)

Vibrational signals (songs) were recorded and compared for two stink bug species, Thyanta pallidovirens and T. custator accerra. Females of both species produced two songs. Male T. pallidovirens also produced two songs, whereas male T. c. accerra produced four. Songs emitted by females of both species were comparable in structure and function, as was one of the male-produced songs. During the courtship phase of mating behavior, males of both species emitted a song with similar function but different temporal and spectral properties. Basic properties of songs, such as the dominant frequencies, were similar to those of songs of other pentatomid species, but the extensive use of frequency modulation and overlapping duets were novel. Differences in songs, combined with differences in male-produced pheromones, may play a role in the reproductive isolation of these congeners.     

Temporal analysis of tone pulses within the courtship songs of two siblingDrosophila species,their interspecific hybrid,and behavioral mutants ofD. melanogaster (Diptera: Drosophilidae)

Temporal analyses were applied to the tone pulses within the courtship songs of Drosophila melanogaster, D. simulans,their interspecific hybrid, and behavioral mutants of D. melanogaster.Linear regression was performed on various parameters of the song pulses (cycles per pulse, absolute peak amplitude, intrapulse frequency, number of peaks in fast Fourier transform, width of the primary frequency peak, and interpulse interval), as a function of their positions within pulse trains. Significant differences in the slope values of these two species and of the mutant genotypes allowed for discriminative quantification of temporal changes within trains. These results are discussed in relation to previous kinds of temporal analyses of Drosophilacourtship songs and also with regard to the mechanisms of song production.     

Vibrational communication and mating behaviour of Dichelops melacanthus (Hemiptera: Pentatomidae) recorded from loudspeaker membranes and plants

Vibrational communication is important for successful mating in various stink bugs species. The vibrational signals from males and females of Dichelops melacanthus Dallas (Hemiptera: Pentatomidae) are recorded from a nonresonant substrate (i.e. a loudspeaker membrane) to characterize the temporal and spectral properties of these vibrational signals, as well as on a resonant substrate (i.e. bean plants) to obtain information about how these signals are altered when they are transmitted through the plants. On the loudspeaker membrane, D. melacanthus males and females emit only one male or one female song, respectively. However, when the insects are placed on bean leaves, a more complex repertoire is recorded, with three different songs for each sex. The first female and male songs appear to have calling functions and the third male and female songs are emitted during courtship. The second female and male songs are emitted after the first song, although their functions in mating behaviour are not clear. The identified repertoire is similar to those of other Neotropical stink bugs, starting with songs 1 and 2 and developing into song 3. Frequency modulation is observed in the female songs recorded from the loudspeaker membrane and the plants. The signals recorded from plants present higher harmonic peaks compared with the signals recorded from the loudspeaker membrane. The presence of species and sex‐specific songs during mating confirms the important role of vibrational communication in mate location and recognition. The temporal and spectral characteristic signals are influenced by the substrate used to record the songs emitted by D. melacanthus.     

Mating behaviour and parapatry in two species of Australian reptile tick

Summary Few quantitative studies have examined the ecological consequences of similarities and/or differences in mating behaviour of parapatric species. Reproductive interference occurs between several parapatric species of Australian reptile tick, due to similarities in their mating behaviour (Andrews et al. 1982a). Attempts to determine whether reproductive interference serves to maintain parapatry between Amblyomma limbatum and Aponomma hydrosauri have been hindered because of difficulties in providing conditions conducive to conspecific mating in Amb. limbatum. The present study examined whether off-host and/or onhost temperature influenced the subsequent mating behaviour (i.e. the proportion of females that mate and the time when mating occurs) of these two species. Irrespective of the temperature experienced by ticks prior to host attachment, specific on-host temperatures were needed to induce mating in Amb. limbatum (i.e. host cloacal temperatures >32° C prior to the time of peak mating activity). Significantly more Amb. limbatum females were mated and the time taken by females to mate decreased with increasing on-host temperatures. mating in Ap. hydrosauri occurred over a wider range of on-host temperatures and the time when mating occurred did not alter at different on-host temperatures. In addition, significantly more Ap. hydrosauri males moved and each male made more moves on hosts than did Amb. limbatum males. It is suggested that Ap. hydrosauri may in consequence have a competitive mating advantage over Amb. limbatum at a boundary. Similarities in mating behaviour, on the other hand, increase the probability of reproductive interference, hence reduce the reproductive fitness of colonizing females of both species. We propose that similarities and differences in mating behaviour could play a critical role in the maintenance of parapatric boundaries.     

Vibratory Communication and its Relevance to Reproductive Isolation in two Sympatric Stink Bug Species (Hemiptera: Pentatomidae: Pentatominae)

Communication is in phytophagous stink bugs of the subfamily Pentatominae related to mating behavior that among others includes location and recognition of the partner during calling and courting. Differences in temporal and frequency parameters of vibratory signals contributes to species reproductive isolation. Chinavia impicticornis and C. ubica are two green Neotropical stink bugs that live and mate on the same host plants. We tested the hypothesis that differences in temporal and spectral characteristics of both species vibratory signals enable their recognition to that extent that it interrupts further interspecific communication and copulation. To confirm or reject this hypothesis we monitored both species mating behaviour and recorded their vibratory songs on the non-resonant loudspeaker membranes and on the plant. The level of interspecific vibratory communication was tested also by playback experiments. Reproductive behavior and vibratory communication show similar patterns in both Chinavia species. Differences observed in temporal and spectral characteristics of female and male signals enable species discrimination by PCA analyses. Insects that respond to heterospecific vibratory signals do not step forward to behaviors leading to copulation. Results suggest that species isolation takes place in both investigated Chinavia species at an early stage of mating behavior reducing reproductive interference and the probability of heterospecific mating.     

Laboratory evaluation of interspecific mating between Zeugodacus fruit flies and Bactrocera dorsalis

The increasing number of tephritid pest invasions worldwide highlights the importance of interspecific interactions among tephritid pests. The melon fly [Zeugodacus cucurbitae (Coquillett)], the pumpkin fruit fly [Zeugodacus tau (Walker)], and the oriental fruit fly [Bactrocera dorsalis (Hendel)] (all Diptera: Tephritidae) are neotropical fruit flies with overlapping distributions. Their interactions during mating hours have rarely been observed in nature due to their nocturnal behavior. Here, laboratory studies were conducted under no-choice and choice conditions to quantify interspecific mating. The interactions during mating hours resulted in interspecific mating, which reduced conspecific mating success and interrupted mating activity patterns. Successful interspecific mating pairs of Z. cucurbitae and Z. tau were recorded in no-choice and choice tests. Interspecific mating between male Z. cucurbitae and female Z. tau significantly reduced conspecific mating in Z. tau. Observations of the diel mating activity patterns showed that male Z. cucurbitae initiated calling behaviors earlier than Z. tau males, giving Z. cucurbitae more chances to court Z. tau. Though males of neither Zeugodacus species formed mating pairs with B. dorsalis, Zeugodacus males reduced conspecific mating in B. dorsalis in the choice trials. Thus, interspecific interactions among Z. cucurbitae, Z. tau, and B. dorsalis affected conspecific mating; interrupted conspecific mating activity patterns were recorded in all three species. This information could be used to improve management practices.     

Oviposition behaviour of two egg parasites,Asolcus mitsukurii Ashmead andTelenomus nakagawai Watanabe [Hym., Proctotrupoidea,Scelionidae]

Résumé Parmi les parasites des œufs deNezara viridula, Asolcus mitsukurii est bisexué et manifeste un comportement d'agressivité dans les 2 sexes, tandis queTelenomus nakagawai est unisexué et non agressif. Les observations sur le comportement des 2 espèces révèlent quelques différences spécifiques dans la reconnaissance de la ponte h?te et le mode d'oviposition. Asolcus mitsukurii a bien plus d'h?tes secondaires queTelenomus nakagawai; le premier est capable de choisir des pontes beaucoup plus petites que celles deNezara viridula, tandis que le second parasite probablement, les pontes comportant un nombre d'œufs élevé, telles que celles deNezara viridula etNezara antennata. La signification écologique du comportement d'agressivité de la femelle est discutée du point de vue des relations intra- et interspécifiques. Le comportement d'agressivité chez le male du genreAsolcus semble avoir une signification écologique différente de celui des femelles.      

Insects in a warmer world: ecological, physiological and life-history responses of true bugs (Heteroptera) to climate change

Focusing on the southern green stink bug, Nezara viridula (Pentatomidae), in central Japan the effects of climate change on true bugs (Insecta: Heteroptera) are reviewed. In the early 1960s, the northern edge of the species's distribution was in Wakayama Prefecture (34.1°N) and distribution was limited by the +5°C coldest month (January) mean temperature isothermal line. By 2000, N. viridula was recorded 70 km further north (in Osaka, 34.7°N). Historical climate data were used to reveal possible causes of the northward range expansion. The increase of mean and lowest winter month temperatures by 1–2°C in Osaka from the 1950s to the 1990s improved potential overwintering conditions for N. viridula. This promoted northward range expansion of the species. In Osaka, adult diapause in N. viridula is induced after mid‐September, much later than in other local seed‐feeding heteropterans. This late diapause induction results in late‐season ineffective reproduction: some females start oviposition in autumn when the progeny have no chance of attaining adulthood and surviving winter. Both reproductive adults and the progeny die. A period from mid‐September to early November represents a phenological mismatch: diapause is not yet induced in all adults, but it is already too late to start reproduction. Females that do not start reproduction but enter diapause in September have reduced postdiapause reproductive performance: they live for a shorter period, have a shorter period of oviposition and produce fewer eggs in smaller egg masses compared with females that emerge and enter diapause later in autumn. To some extent, N. viridula remains maladapted to Osaka environmental conditions. Ecological perspectives on establishment in recently colonized areas are discussed. A review of available data suggests that terrestrial and aquatic Heteroptera species respond to climate change by shifting their distribution ranges, changing abundance, phenology, voltinism, physiology, behaviour, and community structure. Expected responses of Heteroptera to further climate warming are discussed under scenarios of slight (<2°C) and substantial (>2°C) temperature increase.     

Construction of phylogenetic tree forNicotiana species based on RAPD markers

To apply random amplified polymorphic DNA for analysis of phylogenetic relationships, we used 34 synthetic oligonucleotides as primers to examine interspecific and intraspecific variations among 18 genotypes, nine species ofNicotiana. The nine species used in this study belong to sectionsTomentosae andAlatae. In addition, we attempted to clarify the taxonomic position ofN. sylvestris. A total of 354 distinct DNA fragments were obtained by polymerase chain reaction. Pair-wise comparisons of unique and shared amplification products were used to generate Jaccard's similarity coefficients and Nei and Li's similarity coefficients with the computer software of numerical taxonomy and multivariate analysis system. On the basis of the dendrogram constructed with the similarity coefficients, the 18Nicotiana genotypes were divided into two clusters. The classification analyzed by RAPD markers is in accordance with the classification of Goodspeed thatN. sylvestris is a member of sectionAlatae.     

Seasonal body weight, lipid content, and impact of starvation and water stress on adult survivorship and longevity ofNezara viridula andEuschistus heros

Fresh and dry body weights (FW, DW) were greater for adult southern green stink bug,Nezara viridula (L.) than for the brown stink bug,Euschistus heros F. throughout the year in southern Brazil. FemalesN. viridula significantly increased FW and DW in late summer-early autumn, and during mid-spring; femaleE. heros did not show the same rates of increase in FW and DW. FemaleN. viridula were heavier than males, particularly during summer; however, female and maleE. heros were generally similar in weight.E. heros contained significantly greater amounts of lipid thanN. viridula, during mid-autumn to early-spring (April–September). Survivorship (%) and total longevity ofE. heros adults provided water only was greater (34.6–24.6 days, for females and males) than that forN. viridula (14.8–13.0 days); without water and food, longevity was drastically reduced (<7 days) for both species.     

Role of interspecific competition in the coexistence ofApodemus argenteus andA. speciosus (Rodentia: Muridae)

Reciprocal-removal experiments with two replicates were conducted to test for the role of interspecific competition in the coexistence ofApodemus argenteus andA. speciosus. Population density, rate of appearance of new (unmarked) individuals, reproduction, survival rate and habitat use were monitored during pre- and removal periods. In both removal experiments, the removal ofA. argenteus had little effect onA. speciosus, while that ofA. speciosus affected several population characteristics ofA. argenteus. Namely, the removal ofA. speciosus shifted the distribution ofA. argenteus to the habitat with a denser shrub cover in one experiment. Also, the removal increased the population densities and appearance rates of new individuals ofA. argenteus in another experiment. Interspecific interactions between the two species appeared to be a one-way action fromA. speciosus toA. argenteus. In removal periods in both experiments, the rates of appearance of new individuals in each species were the highest on the grid where that species was removed. These results suggest that, though interspecific competition occurred between the two species, intraspecific competition had greater effects than interspecific competition on the abundance and habitat use ofA. argenteus andA. speciosus. This implies that the fundamental niches ofA. argenteus andA. speciosus differ potentially, which may play an important role in the coexistence of the two species.     

Trade-offs between the persistence of foliage and productivity in two<Emphasis Type="Italic"> Pinus</Emphasis> species

We investigated interspecific variation in leaf lifespan (persistence) and consequent differences in leaf biochemistry, anatomy, morphology, patterns of whole-tree carbon allocation and stand productivity. We tested the hypothesis that a species with short-lived foliage, Pinus radiata D. Don (mean leaf lifespan 2.5 years), grows faster than P. pinaster Ait., a species with more persistent foliage (leaf lifespan 5.6 years), and that the faster growth rate of P. radiata is associated with a greater allocation of nitrogen and carbon to photosynthetic tissues across a range of scales. In fully sunlit foliage, the proportion of leaf N in the major photosynthetic enzyme Rubisco (ribulose-1, 5-bisphosphate carboxylase) was greater in P. radiata than in P. pinaster, and, in mid-canopy foliage, the proportion of leaf N in thylakoid proteins was greater in P. radiata. A lesser proportion of needle cross-sectional area was occupied by structural tissue in P. radiata compared to P. pinaster. Foliage mass in stands of P. radiata was 9.7 t ha^–1 compared with 18.2 t ha^–1 in P. pinaster while leaf area index of both species was similar at 4.6 m² m^–2, owing to the compensating effect of differences in specific leaf area. Hence trade-offs between persistence and productivity were apparent as interspecific differences in patterns of whole-tree carbon allocation, needle morphology, anatomy and biochemistry. However, these interspecific differences did not translate into differences at the stand scale since rates of biomass accumulation were similar in both species (P. radiata 6.9±0.9 kg year^–1 tree^–1; P. pinaster 7.4±0.9 kg year^–1 tree^–1). The similarities in performance at larger scales suggest that leaf area index (and radiation interception) determines growth and productivity. Received: 13 July 1999 / Accepted: 31 January 2000     

Species differences in response to conspecific intruders inCallithrix jacchus andSaguinus oedipus

In this study, the first performed on two species of callitrichid primates under identical conditions, the responses elicited in newly mated individuals by conspecific intruders were compared in four pairs of Callithrix jacchusand four pairs of Saguinus oedipus.Intruders were systematically varied in terms of sex and the social context in which they were met. Clear sexual dimorphism was observed in the behavior of Saguinus oedipus,but the behavior of males and females was less dimorphic in Callithrix jacchus.Males and females of both species showed an increase in agonistic and display behavior in the presence of same-sex intruders, but the mode of behavior varied both with sex and species. Social facilitation, as indicated by increased frequencies of agonistic and display responses in the presence of a mate, was observed only in males of both species. Neither C. jacchusnor S. oedipusdisplayed clear evidence of a monogamous mating system like that of Callicebusor of a polygynous mating system like that of Saimiri.Observed differences in the responses to conspecifics between these two species in the laboratory may be explained by facultative differences in mating systems resulting from differences in ranging and foraging behavior under freeranging conditions.     

Mating frequency and interspecific matings in some freshwater cyclopoid copepods

Laboratory investigations with Cyclops vicinus and Metacyclops minutus documented that mating frequency decreased significantly after the initial mating, i.e. re-mating is relatively rare in cyclopoid copepods. Re-mating is unnecessary because females are able to fertilize multiple clutches of viable eggs from one insemination. Similar sized Cyclops vicinus and Cyclops furcifer interbreed frequently. Interbreeding does not occur when size differences and taxonomic differences are as great as between C. vicinus and M. leuckarti. In C. vicinus and M. leuckarti, the duration of the last mating phase (spermatophore transfer until release of the female) and consequently the duration of the entire mating process, is different. I conclude that the low re-mating frequency in cyclopoid copepods probably evolved to accelerate clutch production in unpredictable environments and to reduce predation risk. The occurrence of interspecific mating discourages the co-existence of similarly sized, related species. Mating behaviour may have a considerable influence on zooplankton community structure.     

Complementation betweenPhycomyces mutants of mating type (+) with abnormal phototropism

Summary Twelve mutants ofPhycomyces blakesleeanus with defects in sporangiophore phototropism (genotypemad) were obtained from a wild type of the (+) mating type by mutagenesis with nitrosoguanidine. These mutants were tested for genetic complementation against standard (+)mad mutants derived from sexual crosses between the isogenic (+) strain and established (-)mad mutants (Ootaki et al., 1974; Eslava et al., 1976). Heterokaryons for complementation tests were obtained by grafting stage I sporangiophores. The (+) mutants were also investigated for their sensory responses such as photoinduction of sporangiophores and avoidance. The mutants were grouped into two classes, based on the phenotypic classification scheme of Bergman et al. (1973). There were eleven class 1.2 mutants and one class 2 mutant. Complementation tests revealed that all eleven class 1.2 mutants carry the genemadC and the class 2 mutant carriesmadD. There was no evidence that any were double mutants. These results are consistent with the phenotypic classification and with the complementation results of themad mutants of the (-) mating type.     

A taxonomic revision and species delimitation of the genus Purpuraria Enderlein, 1929 (Orthoptera: Pamphagidae) using an integrative approach

Recent studies on the endemic Canarian genus Purpuraria have shown that the taxonomy of its only recognized species (P. erna) is probably erroneous. In this study, an integrative revision of the genus is performed, based on a large number of specimens and geographical sampling. As a result, (1) the diagnostic characters at the genus level are re‐described, (2) Purpuraria magna n. sp. based on morphological, morphometric and genetic data is described and (3) the taxonomic status of a formerly described subspecies is clarified. Intraspecific and interspecific morphometric differences have been found, indicating that the genus is undergoing a process of morphological diversification. Nevertheless, the possibility of interspecific mating between individuals of the two species is suggested, because no significant differences have been found between their respective calling songs. Genetic analyses using mitochondrial and nuclear DNA sequences suggest that P. erna and P. magna are recent species with evidences of secondary contact episodes in the past.