The life cycle and drumming behavior of Zealeuctra claasseni (Frison) and Zealeuctra hitei ricker and ross (Plecoptera: Leuctridae) in Texas,USA 1

The life histories of Zealeuctra claasseni (Frison) and Zealeuctra hitei (Ricker and Ross) (Plecoptera: Leuctridae) were determined from observations and sampling on a Red River tributary in Cooke County, and N. Pecan Creek, Wise County, Texas, Dec., 1974‐June, 1978. Both species showed peak emergence when daily temperature was ca. 12°. Emergence was diurnal, with teneral adults and mating pairs found from dawn—late evening. Male‐female drumming signals were successfully recorded for both species. Incubation experiments at simulated stream temperatures indicated rapid embryonic development, so that larvae were visible through the chorion within ca. 4 weeks after deposition. Both species have highly flexible seasonal development patterns. Four types of life cycles seem possible, depending on field conditions: (1) slow univoltine, (2) fast univoltine, (3) slow semivoltine, and (4) fast semivoltine.     

Latitudinal clines in alternative life histories in a geometrid moth

The relative roles of genetic differentiation and developmental plasticity in generating latitudinal gradients in life histories remain insufficiently understood. In particular, this applies to determination of voltinism (annual number of generations) in short‐lived ectotherms, and the associated trait values. We studied different components of variation in development of Chiasmia clathrata (Lepidoptera: Geometridae) larvae that originated from populations expressing univoltine, partially bivoltine or bivoltine phenology along a latitudinal gradient of season length. Indicative of population‐level genetic differentiation, larval period became longer while growth rate decreased with increasing season length within a particular phenology, but saw‐tooth clines emerged across the phenologies. Indicative of phenotypic plasticity, individuals that developed directly into reproductive adults had shorter development times and higher growth rates than those entering diapause. The most marked differences between the alternative developmental pathways were found in the bivoltine region suggesting that the adaptive correlates of the direct development evolve if exposed to selection. Pupal mass followed a complex cline without clear reference to the shift in voltinism or developmental pathway probably due to varying interplay between the responses in development time and growth rate. The results highlight the multidimensionality of evolutionary trajectories of life‐history traits, which either facilitate or constrain the evolution of integrated traits in alternative phenotypes.     

Rapid seasonal adaptation of an alien bruchid after introduction: geographic variation in life cycle synchronization and critical photoperiod for diapause induction

Whether alien insects that are introduced into temperate regions adapt to seasonally changing environmental conditions is an important question in evolutionary biology. If rapid evolution has occurred in a non‐native environment, a latitudinal cline in critical photoperiod for diapause induction (i.e., the photoperiod at which half of the individuals enter diapause) and in life cycle synchronization with host plant phenology should be evident among locations. The alien bruchid Acanthoscelides pallidipennis (Motschulsky) (Coleoptera: Bruchidae) is native to North America and introduced into Japan with the host plant Amorpha fruticosa L. (Fabaceae) in the late 1940s. To examine whether seasonal adaptation has occurred in A. pallidipennis, we conducted a laboratory experiment and phenological observations using three latitudinally different populations. We bred F1 eggs at 22 °C and five photoperiodic regimens – L:D = 10:14, 13:11, 14:10, 15:9, or 16:8 hours – and examined whether diapause was induced. The estimated critical photoperiod for diapause induction was longest in the most northern population and shortest in the most southern population. Life cycle was found to be synchronized with host phenology in each location. Also voltinism varied geographically, from univoltine in the northern population to bivoltine in the southern populations. These results showed that A. pallidipennis rapidly adapted to seasonal environmental conditions in Japan after its introduction.     

Climate‐induced increase of moth multivoltinism in boreal regions

Aim An increase in multivoltinism in ectothermic animals has been proposed by several authors as a possible outcome of climate warming, especially in high latitudes. We tested this prediction with large‐scale empirical monitoring data for boreal moth communities. Location Finland, northern Europe. Methods Our data set comprised observations of multivoltine species made in the Finnish moth monitoring scheme ‘Nocturna’ trap sites during the period 1993–2006 along an exceptionally long latitudinal gradient of 1000 km. To compare recent changes in moth multivoltinism with a longer time period, we gathered older time series of moth observations from five locations. We used generalized linear mixed models (GLMMs) to detect possible temporal and geographical trends in the annual occurrence of multivoltinism. We also identified areas where the recent changes in multivoltinism have been greatest. Monthly average temperatures of spring and summer periods and annual sum of growing degree days above 5 °C (GDD5) were used as explanatory variables to distinguish the main climatic correlates of moth multivoltinism. Results We observed a clear increase in the occurrence of moth multivoltinism during the period 1993–2006. The incidence as well as the recent increase in multivoltinism were highest in southernmost Finland and decreased towards the north. We also detected a weaker, although significantly positive, trend of moth multivoltinism in southern Finland during the period 1963–92, suggesting that this increasing trend might already have begun earlier. The most important climatic correlates for the annual occurrence of moth multivoltinism were the mean summer temperature (periods May–July and June–August) and GDD5, but all the tested climatic variables showed a significant univariate relationship with the occurrence of moth multivoltinism. All climatic variables showed an increasing trend during the period 1993–2006. Main conclusions The occurrence of multivoltinism has increased in northern European moth communities during recent decades, apparently as a response to increasing temperatures during the spring and summer seasons. The increase in multivoltinism was greatest in the southernmost parts of Finland, whereas in the northern landscapes recent warming has triggered multivoltinism in only relatively few moth species.     

Diapause induction and termination in a commonly univoltine leaf beetle (Phratora vulgatissima)

Abstract The leaf beetle Phratora vulgatissima (Linnaeus 1758) is commonly univoltine in south‐central Sweden but may sometimes initiate a partial second generation. The current study was set out to investigate under what abiotic conditions the beetles initiate a second generation. Using climate chamber experiments, the beetles were shown to have a facultative reproductive diapause induced by declining day‐length. The critical day‐length (CDL) for diapause induction was estimated to be 18 h and 10 min. In the field, first‐generation beetles developing to adulthood before August in 2009 became reproductively active and produced a second generation, but most individuals emerged later and were in reproductive diapause. P. vulgatissima overwinter as adults and diapause was shown to be maintained until mid‐winter in 2008/2009. The cumulative temperature requirement for oviposition after diapause termination was estimated to be 222 day‐degrees with a 5.5°C temperature threshold. Three different day‐degree models that were developed to predict the phenology of female oviposition in the spring were validated by comparing model results with field data on the timing of oviposition in previous years. The study suggests that P. vulgatissima may initiate a second generation in Sweden if development of the first generation is completed before August. Warmer spring and summer temperatures due to ongoing climate change may cause advanced insect phenology and faster completion of insect life‐cycles at northern latitudes, which will affect the proportion of insects that initiate a second generation.     

Ecological correlates of island incidence and geographical range among British butterflies

The incidence of butterflies on British islands and their geographical (latitudinal) ranges are regressed on ecological and life history variables. The objective has been to investigate the contribution of individual variables and to incorporate information on phylogenetic links. The findings confirm the close relationship of species' incidence on islands with their geographical ranges on mainland Britain and that of species' geographical ranges with ecological variables, particularly migration capacity, hostplant type (variety) and breeding-habitat range. The results for island incidence considering phylogenetic links are virtually identical to those disregarding them. For geographical range, the results are similar. The key variable in each case is dispersal, scored in either one of two different ways. However, hostplant type takes precedence over breeding-habitat range when phylogenetic links are considered. Species categorized for upper and lower quartiles for geographical range form isolated clusters in the first two axes of a principal components analysis on a set of seven ecological variables. This result suggests the combined influence of a number of ecological variables on range size. Species with wide geographical ranges tend to have high migration indices, a wide variety of hostplants and ubiquitous hostplants, long flight periods and are often multi-brooded; those with narrow geographical ranges tend to have low migration indices, sparse and limited hostplant resources, short flight periods and are often univoltine. A number of life history variables are found to correlate significantly with geographical range, but account for only small amounts of variation. The lack of any association between range size and population abundance may well reflect the difficulty of obtaining adequate measures for abundance. However, we caution against expecting a strong correlation between range size and abundance.     

r/K‐like trade‐off and voltinism discreteness: The implication to allochronic speciation in the fall webworm,Hyphantria cunea complex (Arctiidae)

North America has distinct types of Hyphantria moths (Arctiidae) characterized by red (RD)‐ and black (BL)‐headed larvae, of which the taxonomic status is unresolved. Genetic divergence of 26 populations, based on 710 bp of the mtCOI sequence, showed two phylogenetic lineages, which could not be connected in the haplotype network with 95% confidence. The two lineages are separated by 3.1% sequence divergence and should be considered for full species status. The estimated split occurred 1.2–1.6 million years ago. The range of the RD type covered most of the continent, whereas that of the BL type was limited to eastern deciduous forests. Several biological characteristics were differentiated in the zone of cohabitation where BL had more annual generations than RD. Spring emergence of BL precedes that of RD in the field by at least 1 month, because the diapause in BL was shallow, whereas it was deep in RD. Voltinism requires discreteness of numbers, which functions as a sink of hybrids between the two parental lines that have distinct but equally adaptive reproductive strategies; BL may be more r‐strategist‐like and RD more K‐strategist‐like, because fast‐developing BL has multivoltine life cycle, investing less silk proteins as the round‐the‐clock feeder, and slow‐developing RD univoltine one investing more silk as the nocturnal feeder. Also, intensity of diapause, deep in RD and weak in BL, was grossly different, which may enforce segregation of spring adults. Allochronic speciation avoiding coincidental occurrence of adult stages is therefore the most likely scenario. Because the adults never meet in nature, large morphological differentiation is not required.     

Temperature‐dependent development of the great European spruce bark beetle Dendroctonus micans (Kug.) (Coleoptera: Curculionidae: Scolytinae) and its predator Rhizophagus grandis Gyll. (Coleoptera: Monotomidae: Rhizophaginae)

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Fit for succession – community structure and life strategies of leafhoppers in urban brownfields

Abstract.  1. Urban brownfields offer an excellent opportunity to study successional processes. Changes in the frequencies of biological traits during succession are of particular interest. They shed light on the general reasons why species emerge and vanish during the course of succession.
2. Leafhopper (Hemiptera: Auchenorrhyncha) occurrence data (3763 species observations) of 194 species were studied. Data was collected on 246 brownfield plots, aged 0–40 years, in two cities in Northern Germany.
3. Four categorical traits were studied: host-plant type, phagy, dormancy, and voltinism. In these traits, two aspects were analysed: (1) changes in trait category frequencies during succession, and (2) distribution of trait categories (i) within the brownfield species pool versus the German species pool and (ii) within species observations.
4. Trait categories showed clear successional trends. Young successional stages were related to feeding on herbs, polyphagy, egg overwintering, and two generations per year.
5. By analysing combinations of two traits, species could be assigned to four functional groups: species associated with young, intermediate and old sites, and one group indifferent to site age. The pioneer group comprised the least number of species, but the highest number of observations.
6. Categories associated with young site age were over-represented in the brownfield species pool. Moreover, within this already biased species pool, species with pioneer trait categories occurred with higher frequency. For the slow colonisers among leafhoppers, brownfields seem to be habitats that are hard to exploit.