Gas exchange morphometry of the lungs of the tokay,Gekko gecko L. (Reptilia: Squamata: Gekkonidae)

The tokay lizard (Gekko gecko) possesses singlechambered lungs, eacch of which is a mirror image of the other reflected in the midsagittal body plane. When standard techniques are employed for instilling 2% phosphate-buffered glutaraldehyde to three-quarters of the total lung capacity, neither the left nor the right lung is consistently larger. Internally, the lungs are characterized by a row of 11 dorsomedial niches and by honeycomb-like (faveolar) gas exchange tissue, which is deeper cranially than caudally. Based upon mean values for all experimental animals, a 100-g tokay would have an overall anatomical diffusion factor (respiratory surface area divided by the appropriate _ht) of 203 cm²·m^-1·100 g^-1, 61% of which is located on the interfaveolar septa. Of the total septal anatomical diffusion factor, 94% is evenly divided between the anterior and middle thirds of the lung, with 6% in the posterior third. The 39% of the anatomical diffusion factor located on the inner lung wall is predominantly (76%) in the middle and posterior lung thirds, with only 24% in the anterior region. These tendencies toward heterogeneous distribution of anatomical diffusion factor were most pronounced in a 55 g juvenile animal. In this animal the total anatomical diffusion faxtor/body mass was 3.6 times that of a 197 g adult. This difference was attributable to a greater body massspecific lung volume and respiratory surface area as well as to a greater surface-to-volume ratio in the parenchyma and to a thinner air-blood diffusion barrier in the juvenile animal.Abbreviations ADF anatomical diffusion factor - %AR percentage of potential respiratory surface area which makes up S_AR - DtO₂ diffusing capacity for air-blood tissue barrier - IUR isotropic uniform randomly distributed - bm body mass - %P percentage of lung volume devoted to parenchyma - S _A potential respiratory surface area (S _L minus the surface area of the trabeculae) - S _ANR non-respiratory surface area - S _AR respiratory surface area - S _L total internal surface area of the lung - S _v surface area-to-volume ratio in parenchyma - _ht harmonic mean thickness of the air-blood tissue barrier - V _L morphometrically determined volume of both lungs, fixed at 0.75· V _Lm - V _Lm maximal lung volume, similar to total lung capacity in mammals - V _Lr resting lung volume, similar to functional residual capacity in mammals - VP morphometrically determined volume of parenchyma of both lungs, fixed at three-quarters of V_Lm     

Contrasting patterns of genetic variation in the two sympatric geckos Gekko tawaensis and G. japonicus (Reptilia: Squamata) from western Japan,as revealed by allozyme analyses

Allozyme variation in two congeneric sympatric geckos, Gekko tawaensis and G. japonicus, from western Japan was examined. These species show similar densities and spatial arrangements of populations in this region, and their genetic structures are thus expected to have been formed under the influences of comparable geohistorical, environmental, and demographic factors. Results of the analyses, however, revealed strikingly different genetic patterns in the two species. Populations of G. tawaensis invariably showed a remarkably lowered heterozygosity (0-0.017) compared to G. japonicus (0.089-0.124). On the other hand, the genetic heterogeneity among populations is much greater in G. tawaensis (F(ST)=0.726) than in G. japonicus (F(ST)=0.101). The Mantel test failed to detect any significant correlations between log (estimated migration rate) and log (geographic distance) in either species, or between matrices of interpopulation pairwise F(ST) for the two species. These results suggest that, in each species, formation of the current genetic structure in western Japan has been chiefly influenced by stochastic factors, rather than the geohistorical architecture of this region. The high F(ST) and low heterozygosity in G. tawaensis suggest the effects of severe local fragmentation. On the other hand, the relatively low F(ST) and high heterozygosity in G. japonicus imply extensive gene flow among populations. Absence of significant correlations between the estimated migration rate and geographic distance in G. japonicus may suggest that such gene flow is promoted by human-mediated transport of this primarily house-dwelling lizard.     

Chromosomal variation in the scincid genus Mabuya and its arboreal relatives (Reptilia: Squamata)

Karyotypes of four East and Southeast Asian species of the genus Mabuya and representatives of three arboreal genera considered to be closely related to the genus (Apterygodon, Dasia and Lamprolepis) are examined. Mabuya rugifera and M. rudis possess 2n=32 karyotypes, whereas M. longicaudata lacks one small chromosome pair, which makes its diploid number 30. The karyotype of M. macularia quadrifasciata from southern Thailand differs from any known scincid karyotypes, including a previously reported karyotype of the conspecific Indian population, in exhibiting a high diploid number (38) and a gradual change in size from large to small chromosomes. This suggests that M. macularia may consist of more than one biological species. Karyotypes of Apterygodon vittatus, Dasia olivacea and Lamprolepis smaragdinus, while exhibiting a close similarity to most Mabuya karyotypes, suggest the occurrence of slight rearrangements involving either the deletion of two small chromosome pairs (A. vittatus), or the change of centromeric positions in medium and small chromosomes (D. olivacea and L. smaragdinus).     

Biochemical assessment of evolution and taxonomy of the morphologically poorly diverged geckos, Gekko yakuensis and G. hokouensis (Reptilia: Squamata) in Japan, with special reference to their occasional hybridization

We assessed the validity of two gekkonid species, Gekko yakuensis and G. hokouensis, in southern Japan. We first assigned all 398 specimens into 18 samples merely on the basis of localities. By conducting significance test for deviations of genotype frequencies from Hardy‐Weinberg at 11 allozyme loci, we checked the reproductive unity of constituents in each of those local samples, and where necessary, rearranged them into subsamples on the basis of genetic markers so that we recognized minimum reproductively cohesive units. We then compared allele frequencies among all samples and subsamples examined. Results clearly indicated that all but two can be classified into two groups that can be discriminated from each other by remarkable allele frequency differences at four diagnostic loci, and by large genetic distances even between sympatric subsamples. Observations of morphological features of the samples and subsamples confirmed that the two groups correspond to G. yakuensis and G. hokouensis, supporting validities of these two species. Allele frequency comparisons, however, also revealed that the remaining two samples, both from southern Kyushu, possessed ‘marker alleles' of both G. yakuensis and G. hokouensis at all four diagnostic loci. These samples thus were considered to represent populations that have been derived through hybridization of the two species. Detailed analyses for genetic structures demonstrated that all hybrid genotypes in the two samples are post‐Fi generations with only one individual resulting from the back‐cross with a pure line population of G. yakuensis. This finding negates the possibility that the hybrid populations are maintained by a constant supply of newly produced Fj hybrids, but suggests that the hybrid genotypes constitute stable breeding populations. This implies that the genealogical independence of G. yakuensis and G. hokouensis in several other sympatric areas has been maintained by operations of some isolation mechanisms at a pre‐mating phase. Investigations of the morphological variation in each sample or subsample revealed that although the two species can be externally largely discriminated from each other by slight modifications of the currently used diagnoses, it is difficult to detect their hybrids based solely on the morphological features.     

A Century of Hybridization: Decreasing Genetic Distance Between American Black Ducks and Mallards

American black ducks (Anas rubripes) and mallards (A. platyrhynchos) are morphologically and behaviorally similar species that were primarily allopatric prior to European colonization of North America. Subsequent sympatry has resulted in hybridization, and recent molecular analyses of mallards and black ducks failed to identify two distinct taxa, either due to horizontal gene flow, homoplasy, or shared ancestry. We analyzed microsatellite markers in modern and museum specimens to determine if the inter-relatedness of mallards and black ducks was an ancestral or recent character. Gst, a measure of genetic differentiation, decreased from 0.146 for mallards and black ducks living before 1940, to 0.008 for birds taken in 1998. This is a significant reduction in genetic differentiation, and represents a breakdown in species integrity most likely due to hybridization. Using modern specimens, we observed that despite a lower incidence of sympatry, northern black ducks are now no more distinct from mallards than their southern conspecifics.     

Natural and experimental hybridization inArmeria (Plumbaginaceae):A. villosa subsp.carratracensis

An experimental crossing program was carried out in order to test the hypothesis thatArmeria villosa subsp.carratracensis, a serpentine endemic from Southern Spain, is of hybrid origin. Fruit-set and mainly pollen stainability data in artificial hybrids demonstrate that internal interspecific barriers are weak. Two generations of backcrossing with the two putative parents —A. colorata andA. villosa subsp.longiaristata— can restore pollen stainability to an average of 83.2 and 68.7, respectively. A morphometric analysis of 148 specimens belonging to parental species, different artificial hybrid generations and wild putative hybrid race shows that (1) morphological characters have a strong genetic basis and thus are good markers in identifying hybrids and introgression inArmeria; (2) artificial backcrossing produces in morphometrical characters a variation which conforms in both trend and magnitude to what is commonly attributed in the wild to introgression; (3) the position of the putative hybrid race is intermediate between the two parental species used in the program. These results are in accordance with the hypothesis of hybrid origin ofA. villosa subsp.carratracensis. Natural and experimental hybridization inArmeria, I     

Scanning electron-microscopical study of epididymal secretions in the lizard Lacerta vivipara (Reptilia,Squamata) and of their relationships with spermatozoa

Cell and Tissue Research - During the breeding season (April, May) the epididymis of the lizard Lacerta vivipara produces voluminous secretory granules which are abundantly discharged into the...     

Hybridization and evolution inCardamine (Brassicaceae) at Urnerboden, Central Switzerland: Biosystematic and molecular evidence

Hybridization between two diploid (2n = 2x = 16) species ofBrassicaceae, Cardamine rivularis andC. amara, at Urnerboden, Central Switzerland, resulted in the rather unusual triploid hybridC. insueta (2n = 3x = 24), and later on in the amphiploidC. schulzii (2n = 6x = 48). The hybrid and the neopolyploid species colonized successfully some man-made biotopes. Plants ofC. insueta are mostly functional females with non-dehiscent anthers, but true hermaphrodite individuals with partly sterile pollen grains also occur within the population. Analyses of cpDNA and nuclear DNA permitted to establish the parentage of the hybrid: the maternal parent which contributed unreduced egg cells proved to beC. rivularis whereas the normally reduced pollen originated fromC. amara. The pronounced genetic variability inC. insueta revealed by isozyme and RAPD analyses, at variance with the polarized segregation, heterogamy and strong vegetative reproduction of the hybrid, is possibly influenced by recurrent formation ofC. insueta which party results from backcrosses betweenC. insueta andC. rivularis but may also proceed by other pathways. The amphiploidCardamine schulzii has normally developed anthers but its pollen is sometimes highly sterile. The surprisingly uniform genetic make-up of the new amphiploid species might be related to its possible monotopic origin and/or young phylogenetic age but should be further assessed. Site management seems to be very important to a further development of hybridogenous populations and their parent species. In conclusion, the evolution at Urnerboden is discussed in the context of the traditional concept of multiple plant origins.     

Radiation, multiple dispersal and parallelism in the skinks, Chalcides and Sphenops (Squamata: Scincidae), with comments on Scincus and Scincopus and the age of the Sahara Desert

Phylogenetic analysis using up to 1325 base pairs of mitochondrial DNA from 179 specimens and 30 species of Chalcides, Sphenops, Eumeces, Scincopus and Scincus indicates that Sphenops arose twice independently within Chalcides. It is consequently synonymized with that genus. Chalcides in this broader sense originated in Morocco, diversifying into four main clades about 10 Ma, after which some of its lineages dispersed widely to cover an area 40 times as large. Two separate lineages invaded the Canary Islands and at least five main lineages colonized southern Europe. At least five more spread across northern Africa, one extending into southwest Asia. Elongate bodies with reduced limbs have evolved at least four times in Chalcides, mesic 'grass-swimmers' being produced in one case and extensive adaptation to life in loose desert sand in two others. In clade, Chalcides striatus colonized SW Europe from NW Africa 2.6 Ma and C. chalcides mainland Italy 1.4 Ma, both invasions being across water, while C. c. vittatus reached Sardinia more recently, perhaps anthropogenically, and C. guentheri spread 1200km further east to Israel. C. minutus is a composite, with individuals from the type locality forming a long independent lineage and the remaining ones investigated being most closely related to C. mertensi. In the Northern clade, C. boulengeri and C. sepsoides spread east through sandy habitats north of the Sahara about 5 Ma, the latter reaching Egypt. C. bedriagai invaded Spain around the same time, perhaps during the Messinian period when the Mediterranean was dry, and shows considerable diversification. Although it is currently recognized as one species, the C. ocellatus clade exhibits as much phylogenetic depth as the other main clades of Chalcides, having at least six main lineages. These have independently invaded Malta and Sardinia from Tunisia and also southwest Arabia C. o. humilis appears to have spread over 4000 km through the Sahel, south of the Sahara quite recently, perhaps in the Pleistocene. In the Western clade of Chalcides, C. delislei appears to have dispersed in a similar way. There were also two invasions of the Canary Islands: one around 5 Ma by C. simonyi, and the other about 7 Ma by the ancestor of C. viridanus+C. sexlineatus. C. montanus was believed to be related to C. lanzai of the Northern clade, but in the mtDNA tree it is placed within C. polylepis of the Western clade, although this may possibly be an artifact of introgression. The Eumeces schneideri group, Scincopus and Scincus form a clade separate from Chalcides. Within this clade, the geographically disjunct E. schneideri group is paraphyletic. One of its members, E. algeriensis is the sister taxon to Scincopus, and Scincus may also be related to these taxa. The phylogeny suggests Scincopus entered desert conditions in Africa, up to 9.6 Ma and the same may have been true of Scincus up to 11.7 Ma. Scincus appears to have diversified and spread into Arabia around 6 Ma. Dates of origin and divergence of these skinks, desert Chalcides and other squamates agree with recent geological evidence that the Sahara is at least 5-7 My old. The subspecies Chalcides viridanus coeruleopunctatus is upgraded to the species level as C. coeruleopunctatus stat nov., on the basis of its large genetic divergence from C. v. viridanus.     

Two new species of Andean gymnophthalmid lizards of the genus Euspondylus (Reptilia, Squamata) from central and southern Peru

Two new species of lizards assigned to the genus Euspondylus from the montane forests of the Peruvian Andes in the Pasco Department (central Peru) and Ayacucho Department (southern Peru) both at elevations of 2550 and 3450 m, respectively, are described. The new species are distinguishable from all other Peruvian and Ecuadorian species of Euspondylus by a unique combination of morphometric, scalation and color pattern characteristics. Natural history data for the new species and for Euspondylus spinalis are also provided.     

Introgressive hybridization between Galaxias depressiceps and Galaxias sp D (Teleostei: Galaxiidae) in Otago, New Zealand: Secondary contact mediated by water races

Central Otago (New Zealand) was the focus of an intense period ofgold mining in the late 19th century. Mining relied on high waterpressure for sluicing, often requiring extensive systems of water raceslinking headwaters over large distances. On Rough Ridge, races connectedheadwaters of Otago's two major river systems, the Taieri and theClutha. We employed genetic analysis of freshwater fish(Galaxias) populations to assess the biological implications ofrace-development. The two galaxiid taxa found on Rough Ridge (G. spD and G. depressiceps) are reciprocally monophyletic formtDNA and have three fixed allozyme differences. Rough Ridge aside,G. sp D is apparently absent from the Taieri system and G.depressiceps from the Clutha system. Distributions of mitochondrialDNA, allozyme and microsatellite alleles imply that artificialconnections have facilitated bidirectional introgression: movementof G. sp D alleles into the Taieri system and G.depressiceps alleles into the Clutha. The finding of some identicalcontrol region haplotypes (of both lineages) on either side of thecatchment boundary confirms the recency of genetic exchange. Near theinferred region of contact, samples from Linn Burn (Taieri) are pureG. depressiceps for three diagnostic allozymes and mtDNA.Samples from upper Pool Burn (Clutha) are pure G. sp D forthese same four markers. However, other collections from around thecontact zone represent genetic mixtures forming a cline. We fear thatsimilar human-induced mixing may have happened elsewhere in uplandOtago.     

Vibratory Alarm Signals in Two Sympatric Higher Termite Species: Pseudacanthotermes spiniger and P. militaris (Termitidae, Macrotermitinae)

When they are disturbed, soldiers of the two termite species Pseudacanthotermes spiniger and P. militaris hit the substratum with their head, thereby producing sounds. High-speed video recordings allowed us to analyze the movement. The sound emissions were recorded and their temporal structure was analyzed. Artificial stimulation proved that head-banging acts as an alarm signal transmitted through the vibrations produced in the substratum. Perception of these vibrations induced a polyethic response. Workers reacted to head-banging by escaping. Minor soldiers reacted by escaping, becoming immobile, or head-banging, thereby indicating the existence of positive feedback in signal production. Differences in the time patterns of the drumming appeared between both species but could not be shown to play a role in species recognition.     

Natural enemies for the cabbage webworm,Hellula undalis (Fabr.) (Lepidoptera: Pyralidae) in Malaysia

Four species of larval parasitoids were reared from larvae of the cabbage webworm (CWW),Hellula undalis (Fabr.) (Pyralidae: Glaphyriinae) collected from various cruciferous plants and a capparidaceous weed,Cleome rutidosperma (DC). On cabbage, only two species were recorded,viz, Bassus sp. (Braconidae) andTrathala flavoorbitalis (Cam.) (Ichneumonidae). The other parasitoids were braconids,Chelonus sp. andPhanerotoma sp. Egg or pupal parasitoids were not recorded. The parasitoids were not an important mortality factor of CWW on cabbage because they were usually present at the end of the crop season and their numbers were generally low. On the other hand, predator-exclusion experiments indicated that predators were important in determining the density of CWW on cabbage and the within-generation survival in the field. The major predator was the fire-ant,Solenopsis geminata (F.), which foraged on the prepupae and pupae.     

Phylogenetic study on wild allies of Lima bean,Phaseolus lunatus (Fabaceae), and implications on its origin

An investigation was made of the phylogenetic relationships among wild accessions of Lima bean (Phaseolus lunatus) and wild allies of Mesoamerican and Andean origins, using electrophoresis of seed storage proteins and isozymes. Mesoamerican wild species are phylogenetically more distant fromP. lunatus than Andean species, and apparently belong to the tertiary gene pool of Lima bean. The Andean wild species, which are investigated for the first time, reveal a high similarity to the Lima bean, and particularly with its Mesoamerican gene pool. These Andean species probably constitute a secondary gene pool of Lima bean, and are thus of considerable interest in the context of genetic improvement of the crop. Based on these observations, an Andean origin is suggested for the Andean wild species and forP. lunatus. These results point out the importance of collecting and conserving AndeanPhaseolus germplasm.     

Self-, Intra-, and Interspecific Host Discrimination in Telenomus busseolae Gahan and T. isis Polaszek (Hymenoptera: Scelionidae), Sympatric Egg Parasitoids of the African Cereal Stem Borer Sesamia calamistis Hampson (Lepidoptera: Noctuidae)

Oviposition behavior, intra- and interspecific host discrimination, and super- and multiparasitism by the scelionids Telenomus busseolae and T. isis were studied using batches of eggs of the noctuid stalk borer Sesamia calamistis as the host. Both Telenomus species were able to discern eggs already parasitized. As a result, self-superparasitism was only 4.0% for T. busseolae and 5.8% for T. isis. Likewise, intraspecific superparasitism was avoided by both species and was significantly higher for T. busseolae than T. isis, and higher when parasitized eggs were offered immediately (0 h) and after 48 h than after 24 h; apparently, the recognition of parasitized eggs at 24 and 48 h was based on the presence of parasitoid larvae rather than a specific marking substance. Multiparasitism was avoided if the female had a choice between unparasitized and parasitized eggs. In a choice experiment, it was 10.2 and 2.5% for T. busseolae and T. isis, respectively. In a nonchoice experiment, multiparasitism did not vary between species and time treatment; it was low, varying between 9.6 and 24.1%. In the 0-h treatment, T. busseolae always outcompeted T. isis, accounting for 63.4 or 91.7% of the offspring, when T. isis or T. busseolae, respectively, was the first species. In the 24-h treatment, the first species emerged more often than the second did but the host egg mortality, i.e., eggs from which neither borer larvae nor parasitoid emerged, was >40%. Whereas T. busseolae is ubiquitous in Africa, T. isis has never been reported from eastern Africa, and it has been proposed for introduction against the prevailing noctuid pest Bussoela fusca. Based on earlier life table and host suitability studies and on the present findings, it is concluded that T. isis would establish in the midaltitudes but not the highlands of eastern Africa.     

Extensive mtDNA variation within the yellow-pine chipmunk,Tamias amoenus (Rodentia: Sciuridae), and phylogeographic inferences for northwest North America

The yellow-pine chipmunk, Tamias amoenus, is common in xerophytic forests throughout much of northwest North America. We analyzed cytochrome b sequence variation from 155 individuals representing 57 localities across the distribution of T. amoenus including 10 additional species of Tamias. Maximum likelihood and parsimony tree estimation methods were used in conjunction with nested clade analysis to infer both deep and population-level processes. Our results indicate that two currently recognized subspecies of T. amoenus (T. a. canicaudus and T. a. cratericus) are not nested within other samples of T. amoenus. Maximum uncorrected levels of intraspecific sequence divergence within remaining samples of T. amoenus are >7%. Substantial geographic variation is characterized by 12 well-supported clades that correspond to distinct mountain ranges, but do not necessarily follow existing subspecific taxonomy. Significant association between geography and genealogy was detected within many of these clades and can be attributed to different population-level processes including past fragmentation, recent range expansion, and isolation by distance.     

Genetic diversity and environmental associations of wild barley,Hordeum spontaneum (Poaceae), in Iran

Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted.     

Interactions among the entomopathogenic fungus, Beauveria bassiana (Ascomycota: Hypocreales), the parasitoid, Aphidius matricariae (Hymenoptera: Braconidae), and its host, Myzus persicae (Homoptera: Aphididae)

The effect of the entomopathogenic fungus Beauveria bassiana on the biological characteristics and life table of Aphidius matricariae, a parasitoid of the green peach aphid, Myzus persicae, was studied under laboratory conditions. Aphids were first infected with twice the LC₉₅ of B. bassiana for third-instar M. persicae (2 × 10⁸ conidia/ml). Subsequently, at different intervals they were exposed to 1-day-old mated parasitoid females for 24 h. The number of mummies produced per female and the percentage emergence of the F1 generation differed significantly as a function of the time interval between application of the fungus and exposure to the parasitoid. The interference of B. bassiana on parasitoid development was also studied by first exposing the aphid hosts to the parasitoid for 24 h and subsequently applying B. bassiana. The number of mummies produced by a female A. matricariae varied from 11.8 to 24.8 and was significantly different when the aphids were first exposed to the parasitoids and then treated with B. bassiana 24, 48, 72, and 96 h after exposure. There were no significantly different effects of B. bassiana on net reproductive rate (R₀), mean generation time (T), intrinsic rate (r_m) and the finite rate of increase (λ) of A. matricariae as a result of development in hosts exposed to low or high conidial concentrations (1 × 10², 2 × 10⁸ conidia/ml). The parasitoids developed in infected hosts had lower r_m, λ, T and DT (doubling time) values compared with those that developed in uninfected hosts but no differences were observed in R₀ values. With proper timing, A. matricariae and B. bassiana can be used in combination in the successful biological control of M. persicae.     

The status ofBemisia tabaci (Hom.: Aleyrodidae),Trialeurodes vaporariorum (Hom.: Aleyrodidae) and their natural enemies in Crete

The non «B» biotype ofBemisia tabaci (Gennadius) is recorded for the first time in Crete in 1992, in the north east and south east of the island.Trialeurodes vaporariorum (Westwood) is the predominant whitefly on plants in the north and west of the island. Three surveys of Crete were made in 1992 and 1993 for natural enemies ofB. tabaci andT. vaporariorum and resulted in the collection of 4 species ofEncarsia, (plus a number of species that are unidentifiable at this time), anEretmocerus sp. (unidentifiable at this time) and a fungal pathogen,Paecilomyces farinosus (Dickson Ex Fries) Brown &; Smith.Encarsia adrianae was identified fromT. vaporariorum; which constitutes its most westerly distribution point and a new host record respectively.B. tabaci andT. vaporariorum were found on horticultural crops, ornamentals and weeds. Populations of both whitefly species were severely depleted on field hosts throughout the island during the winter of 1992/93. Climatic constraints, competition withT. vaporariorum in otherwise suitable niches, effective natural enemies and an observed low level of polyphagy may explain the present limited distribution of the non «B» biotype ofB. tabaci in Crete.     

Natural enemy spectrum ofAphis spiraephaga (Hom.: Aphididae), an exotic immigrant aphid in Central Europe

Aphis spiraephaga Müller, an aphid of Central Asian origin, dispersed west-wards and reached Central Europe probably before 1956. It now occurs in most European countries. Research undertaken in the Czech Republic mainly in 1991–1993, revealed that the aphid is attacked by a variety of natural enemies, including both parasitoids (Aphelinidae, Aphidiidae) and predators (Anthocoridae, Chrysopidae, Hemerobiidae, Cantharidae, Coccinellidae, Chamaemyidae, Itonididae, Syrphidae). All the natural enemies were identified to species. Attendance by ants (Lasius sp.) was common.A. spiraephaga was also successfully utilised as a new alternate host of two newly introduced parasitoid biocontrol agents (Aphidius colemani Viereck,Lysiphlebus testaceipes (Cresson).