Plant traits mediate effects of predators across pepper (Capsicum annuum) varieties

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Thirteen polymorphic microsatellite loci in the Neotropical fish Prochilodus argenteus (Characiformes,Prochilodontidae)

Prochilodus species inhabit the main river systems of South America and usually present commercial value to inland fishing. In the present study, we describe the isolation and characterization of 13 novel microsatellite loci in Prochilodus argenteus. The number of alleles per polymorphic locus varied from four to 22 and the observed heterozygosity ranged from 0.333 to 0.893. Additionally, cross‐species amplification was successful in two other Prochilodus species. These loci will be useful for studies of the population genetic structure in this fish group.     

Multi-scale assessment of macroinvertebrate richness and composition in Mediterranean-climate rivers

1. Similar constraints in distant, but climatically comparable, regions may be expected to yield biotic assemblages with similar attributes. Environmental factors that constrain communities at smaller scales, however, may be different between climatically similar regions. Thus, patterns observed at large scales may differ from those detected at small scales, and international comparisons should be focussed at multiple scales. 2. Mediterranean‐climate regions (MCRs) are characterized by remarkable seasonal variability in precipitation and temperature. Accordingly, rivers in these regions have seasonal and predictable floods and droughts, and temporary reaches are frequent. Present in six geographical regions of the world, MCRs have similar environmental constraints and are ideal for testing intercontinental similarities between macroinvertebrate communities. 3. We examined aquatic macroinvertebrate taxon richness and composition in MCRs at three scales: regional, reach and macrohabitat. At the regional scale, the Mediterranean Basin had the highest taxon richness at family level, and southwestern Australia the lowest. Taxonomic composition showed c. 85% similarity between the northern hemisphere MCRs of California and the Mediterranean Basin, which were followed in similarity by South Africa. The two Australian MCRs (South west and South) showed a similarity to each other of about 70% whereas the Chilean fauna was the most distinct. 4. At the reach scale, taxon richness was not significantly different between permanent and temporary reaches in any MCR, whereas taxonomic composition was significantly different among northern hemisphere MCRs. At the macrohabitat scale, taxon richness was not significantly different between lotic and lentic macrohabitats within any of the MCRs, but differences in macroinvertebrate communities were found between macrohabitats when considering regions. 5. Our results show that the strength of similarity between distant but climatically similar regions is scale‐dependent, being highest at the macrohabitat scale. Although the similarities in richness and composition at the macrohabitat scale are presumed to be universal, the seasonal predictability of drought in MCRs is expected to result in characteristic macroinvertebrate responses at the reach scale. We suggest, however, that regional evolutionary history and environmental characteristics may override this general pattern of a similar response of MCRs at different scales. The Mediterranean Basin and California, having similar historical and environmental condition, thus appeared as the most similar MCRs at all scales.     

Effect of thermal acclimation on preferred temperatures in two mygalomorph spiders inhabiting contrasting habitats

Variations in the preferred temperatures during the rest periods of Grammostola rosea Walckenaer and Paraphysa parvula Pocock, two mygalomorph spiders occupying different habitats in central Chile, are analyzed. The former inhabits arid and semi‐arid lowland near plant communities, composed of shrubs (evergreens with small leathery leaves) and small trees; the latter is found in the central mountains of the Chilean Andes, above 2000 m.a.s.l. The preferred temperatures of these spiders at different times of day and exposure to cold (15 °C) and warm (25 °C) acclimation temperatures are compared. Body mass does not affect the preferred temperature of the larger spider G. rosea, although P. parvula, a spider with half of the body mass of G. rosea, shows a decrease in preferred temperature with body mass. This can be explained by a higher plasticity and thermal sensitivity of the smaller species as result of increased surface : volume ratio. The preferred temperature increases with the hour of the day under both acclimation conditions in P. parvula and in cold‐acclimated G. rosea, which is likely associated with crepuscular and nocturnal behaviour in both species. Grammostola rosea shows temperature preferences lower than those of P. parvula under both acclimation conditions. The increase of the acclimation temperature from 15 to 25 °C results in an increment of 2–3 °C in the preferred temperature of P. parvula but only 0.2 °C in that of G. rosea. Two contrasting lifestyle strategies are found: a small mygalomorph spider with phenotypic plasticity and adaptation to the fluctuating environment of high altitude, and a large mygalomorph spider with higher thermal inertia adapted to the more stable environment of lowlands.     

Comparative cytogenetic analysis of four species of <Emphasis Type="Italic">Dendropsophus</Emphasis> (Hylinae) from the Brazilian Atlantic forest

We conducted a cytogenetic study of four hyline frog species (Dendropsophus elegans, D. microps, D. minutus and D. werneri) from southern Brazil. All species had 2n = 30 chromosomes, with interspecific and intraspecific variation in the numbers of metacentric, submetacentric, subtelocentric and telocentric chromosomes. C-banding and fluorochrome staining revealed conservative GC-rich heterochromatin localized in the pericentromeric regions of all species. The location of the nucleolus organizer regions, as confirmed by fluorescent in situ hybridization, differed between species. Telomeric probes detected sites that were restricted to the terminal regions of all chromosomes and no interstitial or centromeric signals were observed. Our study corroborates the generic synapomorphy of 2n = 30 chromosomes for Dendropsophus and adds data that may become useful for future taxonomic revisions and a broader understanding of chromosomal evolution among hylids.     

First record of male drumming call of the genus Capnioneura Ris, 1905 (Plecoptera,Capniidae)

The male call of Capnioneura mitis, produced by drumming, is recorded and analyzed for the first time. It also represents the first known signal for the genus. It consists of a highly variable number of beats (2–32) with inter‐beat duration approximately constant along the call, but inter‐beat duration is temperature dependent. Thus, at 13°C the mean inter‐beat duration is 1.397 s (SD = 0.050) while at 21°C it is 1.139 s (SD = 0.093). The call pattern exhibited by this species, as those of the majority of previously studied Capniidae species, can be catalogued as an ancestral or near‐ancestral percussive monophasic signal.     

Environmentally induced spatio-temporal variations in the fecundity of brown trout Salmo trutta L.: trade-offs between egg size and number

1. Resident brown trout Salmo trutta in the Esva River basin (north Spain) live in a patchy environment with tracts of riparian forest or meadow along stream banks. This study assessed whether the reproductive traits of brown trout from four contrasting sites reflected site-specific factors.
2. Length at maturity (10.5–11 cm of 1 + individuals) was the same in the four sites examined but slowest growers in slow-growing sub-populations delayed maturity for 1 year relative to fast-growing fish. The analysis of monthly variations in egg size and number suggest that two 'decisions' in two consecutive years are required to complete spawning. The first concerns the number of eggs, determined when trout are still 0 +, and the second concerns egg size.
3. At three sites, egg size and number did not differ significantly between years but highly significant interannual variations were apparent at another site. Fish length was the major determinant of egg size and number at all sites but for any given length, brown trout at sites where the fish exhibited higher growth rates spawned more, but smaller, eggs than those at slow-growing sites. This spatial pattern was identical to the temporal pattern exhibited by trout at another site. The combination of temporal (year-to-year) and spatial (between rivers) variations in egg size and number showed a significant negative correlation, supporting the operation of a trade-off between these two traits.
4. The trade-off between egg size and number seems to be determined by site-specific factors, with slow-growing trout at sites which are fully covered by canopy spawning fewer, but larger, eggs than fast-growers in unshaded sites.     

Extracellular Killing of Trypanosoma cruzi Amastigotes by Human Eosinophils1

Granules released from human eosinophils upon interaction with Trypanosoma cruzi amastigotes in vitro were seen attached to the surface of non-internalized parasites by electron microscopy. Amastigote damage was preceded by the binding of eosinophil granule material to its membrane, and eosinophil granule major basic protein (MBP) bound to the parasite surface was readily detectable. Additional evidence of eosinophil cytotoxicity for extracellular amastigotes was the observation that amastigotes trapped between two eosinophils, without being ingested by either one, were destroyed at the interface. Amastigotes isolated from the spleens of infected mice or grown in culture were similarly sensitive to the lytic effects of purified MBP. These results demonstrate the ability of human eosinophils to lyse T. cruzi amastigotes extracellularly in the absence of antibody and suggest that MBP may be involved in the effect. Thus, eosinophils, known to be capable of destroying phagocytosed amastigotes, could also contribute to the clearance of these parasites through extracellular killing.     

Host range expansion of an introduced insect pest through multiple colonizations of specialized clones

Asexuality confers demographic advantages to invasive taxa, but generally limits adaptive potential for colonizing of new habitats. Therefore, pre-existing adaptations and habitat tolerance are essential in the success of asexual invaders. We investigated these key factors of invasiveness by assessing reproductive modes and host-plant adaptations in the pea aphid, Acyrthosiphon pisum, a pest recently introduced into Chile. The pea aphid encompasses lineages differing in their reproductive mode, ranging from obligatory cyclical parthenogenesis to fully asexual reproduction. This species also shows variation in host use, with distinct biotypes specialized on different species of legumes as well as more polyphagous populations. In central Chile, microsatellite genotyping of pea aphids sampled on five crops and wild legumes revealed three main clonal genotypes, which showed striking associations with particular host plants rather than sampling locations. Phenotypic analyses confirmed their strong host specialization and demonstrated parthenogenesis as their sole reproductive mode. The genetic relatedness of these clonal genotypes with corresponding host-specialized populations from the Old World indicated that each clone descended from a particular Eurasian biotype, which involved at least three successful introduction events followed by spread on different crops. This study illustrates that multiple introductions of highly specialized clones, rather than local evolution in resource use and/or selection of generalist genotypes, can explain the demographic success of a strictly asexual invader.