Vocal divergence between two disjunct populations of Giant Antshrike (Batara cinerea) is related to environmental conditions

Variation in the avian vocal signals emitted may have a significant impact on species evolution. Vocal divergence in suboscine species like Giant Antshrike (Batara cinerea) may be associated with selective adaptation, since learning has little influence on vocal development and variation in acoustic structure cannot be attributed to learning deviation. Consequently, tracheophone suboscine species are ideal subjects to explore vocal variation, since cultural evolution does not seem to influence vocal variation in this group. Environmental conditions may determine the selection of vocal features because acoustic transmission could be attenuated under certain conditions of temperature, humidity and vegetation cover. Here, we examined vocalizations of Giant Antshrike and assessed possible acoustic variations between two disjunct groups (Andean and Atlantic), correlating the differences to the environmental structure. Univariate and multivariate analysis show temporal and spectral differences between both groups. Andean individuals produce vocalizations with longer duration, faster trill rates, shorter syllable duration and higher frequencies. Environmental features are different between the two populations, and they are correlated to the acoustic structure of vocalizations. Temporal variations arise directly from climatic influence, while spectral divergence could be a secondary effect of morphological adaptation to habitat structure.     

Acoustic preferences and localization performance of blood-sucking flies (Corethrella Coquillett) to tungara frog calls

Mating signals that increase attractiveness of males to femalescan also increase conspicuousness of the signaler to predatorsand parasites. We investigated the acoustic preference of speciesof blood-sucking flies of the genus Corethrella (Diptera: Corethrellidae),which eavesdrop on the sexual advertisement signals of túngarafrogs (Physalaemus pustulosus). Male frogs of this species facultativelyproduce 2 types of mating calls: simple (whines alone) and complex(whines and chucks). We tested the acoustic preference of theflies and their ability to locate their host when the frogsproduce simple or complex calls. The flies exhibited phonotaxisto both types of calls but were preferentially attracted tocomplex calls. We show that acoustic information alone is sufficientfor the flies' accurate localization of calling frogs. Complexcalls, however, were not approached at closer distance or withdecreased landing error (i.e., proportion of landings outsidethe target) than simple calls, suggesting that call structuredoes not influence localization performance. Female túngarafrogs and frog-eating bats (Trachops cirrhosus) also prefercomplex to simple túngara frog calls. Thus, intendedand unintended receivers with different ear morphologies exhibitthe same preference for a specific túngara frog calltype. This result is discussed in the context of the evolutionof call attractiveness in a communication network.     

The body size of the New Zealand orb-weaving spider Waitkera waitakerensis (Uloboridae) is directly related to temperature and affects fecundity

Abstract. Waitkera waitakerensis occupies lowland forests of New Zealand's North Island, where temperatures decrease in a southwestward direction. The mean annual temperatures of 18 collecting sites, as extracted from GIS data, are directly related to the first femur length of adult females. Neither site elevation nor phylogeny affected spider size or other variables examined. The direct relationship between spider body size and environmental temperature followed a pattern observed in other terrestrial arthropods with a univoltine life cycle and can probably be explained by the longer growing season of warmer regions. Egg diameter was uniform across the species. Site temperature and female first femur length were each directly related to the number of eggs deposited in egg sacs. The date of egg sac collection was inversely related to egg number, suggesting that clutch size declines during the reproductive season. Females deposit eggs beneath a triangular platform and then cover them with a lower silk sheet. The area of this upper platform and the volume of the egg sac were each directly related to egg number, but not to female first femur length. The depth of the lower covering was not related to egg number or to spider first femur length. This suggests that spiders use information about the volume of eggs in their abdomens to construct an egg sac whose volume will accommodate the volume of eggs to be laid and that females do so principally by adjusting the size of the sac's upper triangular platform.     

Cutting reduces variation in biomass production of forage crops and allows low‐performers to catch up: A case study of Trifolium pratense L. (red clover)

• Re‐growth of fodder plants after grazing and mowing drives the profitability of their cultivation and is therefore an important target trait for plant breeding and agricultural engineering. However, for some fodder plants little is known about their re‐growth dynamics in response to grazing or mowing.
• We analysed the native response of plant architecture, leaf morphology and growth performance to experimental cutting in wild Trifolium pratense L. (red clover) plants. A total of 150 potted clover plants were established under controlled field conditions, and half of the plants were cut to 5 cm 3 months after sowing. Each plant was measured every week for 5 months.
• The cut and subsequently re‐grown plants carried fewer main branches (?20%), as well as fewer (?13%) and smaller (?32%) leaves than the control plants. However, the cut plants produced an average of 17% more accumulated leaf area (cut + re‐grown leaf area) than the control plants. This discrepancy was explained by variation in the growth strategy of the plants, where the cut plants invariably expressed a second growth phase, while almost half of the untreated plants did not.
• Our results suggest that cutting acted as an artificial trigger initiating a second growth phase in the cut plants and thereby contributed to yield increase. Exploiting this mechanism may set new goals for breeding and optimisation of the mowing regime.