Descripción: This study documents differences in the courtship behavior of wild strains of Ceratitis capitata (Wiedemann) from Madeira (Portugal), Hawaii (U.S.A.), Costa Rica, and Patagonia (Argentina). Some traits showed large variations and others substantial overlaps. The angle at which the male faced toward the female at the moment of transition from continuous wing vibration and intermittent buzzing changed very little during the course of courtship in all strains, but males from Madeira tended to face more directly toward the female than other males. Females tended to look more, and more directly, toward the males as courtship progressed in all strains. The distance between male and female tended to decrease as courtship proceeded in all strains, but the distances at which males initiated continuous vibration, intermittent buzzing, and jumped onto the female were relatively less variable between strains, except for the strain from Costa Rica. Flies of Madeira courted for longer and the male moved his head and buzzed his wings longer than the other strains.

Descripción: We studied the dietary niche of the Barn Owl (Tyto alba) in temperate agroecosystems of central Argentina by describing seasonal and geographic variation in the food habits of this owl in four districts of the Pampean region (Flooding, Inland, Rolling, and Southern Pampas). We identified 21,925 prey items from samples of fresh pellets collected in summer (n = 23) and winter (n = 26). Mammals,' mostly sigmodontine rodents, were the main prey items (91.9%), followed by amphibians (6.5%) and birds (1.6%). Arthropods were also a common prey item (found in 45% of the samples). The consumption of arthropods and amphibians was higher in summer than in winter, indicating that seasonal changes in prey abundances are reflected in the Barn Owl diet. We found no differences in food-niche breadth among the four study districts, but food-niche breadth varied between seasons, being higher during summer. Six rodent species were common to all districts: Calomys spp., Akodon azarae, Oligoryzomys flavescens, Mus musculus, Rattus spp., and Holochilus brasiliensis. Calomys spp. was numerically dominant in 46 of the 49 samples, and together with A. azarae and O. flavescens comprised the bulk of the diet (> 80%). Predation on rodents may reflect population dynamics of the prey species with high predation rates when peaks in abundance of sigmodontine rodents occurred (autumn-winter). © The Neotropical Ornithological Society.

Descripción: Dichroplus elongatus is a grasshopper, which exhibits parallel polymorphisms for B chromosomes and supernumerary segments in chromosomes S10 (SS10), S9 (SS9) and M6 (SS6) in natural populations of Argentina. The patterns of simultaneous variation of different forms of supernumerary heterochromatin from 7 populations of two biogeographic provinces located at Northwest and East regions of this country were analysed. Spatial chromosome differentiation for all heterochromatic variants was observed. Different degree of differentiation among populations for supernumerary segments, evaluated through F(ST), was observed. This suggests that genetic drift and migration may not be the only factors involved in the maintenance of the detected chromosome patterns. The differentiation for SS9 and SS10 may be explained mainly by heterogeneity within the Northwest Region. On the contrary, the differences for SS6 and B chromosomes explained through isolation by distance. However, the absence or the low frequency of both chromosome mutations in some populations may not be explained by historical factors. A principal component analysis showed that the patterns of chromosome variation do not agree with the geographical distribution of the populations. The relationship between frequencies of each supernumerary segment and B chromosome depends on the segment. An analysis of partial correlation showed that the frequencies of B chromosomes were positively correlated with the frequency of SS6 and negatively with the frequency of the SS10. In agreement with this, a multiple regression analysis of B chromosome frequency on supernumerary segment frequencies depends on the incidence of SS6 and SS10. The covariation of the heterochromatic forms may act as another factor that establish limits to stochastic factors, may also affect the probable negative selection on B, and could be involved in the non random pattern detected in D. elongatus.