Seasonal changes in song nuclei and song behavior in Gambel's white-crowned sparrows

In males of several songbird species, the morphology of forebrain nuclei that control song changes seasonally. The only seasonally breeding songbird in which seasonal changes in the structure of song control nuclei have been reported not to occur is the nonmigratory Nuttall's subspecies of white-crowned sparrow. In the present study, we manipulated photoperiod and plasma testosterone concentrations in captive male white-crowned sparrows of the migratory Gambel's subspeices. Males exposed to photoperiods and plasma testosterone concentrations typical of those experienced by wild breeding males had larger song control nuclei than males held on a winter photoperiod. We also found seasonal change in stereotypy of spectral and temporal parameters of song in wild Gambel's white-crowned sparrows. We hypothesize that seasonal changes in song control nuclei may correlate with seasonal changes in song stereotypy. © 1995 John Wiley & Sons, Inc.     

Reproductive biology of a Red Sea goby, Silhouettea aegyptia, and a Mediterranean goby, Pomatoschistus marmoratus, in Lake Timsah, Suez Canal

The reproductive biology of the Red Sea goby Silhouettea aegyptia , and Mediterranean Pomatoschistus marmoratus , has been studied in Lake Timsah, Suez Canal. Male: female sex ratio was 1: 1 7 in S. aegyptia and 1: 2 7 in P. marmoratus . Size at first maturity was 20 mm ( s.l. ) in S. aegyptia and 24 mm in P. marmoratus . The breeding season of S. aegyptia extended from March to September with most gonadal activity in May, whereas in P. marmoratus , it stretched from. November until the following April with a peak in February. Hepatosomatic index for both species exhibited monthly fluctuations and an inverse correlation with gonadosomatic index was evident. Oocyte size-frequency distribution indicated several modes at 400, 600 and 800 μm during the breeding season. Fecundity of S. aegyptia ranged from 152 to 782 with an average of 468 eggs, whereas in P. marmoratus it varied between 293 and 1300 with an average of 603 eggs. Fecundity was related curvilinearly to fish length, body weight and ovary weight. Recruitment of young fish to the adult populations occurred in late July and early August for S. aegyptia and during March for P. marmoratus . Life history pattern indicated that both species of gobies are successful colonists of Lake Timsah, Suez Canal.     

The effects of temperature and season on the O2 consumption of third-instar larvae of the goldenrod gall fly (Eurosta solidaginis)

Abstract. Third-instar larvae of the goldenrod gall fly ( Eurosta solidaginis Fitch) live inside ball galls on goldenrod plants from summer to the following spring.Because galls are highly exposed to the weather, larvae experience substantial variations in body temperature.This study documents the oxygen consumption of gall fly larvae with regard to the effects of ambient temperature, seasonal conditioning, and prior exposure to subzero temperature.The body mass of larvae doubles between the late summer and the autumn; it subsequently undergoes a modest decline by early winter.The O₂, consumption of field-acclimatized larvae increases with ambient temperature, especially between 0 and 10°C (Q₁₀= 2.6-3.4).The thermal sensitivity of metabolism declines at higher ambient temperatures, most notably during the autumn/early winter.After exposure to 15°C for 1 week, autumn and early winter larvae maintain much lower rates of O₂ consumption than do late summer specimens.Prior exposure to -5°C for 24 h did not influence the O₂ consumption of larvae.Low thermal sensitivity of O₂ consumption, especially at higher ambient temperatures, is an energy-sparing mechanism during seasonal inactivity.Indeed, the persistence of this metabolic pattern in larvae exposed to 15°C suggests that they have entered a state of diapause.     

Effective population size and persistence of Anopheles arabiensis during the dry season in West Africa

Abstract. The way that the malaria vectors Anopheles arabiensis and An.gambiae survive the dry season in sub-saharan Sahel or northern Savanna areas of Africa remains enigmatic. We examined this problem by calculating the effective sizes (N_e) of An.arabiensis populations for several locations in West Africa. An indirect/genetic procedure was used, comparing gene frequencies at several time intervals. The amount of drift which occurred provides an estimate of N_e. Most estimates of N_e were approximately 2000 individuals, probably close to the yearly minimum. This supports the hypothesis that populations of An.arabiensis in this region are continuous throughout the year, with many individuals surviving through the dry season, perhaps in a physiologically altered state, rather than extinction or severe bottlenecks during the dry season, followed by recolonization by a few individual survivors or immigrants in the subsequent rainy season.     

Sow level risk factors for early piglet mortality and crushing in organic outdoor production

Piglet mortality is a major problem in organic pig production affecting both farm economy and animal welfare. Knowledge is scarce on the risk factors of piglet mortality in Danish commercial organic pig production. The objectives of this study were to evaluate season, litter size, parity, sow body condition and stillborn littermates as risk factors for early piglet mortality and crushing of liveborn piglets from parturition until castration at day 3 to 5 postpartum (pp). The study was conducted over a 1-year period in nine commercial Danish organic pig herds practicing outdoor farrowing all year round. Data included recordings on 3393 farrowings with 50 284 liveborn piglets of which 14.8% died before castration. A subset of the dead piglets were collected and necropsied to identify crushed piglets. The average number of liveborn piglets per litter was 14.8 (SD=3.7) and the average time from parturition until castration was 4.1 (SD=1.7) days. A negative binomial regression analysis was used to model the effect of the predictive variables on the early piglet mortality accounting for different time periods from parturition to castration. An increase in maternal body condition score (BCS) and parity significantly increased the risk of dying between parturition and castration. Early mortality was found to be lowest during spring (March to May) and highest during summer (June to August). Being born into a litter with one or more stillborn littermates increased the risk of early mortality. The risk factors for crushing of piglets were evaluated using a logistic analysis. A significant effect of parity and litter size was found where the odds of at least one piglet in a litter with mortality was diagnosed as crushed increased with increasing parity and litter size. In conclusion, being born during summer (June to August), high parity and maternal BCS and stillborn littermates were found to be risk factors for piglet mortality between parturition and castration. In addition, parity and increasing litter size were found to be risk factors for crushing of piglets in litters with mortality.     

Selective pollination by fungus gnats potentially functions as an alternative reproductive isolation among five Arisaema species

Background and AimsInterspecific difference in pollinators (pollinator isolation) is important for reproductive isolation in flowering plants. Species-specific pollination by fungus gnats has been discovered in several plant taxa, suggesting that they can contribute to reproductive isolation. Nevertheless, their contribution has not been studied in detail, partly because they are too small for field observations during flower visitation. To quantify their flower visitation, we used the genus Arisaema (Araceae) because the pitcher-like spathe of Arisaema can trap all floral visitors.MethodsWe evaluated floral visitor assemblage in an altitudinal gradient including five Arisaema species. We also examined interspecific differences in altitudinal distribution (geographic isolation) and flowering phenology (phenological isolation). To exclude the effect of interspecific differences in altitudinal distribution on floral visitor assemblage, we established ten experimental plots including the five Arisaema species in high- and low-altitude areas and collected floral visitors. We also collected floral visitors in three additional sites. Finally, we estimated the strength and contribution of these three reproductive barriers using a unified formula for reproductive isolation.Key ResultsEach Arisaema species selectively attracted different fungus gnats in the altitudinal gradient, experimental plots and additional sites. Altitudinal distribution and flowering phenology differed among the five Arisaema species, whereas the strength of geographic and phenological isolations were distinctly weaker than those in pollinator isolation. Nevertheless, the absolute contribution of pollinator isolation to total reproductive isolation was weaker than geographic and phenological isolations, because pollinator isolation functions after the two early-acting barriers in plant life history.ConclusionsOur results suggest that selective pollination by fungus gnats potentially contributes to reproductive isolation. Since geographic and phenological isolations can be disrupted by habitat disturbance and interannual climate change, the strong and stable pollinator isolation might compensate for the weakened early-acting barriers as an alternative reproductive isolation among the five Arisaema species.     

Genetic diversity and population structure of wintering Western Sandpipers from the Sinaloa coast,Mexico

ABSTRACT Although Western Sandpipers (Calidris mauri) are one of the best‐studied shorebirds along the Pacific Flyway, their genetic identity and population structure is poorly known. We studied the genetic population structure of nonbreeding Western Sandpipers at Bahia Santa María in Sinaloa, northwestern Mexico. A 685‐bp fragment of the mtDNA control region was sequenced for 162 individuals, resulting in 29 variable positions that defined 41 haplotypes. The most common haplotype (WESA01) occurred in 44% of all individuals, whereas 15 were unique to single individuals. Nucleotide diversity was low (π= 0.0030 ± 0.0019 [SE]), but haplotype diversity was moderately high (h= 0.802 ± 0.033 [SE]). The main two maternal lineages exhibited a slightly different local scale distribution that appeared to be related to migratory chronology. Lineage A represented 71% of the haplotypes and was evenly distributed across the nonbreeding season and habitat types, whereas Lineage B represented only 29% of the haplotypes and was disproportionately represented in January in some habitat types. Overall, the low level of nucleotide diversity, the star‐shape of the haplotype tree, the mismatch distribution, and the significantly negative Tajima's D values suggest that Western Sandpipers underwent a recent demographic expansion. Although our results are based on a small sample size from one of several wintering sites along the Pacific Flyway, Santa María likely contains a relatively high proportion of the species genetic variability because it is the wintering ground of nearly 10% of the global population.     

Notes on some summer birds of Syria by Wolfgang Baumgart and Max Kasparek

Abstract

A sample of 10 skulls of Vulpes vulpes arabica from the southeastern part of the Sultanate of Oman was investigated craniologically. The measurements fit well into the known datascts of the subspecies. The foxes show the same secondary teeth losses as animals from Europe, but no paradental disease or dental caries. Age structure of the population is more natural than in Europe due to the lower or almost non-existent pressure from human hunting. In relation to the slight seasonal change in climatic conditions, the incremental lines of the tooth cement are more clearly visible than expected.     

Spider assemblages associated with leaf litter of three tree species in central South Africa (Arachnida: Araneae)

Spiders were collected by sifting leaf litter of three common tree species, Cussonia paniculata sinuata, Olea europaea africana and Searsia lancea, in an undisturbed grassland habitat in central South Africa. The study aimed to collect baseline data on spider assemblage structure, seasonality and the effects of litter structure on spider assemblages. In total, 1385 spiders were collected, representing 26 families and 56 species. Four species, Obatala sp. (Amaurobiidae, 22.7%), Camillina maun Platnick & Murphy (Gnaphosidae, 17.0%), Proevippa sp. (Lycosidae, 11.4%) and Zelotes frenchi Tucker (Gnaphosidae, 9.2%) dominated the fauna. Spider abundance was the highest in Olea litter (n = 607), followed by Searsia (n = 453) and Cussonia (n = 325). Searsia had the greatest number of species (41 spp.), followed by Olea (35 spp.) and Cussonia (30 spp.). Both spider abundance and species richness per sample varied significantly between the tree species. Of the ten most abundant species, all but two showed a significant preference for particular litter types. Mean spider abundance and species richness per sample were the lowest in Cussonia litter, which was the deepest litter type, but with the most interstitial space, whereas mean abundance and species richness per sample were the highest in Olea litter, which was the shallowest and moderately compact in structure.