Selection for early emergence, longevity and large body size in wingless, sib-mating ant males

Sexual selection has led to male morphologies and behaviours that either increase male attractiveness or their success in male–male competition. We investigated male traits under selection in the ant Hypoponera opacior, in which wingless males mate with pupal queens inside their natal colony and guard their partners for hours. The lack of female choice and fights among adult males makes this species an ideal study system to investigate sexual selection in the absence of these selective forces. We hypothesised that males, which emerge first and live longer, should have a higher mating success because of more mating opportunities, reduced competition and the ability to kill pupal competitors. We recorded the number and length of matings and tested whether these measures of male-mating success were associated with emergence order, lifespan and body size. Indeed, early emerged males mated more often and longer than their later-emerging rivals. Furthermore, longer-lived and larger males obtained more matings. Body size might be important because larger males either produce more sperm or perform better in mounting females. We found no evidence for a trade-off between body size and emergence time. Moreover, male removal manipulations revealed that males quickly adapt their guarding behaviour to changes in the competitive environment. Under reduced competition, males guarded their partners for shorter periods. In conclusion, these sib-mating ant males are under selection to develop fast, to live long, to be large and to be able to respond to the competitive situation in the nest.     

Ornaments and condition: plumage patch sizes,nutritional reserve state,reserve accumulation,and reserve depletion

Behavioral Ecology and Sociobiology - Cooperation plays a crucial role in primate social life. However, the evolution of large-scale human cooperation from the cognitive fundamentals found in other...     

Autumn migratory fuelling: a response to simulated magnetic displacements in juvenile wheatears, Oenanthe oenanthe

Recent experiments exposing migratory birds to altered magnetic fields simulating geographical displacements have shown that the geomagnetic field acts as an external cue affecting migratory fuelling behaviour. This is the first study investigating fuel deposition in relation to geomagnetic cues in long-distance migrants using the western passage of the Mediterranean region. Juvenile wheatears (Oenanthe oenanthe) were exposed to a magnetically simulated autumn migration from southern Sweden to West Africa. Birds displaced parallel to the west of their natural migration route, simulating an unnatural flight over the Atlantic Ocean, increased their fuel deposition compared to birds experiencing a simulated migration along the natural route. These birds, on the other hand, showed relatively low fuel loads in agreement with earlier data on wheatears trapped during stopover. The experimental displacement to the west, corresponding to novel sites in the Atlantic Ocean, led to a simulated longer distance to the wintering area, probably explaining the observed larger fuel loads. Our data verify previous results suggesting that migratory birds use geomagnetic cues for fuelling decisions and, for the first time, show that birds, on their first migration, can use geomagnetic cues to compensate for a displacement outside their normal migratory route, by adjusting fuel deposition.     

Alternative reproductive tactics and the impact of local competition on sex ratios in the ant Hypoponera opacior

The ant Hypoponera opacior exhibits alternative reproductive morphs of males and females associated with distinct sexual behaviours. Our long-term study reports strong seasonality in sexual production with a mating season in early and one in late summer. Winged (alate) reproductives emerge in June, swarm during the monsoon season and establish new colonies independently. In contrast, wingless worker-like (ergatoid) reproductives that appear in late August mate within their natal or adjacent nests and either do not disperse or establish new nests close by. These divergent dispersal patterns allowed us to analyse the impact of local factors on investment strategies by comparing sex allocation between and within the two reproductive events. The optimal sex ratio for ergatoid reproductives should be influenced both by competition for matings between brothers (local mate competition) and rivalry among young locally dispersing queens for workers, nest sites or food (local resource competition). The greater importance of local resource competition was demonstrated both by a male-biased sex ratio for wingless sexuals and a stronger increase in the number of males with total sexual production than for the number of queens. Microsatellite analysis revealed that inter-nest variation in relatedness asymmetry cannot explain split sex ratios in the August generation. Instead, nests with related ergatoid males raised a male-biased sex ratio contrary to the expectations under local mate competition. In conclusion, male bias in wingless H. opacior indicates that local mate competition is less strong than local resource competition among ergatoid queens over the help of workers during nest foundation.     

Does defoliation induce chemical and morphological defenses in the leaves of silver birch seedlings under changing climate?

Summary.  We examined the effects of defoliation con-currently with elevated temperature and CO₂ on some chemical and morphological characteristics in the leaves of silver birch seedlings (Betula pendula). We also analyzed the consequent changes in the palatability of leaves for adult blue alder leaf beetles (Agelastica alni). Under the different climatic treatments, the seedlings were subjected to three fertilizer treatments (0 kg, 130 kg and 270 kg N ha⁻¹) and defoliation treatments (0%, 25% and 50% of the total leaf area). In each climatic treatment, fertilization increased the nitrogen content in the leaves, but decreased total concentrations of soluble phenolics, detected by high-performance liquid chromatography (HPLC), and insoluble condensed tannins. Defoliation, both independently and in combination with elevated temperature and CO₂, decreased the concentrations of the phenolics. Compared to the intact controls, the leaves of the defoliated seedlings were smaller and tougher. Under elevated temperature, the beetles consumed a smaller amount of the leaves of plants subjected to the high fertilization, while under ambient climatic conditions, fertilization increased the feeding. The total leaf consumption was higher under the ambient climatic conditions than under elevated temperature, elevated CO₂ or the combination of elevated temperature and CO₂.     

Mesomelic campomelia,polydactyly and Dandy–Walker cyst in siblings

The present report describes two fetuses, one female and one male, with thus far undescribed skeletal malformations. The mother was a gravida 2, para 0. Both pregnancies were terminated in the second trimester because of multiple congenital anomalies diagnosed ultrasonographically resembling a short rib-polydactyly syndrome. Both fetuses were found to have postaxial hexadactyly of the hands and feet, marked bilateral campomelia of the forearm and shank bones, and a Dandy–Walker cyst. In addition, the fourth ventricle was dilated in the first sibling and the second sibling had an inverse intestinal malrotation. A literature search failed to reveal similar observations. Copyright © 2001 John Wiley & Sons, Ltd.     

An evaluation of grid rod failure in a mobile bed scrubber

The body of information presented in this paper is directed to those engineers and maintenance personnel involved in the operation of mobile-bed scrubbers. Materials tests were performed on three specimens of austenitic stainless steel to determine the possible causes of grid rod failure in a mobile-bed scrubber controlling particulate emissions from a pulverized-coal-fired, steam-electric generating station. These three specimens were successively placed in an Instrom universal testing machine and loaded in tension until rupture occurred. The results of these tests, in addition to other supporting data, were used in an attempt to determine the cause of the grid rod failure during scrubber operation. It was determined that the grade of stainless steel used, the scrubber water quality, and certain operational problems could be causes of premature failure.     

Hibernation in Malagasy mouse lemurs as a strategy to counter environmental challenge

The spiny forest of southwestern Madagascar is the driest and most unpredictable region of the island. It is characterized by a pronounced seasonality with high fluctuations in ambient temperature, low availability of food, and a lack of water during the cool dry season and, additionally, by changes in environmental conditions between years. One of the few mammalian species that manages to inhabit this challenging habitat is the reddish-gray mouse lemur (Microcebus griseorufus). The aim of our study was to determine whether this small primate uses continuous hibernation as an energy saving strategy, and if so, to characterize its physiological properties. We measured skin temperature of 16 free-ranging individuals continuously over 3 months during the cool dry season using collar temperature data loggers. Prolonged hibernation was found in three mouse lemurs and was not sex dependent (one male, two females). Skin temperature of hibernating individuals tracked ambient temperature passively with a minimum skin temperature of 6.5°C and fluctuated strongly each day (up to 20°C), depending on the insulation capacity of the hibernacula. Individuals remained in continuous hibernation even at an ambient temperature of 37°C. The animals hibernated continuously during the dry season, and hibernation bouts were only interrupted by short spontaneous arousals. The study emphasizes that hibernation is an important measure to counter environmental challenge for more tropical species than previously thought, including primates. It furthermore provides evidence that tropical hibernation is functionally similar among tropical species.