Recent increase in body size of the American marten Martes americana in Alaska

Using museum specimens, we studied recent changes in skull size of the American marten Martes americana , in continental Alaska. In Alaska, global warming has resulted in milder winters that may contribute to an improved food supply in the wild. In the present study, we tested the hypothesis that body size of the marten had increased during the second half of the 20th century, in response to global warming. We found that skull size, and by implication body size, increased significantly during the second half of the 20th century, possibly due to an improved food supply and/or lower metabolic demands in winter. Improved food availability in winter may result from the improved nutritional conditions for prey, and/or from increased access to prey resulting from a longer snow-free season. Longitude had a significant positive effect on skull size and a significant negative effect on teeth size. In Alaska, the climate is milder along the western coast and becomes harsher inland. Hence, the milder climate was associated with larger body size providing further support for our prediction that body size of the American marten was influenced by food availability and reduced energy expenditure. The negative relationship between longitude and teeth size may indicate a trend towards a larger prey in inland marten populations, but we have no data to support or refute this hypothesis.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 701–707.     

Water loss from Jackass Penguin Spheniscus demersus eggs during natural incubation

The water budget of incubating Jackass Penguin eggs was studied on Marcus Island, South Africa, and complementary measurements were made in the laboratory. The mean ambient temperature was 16-5 "C and the mean humidity was 12-4 Torr (89% relative humidity). The temperature of incubated live and water-filled eggs ranged between 14^oCand 37 ^oC. The mean calculated egg temperature was 34-9' C. The mean brood patch temperature was 37-1 ^oC, slightly lower than the cloacal temperature (37.8 ^oC). The mean brood patch area was about 38 cm². The rate of water loss was 411 mg day^-1. The total diffusive water loss during 37 days of incubation was, as predicted, 15-2% of the initial 100-3 g egg mass. The total pore number was 6245 per egg and the shell thickness was 577 fira. It is suggested that the eggshell parameters, incubation length and nesting behaviour are compensated in such a way that an egg-to-nest water vapour pressure difference lower than commonly found is sufficient to bring about the normal total water loss.     

Climatic change and body size in two species of Japanese rodents

Using museum specimens, we studied temporal changes in skull size in two species of Japanese rodents, the large Japanese field mouse ( Apodemus speciosus ) and Pratt's vole ( Eothenomys smithii  =  E. kageus ) during the 20th century. We used the greatest length of the skull (GTL), zygomatic breadth (ZB), narrowest width of the skull across the interorbital region (IC) and the length of the upper cheek teeth row (M) as indicators to such changes. We found that GTL and ZB (but not IC and M) increased during the study period in mice, and that IC and M (but not GTL and ZB) increased marginally in voles. We attribute these changes to elevated ambient minimal temperatures, which increased food availability and energy savings for the mice, and required diet change in the voles.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 263–267.     

INTRASPECIFIC NEST PARASITISM IN BIRDS

(1) The incidence of intraspecific nest parasitism in birds is reviewed. This phenomenon can be identified by various methods, ranging from biochemical examination of protein and enzyme polymorphisms to observations on the sequence of appearance of eggs in the nest as well as on the shape and colour of the eggs. The phenomenon has been reported for at least 53 species (Table I), mostly among precocial birds.
(2) The evidence suggests that the parasites are ( a ) young, unmated birds, ( b ) females which have lost their nests and (c) mated females which also lay in the nests of other females. High proportions of such females, and scarcity of suitable nest sites increase the rate of parasitism.
(3) Breeding success in parasitized nests is reduced by factors such as egg loss, desertion, inefficient incubation, reduced clutch size and late layings. The upper limit of the rate of intraspecific parasitism is discussed. It is argued that its incidence will be higher in the tropics than in extreme zones, for example, high latitudes and deserts, because there is higher synchronization of breeding in the latter, and increased predation in the former zones. Also, it will be more common in species which lay large clutches, such as precocial species.     

Body size of the red fox Vulpes vulpes in Spain: the effect of agriculture

The body size of animals is affected by several factors, including ambient temperature and food availability. Ambient temperature is often negatively related to body size (Bergmann's rule) whereas an improved diet, especially during growth, has a positive effect. Animals commensal with man commonly exploit additional food sources (e.g. garbage dumps), thereby increasing their food supply. Using museum material, we studied morphological variation in skull size (and thus body size) among Spanish red foxes. Four measurements were taken of each skull and were related to the habitat from which the foxes were collected (agricultural and non-agricultural), and to latitude as a proxy for ambient temperature. The skull size of foxes collected in agricultural areas during the late 20th Century was significantly larger than that of those from non-agricultural areas, and was negatively related to latitude, thus contradicting Bergmann's rule. We suggest that increased food availability from animal husbandry is the cause for the observed increase in skull size (and thus body size).  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 729–734.     

Biosynthesis of ethylene: the effect of phosphate*

Abstract Biosynthesis of ethylene in tomato and avocado fruit slices, carrot root, pea seedling and tomato shoot segments, Penicillium expansum and Escherichia coli was found to be inhibited by inorganic phosphate. Compared with microbial systems, relatively high concentrations of phosphate in the incubating medium were necessary to bring about a significant inhibition of ethylene production in higher plants. The degree of inhibition in higher plants correlated with the increased internal cellular concentration of phosphate and not with that of the incubating medium. Phosphate concentrations inhibitory for ethylene biosynthesis did not affect the respiration of tomato fruit slices. The phosphate effect was reversible, confined to only the biological systems and was not due to a change in the ionic strength. The differential inhibitory effects of aminoethoxyvinylglycine on ethylene biosynthesis in tomato fruit slices of various stages of ripening, were markedly influenced by high phosphate concentrations. The data indicate a biological significance to the phosphate control of ethylene biosynthesis.     

Mating system and laying date in birds

The hypothesis that polygynous species start breeding later in the season than monogamous ones was examined using two data sets, each with both monogamous and polygynous species—the eight species of wrens which breed in the USA, and five genera (15 species) of British passerines. Comparisons were made within each of 16 states in the USA from which data were available and for each genus in Britain. The hypothesis is supported for most subsets of data, but in some cases polygynous and monogamous species start breeding at the same time (but in no case do polygynous breed earlier than monogamous species). The late breeding of the polygynous species is probably an outcome of the fact that polygynous males tend to participate less in nest activities than monogamous ones.     

Effect of Sub-Polar Gyre, North Atlantic Oscillation and ambient temperature on size and abundance in the Icelandic Arctic fox

Animals are exposed to environmental factors that influence their life history and body size. Here we used the Arctic fox ( Vulpes lagopus ) as an indicator of the complex links between largescale environmental variables that influence both marine and tundra trophic dynamics to demonstrate how they affect the fox's body size and abundance. The Arctic fox inhabits throughout Iceland, where it preys mainly on birds. We studied the effects of the Sub-Polar Gyre (SPG), winter and summer North Atlantic Oscillation (NAO), mean annual winter and summer temperature, and geographic sector (eastern and western Iceland, which differ in their ecology) on variations in mandible size (6345 specimens) and body mass (2732 specimens) as well as abundance on the Arctic fox in Iceland. We found that (a) SPG index negatively affected male mandible length as well as body mass of both sexes. SPG was also negatively related to fox abundance. (b) Summer NAO had a negative effect on Arctic foxes, that is, cold summers were correlated with shorter mandibles and lower body mass. (c) Winter NAO had a significant negative effect (although weaker than that of summer NAO) on female mandible length, but not on body mass. (d) Summer temperature had a positive effect on female mandible length, but no effect on body mass. However, winter temperature had no effect on either the mandible or body mass. (e) Foxes in the eastern sector had shorter mandibles and were of lighter mass than those in the western sector. We suggest that climate conditions during the growth period of the young affected their final size both directly, by influencing energy metabolism for maintenance, but mainly through their effects on food availability. As far as we are aware, this is the first report that the SPG has an effect on vertebrates, let alone terrestrial ones.     

Clutch size of passerines at mid-latitudes: the possible effect of competition with migrants

The clutch sizes of the passerines of Israel and the Cape Province, South Africa, which lie at similar latitudinal range, were compared. Mean clutch sizes in Israel and the Cape Province are 4.09 and 2.87, respectively. Mean clutch size of Israeli migrants is larger than that of residents (4.45 and 3.93, respectively), but no such difference exists in the Cape Province.
It is suggested that the larger clutch size in Israel is a result of two factors: (1) the higher proportion of wintering birds in Israel in comparison with the Cape Province and the presence of many transients there which may compete with resident birds and cause high winter mortality among them and (2) a higher proportion of migrants in the Israel avifauna, which suffer heavy losses during their trans-Saharan migration in comparison with Cape Province migrants, which travel shorter routes. The resulting reduced competition for food during the breeding season in Israel enables passerines there to lay larger clutches as predicted by Ashmole (1963) and Ricklefs (1980).