Jennifer Butterfield

Carabid life-cycle strategies and climate change: a study on an altitude transect

Abstract. 1 There was little overlap in the species composition of carabid beetle assemblages sampled below 450 m and above 800 m on an altitude transect and the first axis of a DECORANA ordination was closely correlated with altitude (r11= 0.93, P < 0.001), probably reflecting the differing temperature requirements of different species. 2 Life‐cycle strategies of two low‐altitude species, found predominantly below 600 m, and two species caught above 600 m a.s.l., have been determined, using mandible wear to identify whether the females breed in the calendar year that they emerge as adults or in the year following. 3 Nebria salina has an annual cycle at 630 m. Pterostichus madidus and Calathus fuscipes were both biennial at altitudes above 300 m although predominantly annual at low altitude. N.gyllenhali was biennial above 600 m and it is not known whether it is able to switch to an annual cycle at low altitude. 4 Both N.salina and N.gyllenhali ceased activity soon after emergence, an adaptation which preserves their mandibles from wear. 5 At altitudes of 305 m and 430 m, P.madidus and C.fuscipes entered the breeding season with 33% and 56% reduction in mandible tip length, possibly reducing their reproductive output. 6 The necessity for relatively sharp mandibles on entry into the breeding season may restrict the capacity of carabids to respond to a temperature change by switching from annual to biennial cycles, and vice versa, adding support to the suggestion that carabids are more likely to respond to climate change by shifting distributions than by physiological adaptation.

The herring gull Larus argentatus as a likely transmitting agent of Salmonella montevideo to sheep and cattle.

This paper presents evidence for the involvement of herring gulls (Larus argentatus) as vectors in the recent outbreaks of Salmonella montevideo in sheep and cattle in Scotland and suggests that the transfer can take place over considerable distances. The breeding area in Scotland of herring gulls which overwinter in N.E. England is remarkably similar to the geographical distribution of the outbreaks. This pattern, together with the feeding behaviour of herring gulls on farmland, the presence of S. montevideo in herring gulls just before their departure from the wintering area and the timing of the return just before the peak of outbreaks are all circumstantial evidence implicating this gull in the outbreaks. The rapid return of these gulls to their breeding areas means that S. montevideo can be transported long distances in one day and raises the possibility that the original source of S. montevideo could have been in N.E. England rather than in Scotland.

The herring gull Larus argentatus as a carrier of salmonella

The proportion of salmonella carriers among town-nesting herring gulls increased significantly from 2.1% in 1975-6 to 8.4% in 1979. The range of serotypes carried by herring gulls was similar to that causing infection in man, and it is likely that the gulls ingest these serotypes when feeding at untreated sewage outfalls on the coast. This is supported by the proportion of salmonella carriers being higher among first-year birds (9.7%) than among older birds (2.0%), as it is known that higher proportions of immature herring gulls feed on the coast. Herring gulls carrying salmonellas appeared healthy at the time of capture and at a later date it was assumed that they were not themselves infected. However, their habit of congregating in large numbers on reservoirs and rubbish tips and also at resting sites on farmland often far from feeding and roosting areas, multiplies the pollution problem and increases the potential health hazard for both man and farm stock. Herring gulls feed at a variety of sites and fly many miles from food source to food source and from feeding areas to the roost. Thus, even within the same day, there is the possibility of the transfer of salmonellas over a much wider area than previously considered.

Changes in life-cycle strategies of Carabus problematicus over a range of altitudes in Northern England

ABSTRACT. 1 Mandible tip length has been used to estimate the age of individual C.problematicus Herbst caught over an altitude range of more than 700 m in northern England. 2 At 100 m the great majority of females laid eggs in the summer of their emergence as adults. The female life‐cycle is predominantly annual and 24% only of the egg‐bearing individuals were in their second year. 3 Above 250 m, most females did not reproduce until the summer of the year following emergence, giving a biennial life‐cycle. 96% of egg‐bearing females caught above 830 m were in their second year. 4 All the males caught during the breeding season at 100 m had emerged within that calendar year and it is concluded that the male life‐cycle is annual at this altitude. 5 Above 250 m, 83% of the males caught during the breeding season were in their first calendar year, suggesting that recently emerged males may inseminate second year females and also that the male life‐cycle is predominantly annual over the whole altitude range studied. 6 At the higher temperatures of the lowland site females not only produce eggs in the year of emergence, they also produce more eggs per individual than at the higher sites. Egg production depends on food intake which involves mandible wear and individuals at the lowland site have significantly higher rate of mandible wear than at the sites above 250 m.

Studies on a colony of colour-ringed Herring Gulls Larus argentatus: I. Adult survival rates

Colour-ringed Herring Gulls breeding in a small colony in NE England were used to estimate the average annual adult survival rates of males and females in 6 successive years. Although the female survival rate was higher than that of the males in most years, the difference was not significant. The average annual survival rate for both sexes combined was 91.7%, giving an average expectation of adult life (which is also the number of breeding seasons in which an average Herring Gull can breed) of over 11 years. More data are required to test whether there are sex differences in survival and to give a more precise measure of the expectation of life. The peak of mortality is between July and September and is lowest during the winter, which is in agreement with previous findings in Britain.

Terrestrial invertebrates and climate change: Physiological and life-cycle adaptations

Invertebrates are ectotherms and their growth rates are directly dependent on environmental temperatures; being small, they are also highly susceptible to desiccation (Andrewartha & Birch 1954). Changes in temperature and rainfall regimes thus are likely to have major direct effects on invertebrate distributions. Equally important, climate change will have indirect effects through its effect on food plant distributions and phenologies. Many specialist herbivores have shifted their distributions in response to changes in plant distributions in the past (Hengeveld 1990), others must have adapted to changed timing of budburst and early leaf growth in their host plant (Dixon 1985; Murray et al . 1989).

Scandinavian Herring Gulls wintering in Britain

Biometric information was obtained from 13000 Herring Gulls Larus argentatus caught and ringed in northern England and southern Scotland outside the breeding season between 1978 and 1983. Morphological differences between males and females and between British and Scandinavian Herring Gulls have been used to identify both the sex and race of the birds. We describe the wintering distribution of the Scandinavian birds in Britain, their age and sex ratios and their time of arrival in and departure from Britain. Scandinavian Herring Gulls start to arrive in Britain in small numbers in September. The proportion of Scandinavian birds increases to a peak in December-January and the birds depart abruptly in late January or early February. Very few Scandinavian Gulls penetrate to the west side of Britain, while on the east side there is considerable regional variation in the proportion of Scandinavian birds. Between 70% and 80% of the adult Scandinavian birds examined were female. The proportion of adults amongst Scandinavian birds was much higher than amongst British birds.

Effect of photoperiod on a winter and on a summer diapause in two species of cranefly (Tipulidae)

Abstract Two craneflies, Tipula subnodicornis and Tipula pagana , both undergo diapause in the final larval instar. The species showed differences in the intensity of diapause and in the timing of the photoperiodic reaction during diapause, that could be related to season. Tipula subnodicornis undergoes a winter diapause that is induced and maintained in its early stages by short photoperiod (L:D:6:18). In the laboratory individuals in the early stages of diapause terminated diapause and pupated earlier when they were exposed to daylengths of, or greater than, 12 hr. However, it is suggested that in the field diapause is broken before the natural daylength is long enough to have any accelerating effect on development. Tipula pagana has a summer diapause which is of greater intensity than that of Tipula subnodicornis and some larvae were maintained for 197 days in the laboratory, without pupating, on an 18 hr daylength. Diapause was broken by a L:D;16:8 photoperiod and development was accelerated by a further decrease in daylength. The acceleration in development rate was attended by a decrease in the variance about the mean date of emergence and resulted in a highly synchronised emergence period. It is suggested that this quantitative response to daylength is particularly important to a species that emerges in the autumn when the temperature in the field is falling.

Movements of British Herring Gulls

This analysis shows that there is considerable regional variation in the mobility of Herring Gulls in the British Isles, and that long distance movement is more frequent in birds reared in the north of Britain.

The response of development rate to temperature in the univoltine cranefly, Tipula subnodicornis Zetterstedt

SummaryThe cranefly, Tipula subnodicornis, emerges as an adult in the spring and has an annual life-cycle in the British Isles. This is maintained partly through the presence of a winter diapause but the response of development rate to temperature also acts to preserve the timing of the cycle. During development under constant temperature conditions in the laboratory the optimum temperature (taken as the temperature which promoted the most rapid development) dropped from 25°C, or above, in the egg stage to below 20°C in the late larval stages. It is suggested that at the warmer, southern limits of the geographical range rapid early development may be compensated by a retardation in late larval growth. In addition, the response of growth rate to change in temperature was small in the fourth, final, instar and resulted in low Q10 values; 2.4 between 7° and 10°C, 1.5 between 10° and 15°C and 0.9 between 15° and 20°C. As the fourth instar comprises the greater part of the growth period, this has the effect of minimising the effect of temperature differences which are the result of differences of latitude or altitude. Even at optimum temperatures the growth period was prolonged and larvae in the field do not reach maximum weight, and the photosensitive stage, until late autum when short daylength promotes diapause. Subsequent development in the spring, before pupation and during the pupal period, showed a reversion to the higher Q10 figures of the early stages in development.The development of final instar Tipula subnodicornis larvae is contrasted with that of Tipula melanoceros. Tipula melanoceros emerges as an adult in September and it is likely that it has an egg diapause. Consequently larval development is confined to a short period between April and late July and growth must be rapid during this period. Under constant temperature conditions in the laboratory the growth of final instar larvae showed a marked contrast to that of Tipula subnodicornis in that the response to temperature was large and remained positive over a wider temperature range.