No abstract

In a small stream of southern Tuscany (Fossa Calda), fed by hot springs, we discovered a fish community dominated by tropical species, some of which have never previously been reported in Euro-Mediterranean natural freshwater environments. The aim of our research was to ascertain whether the three most abundant and widespread species (Amatitlania nigrofasciata, Hemichromis sp. and Oreochromis niloticus) have become established. Analysis of size class distribution and growth curves showed that the populations of these species are quite large and made up of juveniles, subadults and adults, as is the case in self-sustaining populations. These fishes were probably released intentionally, since they are widely used in aquariums and aquaculture and their survival in Fossa Calda was possible because of the constant high temperature of thermal waters. Spread to other streams seems unlikely. In fact, at some distance from the hot springs, where water temperatures are lower, populations of the tropical species were small.

No abstract

In terrestrial snails, thermal selection acts on shell coloration. However, the biological relevance of small differences in the intensity of shell pigmentation and the associated thermodynamic, physiological, and evolutionary consequences for snail diversity within the course of environmental warming are still insufficiently understood. To relate temperature‐driven internal heating, protein and membrane integrity impairment, escape behavior, place of residence selection, water loss, and mortality, we used experimentally warmed open‐top chambers and field observations with a total of >11,000 naturally or experimentally colored individuals of the highly polymorphic species Theba pisana (O.F. MÜLLER, 1774). We show that solar radiation in their natural Mediterranean habitat in Southern France poses intensifying thermal stress on increasingly pigmented snails that cannot be compensated for by behavioral responses. Individuals of all morphs acted neither jointly nor actively competed in climbing behavior, but acted similarly regardless of neighbor pigmentation intensity. Consequently, dark morphs progressively suffered from high internal temperatures, oxidative stress, and a breakdown of the chaperone system. Concomitant with increasing water loss, mortality increased with more intense pigmentation under simulated global warming conditions. In parallel with an increase in mean ambient temperature of 1.34°C over the past 30 years, the mortality rate of pigmented individuals in the field is, currently, about 50% higher than that of white morphs. A further increase of 1.12°C, as experimentally simulated in our study, would elevate this rate by another 26%. For 34 T. pisana populations from locations that are up to 2.7°C warmer than our experimental site, we show that both the frequency of pigmented morphs and overall pigmentation intensity decrease with an increase in average summer temperatures. We therefore predict a continuing strong decline in the frequency of pigmented morphs and a decrease in overall pigmentation intensity with ongoing global change in areas with strong solar radiation.

A total of 213 males and 234 females of the tiger-beetle Cephalota circumdata leonschaeferi (Cassola) were individually colour marked in the three years of study (1984, 1985, 1986). The maximum number of days in which marked individuals were resighted was 37. These tiger-beetles dispersed within a radius of 30 m from their respective marking places. Re-sightings were rare beyond this dis tance; one individual was observed at about 100 m from its marking place. The ground temperature proved to be a key-factor influencing the activity and viability of the population; optimal ground temperature ranged between 32-33°C as to number of individuals present, but a temperature of 34-35°C determined the greatest number of matings. A negative influence on C. c. leonschaeferi survival and activity was exerted by cloudy and, particularly, rainy weather. Wind force influenced the habitat selection: an increase of wind force generated a greater use of terrain without vegetation (Salicornia). Apparently the increased hunting success of these beetles in open ground at wind force 3-4 (Beaufort scale) determined the habitat selection. Males proved significantly more active than females by covering greater daily distances. Both sexes showed two peaks of activity in the early morning and in the afternoon, but they were inactive in the central hours of the day, when the ground temperatures were beyond 36-37°C. ACKNOWLEDGEMENTS