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Favourable Season (favourable + season)
Selected AbstractsHatching fraction and timing of resting stage production in seasonal environments: effects of density dependence and uncertain season lengthJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2001M. Spencer Many organisms survive unfavourable seasons as resting stages, some of which hatch each favourable season. Hatching fraction and timing of resting stage production are important life history variables. We model life cycles of freshwater invertebrates in temporary pools, with various combinations of uncertain season length and density-dependent fecundity. In deterministic density-independent conditions, resting stage production begins suddenly. With uncertain season length and density independence, resting stage production begins earlier and gradually. A high energetic cost of resting stages favours later resting stage production and a lower hatching fraction. Deterministic environments with density dependence allow sets of coexisting strategies, dominated by pairs, each switching suddenly to resting stage production on a different date, usually earlier than without density dependence. Uncertain season length and density dependence allow a single evolutionarily stable strategy, around which we observe many mixed strategies with negatively associated yield (resting stages per initial active stage) and optimal hatching fraction. [source] Photoperiod and temperature affect the life cycle of a subtropical cockroach, Opisoplatia orientalis: seasonal pattern shaped by winter mortalityPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2004Dao-Hong Zhu Abstract.,Opisoplatia orientalis is an ovoviviparous cockroach living in the subtropical areas in Japan. Both adults and nymphs overwinter on Hachijo Island (33°N). The nymphs sampled before and after overwintering showed a similar pattern in frequency distribution of head widths with a definite peak of fifth instars. The present study was conducted to determine how this pattern was formed by investigating the effects of photoperiod and temperature on development and reproduction. Photoperiod influenced the number of nymphal instars, resulting in a longer duration of nymphal development at LD 12 : 12 h than at LD 16 : 8 h. However, the rate of development at each instar was only affected to a small extent by photoperiod and no sign of diapause was detected. It was suggested that the photoperiodic response controlling the number of nymphal instars might have evolved to adjust the timing of adult emergence and reproduction to the favourable season. The prereproductive period and time intervals between nymph depositions were prolonged as temperature declined, but there was no evidence for diapause in adults. Mortality occurred in eggs and embryos inside of the body of the females during winter. Thus, it was inferred that female adults would reset ovarian development in spring and deposit nymphs in summer simultaneously, and these nymphs would reach the fifth instar before winter comes. This winter mortality hypothesis was supported by experiments in which reproductive activity and mortality were monitored for field-collected adults under either constant or changing temperature conditions simulating those in the field. [source] Low-temperature resistance in Polylepis tarapacana, a tree growing at the highest altitudes in the worldPLANT CELL & ENVIRONMENT, Issue 3 2001F. Rada ABSTRACT The Polylepis tarapacana forests found in Bolivia are unique with respect to their altitudinal distribution (4200,5200 m). Given the extreme environmental conditions that characterize these altitudes, this species has to rely on distinct mechanisms to survive stressful temperatures. The purpose of this study was to determine low-temperature resistance mechanisms in P. tarapacana. Tissue was sampled for carbohydrate and proline contents and micro-climatic measurements were made at two altitudes, 4300 and 4850 m, during both the dry cold and wet warm seasons. Supercooling capacity (,3 to ,6 °C for the cold dry and ,7 to ,9 °C for the wet warm season) and injury temperatures (,18 to ,23 °C for both seasons), determined in the laboratory, indicate that P. tarapacana is a frost-tolerant species. On the other hand, an increase in supercooling capacity, as the result of significant increase in total soluble sugar and proline contents, occurs during the wet warm season as a consequence of higher metabolic activity. Hence, P. tarapacana, a frost-tolerant species during the colder unfavourable season, is able to avoid freezing during the more favourable season when minimum night-time temperatures are not as extreme. [source] Evolutionary innovations of squamate reproductive and developmental biology in the family ChamaeleonidaeBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010ROBIN M. ANDREWS The availability of molecular phylogenies has greatly accelerated our understanding of evolutionary innovations in the context of their origin and rate of evolution. Here, we assess the evolution of reproductive mode, developmental rate and body size in a group of squamate reptiles: the chameleons. Oviparity is ancestral and viviparity has evolved at least twice: Bradypodion and members of the Trioceros bitaeniatus clade are viviparous. Viviparous species are medium-sized as a result of convergence from either small-sized ancestors or large-sized ancestors, respectively, but do not differ from oviparous species in clutch size, hatchling size or the trade-off between clutch and hatchling size. Basal chameleons (Brookesia, Rhampholeon and Rieppeleon) are small-sized and have developmental rates comparable with those of other lizards. Derived chameleons (Calumma, Chamaeleo, Trioceros and Furcifer) are mostly large-sized and all have relatively slow developmental rates. Several clades of derived chameleons also exhibit developmental arrest (embryonic diapause or embryonic diapause plus cold torpor) and incubation periods extend to 6,10 months or more. Developmental arrest is associated with dry, highly seasonal climates in which the period favourable for oviposition and hatching is short. Long incubation periods thus ensure that hatching occurs during the favourable season following egg laying. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 656,668. [source] | ||||||||||