Hatching asynchrony, survival, and the fitness of alternative adult morphs in \u3ci\u3eAmbystoma talpoideum\u3c/i\u3e

The mole salamander, Ambystoma talpoideum, exhibits both aquatic (gilled) and terrestrial (metamorphosed) adult morphologies. Previous studies have shown the existence of body-size advantages associated with the terrestrial morph in A. talpoideum and other polymorphic salamanders (e.g., A. tigrinum). However, aquatic adult A. talpoideum mature at a younger age and often breed earlier than terrestrial adults. We tested the hypothesis that early maturation and reproduction in aquatic adults increase fitness (irrespective of body size). We reared larval A. talpoideum in mesocosms and varied the timing of hatching, with early-hatching larvae representing the offspring from early-breeding aquatic adults, and late-hatching larvae representing the offspring of later-breeding terrestrial adults. Our results demonstrate significantly higher survival rates among early-hatchlings relative to late-hatching conspecifics, supporting the hypothesis that early reproduction may be an important mechanism mediating the polymorphism in A. talpoideum. We discuss our results within the context of size-based models of the fitness of alternative life-cycles

Effects of hydroperiod on metamorphosis in \u3ci\u3eRana sphenocephala\u3c/i\u3e

Hydroperiod, the time a temporary pond holds water, is an important factor influencing recruitment in amphibian populations and structuring amphibian communities. We conducted an experiment to test the effect of hydroperiod on metamorphic traits of the southern leopard frog (Rana sphenocephala), a common amphibian in the southeastern United States. We reared larval R. sphenocephala in artificial ponds at a density of 32 larvae per tank (initial volume = approximately 650 liter). We dried the tanks according to natural patterns, using three different hydroperiods (60, 75 and 90 d). Experimental hydroperiods had a significant effect on the number of metamorphs and the length of the larval period, but not on overall survival (larvae + metamorphs) nor size at metamorphosis. Our findings confirm a pattern observed in field studies and are similar to results of experimental investigations of closely related ranid frogs. Our results demonstrate that relatively small differences in hydroperiod length (i.e., as little as 15 d) may have large effects on juvenile recruitment in R. sphenocephala

Evaluation of Level of Milk Potential on Nutrient Balance in 2- and 4- Year- Old May- Calving Range Cows Grazing Sandhills Upland Range

A modeling study evaluated the effects of milk production level on nutrient balance in May- calving cows grazing Sandhills upland range during the breeding season. Forage quality of upland range peaks in June and steadily declines in July until November. With timing of forage quality decline and increasing nutrient demands due to lactation, cows were in a negative energy balance in late June and early July prior to deficiency of metabolizable protein. Supplementation to meet energy deficiencies in June and July and MP deficiencies in July with distiller grains that is high ruminally undegradable protein and high fiber energy may be needed in May- calving cowherds. Selection for milk over 23 lb at peak lactation creates deficiencies early post- calving and increases the need for additional supplementation to correct the nutrient deficiency. In an effort to match cow type to environment in the Sandhills and optimize performance, producers should consider selecting against high milk potential

A chronology of turning points in economic activity: Spain 1850-2011

This paper codifies in a systematic and transparent way a historical chronology of business cycle turning points for Spain reaching back to 1850 at annual frequency, and 1939 at monthly frequency. Such an exercise would be incomplete without assessing the new chronology itself and against others —this we do with modern statistical tools of signal detection theory. We also use these tools to determine which of several existing economic activity indexes provide a better signal on the underlying state of the economy. We conclude by evaluating candidate leading indicators and hence construct recession probability forecasts up to 12 months in the future.Business cycles ; Spain