Most vascular plants form symbioses with mycorrhizal fungi that associate with roots and provide nutrients to hosts in exchange for carbohydrates, as well as serve a range of other functions. Mycorrhizal fungi have been studied extensively in upland ecosystems, but we know less about their ecology at aquatic-terrestrial interfaces, especially their distributions at depth. Our objectives were to determine whether abundances of arbuscular mycorrhizal fungi (AMF) change as floodplain islands develop and to describe vertical distributions of AMF from the forest floor to the water table along the freely flowing Tagliamento River in northeastern Italy. We sampled surface sediments (0-10 cm) from three stages of island development on the floodplain-fresh deposits, pioneer islands, and established islands. We also sampled sediments vertically (0-150 cm) from the ground surface to the water table on an established island. We characterized abundance of AMF propagules (colonized roots, spores, and hyphae) within sediments. Roots available to host fungi were absent on fresh deposits; however, some viable spores and hyphae were available at these sites. Pioneer and established islands each had similar hyphal lengths (*860 cm cm -3 ) and colonized root lengths (*3 cm cm -3 ). Abundance of spores increased from depositional (3.5 ± 0.9 (±SE) cm -3 ) to pioneer (17 ± 6.1 cm -3 ) to established (32 ± 6.3 cm -3 ) islands. On an established island, AMF propagules were present at all depths sampled, including at the water table, providing first documentation of these symbionts to such depths in a riparian setting. Mycorrhizal fungi likely link aquatic and terrestrial habitats by connecting plants, soil, and ground water and may influence nutrient transfers among these subsystems.

European starlings (Sturnus vulgaris) were fed either a low- or high-quality diet to test the effects of dietary quality on basal metabolic rate (BMR) and internal morphology. Basal metabolic rate did not differ significantly between the two dietary groups, but internal morphology differed greatly. Starlings fed the low-quality diet had heavier gastrointestinal tracts, gizzards, and livers. Starlings fed the high-quality diet had heavier breast muscles. Starlings on the low-quality diet maintained mass, while starlings on the high-quality diet gained mass. Dry matter digestibility and energy digestibility were lower for starlings fed the low-quality diet, and their food and water intake were greater than starlings on the high-quality diet. The lack of dietary effect on BMR may be the result of increased energy expenditure of digestive organs paralleling a reduction of energy expenditure of organs and tissues not related to digestion (i.e., skeletal muscle). This trade-off in energy allocation among organs suggests a mechanism by which organisms may alter BMR in response to a change in seasonal variation in food availability.

a b s t r a c t Currently, four species of Myotis are known from the islands of the Caribbean (Myotis dominicensis, M. martiniquensis, M. nesopolus, and M. nigricans). Myotis dominicensis and M. martiniquensis are endemic to the Lesser Antilles, whereas M. nesopolus and M. nigricans are considered conspecific with mainland populations. Recent phylogenetic and phylogeographic studies provided hypotheses regarding the origin and diversification of M. dominicensis and M. martiniquensis.However, these studies focused primarily on convergent morphology or distribution patterns of this genus and not on the evolutionary history of Caribbean Myotis. Here, we explore variation across multiple datasets generated from Caribbean Myotis. We present morphologic and genetic (mitochondrial and nuclear) data from an extensive sample of Caribbean Myotis species, including the previously unsampled taxa M. martiniquensis nyctor and M. nesopolus. Our data indicate that the historically recognized subspecies M. m. nyctor is genetically and morphologically distinct from M. martiniquensis, warranting recognition of a third Caribbean endemic-Myotis nyctor. Moreover, we provide evidence of unrecognized species-level variation in Caribbean and northern South American populations of Myotis.

Summary 1.Understanding an animal's ecology requires knowledge of how individual variation in behaviour and physiology interact with each other and with the environment that an animal experiences. 2. Environmental variation affects behaviour, but whether individual variation in physiological performance also affects behaviour is poorly known. 3. We studied a high-altitude population of Deer Mice ( Peromyscus maniculatu s) inhabiting an environment cold enough that above-ground activity (behaviour) may be limited by the thermogenic capacity (maximal rate of oxygen consumption [ V o 2 max ] during cold exposure) of mice. 4. We measured thermogenic capacity and operative environmental temperature (an integrated measure of the thermal environment), and then used robust-design capturemark-recapture (CMR) models to test whether the thermal environmental and individual variation in thermogenic capacity affected capture probabilities (a likely indicator of above-ground activity). 5. Models including environmental covariates and thermogenic capacity were strongly favoured over models that did not include them. 6. Our results demonstrate that individual variation in physiological performance may constrain behaviour in nature. 7. Besides contributing to our understanding of interactions in the multivariate phenotype, our results suggest that it may be possible to elucidate the mechanistic factors influencing capture probabilities. Such information could be valuable to ecologists, life historians and wildlife managers.

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