Sucrose digestion capacity in birds shows convergent coevolution with nectar composition across continents

The major lineages of nectar-feeding birds (hummingbirds, sunbirds, honey-eaters, flowerpiercers, and lorikeets) are considered examples of convergentevolution. We compared sucrose digestion capacity and sucrase enzymatic activ-ity per unit intestinal surface area among 50 avian species from the New World,Africa, and Australia, including 20 nectarivores. With some exceptions, nectari-vores had smaller intestinal surfaces, higher sucrose hydrolysis capacity, andgreater sucrase activity per unit intestinal area. Convergence analysis showedhigh values for sucrose hydrolysis and sucrase activity per unit intestinal surfacearea in specialist nectarivores, matching the high proportion of sucrose in thenectar of the plants they pollinate. Plants pollinated by generalist nectar-feedingbirds in the Old and New Worlds secrete nectar in which glucose and fructose arethe dominant sugars. Matching intestinal enzyme activity in birds and nectarcomposition in flowers appears to be an example of convergent coevolution be-tween plants and pollinators on an intercontinental scale.Todd J. McWhorter, Jonathan A. Rader, Jorge E. Schondube, Susan W. Nicolson, Berry Pinshow, Patricia A. Fleming, Yocelyn T. Gutie, rrez-Guerrero, and Carlos Martı, nez del Ri

Biannual Cycles of the Cinnamon-bellied Flowerpiercer

Biannual cycles of reproduction and molt are rare in birds, with most species exhibiting a single annual cycle. We studied the breeding and molting phenology of the Cinnamon-bellied Flowerpiercet (Diglossa baritula), a nectar feeding passetine, in western Mexico. Monthly captures from December 1994 to May 1998 revealed clear biannual breeding and molting cycles. The two breeding seasons took place from January to April (dry season) and from July to October (rainy season). Their July to October breeding season coincided with the single breeding season exhibited by resident hummingbirds at our study site. Even though flowerpiercers and hummingbirds use the same food resources, hummingbirds only molt and breed once a year. Male flowerpiercers breed and molt flight feathers twice a year, whereas females appear to breed only once. A higher proportion of females bred in the rainy season (90%) than in the dry season (30%), and they underwent a complete molt only during the rainy season. Proportions of males in breeding condition during the dry and the rainy season were similar (86 and 92%). Some males (40%) showed an incomplete molt in the dry season, while most males (80%) underwent a complete molt in the rainy season. Differences in proportions of breeding and molting individuals between the dry and the rainy season suggest that the dry season cycle is limited by food availability. We hypothesize that D. baritula individuals use soft fruits in addition to flowers to fuel their breeding during the dry season

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Understanding the structure and evolution of ecological communities requires an examination of the factors that influence plant-animal mutualistic interactions. These interactions are affected by factors that are both extrinsic and intrinsic to the animals. We used a meta-analysis technique to examine such factors affecting the interactions between frugivorous animals and the plants they feed upon, using 3 common Neotropical frugivorous bat genera (Carollia, Sturnira, and Artibeus) as a model. We assessed whether latitude, altitude, ecoregion, and bat body size were related to the proportions of the most important plant genera in the diet of the bats. Our results show that extrinsic factors did not affect the proportion of Piper in the diet of Carollia. The proportion of Solanum in the diet of Sturnira was positively correlated with latitude and decreased in the mountain, moist, and bahia interior ecoregions. The proportion of Ficus and Cecropia in the diet of Artibeus decreased in high-elevation ecoregions and was negatively correlated with altitude. The large Artibeus species featured more Ficus and Cecropia in their diets compared to the small species of this genus. Our work demonstrates that mutualistic interaction between Neotropical bats and their core plant taxa is mediated by geographic and morphological factors. 2013 American Society of Mammalogists

Sucrose digestion capacity in birds shows convergent coevolution with nectar composition across continents

The major lineages of nectar feeding birds (hummingbirds, sunbirds, honeyeaters, flower-piercers, and lorikeets) are considered examples of convergent evolution. We compared sucrose digestion capacity and sucrase enzymatic activity per unit intestinal surface area among 50 avian species from the New World, Africa, and Australia, including 20 nectarivores. With some exceptions, nectarivores had smaller intestinal surfaces, higher sucrose hydrolysis capacity, and greater sucrase activity per unit intestinal area. Convergence analysis showed high values for sucrose hydrolysis and sucrase activity per unit intestinal surface area in specialist nectarivores, matching the high proportion of sucrose in the nectar of the plants they pollinate. Plants pollinated by generalist nectar-feeding birds in the Old and New Worlds secrete nectar in which glucose and fructose are the dominant sugars. Matching intestinal enzyme activity in birds and nectar composition in flowers appears to be an example of convergent coevolution between plants and pollinators on an intercontinental scale

Impact of landscape composition and configuration on forest specialist and generalist bird species in the fragmented Lacandona rainforest, Mexico

With accelerated land-use change throughout the tropics, an increasing proportion of global biodiversity is located in human-modified landscapes. Understanding the relative effects of landscape composition and configuration on biodiversity is needed to design effective conservation strategies. Yet this topic is poorly understood because most studies have been performed at the patch scale, and do not assess the impact of landscape structure on species. Using a multi-model inference approach, we assessed the relative effect of landscape composition (i.e. percentage of forest cover and matrix composition) and landscape configuration (i.e. number of forest patches and forest edge density) on α- and β-diversity of birds in 17 forest fragments and three areas of continuous forest within the Lacandona rainforest, Mexico. We tested these impacts at two spatial scales (100 and 500. ha) for forest specialist and generalist birds. In general, forest specialist birds showed stronger responses to landscape characteristics than generalist species, particularly to variations in landscape composition at the 100-ha scale. The loss of forest cover represented the main threat to forest specialist birds, with a negative impact on α-diversity that was consistent across the two spatial scales. In contrast, at the two spatial scales generalist birds seemed to be favored