Seed Consumption and Dispersal by the Spur-Thighed Tortoise Testudo graeca

Cobo, Margarita; Andreu, Ana C.

doi:10.2307/3565307

Cited by 43 publications

(19 citation statements)

References 18 publications

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“…Although studies conducted in arid regions indicated that tortoises of the family Testudinidae may be effective seed dispersal agents (Cobo and Andreu 1988;Varela and Bucher 2002;Liu et al 2004), in tropical forests the role played by this group in seed dispersal has received little attention (see Strong and Fragoso 2006;Guzmán and Stevenson 2008).…”

Section: Introductionmentioning

confidence: 99%

Are tortoises important seed dispersers in Amazonian forests?

2009

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According to most studies on seed dispersal in tropical forests, mammals and birds are considered the main dispersal agents and the role played by other animal groups remains poorly explored. We investigate qualitative and quantitative components of the role played by the tortoise Chelonoidis denticulata in seed dispersal in southeastern Amazon, and the influence of seasonal variation in tortoise movement patterns on resulting seed shadows. Seed shadows produced by this tortoise were estimated by combining information on seed passage times through their digestive tract, which varied from 3 to 17 days, with a robust dataset on movements obtained from 18 adult C. denticulata monitored with radio transmitters and spoon-and-line tracking devices. A total of 4,206 seeds were found in 94 collected feces, belonging to 50 seed morphotypes of, at least, 25 plant genera. Very low rates of damage to the external structure of the ingested seeds were observed. Additionally, results of germination trials suggested that passage of seeds through C. denticulata's digestive tract does not seem to negatively affect seed germination. The estimated seed shadows are likely to contribute significantly to the dispersal of seeds away from parent plants. During the dry season seeds were dispersed, on average, 174.1 m away from the location of fruit ingestion; during the rainy season, this mean dispersal distance increased to 276.7 m. Our results suggest that C. denticulata plays an important role in seed dispersal in Amazonian forests and highlight the influence of seasonal changes in movements on the resulting seed shadows.

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Section: Introductionmentioning

confidence: 99%

Are tortoises important seed dispersers in Amazonian forests?

2009

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“…De forma similar ao presente trabalho, outros estudos têm reportado a ausên-cia de efeito do trato digestivo de répteis sobre a germinação de sementes (Valido & Nogales 1994, Castilla 2000, Traveset & Verdú 2002, embora outros têm registrado um aumento na germinação (Cobo & Andreu 1988, Figueira et al 1994, Valido & Nogales 1994.…”

Section: Distribuição Espacialunclassified

Dispersão de sementes de Melocactus glaucescens e M. paucispinus (Cactaceae), no Município de Morro do Chapéu, Chapada Diamantina - BA

2012

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RESUMO(Dispersão de sementes de Melocactus glaucescens e M. paucispinus (Cactaceae), no município de Morro do Chapéu, Chapada Diamantina -BA). Objetivou-se identifi car os dispersores de duas espécies de Melocactus, verifi car o padrão de liberação dos frutos, correlacionando-o com a remoção por frugívoros e variação térmica do cefálio, bem como caracterizar a distribuição espacial. Para tanto, foram realizadas observações focais, testes de germinação, registros da emergência, extrusão e remoção de frutos, da temperatura do cefálio, de interações formigas-diásporos e distribuição espacial. Lagartos (2 espécies) e formigas (3 espécies) foram os dispersores das espécies estudadas. A dormência das sementes não foi quebrada pela passagem pelo trato digestivo dos lagartos. As maiores taxas de remoção dos frutos pelos lagartos ocorreram nas horas centrais do dia, coincidindo ou sendo posterior aos picos de extrusão. As taxas de emergência e extrusão foram mais intensas pela manhã, o que aumentou as chances de remoção dos frutos no dia da liberação, evitando dissecação e predação. Não houve correlação entre a liberação dos frutos e a variação térmica do cefálio. O desenvolvimento do fruto gera tensão nas fi bras do cefálio que promove sua emergência ou expulsão. A expulsão de frutos emergidos pode ser auxiliada pela dilatação das fi bras em resposta ao aquecimento, tensão da união das fi bras na base e saída de outros frutos. A distribuição espacial dos indivíduos parece ser infl uenciada pelo comportamento dos dispersores. Focal observations were made of fruit emergence, extrusion and removal, cephalium temperature, ant-diaspore interactions, and plant spatial distribution. Germination tests were also made. Two lizard and three ant species were dispersers of the two species of Melocactus. Seed dormancy was not broken in the digestive tracts of the lizards. Th e greatest rates of fruit removal by the lizards occurred during the mid hours of the day, coinciding with or following the extrusion peak. Fruit emergence and extrusion rates were highest in the morning, increasing their chances of being taken on the same day, thus avoiding desiccation and predation. No correlation was observed between fruit liberation and thermal variations of the cephalium. Fruit development generates tension within the fi ber mass of the cephalium that provokes fruit emergence/expulsion. Th e expulsion of the fruits may also be aided by the dilation of the cephalium fi bers as they warm, tension generated at the cephalium base where the fi bers unite, and by the expulsion of other fruits. Th e spatial distribution of these cacti is infl uenced by disperser behavior.

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“…Various studies have already been conducted on population dynamics (Bayley and Highfield, 1996;El Mouden et al, 2001;Slimani et al, 2001), general ecology (Lambert, 1969(Lambert, , 1981(Lambert, , 1983, geographic variations (Highfield, 1990a, b) and impact of trade (Highfield, 1994;Bayley and Highfield, 1996). Unfortunately, food habits are still poorly known and limited to brief notes in the literature (Cobo and Andreu, 1988;Highfield, 1989;Bayley and Highfield, 1996;Andreu et al, 2000). Precise qualitative and quantitative information about tortoise feeding ecology are nevertheless fundamental to conservation purpose in overgrazing area.…”

Section: Introductionmentioning

confidence: 97%