Abstract
We analysed the germination of seeds after their passage through the digestive tract of small floodplain fishes. Samples were collected in five open flooded fields of the northern Pantanal in March 2011. All fishes were sacrificed and their intestinal contents were removed. The fecal material was weighed and stored at 4°C in a GF/C filter wrapped in aluminum foil. The material was then transferred to a receptacle containing sterilised soil from the sampling area. The fecal samples were kept in a germination chamber for 68 days and then transferred to a greenhouse for another 67 days. We collected a total of 45 fish species and 1014 individuals which produced a total amount of 32 g of fresh fecal mass and 11 seedlings. We were able to identify six seedlings: two Banara arguta, two Steinchisma laxa, one Hymenachne amplexicaulis and one Luziola sp.. The fish species that produced samples with seedlings were Astyanax assuncionensis, Metynnis mola, Plesiolebias glaucopterus, Acestrorhyncus pantaneiro and Anadoras wendelli. With the exception of B. arguta the remaining plant species and all fish species were not known to be associated with the seed dispersal process of these plants. We found a ratio of 0.435 seedlings.g-1 of fresh fecal material, which is 100 times higher than the amount of seedlings encountered in fresh soil mass (92,974 grams) in seed bank studies conducted in the same study area. In particular, Astyanax assuncionensis and Metynnis mola were among the most frequent and most abundant fish taxa in the area. Together with the high seed concentration in the fish fecal material, this evidence allows us to conclude that such fish species may play an important role in seed dispersal in the herbaceous plants of the Pantanal.
Highlights
Life history traits determine the relationship between the number and competitive ability of offspring
We address the relative contributions of seed dispersal by fish and by water, comparing the amount of seedlings produced by fish feces with the amount of seedlings produced in a nearby soil seed bank study
We obtained seedlings from fishes belonging to many different functional groups, including the piscivore Acestrorhyncus pantaneiro, the invertivores Plesiolebias glaucopterus and Astyanax assuncionensis, the herbivore Metynnis mola and the planktivore/detritivore Anadoras wendelli
Summary
Life history traits determine the relationship between the number and competitive ability of offspring. Tradeoffs in plant reproductive strategies are not limited to quantitative vs qualitative aspects of seed production. The passage through the digestive trait may exert a positive or a negative effect on seed viability and on the timing of seed germination. For most plants with small seeds, the time spent in the vector’s gut tends to be longer. This longer passage of time may cause more damage to soft-skinned seeds, but the seeds may be transported farther (Traveset, 1998). The passage through the digestive tract in birds and bats increases the seed germination rate by 55% and 58%, respectively. Most authors are aware of the substantial potential of fishes as seed dispersers, in the tropics (Gottsberger, 1978; Goulding, 1980, 1983; Kubitzki and Ziburski, 1994; Waldhoff et al, 1996; Horn, 1997; Pilati et al, 1999; Banack et al, 2002; Mannheimer et al, 2003; Gomiero and Braga, 2003; Maia et al, 2007; Lucas, 2008; Galetti et al, 2008; Anderson et al, 2009; Pollux, 2011; Anderson et al, 2011; Horn et al, 2011)
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