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Niche partitioning and the role of intraspecific niche variation in structuring a guild of generalist anurans

View Article: PubMed Central - PubMed

ABSTRACT

Intra-population niche differences in generalist foragers have captured the interest of ecologists, because such individuality can have important ecological and evolutionary implications. Few researchers have investigated how these differences affect the relationships among ecologically similar, sympatric species. Using stable isotopes, stomach contents, morphology and habitat preference, we examined niche partitioning within a group of five anurans and determined whether variation within species could facilitate resource partitioning. Species partitioned their niches by trophic level and by foraging habitat. However, there was considerable intraspecific variation in trophic level, with larger individuals generally feeding at higher trophic levels. For species at intermediate trophic levels, smaller individuals overlapped in trophic level with individuals of smaller species and larger individuals overlapped with the smallest individuals from larger species. Species varied in carbon isotopes; species with enriched carbon isotope ratios foraged farther from ponds, whereas species with depleted carbon isotope values foraged closer to ponds. Our study shows that these species partition their niches by feeding at different trophic levels and foraging at different distances from ponds. The intraspecific variation in trophic level decreased the number of individuals from each species that overlapped in trophic level with individuals from other species, which can facilitate species coexistence.

No MeSH data available.


Group membership for (a) δ15N and (b) δ13C by species as determined by hierarchical clustering. Group number indicates which group an individual frog was placed in according to the clustering analysis. For both isotope types, L. catesbeianus is most frequently found in higher-numbered groups. For δ15N, A. americanus, L. clamitans and L. sphenocephalus most frequently cluster in intermediate-numbered groups but are present in all groups. Anaxyrus fowleri cluster most frequently in lower-numbered groups. For δ13C, both A. americanus and A. fowleri cluster in lower-numbered groups. Lithobates sphenocephalus cluster in intermediate-numbered groups, and both L. catesbeianus and L. clamitans cluster in higher-numbered groups. The clustering pattern for δ13C generally follows the pattern of distance from pond at which each species was found, as shown in the electronic supplementary material, figure S2b.
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RSOS170060F4: Group membership for (a) δ15N and (b) δ13C by species as determined by hierarchical clustering. Group number indicates which group an individual frog was placed in according to the clustering analysis. For both isotope types, L. catesbeianus is most frequently found in higher-numbered groups. For δ15N, A. americanus, L. clamitans and L. sphenocephalus most frequently cluster in intermediate-numbered groups but are present in all groups. Anaxyrus fowleri cluster most frequently in lower-numbered groups. For δ13C, both A. americanus and A. fowleri cluster in lower-numbered groups. Lithobates sphenocephalus cluster in intermediate-numbered groups, and both L. catesbeianus and L. clamitans cluster in higher-numbered groups. The clustering pattern for δ13C generally follows the pattern of distance from pond at which each species was found, as shown in the electronic supplementary material, figure S2b.

Mentions: Individuals that were grouped by δ15N values in a cluster analysis differed according to species (figure 4a; F = 36.76, d.f. = 4, 261, p < 0.001), and in general larger individuals were placed in higher-numbered groups (electronic supplementary material, figure S2a). Individuals from A. americanus, L. clamitans and L. sphenocephalus did not differ in the groups to which they belonged (figure 4a). Individuals from L. catesbeianus were grouped higher than all other species (p < 0.001 for all comparisons) but did overlap with some individuals from A. americanus, L. clamitans and L. sphenocephalus (figure 4a). Individuals from A. fowleri were grouped lower than the other species (figure 4a; p < 0.001 for all comparisons), but some individuals overlapped with A. americanus, L. clamitans and L. sphenocephalus (figure 4a). Individuals from higher groups had higher SVL (F = 105.2, d.f. = 1, 264, p < 0.001, R2 = 0.282).Figure 4.


Niche partitioning and the role of intraspecific niche variation in structuring a guild of generalist anurans
Group membership for (a) δ15N and (b) δ13C by species as determined by hierarchical clustering. Group number indicates which group an individual frog was placed in according to the clustering analysis. For both isotope types, L. catesbeianus is most frequently found in higher-numbered groups. For δ15N, A. americanus, L. clamitans and L. sphenocephalus most frequently cluster in intermediate-numbered groups but are present in all groups. Anaxyrus fowleri cluster most frequently in lower-numbered groups. For δ13C, both A. americanus and A. fowleri cluster in lower-numbered groups. Lithobates sphenocephalus cluster in intermediate-numbered groups, and both L. catesbeianus and L. clamitans cluster in higher-numbered groups. The clustering pattern for δ13C generally follows the pattern of distance from pond at which each species was found, as shown in the electronic supplementary material, figure S2b.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383860&req=5

RSOS170060F4: Group membership for (a) δ15N and (b) δ13C by species as determined by hierarchical clustering. Group number indicates which group an individual frog was placed in according to the clustering analysis. For both isotope types, L. catesbeianus is most frequently found in higher-numbered groups. For δ15N, A. americanus, L. clamitans and L. sphenocephalus most frequently cluster in intermediate-numbered groups but are present in all groups. Anaxyrus fowleri cluster most frequently in lower-numbered groups. For δ13C, both A. americanus and A. fowleri cluster in lower-numbered groups. Lithobates sphenocephalus cluster in intermediate-numbered groups, and both L. catesbeianus and L. clamitans cluster in higher-numbered groups. The clustering pattern for δ13C generally follows the pattern of distance from pond at which each species was found, as shown in the electronic supplementary material, figure S2b.
Mentions: Individuals that were grouped by δ15N values in a cluster analysis differed according to species (figure 4a; F = 36.76, d.f. = 4, 261, p < 0.001), and in general larger individuals were placed in higher-numbered groups (electronic supplementary material, figure S2a). Individuals from A. americanus, L. clamitans and L. sphenocephalus did not differ in the groups to which they belonged (figure 4a). Individuals from L. catesbeianus were grouped higher than all other species (p < 0.001 for all comparisons) but did overlap with some individuals from A. americanus, L. clamitans and L. sphenocephalus (figure 4a). Individuals from A. fowleri were grouped lower than the other species (figure 4a; p < 0.001 for all comparisons), but some individuals overlapped with A. americanus, L. clamitans and L. sphenocephalus (figure 4a). Individuals from higher groups had higher SVL (F = 105.2, d.f. = 1, 264, p < 0.001, R2 = 0.282).Figure 4.

View Article: PubMed Central - PubMed

ABSTRACT

Intra-population niche differences in generalist foragers have captured the interest of ecologists, because such individuality can have important ecological and evolutionary implications. Few researchers have investigated how these differences affect the relationships among ecologically similar, sympatric species. Using stable isotopes, stomach contents, morphology and habitat preference, we examined niche partitioning within a group of five anurans and determined whether variation within species could facilitate resource partitioning. Species partitioned their niches by trophic level and by foraging habitat. However, there was considerable intraspecific variation in trophic level, with larger individuals generally feeding at higher trophic levels. For species at intermediate trophic levels, smaller individuals overlapped in trophic level with individuals of smaller species and larger individuals overlapped with the smallest individuals from larger species. Species varied in carbon isotopes; species with enriched carbon isotope ratios foraged farther from ponds, whereas species with depleted carbon isotope values foraged closer to ponds. Our study shows that these species partition their niches by feeding at different trophic levels and foraging at different distances from ponds. The intraspecific variation in trophic level decreased the number of individuals from each species that overlapped in trophic level with individuals from other species, which can facilitate species coexistence.

No MeSH data available.