Morphological variation and trophic individual specialization of <i>Imparfinis schubarti</i> (Gomes, 1956)

Selinger, Amanda; Sandri, Leticia Mazzuco; Costa, João Henrique Alliprandini da; Kliemann, Bruna Caroline Kotz; Delariva, Rosilene Luciana

doi:10.1590/S2179-975X5425

person Amanda Selinger *

schoolLaboratório de Ictiologia, Ecologia e Biomonitoramento – LIEB, Universidade Estadual do Oeste do Paraná – UNIOESTE, Rua Universitária, 1619, Universitário, CEP 85819-110, Cascavel, PR, BrasilschoolPrograma de Pós-Graduação em Biodiversidade de Ambientes Costeiros, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Campus do Litoral Paulista, Praça Infante Dom Henrique, s/n, Parque Bitaru, CEP 11330-900, São Vicente, SP, Brasil

0000-0001-8889-6531

person Leticia Mazzuco Sandri

schoolPrograma de Pós-Graduação em Biologia Comparada, Universidade Estadual de Maringá – UEM, Avenida Colombo, 5790, Jardim Universitário, CEP 87020-900, Maringá, PR, Brasil

0000-0001-9370-7424

person João Henrique Alliprandini da Costa

schoolPrograma de Pós-Graduação em Biodiversidade de Ambientes Costeiros, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Campus do Litoral Paulista, Praça Infante Dom Henrique, s/n, Parque Bitaru, CEP 11330-900, São Vicente, SP, Brasil

0000-0001-7594-6819

person Bruna Caroline Kotz Kliemann

schoolLaboratório de Ecologia de Peixes – Pirá, Faculdade de Engenharia de Ilha Solteira, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Campus Ilha Solteira, Rua Monção, 226, Zona Norte, CEP 15385-000, Ilha Solteira, SP, Brasil

0000-0002-7972-2043

person Rosilene Luciana Delariva

schoolLaboratório de Ictiologia, Ecologia e Biomonitoramento – LIEB, Universidade Estadual do Oeste do Paraná – UNIOESTE, Rua Universitária, 1619, Universitário, CEP 85819-110, Cascavel, PR, Brasil

0000-0002-6489-2437

person*e-mail:
amandaselinger@gmail.com

Associate Editor:

Priscilla de Carvalho.

Figures (5)
Tables (2)

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Figure 1 Areia stream location, at the Piquiri River Basin, northwest Paraná.

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Figure 2 Individual of Imparfinis schubarti with 14 landmarks: 1) anterior tip of snout; 2) point above the upper margin of the eye socket; 3) posterior tip of head; 4) origin of dorsal fin; 5) insertion of dorsal fin; 6) origin of adipose fin; 7) insertion of adipose fin; 8) origin of anterior dorsal ray of caudal fin; 9) origin of anterior ventral ray of caudal fin; 10) origin of anal fin; 11) insertion of anal fin; 12) origin of pelvic fin; 13) intersection of gill opening and ventral margin of body; and 14) origin of pectoral fin.

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Figure 3 Result of principal component analysis (PCA) showing the intraspecific morphological differences of Imparfinis schubarti and their relationships along the standard length (SL) in Areia stream, Paraná, Brazil. The graph shows the deformation plates demonstrating the variation between the shape of the individuals.

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Figure 4 Distribution of the Proportional Similarity index (PS_i) values for individual diets in Imparfinis schubarti. PSi theoretically ranges from 0 (no overlap with the population diet) to 1 (complete overlap). In this study, observed PSi values ranged from 0.056 to 0.644. Lower PSi values indicate higher individual specialization, while higher values indicate more generalist individuals.

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Figure 5 Weighted network of pairwise dietary similarity among individuals of Imparfinis schubarti. Each node represents an individual, and edge thickness is proportional to the individual pairwise diet composition similarity.

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Table 1 Food items recorded in the diet of Imparfinis schubarti, categorized by origin. Values represent the relative volume (%) of each item across all stomachs analyzed.

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Table 2 Summary of indices used in this study, including their ecological meaning, conceptual description, R functions, and theoretical references. All indices were calculated in R using the RInSp package (Zaccarelli et al., 2013).

Items	Relative volume (%)
Algae	1.01
Aquatic plants	12.19
Bivalvia	0.61
Coleoptera (adults)	0.34
Coleoptera (larvae)	0.27
Detritus	1.41
Diptera (adults)	0.40
Diptera (larvae)
Chironomidae	24.08
Simulidae	1.89
Diptera (pupae)	9.83
Ephemeroptera (nymphs)	8.02
Fish scales	0.34
Hemiptera (nymphs)	0.07
Hymenoptera (adults)	0.94
Insect fragments	4.11
Lepidoptera (larvae)	2.22
Nematoda	0.13
Odonata (nymphs)	0.27
Trichoptera (larvae)	31.87

Index	What it measures	Description	R function	References
PSi (Proportional Similarity index)	Individual–population diet overlap	Quantifies the overlap between the proportional use of each resource by an individual and the proportional use of the same resources by the population as a whole. Values range from 0 (no overlap) to 1 (complete overlap). Lower values indicate narrower individual niches relative to the population niche	PSicalc()	Bolnick et al. (2002); Bolnick et al. (2003)
IS (Individual Specialization index)	Population-level degree of individual specialization	Calculated as the mean PSi across all individuals in the population. Low IS values indicate strong individual specialization, whereas values close to 1 indicate that individuals closely match the population diet	PSicalc()	Bolnick et al. (2002); Bolnick et al. (2003)
E (Individual specialization index based on pairwise overlap)	Degree of dietary differentiation among individuals	Measures the average pairwise dissimilarity in resource use among individuals, based on dietary overlap matrices. Values range from 0 (all individuals use the same resources in identical proportions) to 1 (each individual uses completely different resources)	Eindex()	Araújo et al. (2008)
Adjusted E	Individual specialization corrected for sampling effects	Standardizes the observed E value by comparing it to the mean E obtained from null models generated by Monte Carlo simulations, correcting for inflation when individuals consume few resource types	Emc()	Araújo et al. (2008); Zaccarelli et al. (2013)
Cws (Weighted modularity index)	Modularity in individual diets	Quantifies whether individuals form modules (subgroups) that share similar subsets of resources. Values near −1 indicate overdispersed diets, values near 0 indicate random structure, and values near +1 indicate strong modularity. Statistical significance is evaluated using null models	Emc()	Araújo et al. (2008); Zaccarelli et al. (2013)
NODF	Nestedness of individual diets	Measures whether diets of specialist individuals form subsets of diets of generalist individuals, using a binary diet matrix. Values range from 0 (no nestedness) to 100 (perfect nestedness)	NODF()	Almeida-Neto et al. (2008)

Morphological variation and trophic individual specialization of Imparfinis schubarti (Gomes, 1956)

Variação morfológica e especialização trófica individual de Imparfinis schubarti (Gomes, 1956)