DOI: 10.5061/dryad.kwh70rz9m
title: Data for: Morphometric parameters in males of the social wasp Polistes simillimus

description: Sperm competition and male mating rate are two non-mutually exclusive key
 evolutionary pressures selecting for larger testes within and across
 animal taxa. A few studies have tried to disentangle their effects (e.g.,
 testing the role of mating rate in the absence of sperm competition).
 Under the mating rate hypothesis, particular phenotypes of a given
 population which are expected to gain more mates (e.g. more ornamented
 males) are expected to make higher investment in testes size (a proxy for
 sperm production). We test this prediction in Polistes simillimus, a
 neotropical paper wasp in which females are single-mated (no sperm
 competition) and males can mate with multiple partners. According to
 linear mixed model analyses, testes size was predicted by body size
 (positive association), sexual ornamentation (negative association), and
 their interaction (among small males, testes size was positively related
 to ornamentation but the opposite pattern was observed among large males).
 We propose that small-bodied well-ornamented males may face the highest
 risk of sperm depletion. Nevertheless, small-bodied males make relatively
 higher investment in testes size when sexy (more ornamented). This
 strategy might be less profitable to large males, as they have overall
 larger testes. Our results provide strong evidence for the mating rate
 hypothesis.
description: In April 2022, male-producing colonies of
 <em>P. simillimus</em> (N = 11) were collected in the
 municipality of Muzambinho, Minas Gerais state, and brought to the
 University of São Paulo, Ribeirão Preto. In the laboratory, the nests full
 of pupae (without adult wasps) were individually kept in plastic
 containers of 5 L. Subsequently, we inspected the nests daily to check for
 the presence of adult wasps. Newly emerged males were removed and used for
 morphometric measurements (N = 168 males, mean = 18, SE =
 ± 14, range = 4 – 41 males per
 colony). For each
 newly-emerged male, we measured the testes size, the sexual ornamentation
 and the body size. Males were anaesthetized by cooling for 2 min then
 dissected in insect buffer (0.1 M phosphate buffer, pH 7.2) under a
 stereomicroscope. Testes size was approximated from pictures of the
 bidimensional testes area. Sexual ornamentation was measured as the
 proportion of black pigmented vertex, as this seem to be the active signal
 component mediating female mate choice. We also measured the maximum head
 width of each male, which is a good correlate of male body
 size.
description: # Morphometric parameters in males of the social wasp *Polistes
 simillimus* \--- This dataset contains a table (a.csv and an equivalent
 .xlsx) about morphometric measurements on males of the social wasp
 *Polistes simillimus*. It was also updated to include several pictures of
 wasp testes. Abstract: Sperm competition and male mating rate are two
 non-mutually exclusive key evolutionary pressures selecting for larger
 testes within and across animal taxa. A few studies have tried to
 disentangle their effects (e.g., testing the role of mating rate in the
 absence of sperm competition). Under the mating rate hypothesis,
 particular phenotypes of a given population which are expected to gain
 more mates (e.g. more ornamented males) are expected to make higher
 investment in testes size (a proxy for sperm production). We test this
 prediction in Polistes simillimus, a neotropical paper wasp in which
 females are single-mated (no sperm competition) and males can mate with
 multiple partners. According to linear mixed model analyses, testes size
 was predicted by body size (positive association), sexual ornamentation
 (negative association), and their interaction (among small males, testes
 size was positively related to ornamentation but the opposite pattern was
 observed among large males). We propose that small-bodied well-ornamented
 males may face the highest risk of sperm depletion. Nevertheless,
 small-bodied males make relatively higher investment in testes size when
 sexy (more ornamented). This strategy might be less profitable to large
 males, as they have overall larger testes. Our results provide strong
 evidence for the mating rate hypothesis. Methods:In April 2022,
 male-producing colonies of P. simillimus (N = 11) were collected in the
 municipality of Muzambinho, Minas Gerais state, and brought to the
 University of São Paulo, Ribeirão Preto. In the laboratory, the nests full
 of pupae (without adult wasps) were individually kept in plastic
 containers of 5 L. Subsequently, we inspected the nests daily to check for
 the presence of adult wasps. Newly emerged males were removed and used for
 morphometric measurements (N = 203 males, mean = 18, SE = ± 13, range = 4
 -- 41 males per colony). For each newly-emerged male, we measured the
 testes size, the sexual ornamentation and the body size. Males were
 anaesthetized by cooling for 2 min then dissected in insect buffer (0.1 M
 phosphate buffer, pH 7.2) under a stereomicroscope. Testes size was
 approximated from the bidimensional testes area. Sexual ornamentation was
 measured as the proportion of black pigmented vertex, as this seem to be
 the active signal component mediating female mate choice. We also measured
 the maximum head width of each male, which is a good correlate of male
 body size. \\## Description of the data and file structure In the data
 table, each line represents a male and each column has a specific
 information about it.