DOI: 10.6084/m9.figshare.20442891.v1
title: Data from "Hunger for sex: abundant, heterogeneous resources select for sexual reproduction in the field"

description: <strong>The data presented here are part of the study "Hunger for sex: abundant, heterogeneous resources select for sexual reproduction in the field", and have been assembled to investigate the role of resource abundance and heterogeneity in imposing natural selection on reproductive mode in the field.</strong> To this aim, we studied natural communities of soil oribatid mites (Acari: Oribatida), whose species vary in reproductive mode (sexual vs. asexual) and occur along natural gradients of resource abundance (litter amount), resource heterogeneity (tree species richness) and abiotic conditions (soil water content). The study had two parts: (1) investigating relationships between the prevalence of reproductive modes in natural communities and these environmental factors, using data sampled in an Amazonian rainforest; and (2) investigating differences in trophic niche between species with different reproductive modes, using data assembled from the literature. The data are organized in three tables, as follows: <br> <strong>1) Supporting Information_Table_S1_community_data.csv</strong> This table contains the community data. Each row represents one oribatid mite community sampled along a transect, and each column represents one community attribute, named from left to right as follows: site (transect identifier); X coordinate (m) (X coordinate across the sampled area); Y coordinate (m) (Y coordinate across the sampled area); Soil water content (%); Mean litter amount (g); Tree species richness (number of tree species); Observed proportion of sexual species; Standardized Effect Size of proportion of sexual species (measure of selection for sex based on null model); Species names (abundance of named species). <br> <strong>2) Supporting Information_Table_S2_trait_data.csv</strong> This table contains data on reproductive modes of the species present in the studied communities. Each row represents one species, and each column represents one species attribute, named from left to right as follows: Supercohort (taxonomic classification); Cohort (taxonomic classification); Superfamily (taxonomic classification); Family (taxonomic classification); Genus (taxonomic classification); Species (taxonomic classification); Reproductive mode (sexual or asexual); Criterion (rule used to consider the species asexual); Reference (reference on species reproductive mode). <strong>3) Supporting Information_Table_S3_isotope_data.csv</strong> This table contains data on the trophic niches (based on stable isotope ratios) and reproductive modes of tropical species of oribatid mites, gathered from the literature. Each row represents one species, and each column represents one species attribute, named from left to right as follows: Supercohort (taxonomic classification); Cohort (taxonomic classification); Superfamily (taxonomic classification); Family (taxonomic classification); Genus (taxonomic classification); Species name in original publication; Species name updated for this study; Country (where the species was sampled); Site (where the species was sampled); Habitat (where the species was sampled); Sample size of stable isotope ratios (number of individual measurements); Mean delta 15N (mean nitrogen isotope ratio); Baseline delta 15N (environmental nitrogen isotope ratio used as baseline for intersite comparison); Mean delta 13C (mean carbon isotope ratio); Baseline delta 13C (environmental carbon isotope ratio used as baseline for intersite comparison); Reference of stable isotope ratios; Reproductive mode; Criterion for parthenogenesis; Reference for parthenogenesis. <br> <strong>Details on data collection</strong> <em>Data on Amazonian oribatid mite communities</em> Data were obtained from the Brazilian Program for Biodiversity Research (PPBio) in Reserva Ducke, a large tropical rainforest reserve (10 × 10 km) managed by the Brazilian Institute for Amazonia Research (INPA) in Manaus, Brazilian Amazonia (2°57′ S, 59°56′ W). Topography encompasses an alternation between sandy bottomlands subject to waterlogging and drier, clayish uplands connected by mixed-soil slopes, with altitude ranging between ca. 50 and 100 m a.s.l. Vegetation structure and species composition vary in close association with hydroedaphic gradients. Mean daily temperature and mean annual rainfall between 1992 and 2002 were 26.7 °C and 2479 mm, respectively, with monthly rainfall below 100 mm from July to September. Oribatid mites were sampled from March 18 to May 13, 2002 across 48 sites regularly distributed over the reserve, with at least 1 km between them. On each site, one soil core (3.5 cm × 3.5 cm × 5 cm) was sampled each 12.5 m along a 250-m transect following a topographic contour line, totalling 20 cores per transect. Each quartet of consecutive soil cores was combined into a single plastic container to reduce the processing load and taken to the Laboratory of Systematics and Ecology of Terrestrial Arthropods at INPA’s campus in Manaus. Mites were extracted with a Berlese-Tullgren apparatus. Temperature was gradually increased from 28 to 45 °C until soil reached a constant mass, which took from six to seven days. Specimens were preserved in 4% formaldehyde solution, and adult oribatid mites were sorted into morphospecies. Whenever possible, morphospecies (hereafter species) were identified with the aid of taxonomic keys and original descriptions, by clarifying specimens with lactic acid and mounting them in temporary slides for examination under a compound microscope. Immatures were not considered but represented only 8% of extracted individuals. Voucher specimens were stored in the Entomological Collection of INPA. Reproductive mode was inferred from published records. In oribatid mites, thelytoky (production of diploid females from unfertilized eggs) is obligatory for the species in which it occurs; males are rare and sterile. Hence, species were conservatively assumed sexual unless asexuality was evidenced from rearing (reproduction of unmated females), sex ratios (&gt;95% females), or the species was in a genus or family without known sexual species. Overall, we collected 1940 adult oribatid mites from 127 (morpho)species over the 48 transects, with 832 individuals (43%) in 20 species (16%) considered asexual. Soil water content (%) was measured as one minus the ratio between the dry mass and the wet mass of the soil samples used for mite extraction, averaged for each site. Litter amount was measured for each transect by harvesting all fine litter (leaves, fruits, and woody items with diameter &lt;2 cm) in five quadrats (0.4 m × 0.6 m) with regular spacing of 50 m. Litter was dried at 65°C until it reached constant mass, to determine the average dry mass (g) per transect. Tree species richness was determined by first surveying trees with diameter at breast height (dbh) &gt; 30 cm, which were marked within a 250 × 40 m plot aligned and centralized over the transect. Then, trees with dbh 10-30 cm were marked in an inner 250 × 20 m plot, and trees with dbh 1-10 cm were marked in an innermost 250 × 4 plot. Trees were morphotyped and identified as possible by specialists with reference to INPA’ botanical collection and the taxonomic literature. <br> <em>Comparative data on tropical oribatid mite species</em> We used literature data to investigate the relation between species trophic niche and reproductive mode more generally. We inferred species trophic niche using stable isotope ratios. In soil organisms, nitrogen isotope ratio (δ15N) generally increases with trophic level, from primary decomposers (feeding on litter or roots) to secondary decomposers (feeding on fungi) to scavengers and predators (feeding on animal tissue); whereas carbon istope ratio (δ13C) mainly reflects the basal carbon source of the food chain, increasing from fresh, plant-derived carbon to older, microbial carbon. Estimates of δ15N and δ13C for soil oribatid mites were searched for using Google Scholar, along with the reference lists of identified studies. Because such data are not available for oribatid mites from Brazilian Amazonia, we considered tropical species in general, given that many genera have pantropical distribution and that trophic niches of oribatid species tend to be conserved within genera. We searched for the terms “oribatid”, “stable isotope” and “tropical”. Our search included studies indexed until December 2021. We obtained the mean δ15N and δ13C of a given species within a given study area, subtracted from the respective values of the baseline informed by the study (typically litter) to standardize for environmental variation in isotopic signatures. We avoided data from disturbed sites to minimize anthropic influence on niche measurements. If data were presented in figures, we used WebPlotDigitizer 4.1 to extract the values. Because oribatid mites are so small (generally &lt; 1 mm long), each measurement typically represented several pooled individuals. For each species, we obtained data on reproductive mode (sexual or asexual) either from the original studies or from the literature as above. The final comparative dataset included 82 species (62 sexual and 20 asexual), collected by four studies across three countries (Ecuador, Indonesia and Vietnam). Remarkably, 70% of the species collected in Reserva Ducke belonged to genera included in the comparative dataset.