DOI: 10.5061/dryad.5x69p8d09
title: Disentangling the coexistence strategies of mud-daubing wasp species through trophic analysis in oases of Baja California peninsula

description: Species within the same trophic level show different strategies to avoid
 competition. Among these mechanisms, differences in body size,
 spatio-temporal segregation, and diet preference often leads to a niche
 partitioning. Nonetheless, little attention on coexisting predatory
 insects and their network interactions has been paid. In this study, we
 analyzed the strategies to avoid competition among three sympatric
 mud-daubing wasps of the genus Trypoxylon (Hymenoptera: Crabronidae) in
 oases and their surrounding xeric area from the Baja California peninsula,
 Mexico. We compared the prey richness, composition and proportion of
 spider guilds that were captured by the wasps. We tested whether the
 differences in wasp body size explained the niche breadth, niche overlap
 and the size of spider prey. We assessed the spider-wasp interactions
 through a network analysis. With the use of trap-nests, we collected 52
 spider species captured by the wasps. Both the guild and species
 composition of preyed spiders was different between the three wasp
 species. Differential proportions in the capture of spider guilds and a
 little diet overlap were found among the wasp species. We found that the
 wasp body size was positively correlated with prey size, but it was not a
 proxy of niche breadth. Moreover, the largest wasp species was able to
 nest in both mesic and xeric habitats, while the two smaller species were
 restricted to the oases. This study reveals that the diversity of spiders
 in oases of Baja California peninsula is crucial to maintain highly
 specialized oasis-dependent wasp species. The niche partitioning between
 mud-daubing wasps can be shaped by their inherent body size limitations
 and hunting strategies through foraging specialization for specific spider
 guilds. Food selection and slight differences in body size reduce
 competition and allow the coexistence of sympatric wasps. Our study is the
 first approach exploring the interaction networks between mud-daubing
 wasps and their spider preys, highlighting new insights into the
 morphological and ecological factors that shape antagonistic interactions,
 and allow the coexistence of predators in deserts.
description: We used artificial cavities to collect the wasp´s nests and
 identify their composition (i.e. spider prey). We set the traps in both
 the oases and the surrounding desert to evaluate the prey composition
 between habitats. The traps were set in gradual distances from the edge of
 the waterbody (inside the oasis) towards the desert area. That is, from
 around 5.0 m to 3,500 m away from the waterbody. From April to September
 2016 we sampled the southernmost oases: Santiago (SA), El Pilar (EP), and
 La Purísima (LP). From April to September 2017, the northernmost oases
 were sampled: El Sauzal (ES), San Borja (SB), and San Fernando (SF). In
 both years, we monthly replaced the occupied traps.  In order to
 determine the relative level of dietary specialization and niche
 segregation of the species, the niche breadth and niche overlap were
 calculated for the three <i>Trypoxylon</i> wasps.
 Hurlbert's formula was applied to obtain the standardized niche
 breadth (Bj). We used the Pianka´s index to measure niche overlap. Niche
 breadth index ranges from 0 to 1, where values close to 1 indicate more
 specialization. Pianka´s index also ranges from 0 to 1, where values close
 to 1 indicate a higher diet overlap. We used the <i>spaa
 </i>package to compute these indexes. We built a bipartite network
 (predator-prey) to calculate the complementary specialization index
 (H<sub>2</sub>´) and Shannon diversity of interactions between
 both trophic groups. H<sub>2</sub>´ index ranges between 0 (no
 specialization) and 1 (complete specialization). Since this index can be
 sensitive to matrices constructed with few species, we compared our data
 against 1000 random null models that avoid biases regardless the matrix
 size. With the null model approach, we assessed that the spider-wasp
 interactions are not being reflections of the sampling properties, thus
 producing random links between predator and prey. The network analysis was
 done with the package <i>bipartite </i>in R.
 To test whether the size of predators influenced the niche
 breadth and prey size selection, we measured morphological attributes of
 size on both wasps and spiders. We obtained the values of body length,
 facial and intertegular distance from the three <i>Trypoxylon
 </i>species. We used a Linear Discriminant Analysis (LDA) to
 evaluate whether the three wasp species were well separated according to
 the morphological measurements. LDA was calculated with the
 <i>psych</i> package in R.
description: Readme.txt With these data, the reader is able
 to reproduce the analyses of niche breadth, niche overlap and discriminant
 analysis as it was indicated in the manuscript: Disentangling the
 coexistence strategies of mud-daubing wasp species through trophic
 analysis in oases of Baja California peninsula The
 codes an steps to reproduce each analysis is given, indicating which
 library was used. The dataset for niche overlap and
 niche breadth is contained in "Falcon-Brindis_general_table.csv"
 file. The scripts for this analysis are in the file
 "Niche_overlap_niche_breadth.R" The general table contains four
 columns: Spider = spider species name, T. scu = number of spiders captured
 by T. sculleni, T. dub = number of spiders captured by T. dubium, T. tri
 = number of spiders captured by T. tridentatum. To
 compute the Linnear Discriminant Analysis (LDA), please open the file
 "LDA_wasp.R" and use the dataset
 "Falcon-Brindis_Wasp_body_measurements". The measurement data
 contains five columns: sex = the ID of each individual measure, thorax_L =
 thorax length, scutum = intertegular distance on scutum, head_w = head
 width, head_h = head high, wasp = wasp species.