Islands in the desert for cavity-nesting bees and wasps: Ecology, patterns of diversity, and conservation at oases of Baja California Peninsula.

María Luisa Jiménez Jiménez,Ricardo Rodríguez‐Estrella,Armando Falcón‐Brindis

doi:10.1002/ece3.5927

María Luisa Jiménez Jiménez, Ricardo Rodríguez‐Estrella + Show 1 more

Open Access

https://doi.org/10.1002/ece3.5927

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Abstract

AimsThe oases of Baja California Peninsula (BCP) have been proposed as important hotspots of biodiversity that hold an exceptional richness in the middle of desert conditions. We tested the effect of habitat and anthropogenic disturbance on communities of cavity‐nesting taxa, with specific emphasis on bees, wasps, and their natural enemies.MethodsIn oases of BCP and desert neighbor environments, trap‐nesting taxa were evaluated in response to factors affecting the nest abundance, richness, and community structure. We used statistical models to find correlates of nest abundance and patterns of diversity, as well as ecological analyses to determine the effect of habitat and human disturbance on species diversity and community structure.ResultsSolar irradiation, distance to a perennial waterbody and relative humidity influenced the presence of nests, number of brood cells, and parasitism. In general, abundance, species richness, and parasitism were higher in oases, especially in those with less human disturbance. Bees did not discriminate between oases and deserts to nest, whereas mud‐daubing wasps were more dependent of oases. The degree of anthropogenic disturbance did not affect the occurrence of parasitism, but it had an adverse effect on the parasitism intensity (number of attacked cells). The community structure was more complex and even in oases and low‐disturbed sites. The similarity between sites did not exceed 30%, and the proportion of shared species between oases and deserts varied from 2.7% to 26.6%.Main conclusionsThe oases of Baja California are functioning as mesic islands in the desert, each oasis hosting a unique community of cavity‐nesting taxa. About 65% of the nests and 50% of species occurred exclusively in the oasis. Thus, cavity‐nesting species that depend on mesic conditions could be threatened if the oases of BCP disappear in the future. Local conditions in the oases and deserts of the BCP are shaping the community structure. However, large‐scale factors such as climate can influence the seasonality and occurrence of species within the community of cavity‐nesting dwellers. Since habitat loss and fragmentation can degrade the oases’ functionality, strategies to maintain the ecosystem services of pollination and biological control should be included in the conservation programs of these fragile habitats.

Highlights

Complex geological and paleoclimatic events have allowed the presence of oases in the desert of the Baja California Peninsula (BCP; Grismer, 2000)
We evaluated the effect of climatic variation in the BCP over the trap-nesting communities as a complement to explain the variation in species composition and seasonality (Figure 1)
To evaluate the effect of water closeness on the reproductive fitness of bees and wasps, we considered the largest perennial waterbody of each oasis as the focal point, we set the traps in gradual distances from the edge of the waterbody toward the desert area

Summary

| INTRODUCTION

Complex geological and paleoclimatic events have allowed the presence of oases in the desert of the Baja California Peninsula (BCP; Grismer, 2000). That is the case of keystone groups such as bees and wasps, which contribute in ecosystem functions through pollination (i.e., bees) and population control of small-to-moderate-sized arthropods (i.e., wasps; Tscharntke, Gathmann, & Steffan-Dewenter, 1998) Within these groups, the diversity of cavity-nesting bees and wasps can positively respond to mesic habitats, which allow the prevalence of complex vegetation, offering a great amount of food and nesting resources (Flores, Zanette, & Araujo, 2018). Bees are well known to be more diverse in the xeric areas of the world (Michener, 1979), their distributional patterns across BCP remain unknown, especially since a great extension of the BCP is dominated by the Sonoran desert (Wiggins, 1980) Within this framework, we evaluated the effect of climatic variation in the BCP over the trap-nesting communities as a complement to explain the variation in species composition and seasonality (Figure 1)

| METHODS

Findings

| DISCUSSION