Methods

BeeConnect combines population genomic analyses with landscape ecological methods to investigate the relationships between habitat connectivity, genetic diversity and gene flow in wild bee populations. In addition, the occurrence of diploid males provides further indications of potential inbreeding within populations. Pollen analyses are used to identify the floral resources available to wild bees in the respective study areas.

By integrating genetic, landscape and floral resource data, the project aims to identify factors influencing genetic diversity and connectivity among wild bee populations. Particular emphasis is placed on the role of habitat connectivity.

The study includes four model species from the genera Bombus, Lasioglossum and Halictus. For each species, populations from all four administrative regions of Baden-Württemberg are included. The selection of study sites is based on data from the state-wide insect monitoring programme in Baden-Württemberg, which has been conducted since 2018, and takes into account differences in the surrounding landscape and habitat connectivity.

At the monitoring sites, surveys are conducted on a four-year cycle. BeeConnect therefore has access to samples collected at two time points, four years apart. Comparing these time points allows both spatial differences between populations and temporal changes in genetic diversity to be investigated.

The combination of different study sites, landscape contexts and sampling periods makes it possible to analyse genetic patterns across space and time and examine their relationship with habitat connectivity.

Population Genomics

Whole-genome sequencing (WGS) is used for the population genomic analyses. The genomes of the four model species are sequenced and compared with their respective reference genomes. The focus is on single nucleotide polymorphisms (SNPs), which are used as genetic markers to analyse genetic diversity, genetic differentiation and gene flow between populations. Comparing the two sampling time points also allows temporal changes in genetic patterns to be investigated.

Pollen Analysis

DNA metabarcoding is used to analyse pollen samples and identify the plant species utilised by wild bees, thereby determining their food resources. This makes it possible to assess differences in food availability and resource use between study areas and relate these findings to the genetic data.

Diploid Males

The frequency of diploid males is assessed as an additional indicator of inbreeding and genetic erosion in populations. Based on these findings, potential population dynamics are modelled, taking into account a possible "diploid male vortex", and the resulting risk to the long-term stability of populations is evaluated.